[Percutaneous ablation of malignant kidney tumors in rabbits by low frequency radio energy].

PubMed

Moskovitz, B; Nativ, O; Sabo, E; Barbara, Y; Mordohovich, D; Kaftori, Y; Shalhav, A; Goldwasser, B

1998-01-01

Radio-frequency (RF) current has been used successfully to ablate normal human tissue. To investigate further the clinical application of this modality in tumors, we studied the potential of using RF percutaneously to destroy experimental kidney tumors. 35 outbred albino rabbits underwent direct-implantation of renal VX2 tumor during open surgery. After 21 days, ultrasonography was performed to show tumor presence and size. A shielded RF needle was designed to be inserted percutaneously through an introduction needle. An electrical insulation shield covering the RF needle was retractable, controlling the length of exposure of the RF needle inside the tissue. 22 days after tumor implantation, RF was applied via this special needle using a ZoMed International RF generator. In one group of rabbits the procedure was performed under direct vision during open surgery, while in another group treatment was percutaneous, the needle guided by palpation of the tumor. Rabbits were killed 3 days later and revealed 4-25 mm intra-tumoral RF-induced lesions. A direct relation was found between lesion size and the power and duration of RF applied (at 7.5 W, R = 0.48, and P = 0.32). Based on our preliminary results we can conclude that RF may have clinical applications in the near future for percutaneous local tumor control in parenchymal organs.

Thermal magnetic resonance: physics considerations and electromagnetic field simulations up to 23.5 Tesla (1GHz).

PubMed

Winter, Lukas; Oezerdem, Celal; Hoffmann, Werner; van de Lindt, Tessa; Periquito, Joao; Ji, Yiyi; Ghadjar, Pirus; Budach, Volker; Wust, Peter; Niendorf, Thoralf

2015-09-22

Glioblastoma multiforme is the most common and most aggressive malign brain tumor. The 5-year survival rate after tumor resection and adjuvant chemoradiation is only 10 %, with almost all recurrences occurring in the initially treated site. Attempts to improve local control using a higher radiation dose were not successful so that alternative additive treatments are urgently needed. Given the strong rationale for hyperthermia as part of a multimodal treatment for patients with glioblastoma, non-invasive radio frequency (RF) hyperthermia might significantly improve treatment results. A non-invasive applicator was constructed utilizing the magnetic resonance (MR) spin excitation frequency for controlled RF hyperthermia and MR imaging in an integrated system, which we refer to as thermal MR. Applicator designs at RF frequencies 300 MHz, 500 MHz and 1GHz were investigated and examined for absolute applicable thermal dose and temperature hotspot size. Electromagnetic field (EMF) and temperature simulations were performed in human voxel models. RF heating experiments were conducted at 300 MHz and 500 MHz to characterize the applicator performance and validate the simulations. The feasibility of thermal MR was demonstrated at 7.0 T. The temperature could be increased by ~11 °C in 3 min in the center of a head sized phantom. Modification of the RF phases allowed steering of a temperature hotspot to a deliberately selected location. RF heating was monitored using the integrated system for MR thermometry and high spatial resolution MRI. EMF and thermal simulations demonstrated that local RF hyperthermia using the integrated system is feasible to reach a maximum temperature in the center of the human brain of 46.8 °C after 3 min of RF heating while surface temperatures stayed below 41 °C. Using higher RF frequencies reduces the size of the temperature hotspot significantly. The opportunities and capabilities of thermal magnetic resonance for RF hyperthermia interventions of intracranial lesions are intriguing. Employing such systems as an alternative additive treatment for glioblastoma multiforme might be able to improve local control by "fighting fire with fire". Interventions are not limited to the human brain and might include temperature driven targeted drug and MR contrast agent delivery and help to understand temperature dependent bio- and physiological processes in-vivo.

T-gate aligned nanotube radio frequency transistors and circuits with superior performance.

PubMed

Che, Yuchi; Lin, Yung-Chen; Kim, Pyojae; Zhou, Chongwu

2013-05-28

In this paper, we applied self-aligned T-gate design to aligned carbon nanotube array transistors and achieved an extrinsic current-gain cutoff frequency (ft) of 25 GHz, which is the best on-chip performance for nanotube radio frequency (RF) transistors reported to date. Meanwhile, an intrinsic current-gain cutoff frequency up to 102 GHz is obtained, comparable to the best value reported for nanotube RF transistors. Armed with the excellent extrinsic RF performance, we performed both single-tone and two-tone measurements for aligned nanotube transistors at a frequency up to 8 GHz. Furthermore, we utilized T-gate aligned nanotube transistors to construct mixing and frequency doubling analog circuits operated in gigahertz frequency regime. Our results confirm the great potential of nanotube-based circuit applications and indicate that nanotube transistors are promising building blocks in high-frequency electronics.

Comprehensive analysis of sub-20 nm black phosphorus based junctionless-recessed channel MOSFET for analog/RF applications

NASA Astrophysics Data System (ADS)

Kumar, Ajay; Tripathi, M. M.; Chaujar, Rishu

2018-04-01

In this work, a comprehensive analog and RF performance of a novel Black Phosphorus-Junctionless-Recessed Channel (BP-JL-RC) MOSFET has been explored at 45 nm technology node (Gate length = 20 nm). The integration of black phosphorus with junctionless recessed channel MOSFET, leads to higher drain current of about 0.3 mA and excellent switching ratio (of the order of 1011) due to reduced off-current which leads to improvement in sub-threshold slope (SS) (67mV/dec). Further, RF performance metrics have also been studied with an aim to analyze high-frequency performance. The following FOMs have been evaluated: cut-off frequency (fT), maximum oscillator frequency (fMAX), stern stability factor, various power gains and parasitic capacitances at THz frequency range. Thus, in addition to the high packing density offered by RC MOSFET, the proposed design finds numerous application at THz frequency making it a promising candidate at wafer scale integration level.

Integrating Nano-patterned Ferromagnetic and Ferroelectric Thin Films for Electrically Tunable RF Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Tengxing; Peng, Yujia; Jiang, Wei

Tunable radio frequency (RF) components are pivotal elements in frequency-agile and multifunctional systems. However, there is a technical barrier to achieve miniaturized fully electrically tunable RF components. This paper provides and demonstrates the efficacy of a first unique design methodology in developing fully electrically tunable RF components by integrating ferromagnetic (e.g., Permalloy) and ferroelectric (e.g., Lead Zirconate Titanate: PZT) thin films patterns. Permalloy thin film has been patterned in nanometer scale to improve its ferromagnetic resonance frequency (FMR) for RF applications. Tunable inductors are developed with the utilization of different thickness of Permalloy thin film, which show over 50% incrementmore » in inductance and over 4% in tunability with DC current. More tunability can be achieved with multiple layers of Permalloy thin film and optimized thickness. A fully electrically tunable slow wave RF transmission line with simultaneously variable inductance and capacitance density has been implemented and thoroughly investigated for the first time. Measured results show that a fixed phase shift of 90° can be achieved from 1.5 GHz to 1.85 GHz continuously by applying external DC current from 0 to 200 mA and external DC voltage from 0 to 15 Volts, respectively.« less

Integrating Nano-patterned Ferromagnetic and Ferroelectric Thin Films for Electrically Tunable RF Applications

DOE PAGES

Wang, Tengxing; Peng, Yujia; Jiang, Wei; ...

2016-10-31

Tunable radio frequency (RF) components are pivotal elements in frequency-agile and multifunctional systems. However, there is a technical barrier to achieve miniaturized fully electrically tunable RF components. This paper provides and demonstrates the efficacy of a first unique design methodology in developing fully electrically tunable RF components by integrating ferromagnetic (e.g., Permalloy) and ferroelectric (e.g., Lead Zirconate Titanate: PZT) thin films patterns. Permalloy thin film has been patterned in nanometer scale to improve its ferromagnetic resonance frequency (FMR) for RF applications. Tunable inductors are developed with the utilization of different thickness of Permalloy thin film, which show over 50% incrementmore » in inductance and over 4% in tunability with DC current. More tunability can be achieved with multiple layers of Permalloy thin film and optimized thickness. A fully electrically tunable slow wave RF transmission line with simultaneously variable inductance and capacitance density has been implemented and thoroughly investigated for the first time. Measured results show that a fixed phase shift of 90° can be achieved from 1.5 GHz to 1.85 GHz continuously by applying external DC current from 0 to 200 mA and external DC voltage from 0 to 15 Volts, respectively.« less

Radio frequency telemetry system for sensors and actuators

NASA Technical Reports Server (NTRS)

Simons, Rainee N. (Inventor); Miranda, Felix A. (Inventor)

2003-01-01

The present invention discloses and teaches apparatus for combining Radio Frequency (RF) technology with novel micro-inductor antennas and signal processing circuits for RF telemetry of real time, measured data, from microelectromechanical system (MEMS) sensors, through electromagnetic coupling with a remote powering/receiving device. Such technology has many applications, but is especially useful in the biomedical area.

Radio Frequency Telemetry System for Sensors and Actuators

NASA Technical Reports Server (NTRS)

Simons, Rainee N. (Inventor); Miranda, Felix A. (Inventor)

2003-01-01

The present invention discloses and teaches apparatus for combining Radio Frequency (RF) technology with novel micro-inductor antennas and signal processing circuits for RF telemetry of real time, measured data, from microelectromechanical system (MEMS) sensors, through electromagnetic coupling with a remote poweringheceiving device. Such technology has many applications, but is especially useful in the biomedical area.

Superconductor Digital-RF Receiver Systems

NASA Astrophysics Data System (ADS)

Mukhanov, Oleg A.; Kirichenko, Dmitri; Vernik, Igor V.; Filippov, Timur V.; Kirichenko, Alexander; Webber, Robert; Dotsenko, Vladimir; Talalaevskii, Andrei; Tang, Jia Cao; Sahu, Anubhav; Shevchenko, Pavel; Miller, Robert; Kaplan, Steven B.; Sarwana, Saad; Gupta, Deepnarayan

Digital superconductor electronics has been experiencing rapid maturation with the emergence of smaller-scale, lower-cost communications applications which became the major technology drivers. These applications are primarily in the area of wireless communications, radar, and surveillance as well as in imaging and sensor systems. In these areas, the fundamental advantages of superconductivity translate into system benefits through novel Digital-RF architectures with direct digitization of wide band, high frequency radio frequency (RF) signals. At the same time the availability of relatively small 4K cryocoolers has lowered the foremost market barrier for cryogenically-cooled digital electronic systems. Recently, we have achieved a major breakthrough in the development, demonstration, and successful delivery of the cryocooled superconductor digital-RF receivers directly digitizing signals in a broad range from kilohertz to gigahertz. These essentially hybrid-technology systems combine a variety of superconductor and semiconductor technologies packaged with two-stage commercial cryocoolers: cryogenic Nb mixed-signal and digital circuits based on Rapid Single Flux Quantum (RSFQ) technology, room-temperature amplifiers, FPGA processing and control circuitry. The demonstrated cryocooled digital-RF systems are the world's first and fastest directly digitizing receivers operating with live satellite signals in X-band and performing signal acquisition in HF to L-band at ˜30GHz clock frequencies.

Requirements for Remote RF Laboratory Applications: An Educators' Perspective

ERIC Educational Resources Information Center

Cagiltay, N. E.; Aydin, E.; Oktem, R.; Kara, A.; Alexandru, M.; Reiner, B.

2009-01-01

This paper discusses the results of a study of the requirements for developing a remote RF laboratory. This study draws on the perspectives of educators in university electrical engineering departments and in technical colleges, on the teaching of the radio frequency (RF) domain. The study investigates how these educators would like the technical…

RF-DC converter for HF RFID sensing applications powered by a near-field loop antenna

NASA Astrophysics Data System (ADS)

Colella, R.; Pasca, M.; Catarinucci, L.; Tarricone, L.; D'Amico, S.

2016-07-01

In this paper, an RF-DC converter operating at 13.56 MHz (HF radio frequency identification (RFID) frequency band) is presented. Its architecture provides RF to load isolation, reducing the losses due to the reverse saturation current and improving the sensitivity. Fed by a loop antenna, the RF-DC converter is made by a Dickson's RF-DC rectifier and an additional Pelliconi's charge pump driven by a fully integrated 50 kHz ring oscillator realized using an application-specific integrated circuit (ASIC). The input RF signal from the reader is converted to DC supply voltage and stored on a 1 μF capacitor. Mathematical model of the converter is developed and verified through measurements. Silicon prototypes of the ASIC have been realized in 350 nm complementary metal-oxide semiconductor technology. Measurements have been done on 10 different samples showing an output voltage in the range of 0.5 V-3.11 V in correspondence of an RF input signal power in the range of -19 dBm-0 dBm. These output voltage levels are suitable to power HF RFID sensing platforms and sensor nodes of body sensor networks.

Frequency set on systems

NASA Astrophysics Data System (ADS)

Wilby, W. A.; Brett, A. R. H.

Frequency set on techniques used in ECM applications include repeater jammers, frequency memory loops (RF and optical), coherent digital RF memories, and closed loop VCO set on systems. Closed loop frequency set on systems using analog phase and frequency locking are considered to have a number of cost and performance advantages. Their performance is discussed in terms of frequency accuracy, bandwidth, locking time, stability, and simultaneous signals. Some experimental results are presented which show typical locking performance. Future ECM systems might require a response to very short pulses. Acoustooptic and fiber-optic pulse stretching techniques can be used to meet such requirements.

Active stabilization of ion trap radiofrequency potentials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, K. G.; Wong-Campos, J. D.; Restelli, A.

2016-05-15

We actively stabilize the harmonic oscillation frequency of a laser-cooled atomic ion confined in a radiofrequency (rf) Paul trap by sampling and rectifying the high voltage rf applied to the trap electrodes. We are able to stabilize the 1 MHz atomic oscillation frequency to be better than 10 Hz or 10 ppm. This represents a suppression of ambient noise on the rf circuit by 34 dB. This technique could impact the sensitivity of ion trap mass spectrometry and the fidelity of quantum operations in ion trap quantum information applications.

RF-MEMS tunable interdigitated capacitor and fixed spiral inductor for band pass filter applications

NASA Astrophysics Data System (ADS)

Bade, Ladon Ahmed; Dennis, John Ojur; Khir, M. Haris Md; Wen, Wong Peng

2016-11-01

This research presents the tunable Radio Frequency Micro Electromechanical Systems (RF-MEMS) coupled band-pass filter (BPF), which possess a wide tuning range and constructed by using the Chebyshev fourth degree equivalent circuit consisting of fixed inductors and interdigitated tunable capacitors. The suggested method was authenticated by designing a new tunable BPF with a 100% tuning range from 3.1 GHz to 4.9 GHz. The Metal Multi-User MEMS Process (Metal MUMPs) was involved in the process of design of this band-pass filter. It aimed to achieve the reconfiguration of frequencies and show high efficiency of RF in the applications that using Ultra Wide Band (UWB) such as wireless sensor networks. The RF performance of this filter was found to be very satisfactory due to its simple fabrication. Moreover, it showed less insertion loss of around 4 dB and high return loss of around 20 dB.

rf breakdown tests of mm-wave metallic accelerating structures

DOE PAGES

Dal Forno, Massimo; Dolgashev, Valery; Bowden, Gordon; ...

2016-01-06

In this study, we explore the physics and frequency-scaling of vacuum rf breakdowns at sub-THz frequencies. We present the experimental results of rf tests performed in metallic mm-wave accelerating structures. These experiments were carried out at the facility for advanced accelerator experimental tests (FACET) at the SLAC National Accelerator Laboratory. The rf fields were excited by the FACET ultrarelativistic electron beam. We compared the performances of metal structures made with copper and stainless steel. The rf frequency of the fundamental accelerating mode, propagating in the structures at the speed of light, varies from 115 to 140 GHz. The traveling wavemore » structures are 0.1 m long and composed of 125 coupled cavities each. We determined the peak electric field and pulse length where the structures were not damaged by rf breakdowns. We calculated the electric and magnetic field correlated with the rf breakdowns using the FACET bunch parameters. The wakefields were calculated by a frequency domain method using periodic eigensolutions. Such a method takes into account wall losses and is applicable to a large variety of geometries. The maximum achieved accelerating gradient is 0.3 GV/m with a peak surface electric field of 1.5 GV/m and a pulse length of about 2.4 ns.« less

Radio frequency sheaths in an oblique magnetic field

DOE PAGES

Myra, James R.; D'Ippolito, Daniel A.

2015-06-01

The physics of radio-frequency (rf) sheaths near a conducting surface is studied for plasmas immersed in a magnetic field that makes an oblique angle θ with the surface. A set of one-dimensional equations is developed that describe the dynamics of the time-dependent magnetic presheath and non-neutral Debye sheath. The model employs Maxwell-Boltzmann electrons, and the magnetization and mobility of the ions is determined by the magnetic field strength, and wave frequency, respectively. The angle, θ assumed to be large enough to insure an electron-poor sheath, is otherwise arbitrary. Concentrating on the ion-cyclotron range of frequencies, the equations are solved numericallymore » to obtain the rectified (dc) voltage, the rf voltage across the sheath and the rf current flowing through the sheath. As an application of this model, the sheath voltage-current relation is used to obtain the rf sheath impedance, which in turn gives an rf sheath boundary condition for the electric field at the sheath-plasma interface that can be used in rf wave codes. In general the impedance has both resistive and capacitive contributions, and generalizes previous sheath boundary condition models. The resistive part contributes to parasitic power dissipation at the wall.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rowe, Nathan C; Younkin, James R; Pickett, Chris A

Radio-Frequency (RF) devices have revolutionized many aspects of modern industrial processes. RF technology can enable wireless communication for tag identification, sensor communication, and asset tracking. Radio-frequency identification (RFID) is a technology that utilizes wireless communication to interrogate and identify an electronic tag attached to an item in order to identify the item. The technology can come in many forms: passive or active tags, low to ultra-wideband frequencies, small paper-thin tags to brick-sized units, and simple tags or highly integrated sensor packages. RF technology, and specifically RFID, has been applied widely in commercial markets for inventory, supply chain management, and assetmore » tracking. Several recent studies have demonstrated the safeguards benefits of utilizing RFID versus conventional inventory tagging methods for tracking nuclear material. These studies have indicated that the RF requirements for safeguards functions are more stringent than the RF requirements for other inventory tracking and accounting applications. Additionally, other requirements must be addressed, including environmental and operating conditions, authentication, and tag location and attachment. Facility restrictions on radio spectrum, method of tag attachment, and sensitivity of the data collected impact the tag selection and system design. More important, the intended use of the system must be considered. The requirements for using RF to simply replace or supplement container identifiers such as bar codes that facilitate the inventory function will differ greatly from the requirements for deploying RF for unattended monitoring applications. Several studies have investigated these considerations to advance commercial RF devices for safeguards use, and a number of system concepts have been developed. This paper will provide an overview of past studies and current technologies, and will investigate the requirements, existing gaps, and several potential next steps for advancing RF techniques for safeguards use.« less

Radio frequency multicusp ion source development (invited)

NASA Astrophysics Data System (ADS)

Leung, K. N.

1996-03-01

The radio-frequency (rf) driven multicusp source was originally developed for use in the Superconducting Super Collider injector. It has been demonstrated that the source can meet the H- beam current and emittance requirements for this application. By employing a porcelain-coated antenna, a clean plasma discharge with very long-life operation can be achieved. Today, the rf source is used to generate both positive and negative hydrogen ion beams and has been tested in various particle accelerator laboratories throughout the world. Applications of this ion source have been extended to other fields such as ion beam lithography, oil-well logging, ion implantation, accelerator mass spectrometry and medical therapy machines. This paper summarizes the latest rf ion source technology and development at the Lawrence Berkeley National Laboratory.

Intelligent signal analysis and recognition

NASA Technical Reports Server (NTRS)

Levinson, Robert; Helman, Daniel; Oswalt, Edward

1987-01-01

Progress in the research and development of self-organizing database system that can support the identification and characterization of signals in an RF environment is described. As the radio frequency spectrum becomes more crowded, there are a number of situations that require a characterization of the RF environment. This database system is designed to be practical in applications where communications and other instruments encounter a time varying and complex RF environment. The primary application of this system is the guidance and control of NASA's SETI Microwave Observing Project. Other possible applications include selection of telemety bands for communication with spacecraft, and the scheduling of antenna for radio astronomy are two examples where characterization of the RF environment is required. In these applications, the RF environment is constantly changing, and even experienced operators cannot quickly identify the multitude of signals that can be encountered. Some of these signals are repetitive, others appear to occur sporadically.

Validation of Radio Frequency Telemetry Concept in the Presence of Biological Tissue-Like Stratified Media

NASA Technical Reports Server (NTRS)

Miranda, Felix A.; Simons, Rainee N.; Haal, David G.

2004-01-01

In this paper we discuss a novel radio frequency (RF) telemetry concept for biomedical applications. The concept consists of a miniaturized spiral inductor/antenna for bio-MEMS sensors and an external pick-up antenna integrated into a handheld device. The measured relative signal strength in the presence of biological phantoms ranged from 5.9 to 7.5 dB for antenna separations of 5 and 10 cm. These relative signal strengths are easily measurable, therefore validating the RF telemetry concept for biomedical applications.

Radio Relays Improve Wireless Products

NASA Technical Reports Server (NTRS)

2009-01-01

Signal Hill, California-based XCOM Wireless Inc. developed radio frequency micromachine (RF MEMS) relays with a Phase II Small Business Innovation Research (SBIR) contract through NASA?s Jet Propulsion Laboratory. In order to improve satellite communication systems, XCOM produced wireless RF MEMS relays and tunable capacitors that use metal-to-metal contact and have the potential to outperform most semiconductor technologies while using less power. These relays are used in high-frequency test equipment and instrumentation, where increased speed can mean significant cost savings. Applications now also include mainstream wireless applications and greatly improved tactical radios.

Design study of an S-band RF cavity of a dual-energy electron LINAC for the CIS

NASA Astrophysics Data System (ADS)

Lee, Byeong-No; Park, Hyungdal; Song, Ki-baek; Li, Yonggui; Lee, Byung Cheol; Cha, Sung-su; Lee, Jong-Chul; Shin, Seung-Wook; Chai, Jong-seo

2014-01-01

The design of a resonance frequency (RF) cavity for the dual-energy S-band electron linear accelerator (LINAC) has been carried out for the cargo inspection system (CIS). This Standing-wave-type RF cavity is operated at a frequency under the 2856-MHz resonance frequency and generates electron beams of 9 MeV (high mode) and 6 MeV (low mode). The electrons are accelerated from the initial energy of the electron gun to the target energy (9 or 6 MeV) inside the RF cavity by using the RF power transmitted from a 5.5-MW-class klystron. Then, electron beams with a 1-kW average power (both high mode and low mode) bombard an X-ray target a 2-mm spot size. The proposed accelerating gradient was 13 MV/m, and the designed Q value was about 7100. On going research on 15-MeV non-destructive inspections for military or other applications is presented.

Programmable optical processor chips: toward photonic RF filters with DSP-level flexibility and MHz-band selectivity

NASA Astrophysics Data System (ADS)

Xie, Yiwei; Geng, Zihan; Zhuang, Leimeng; Burla, Maurizio; Taddei, Caterina; Hoekman, Marcel; Leinse, Arne; Roeloffzen, Chris G. H.; Boller, Klaus-J.; Lowery, Arthur J.

2017-12-01

Integrated optical signal processors have been identified as a powerful engine for optical processing of microwave signals. They enable wideband and stable signal processing operations on miniaturized chips with ultimate control precision. As a promising application, such processors enables photonic implementations of reconfigurable radio frequency (RF) filters with wide design flexibility, large bandwidth, and high-frequency selectivity. This is a key technology for photonic-assisted RF front ends that opens a path to overcoming the bandwidth limitation of current digital electronics. Here, the recent progress of integrated optical signal processors for implementing such RF filters is reviewed. We highlight the use of a low-loss, high-index-contrast stoichiometric silicon nitride waveguide which promises to serve as a practical material platform for realizing high-performance optical signal processors and points toward photonic RF filters with digital signal processing (DSP)-level flexibility, hundreds-GHz bandwidth, MHz-band frequency selectivity, and full system integration on a chip scale.

Stable optical frequency comb generation and applications in arbitrary waveform generation, signal processing and optical data mining

NASA Astrophysics Data System (ADS)

Ozharar, Sarper

This thesis focuses on the generation and applications of stable optical frequency combs. Optical frequency combs are defined as equally spaced optical frequencies with a fixed phase relation among themselves. The conventional source of optical frequency combs is the optical spectrum of the modelocked lasers. In this work, we investigated alternative methods for optical comb generation, such as dual sine wave phase modulation, which is more practical and cost effective compared to modelocked lasers stabilized to a reference. Incorporating these comblines, we have generated tunable RF tones using the serrodyne technique. The tuning range was +/-1 MHz, limited by the electronic waveform generator, and the RF carrier frequency is limited by the bandwidth of the photodetector. Similarly, using parabolic phase modulation together with time division multiplexing, RF chirp extension has been realized. Another application of the optical frequency combs studied in this thesis is real time data mining in a bit stream. A novel optoelectronic logic gate has been developed for this application and used to detect an 8 bit long target pattern. Also another approach based on orthogonal Hadamard codes have been proposed and explained in detail. Also novel intracavity modulation schemes have been investigated and applied for various applications such as (a) improving rational harmonic modelocking for repetition rate multiplication and pulse to pulse amplitude equalization, (b) frequency skewed pulse generation for ranging and (c) intracavity active phase modulation in amplitude modulated modelocked lasers for supermode noise spur suppression and integrated jitter reduction. The thesis concludes with comments on the future work and next steps to improve some of the results presented in this work.

RF power harvesting: a review on designing methodologies and applications

NASA Astrophysics Data System (ADS)

Tran, Le-Giang; Cha, Hyouk-Kyu; Park, Woo-Tae

2017-12-01

Wireless power transmission was conceptualized nearly a century ago. Certain achievements made to date have made power harvesting a reality, capable of providing alternative sources of energy. This review provides a summ ary of radio frequency (RF) power harvesting technologies in order to serve as a guide for the design of RF energy harvesting units. Since energy harvesting circuits are designed to operate with relatively small voltages and currents, they rely on state-of-the-art electrical technology for obtaining high efficiency. Thus, comprehensive analysis and discussions of various designs and their tradeoffs are included. Finally, recent applications of RF power harvesting are outlined.

Coupled oscillations of vortex cores confined in a ferromagnetic elliptical disk

NASA Astrophysics Data System (ADS)

Hata, Hiroshi; Goto, Minori; Yamaguchi, Akinobu; Sato, Tomonori; Nakatani, Yoshinobu; Nozaki, Yukio

2014-09-01

By solving the Thiele equation with simultaneous application of a radio-frequency (rf) magnetic field (hrf) and an rf spin current (jsp), the dynamic susceptibility of exchange-coupled vortices in response to hrf and jsp was obtained. It was found that the four eigenmodes expected for two vortices trapped in a magnetic elliptical disk were coupled to different components of hrf and jsp. As a consequence, orthogonal hrf and jsp (which are simultaneously generated by the application of an rf current to an elliptical disk) can excite two modes with different eigenfrequencies. This result suggests that a fieldlike nonadiabatic torque caused by an rf spin current can be spectroscopically distinguished from the one caused by the rf magnetic field.

Modeling of an 8-12 GHz receiver front-end based on an in-line MEMS frequency discriminator

NASA Astrophysics Data System (ADS)

Chu, Chenlei; Liao, Xiaoping

2018-06-01

This paper focuses on the modeling of an 8-12 GHz RF (radio frequency) receiver front-end based on an in-line MEMS (microelectromechanical systems) frequency discriminator. Actually, the frequency detection is realized by measuring the output dc thermal voltage generated by the MEMS thermoelectric power sensor. Based on this thermal voltage, it has a great potential to tune the resonant frequency of the VCO (voltage controlled oscillator) in the RF receiver front-end application. The equivalent circuit model of the in-line frequency discriminator is established and the measurement verification is also implemented. Measurement and simulation results show that the output dc thermal voltage has a nearly linear relation with frequency. A new construction of RF receiver front-end is then obtained by connecting the in-line frequency discriminator with the voltage controlling port of VCO. Lastly, a systemic simulation is processed by computer-aided software and the real-time simulation waveform at each key point is observed clearly.

Non-Destructive Testing with Atmospheric Pressure Radio-Frequency Plasma

NASA Astrophysics Data System (ADS)

May, A.; Andarawis, E.

2007-03-01

We summarize our recent work using radio-frequency (RF) atmospheric pressure plasma (APP) for non-destructive evaluation (NDE), specifically for: (1) Clearance sensing (0-5mm) on rotating components, and (2) Generation of broadband ultrasound in air at 900kHz. RF-APP showed potential in both of these common NDE requirements, but further work is required to better characterize and optimize the performance of the new techniques. Application of RF-APP to other NDE disciplines, such as plasma spectroscopy and gas flow measurement, is also likely to be advantageous, especially in harsh environments where existing approaches are prohibitively expensive or complex.

A novel photonic oscillator

NASA Technical Reports Server (NTRS)

Yao, X. S.; Maleki, L.

1995-01-01

We report a novel oscillator for photonic RF systems. This oscillator is capable of generating high-frequency signals up to 70 GHz in both electrical and optical domains and is a special voltage-controlled oscillator with an optical output port. It can be used to make a phase-locked loop (PLL) and perform all functions that a PLL is capable of for photonic systems. It can be synchronized to a reference source by means of optical injection locking, electrical injection locking, and PLL. It can also be self-phase locked and self-injection locked to generate a high-stability photonic RF reference. Its applications include high-frequency reference regeneration and distribution, high-gain frequency multiplication, comb-frequecy and square-wave generation, carrier recovery, and clock recovery. We anticipate that such photonic voltage-controlled oscillators (VCOs) will be as important to photonic RF systems as electrical VCOs are to electrical RF systems.

Arrays of Carbon Nanotubes as RF Filters in Waveguides

NASA Technical Reports Server (NTRS)

Hoppe, Daniel; Hunt, Brian; Hoenk, Michael; Noca, Flavio; Xu, Jimmy

2003-01-01

Brushlike arrays of carbon nanotubes embedded in microstrip waveguides provide highly efficient (high-Q) mechanical resonators that will enable ultraminiature radio-frequency (RF) integrated circuits. In its basic form, this invention is an RF filter based on a carbon nanotube array embedded in a microstrip (or coplanar) waveguide, as shown in Figure 1. In addition, arrays of these nanotube-based RF filters can be used as an RF filter bank. Applications of this new nanotube array device include a variety of communications and signal-processing technologies. High-Q resonators are essential for stable, low-noise communications, and radar applications. Mechanical oscillators can exhibit orders of magnitude higher Qs than electronic resonant circuits, which are limited by resistive losses. This has motivated the development of a variety of mechanical resonators, including bulk acoustic wave (BAW) resonators, surface acoustic wave (SAW) resonators, and Si and SiC micromachined resonators (known as microelectromechanical systems or MEMS). There is also a strong push to extend the resonant frequencies of these oscillators into the GHz regime of state-of-the-art electronics. Unfortunately, the BAW and SAW devices tend to be large and are not easily integrated into electronic circuits. MEMS structures have been integrated into circuits, but efforts to extend MEMS resonant frequencies into the GHz regime have been difficult because of scaling problems with the capacitively-coupled drive and readout. In contrast, the proposed devices would be much smaller and hence could be more readily incorporated into advanced RF (more specifically, microwave) integrated circuits.

Micro-miniature radio frequency transmitter for communication and tracking applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crutcher, R.I.; Emery, M.S.; Falter, K.G.

1996-12-31

A micro-miniature radio frequency (rf) transmitter has been developed and demonstrated by the Oak Ridge National Laboratory. The objective of the rf transmitter development was to maximize the transmission distance while drastically shrinking the overall transmitter size, including antenna. Based on analysis and testing, an application-specific integrated circuit (ASIC) with a 16-GHz gallium arsenide (GaAs) oscillator and integrated on-chip antenna was designed and fabricated using microwave monolithic integrated circuit (MMIC) technology. Details of the development and the results of various field tests will be discussed. The rf transmitter is applicable to covert surveillance and tracking scenarios due to its smallmore » size of 2.2 x 2.2 mm, including the antenna. Additionally, the 16-GHz frequency is well above the operational range of consumer-grade radio scanners, providing a degree of protection from unauthorized interception. Variations of the transmitter design have been demonstrated for tracking and tagging beacons, transmission of digital data, and transmission of real-time analog video from a surveillance camera. Preliminary laboratory measurements indicate adaptability to direct-sequence spread-spectrum transmission, providing a low probability of intercept and/or detection. Concepts related to law enforcement applications will be presented.« less

REGENERATION/REACTIVATION OF CARBON ADSORBENTS BY RADIO FREQUENCY (RF) INDUCTION HEATING

EPA Science Inventory

We will use the experimental results to verify the numerical models and then use the models in parametric studies to determine the relative importance of each of the governing phenomena: electrical properties, heat transfer, RF applicator and adsorbent bed geometry...

Wireless RF communication in biomedical applications

NASA Astrophysics Data System (ADS)

Jones, Inke; Ricciardi, Lucas; Hall, Leonard; Hansen, Hedley; Varadan, Vijay; Bertram, Chris; Maddocks, Simon; Enderling, Stefan; Saint, David; Al-Sarawi, Said; Abbott, Derek

2008-02-01

This paper focuses on wireless transcutaneous RF communication in biomedical applications. It discusses current technology, restrictions and applications and also illustrates possible future developments. It focuses on the application in biotelemetry where the system consists of a transmitter and a receiver with a transmission link in between. The transmitted information can either be a biopotential or a nonelectric value like arterial pressure, respiration, body temperature or pH value. In this paper the use of radio-frequency (RF) communication and identification for those applications is described. Basically, radio-frequency identification or RFID is a technology that is analogous to the working principle of magnetic barcode systems. Unlike magnetic barcodes, passive RFID can be used in extreme climatic conditions—also the tags do not need to be within close proximity of the reader. Our proposed solution is to exploit an exciting new development in making circuits on polymers without the need for battery power. This solution exploits the principle of a surface acoustic wave (SAW) device on a polymer substrate. The SAW device is a set of interdigitated conducting fingers on the polymer substrate. If an appropriate RF signal is sent to the device, the fingers act as microantennas that pick up the signal, and this energy is then converted into acoustic waves that travel across the surface of the polymer substrate. Being a flexible polymer, the acoustic waves cause stresses that can either contract or stretch the material. In our case we mainly focus on an RF controllable microvalve that could ultimately be used for fertility control.

Analysis of RF emissions from laser induced breakdown of atmospheric air and metals

NASA Astrophysics Data System (ADS)

Paturi, Prem Kiran; Lakshmi, Vinoth Kumar; Elle, Manikanta; Chelikani, Leela

2013-10-01

The low frequency (RF, microwave) emissions from laser produced plasma (LPP) are of great interest because of their variety of applications. The RF waves emitted by the nanosecond LPP of atmospheric air and metal (Al, Cu) targets were detected using antennas over frequency ranges (30 MHz-18 GHz) and were monitored using a spectrum analyzer (3 Hz-50 GHz). With different target materials, the dominant emission lines were observed to fall in different specific frequency ranges within the detection limit. The emissions from Cu were in the higher frequency range (100-200 MHz) than that of Al (30-100 MHz) may be due to the higher electron density of Cu, which contributes to the LPP conductivity. From the LPP of atmospheric air, the RF output was found to be increasing with the input laser energy up to certain value, beyond which almost no emission was observed. This effect is attributed to the modification in the net induced dipole moment due to the multiple plasma sources in the LPP at higher input laser energies. The detected radiation was observed to be dependent on laser and antenna polarization. Further studies may lead to an efficient technique for material identification from the RF characteristic peaks.

Dynamic Data Driven Applications Systems (DDDAS)

DTIC Science & Technology

2013-03-06

INS •  Chip-scale atomic clocks •  Ad hoc networks •  Polymorphic networks •  Agile networks •  Laser communications •  Frequency-agile RF...atomi clocks •  Ad hoc networks •  Polymorphic networks •  Agile networks •  Laser co munications •  Frequency-agile RF systems...Real-Time Doppler Wind Wind field Sensor observations Energy Estimation Atmospheric Models for On-line Planning Planning and Control

KAHVE Laboratory RF circulator and transmission line project

NASA Astrophysics Data System (ADS)

Cetinkaya, Hakan; ćaǧlar, Aslıhan; ćiçek, Cihan; Özbey, Aydın; Sunar, Ezgi; Türemen, Görkem; Yıldız, Hüseyin; Yüncü, Alperen; Özcan, Erkcan; Ünel, Gökhan; Yaman, Fatih

2018-02-01

An 800 MHz RF circulator and transmission line project has recently started at the newly commissioned Kandilli Detector, Accelerator and Instrumentation (KAHVE) Laboratory at the Boğaziçi University. The aims are to design, build and construct an RF circulator and transmission line in Turkey for high power and high frequency applications. The project consists of 8 transmission line elements: 800 MHz RF generator with 60 kW power (klystron), klystron to waveguide converter, waveguides, E and H bends, 3-port circulator and waveguide to coaxial converter to transmit RF power to a pillbox RF cavity. Design studies and details of the ongoing project will be presented.

NASA Standard Initiator Susceptibility to UHF and S-Band Radio Frequency Power and Lightning Strikes

NASA Technical Reports Server (NTRS)

Burnham, Karen; Scully, Robert; Norgard, John

2013-01-01

The NASA Standard Initiator (NSI) is an important piece of pyrotechnic equipment used in many space applications. This presentation will outline the results of a series of tests done at UHF and S-Band frequencies to determine NSI susceptibility to Radio Frequency (RF) power. The results show significant susceptibility to pulsed RF power in the S-Band region. Additional testing with lightning pulses injected into the firing line harness, modelling the indirect effects of a lightning strike to a spacecraft, showed no vulnerability

NASA Standard Initiator Susceptibility to UHF and S-Band Radio Frequency Power and Lightning Strikes

NASA Technical Reports Server (NTRS)

Burnham, Karen; Scully, Robert C.; Norgard, John D.

2013-01-01

The NASA Standard Initiator (NSI) is an important piece of pyrotechnic equipment used in many space applications. This paper outlines the results of a series of tests done at UHF and S-Band frequencies to determine NSI susceptibility to Radio Frequency (RF) power. The results show significant susceptibility to pulsed RF power in the S-Band region. Additional testing with lightning pulses injected into the firing line harness, modelling the indirect effects of a lightning strike to a spacecraft, showed no vulnerability.

Advanced RF and microwave functions based on an integrated optical frequency comb source.

PubMed

Xu, Xingyuan; Wu, Jiayang; Nguyen, Thach G; Shoeiby, Mehrdad; Chu, Sai T; Little, Brent E; Morandotti, Roberto; Mitchell, Arnan; Moss, David J

2018-02-05

We demonstrate advanced transversal radio frequency (RF) and microwave functions based on a Kerr optical comb source generated by an integrated micro-ring resonator. We achieve extremely high performance for an optical true time delay aimed at tunable phased array antenna applications, as well as reconfigurable microwave photonic filters. Our results agree well with theory. We show that our true time delay would yield a phased array antenna with features that include high angular resolution and a wide range of beam steering angles, while the microwave photonic filters feature high Q factors, wideband tunability, and highly reconfigurable filtering shapes. These results show that our approach is a competitive solution to implementing reconfigurable, high performance and potentially low cost RF and microwave signal processing functions for applications including radar and communication systems.

Effects of radio frequency and high pressure steam sterilisation on the colour and flavour of prepared Nostoc sphaeroides.

PubMed

Xu, Jicheng; Zhang, Min; An, Yanjun; Roknul, Azam Sm; Adhikari, Benu

2018-03-01

Nostoc sphaeroides has been used as a highly effective herbal medicine and dietary supplement for thousands of years. The desired dark green colour of fresh N. sphaeroides is converted into an undesirable dark brown during conventional high pressure (HP) steam sterilisation. Radio frequency (RF) sterilisation technology was used in this study to determine its effectiveness in sterilising N. sphaeroides and to achieve better preservation of natural colour and desirable flavour. Sterilisation was carried out using a 6 kW, 27 MHz RF instrument for 10, 20 and 30 min. The degree of microbial kill and the effects of RF sterilisation on colour and flavour were determined and compared with those obtained from HP steam (121 °C, 30 min) sterilisation. The effects of RF sterilisation on colour and flavour (measured using electronic nose) parameters were significantly lower than that in HP steam sterilisation. The RF sterilisation carried out for 20 min achieved logarithmic reduction of bacterial population and met China's national standard while preserving the colour and flavour better. Results of the present study indicated that application of RF sterilisation would improve the quality of sterilised N. sphaeroides and broaden its application in the food and health food industries. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Computer simulation for improving radio frequency (RF) heating uniformity of food products: A review.

PubMed

Huang, Zhi; Marra, Francesco; Subbiah, Jeyamkondan; Wang, Shaojin

2018-04-13

Radio frequency (RF) heating has great potential for achieving rapid and volumetric heating in foods, providing safe and high-quality food products due to deep penetration depth, moisture self-balance effects, and leaving no chemical residues. However, the nonuniform heating problem (usually resulting in hot and cold spots in the heated product) needs to be resolved. The inhomogeneous temperature distribution not only affects the quality of the food but also raises the issue of food safety when the microorganisms or insects may not be controlled in the cold spots. The mathematical modeling for RF heating processes has been extensively studied in a wide variety of agricultural products recently. This paper presents a comprehensive review of recent progresses in computer simulation for RF heating uniformity improvement and the offered solutions to reduce the heating nonuniformity. It provides a brief introduction on the basic principle of RF heating technology, analyzes the applications of numerical simulation, and discusses the factors influencing the RF heating uniformity and the possible methods to improve heating uniformity. Mathematical modeling improves the understanding of RF heating of food and is essential to optimize the RF treatment protocol for pasteurization and disinfestation applications. Recommendations for future research have been proposed to further improve the accuracy of numerical models, by covering both heat and mass transfers in the model, validating these models with sample movement and mixing, and identifying the important model parameters by sensitivity analysis.

Feasibility of frequency-modulated wireless transmission for a multi-purpose MEMS-based accelerometer.

PubMed

Sabato, Alessandro; Feng, Maria Q

2014-09-05

Recent advances in the Micro Electro-Mechanical System (MEMS) technology have made wireless MEMS accelerometers an attractive tool for Structural Health Monitoring (SHM) of civil engineering structures. To date, sensors' low sensitivity and accuracy--especially at very low frequencies--have imposed serious limitations for their application in monitoring large-sized structures. Conventionally, the MEMS sensor's analog signals are converted to digital signals before radio-frequency (RF) wireless transmission. The conversion can cause a low sensitivity to the important low-frequency and low-amplitude signals. To overcome this difficulty, the authors have developed a MEMS accelerometer system, which converts the sensor output voltage to a frequency-modulated signal before RF transmission. This is achieved by using a Voltage to Frequency Conversion (V/F) instead of the conventional Analog to Digital Conversion (ADC). In this paper, a prototype MEMS accelerometer system is presented, which consists of a transmitter and receiver circuit boards. The former is equipped with a MEMS accelerometer, a V/F converter and a wireless RF transmitter, while the latter contains an RF receiver and a F/V converter for demodulating the signal. The efficacy of the MEMS accelerometer system in measuring low-frequency and low-amplitude dynamic responses is demonstrated through extensive laboratory tests and experiments on a flow-loop pipeline.

Characteristics of Radio-Frequency Circuits Utilizing Ferroelectric Capacitors

NASA Technical Reports Server (NTRS)

Eskridge, Michael; Gui, Xiao; MacLeod, Todd; Ho, Fat D.

2011-01-01

Ferroelectric capacitors, most commonly used in memory circuits and variable components, were studied in simple analog radio-frequency circuits such as the RLC resonator and Colpitts oscillator. The goal was to characterize the RF circuits in terms of frequency of oscillation, gain, etc, using ferroelectric capacitors. Frequencies of oscillation of both circuits were measured and studied a more accurate resonant frequency can be obtained using the ferroelectric capacitors. Many experiments were conducted and data collected. A model to simulate the experimental results will be developed. Discrepancies in gain and frequency in these RF circuits when conventional capacitors are replaced with ferroelectric ones were studied. These results will enable circuit designers to anticipate the effects of using ferroelectric components in their radio- frequency applications.

Direct digital RF synthesis and modulation for MSAT mobile applications

NASA Technical Reports Server (NTRS)

Crozier, Stewart; Datta, Ravi; Sydor, John

1993-01-01

A practical method of performing direct digital RF synthesis using the Hilbert transform single sideband (SSB) technique is described. It is also shown that amplitude and phase modulation can be achieved directly at L-band with frequency stability and spurii performance exceeding stringent MSAT system requirements.

A two-dimensional (2D) analytical subthreshold swing and transconductance model of underlap dual-material double-gate (DMDG) MOSFET for analog/RF applications

NASA Astrophysics Data System (ADS)

Narendar, Vadthiya; Rai, Saurabh; Tiwari, Siddharth; Mishra, R. A.

2016-12-01

The double-gate (DG) metal-oxide-semiconductor field effect transistors (MOSFETs) are the choice of technology in sub -100 nm regime of leading microelectronics industry. To enhance the analog and RF performance of DG MOSFET, an underlap dual-material (DM) DG MOSFET device structure has been considered because, it has the advantages of both underlap as well as that of dual-material gate (DMG). A 2D analytical surface potential, subthreshold current, subthreshold swing as well as transconductance modelling of underlap DMDG MOSFET has been done by solving the Poisson's equation. It has also been found that, numerically simulated data approves the analytically modelled data with commendable accuracy. As underlap length (Lun) increases, a substantial reduction of subthreshold current due to enhanced gate control over channel regime is observed. DMG structure facilitates to improve the average velocity of carriers which leads to superior drive current of the device. The underlap DMDG MOSFET device structure demonstrates an ameliorated subthreshold characteristic. The analog figure of merits (FOMs) such as transconductance (gm), transconductance generation factor (TGF), output conductance (gd), early voltage (VEA), intrinsic gain (AV) and RF FOMs namely cut-off frequency (fT), gain frequency product (GFP), transconductance frequency product (TFP) and gain transconductance frequency product (GTFP) have been evaluated. The aforesaid analysis revels that, the device is best suited for communication related Analog/RF applications.

Advances in radio frequency tumor ablation therapy: technical considerations, strategies for increasing coagulation necrosis volume, and preliminary clinical results

NASA Astrophysics Data System (ADS)

Goldberg, S. Nahum; Gazelle, G. Scott

1998-04-01

Radiofrequency (RF) tumor ablation has been demonstrated as a reliable method for creating thermally induced coagulation necrosis using either a percutaneous approach with image- guidance or direct surgical application of thin electrodes into treated tissues. Early clinical trials with this technology have studied the treatment of hepatic, cerebral, and bony malignancies. The extent of coagulation necrosis induced with conventional monopolar radiofrequency electrodes is dependent on overall energy deposition, the duration of RF application, and RF electrode tip length and gauge. This article will discuss these technical considerations with the goal of defining optimal parameters for RF ablation. Strategies to further increase induced coagulation necrosis including: multiprobe and bipolar arrays, and internally-cooled RF electrodes, with or without pulsed-RF or cluster technique will be presented. The development and laboratory results for many of these radiofrequency techniques, initial clinical results, and potential biophysical limitations to RF induced coagulation, such as perfusion mediated tissue cooling (vascular flow) will likewise be discussed.

Application of extremum seeking for time-varying systems to resonance control of RF cavities

DOE PAGES

Scheinker, Alexander

2016-09-13

A recently developed form of extremum seeking for time-varying systems is implemented in hardware for the resonance control of radio-frequency cavities without phase measurements. Normal conducting RF cavity resonance control is performed via a slug tuner, while superconducting TESLA-type cavity resonance control is performed via piezo actuators. The controller maintains resonance by minimizing reflected power by utilizing model-independent adaptive feedback. Unlike standard phase-measurement-based resonance control, the presented approach is not sensitive to arbitrary phase shifts of the RF signals due to temperature-dependent cable length or phasemeasurement hardware changes. The phase independence of this method removes common slowly varying drifts andmore » required periodic recalibration of phase-based methods. A general overview of the adaptive controller is presented along with the proof of principle experimental results at room temperature. Lastly, this method allows us to both maintain a cavity at a desired resonance frequency and also to dynamically modify its resonance frequency to track the unknown time-varying frequency of an RF source, thereby maintaining maximal cavity field strength, based only on power-level measurements.« less

Comparative study of laminar and turbulent flow model with different operating parameters for radio frequency-inductively coupled plasma torch working at 3  MHz frequency at atmospheric pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Punjabi, Sangeeta B., E-mail: p.sangeeta@gmail.com; Department of Physics, University of Mumbai, Kalina, Santacruz; Sahasrabudhe, S. N.

2014-01-15

This paper provides 2D comparative study of results obtained using laminar and turbulent flow model for RF (radio frequency) Inductively Coupled Plasma (ICP) torch. The study was done for the RF-ICP torch operating at 50 kW DC power and 3 MHz frequency located at BARC. The numerical modeling for this RF-ICP torch is done using ANSYS software with the developed User Defined Function. A comparative study is done between laminar and turbulent flow model to investigate how temperature and flow fields change when using different operating conditions such as (a) swirl and no swirl velocity for sheath gas flow rate, (b) variationmore » in sheath gas flow rate, and (c) variation in plasma gas flow rate. These studies will be useful for different material processing applications.« less

Simple coil-powering techniques for generating 10KA/m alternating magnetic field at multiple frequencies using 0.5KW RF power for magnetic nanoparticle hyperthermia

NASA Astrophysics Data System (ADS)

Piao, Daqing; Sun, Tengfei; Ranjan, Ashish

2017-02-01

Alternating magnetic field (AMF) configurable at a range of frequencies is a critical need for optimization of magnetic nanoparticle based hyperthermia, and for their application in targeted drug delivery. Currently, most commercial AMF devices including induction heaters operate at one factory-fixed frequency, thereby limiting customized frequency configuration required for triggered drug release at mild hyperthermia (40-42°C) and ablations (>55°C). Most AMF devices run as an inductor-capacitor resonance network that could allow AMF frequencies to be changed by changing the capacitor bank or the coil looped with it. When developing AMF inhouse, the most expensive component is usually the RF power amplifier, and arguably the most critical step of building a strong AMF field is impedance-matched coupling of RF power to the coolant-cooled AMF coil. AMF devices running at 10KA/m strength are quite common, but generating AMF at that level of field strength using RF power less than 1KW has remained challenging. We practiced a few techniques for building 10KA/m AMFs at different frequencies, by utilizing a 0.5KW 80-800KHz RF power amplifier. Among the techniques indispensable to the functioning of these AMFs, a simple cost-effective technique was the tapping methods for discretely or continuously adjusting the position of an RF-input-tap on a single-layer or the outer-layer of a multi-layer AMF coil for maximum power coupling into the AMF coil. These in-house techniques when combined facilitated 10KA/m AMF at frequencies of 88.8 KHz and higher as allowed by the inventory of capacitors using 0.5KW RF power, for testing heating of 10-15nm size magnetic particles and on-going evaluation of drug-release by low-level temperature-sensitive liposomes loaded with 15nm magnetic nanoparticles.

Structural health monitoring and remote sensing of transportation infrastructure using embedded frequency selective surfaces.

DOT National Transportation Integrated Search

2014-07-01

The objective of this project was to investigate the use of Frequency Selective Surfaces (FSS) for structural health monitoring applications. Frequency Selective Surfaces (FSS) have long been used in the RF/microwave community to control scattering f...

Design and simulation of RF MEMS SPST shunt and SPDT shunt-shunt switches for X-band and Ku-band applications

NASA Astrophysics Data System (ADS)

Lenka, Manas K.; Sharma, Amit; Sharma, Jaibir; DasGupta, Amitava

2012-10-01

This paper describes the design and simulation of RF MEMS SPST shunt and SPDT shunt-shunt switches with modified coplanar waveguide (CPW) configuration for X-band and Ku-band applications exhibiting high isolation and low insertion loss. By modifying the basic CPW structure for a six-strip membrane having length 720 μm, the resonant frequency can be reduced from 33.5 GHz to 13.5 GHz with isolation as high as -30 dB(-63 dB at resonant frequency) in Ku-band. Similar results are also found in case SPST and SPDT switches with other membrane types.

Numerical design of RF ablation applicator for hepatic cancer treatment

NASA Astrophysics Data System (ADS)

Rakhmadi, Aditya; Basari

2017-02-01

Currently, cancer has become one of health problems that is difficult to be overcomed. This disease is not only difficult to be cured, but also to be detected and may cause death. For this reason, RF ablation treatment method is proposed to cure cancer. RF ablation therapy is a method in which an applicator is inserted into the body to kill cancer cells by heating the cells. The cancer cells are exposed to the temperature more than 60°C in short duration (few second to few minutes) so thus cell destruction occurs locally. For the sake of the successful treatment, a minimally invasive method is selected in order for perfect local temperature distribution in cancer cells can be achieved. In this paper, a coax-fed dipole-type applicator with interstitial irradiation technique is proposed aimed at RF ablation into hepatic cells. Numerical simulation is performed to obtain a suitable geometric dimension at operating frequency around 2.45 GHz, in order to localize the ablation area. The proposed applicator is inserted into a simple phantom representing an adult human body model in which normal and cancerous liver cells. The simulated results show that the proposed applicator is able to operate at center frequency of 2.355 GHz with blood droplet-type ablation zone and the temperature around the cancer cell by 60°C can be achieved.

Space evaluation of optical modulators for microwave photonic on-board applications

NASA Astrophysics Data System (ADS)

Le Kernec, A.; Sotom, M.; Bénazet, B.; Barbero, J.; Peñate, L.; Maignan, M.; Esquivias, I.; Lopez, F.; Karafolas, N.

2017-11-01

Since several years, perspectives and assets offered by photonic technologies compared with their traditional RF counterparts (mass and volume reduction, transparency to RF frequency, RF isolation), make them particularly attractive for space applications [1] and, in particular, telecommunication satellites [2]. However, the development of photonic payload concepts have concurrently risen and made the problem of the ability of optoelectronic components to withstand space environment more and more pressing. Indeed, photonic components used in such photonic payloads architectures come from terrestrial networks applications in order to benefit from research and development in this field. This paper presents some results obtained in the frame of an ESA-funded project, carried out by Thales Alenia Space France, as prime contractor, and Alter Technology Group Spain (ATG) and Universidad Politecnica de Madrid (UPM), as subcontractors, one objective of which was to assess commercial high frequency optical intensity modulators for space use through a functional and environmental test campaign. Their potential applications in microwave photonic sub-systems of telecom satellite payloads are identified and related requirements are presented. Optical modulator technologies are reviewed and compared through, but not limited to, a specific figure of merit, taking into account two key features of these components : optical insertion loss and RF half-wave voltage. Some conclusions on these different technologies are given, on the basis of the test results, and their suitability for the targeted applications and environment is highlighted.

Feasibility of Frequency-Modulated Wireless Transmission for a Multi-Purpose MEMS-Based Accelerometer

PubMed Central

Sabato, Alessandro; Feng, Maria Q.

2014-01-01

Recent advances in the Micro Electro-Mechanical System (MEMS) technology have made wireless MEMS accelerometers an attractive tool for Structural Health Monitoring (SHM) of civil engineering structures. To date, sensors' low sensitivity and accuracy—especially at very low frequencies—have imposed serious limitations for their application in monitoring large-sized structures. Conventionally, the MEMS sensor's analog signals are converted to digital signals before radio-frequency (RF) wireless transmission. The conversion can cause a low sensitivity to the important low-frequency and low-amplitude signals. To overcome this difficulty, the authors have developed a MEMS accelerometer system, which converts the sensor output voltage to a frequency-modulated signal before RF transmission. This is achieved by using a Voltage to Frequency Conversion (V/F) instead of the conventional Analog to Digital Conversion (ADC). In this paper, a prototype MEMS accelerometer system is presented, which consists of a transmitter and receiver circuit boards. The former is equipped with a MEMS accelerometer, a V/F converter and a wireless RF transmitter, while the latter contains an RF receiver and a F/V converter for demodulating the signal. The efficacy of the MEMS accelerometer system in measuring low-frequency and low-amplitude dynamic responses is demonstrated through extensive laboratory tests and experiments on a flow-loop pipeline. PMID:25198003

Active shielding of cylindrical saddle-shaped coils: application to wire-wound RF coils for very low field NMR and MRI.

PubMed

Bidinosti, C P; Kravchuk, I S; Hayden, M E

2005-11-01

We provide an exact expression for the magnetic field produced by cylindrical saddle-shaped coils and their ideal shield currents in the low-frequency limit. The stream function associated with the shield surface current is also determined. The results of the analysis are useful for the design of actively shielded radio-frequency (RF) coils. Examples pertinent to very low field nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) are presented and discussed.

Dielectric Heaters for Testing Spacecraft Nuclear Reactors

NASA Technical Reports Server (NTRS)

Sims, William Herbert; Bitteker, Leo; Godfroy, Thomas

2006-01-01

A document proposes the development of radio-frequency-(RF)-driven dielectric heaters for non-nuclear thermal testing of the cores of nuclear-fission reactors for spacecraft. Like the electrical-resistance heaters used heretofore for such testing, the dielectric heaters would be inserted in the reactors in place of nuclear fuel rods. A typical heater according to the proposal would consist of a rod of lossy dielectric material sized and shaped like a fuel rod and containing an electrically conductive rod along its center line. Exploiting the dielectric loss mechanism that is usually considered a nuisance in other applications, an RF signal, typically at a frequency .50 MHz and an amplitude between 2 and 5 kV, would be applied to the central conductor to heat the dielectric material. The main advantage of the proposal is that the wiring needed for the RF dielectric heating would be simpler and easier to fabricate than is the wiring needed for resistance heating. In some applications, it might be possible to eliminate all heater wiring and, instead, beam the RF heating power into the dielectric rods from external antennas.

Dipolar DC Collisional Activation in a "Stretched" 3-D Ion Trap: The Effect of Higher Order Fields on rf-Heating

NASA Astrophysics Data System (ADS)

Prentice, Boone M.; McLuckey, Scott A.

2012-04-01

Applying dipolar DC (DDC) to the end-cap electrodes of a 3-D ion trap operated with a bath gas at roughly 1 mTorr gives rise to `rf-heating' and can result in collision-induced dissociation (CID). This approach to ion trap CID differs from the conventional single-frequency resonance excitation approach in that it does not rely on tuning a supplementary frequency to coincide with the fundamental secular frequeny of the precursor ion of interest. Simulations using the program ITSIM 5.0 indicate that application of DDC physically displaces ions solely in the axial (inter end-cap) dimension whereupon ion acceleration occurs via power absorption from the drive rf. Experimental data shows that the degree of rf-heating in a stretched 3-D ion trap is not dependent solely on the ratio of the dipolar DC voltage/radio frequency (rf) amplitude, as a model based on a pure quadrupole field suggests. Rather, ion temperatures are shown to increase as the absolute values of the dipolar DC and rf amplitude both decrease. Simulations indicate that the presence of higher order multi-pole fields underlies this unexpected behavior. These findings have important implications for the use of DDC as a broad-band activation approach in multi-pole traps.

Radio-frequency flexible and stretchable electronics: the need, challenges and opportunities

NASA Astrophysics Data System (ADS)

Jung, Yei Hwan; Seo, Jung-Hun; Zhang, Huilong; Lee, Juhwan; Cho, Sang June; Chang, Tzu-Hsuan; Ma, Zhenqiang

2017-05-01

Successful integration of ultrathin flexible or stretchable systems with new applications, such as medical devices and biodegradable electronics, have intrigued many researchers and industries around the globe to seek materials and processes to create high-performance, non-invasive and cost-effective electronics to match those of state-of-the-art devices. Nevertheless, the crucial concept of transmitting data or power wirelessly for such unconventional devices has been difficult to realize due to limitations of radio-frequency (RF) electronics in individual components that form a wireless circuitry, such as antenna, transmission line, active devices, passive devices etc. To overcome such challenges, these components must be developed in a step-by-step manner, as each component faces a number of different challenges in ultrathin formats. Here, we report on materials and design considerations for fabricating flexible and stretchable electronics systems that operate in the microwave level. High-speed flexible active devices, including cost effective Si-based strained MOSFETs, GaAs-based HBTs and GaN-based HEMTs, performing at multi-gigahertz frequencies are presented. Furthermore, flexible or stretchable passive devices, including capacitors, inductors and transmission lines that are vital parts of a microwave circuitry are also demonstrated. We also present unique applications using the presented flexible or stretchable RF components, including wearable RF electronics and biodegradable RF electronics, which were impossible to achieve using conventional rigid, wafer-based technology. Further opportunities like implantable systems exist utilizing such ultrathin RF components, which are discussed in this report as well.

Coherent detection of THz laser signals in optical fiber systems.

PubMed

Folland, Thomas G; Marshall, Owen P; Beere, Harvey E; Ritchie, David A; Chakraborty, Subhasish

2017-10-16

Terahertz (THz) coherent detectors are crucial for the stabilization and measurement of the properties of quantum cascade lasers (QCLs). This paper describes the exploitation of intra-cavity sum frequency generation to up-convert the emission of a THz QCL to the near infrared for detection with fiber optic coupled components alone. Specifically, a low cost infrared photodiode is used to detect a radio frequency (RF) signal with a signal-to-noise ratio of approximately 20dB, generated by beating the up-converted THz wave and a near infrared local oscillator. This RF beat note allows direct analysis of the THz QCL emission in time and frequency domains. The application of this technique for QCL characterization is demonstrated by analyzing the continuous tuning of the RF signal over 2 GHz, which arises from mode tuning across the QCL's operational current range.

Development of a multilayered polymeric DNA biosensor using radio frequency technology with gold and magnetic nanoparticles.

PubMed

Yang, Cheng-Hao; Kuo, Long-Sheng; Chen, Ping-Hei; Yang, Chii-Rong; Tsai, Zuo-Min

2012-01-15

This study utilized the radio frequency (RF) technology to develop a multilayered polymeric DNA sensor with the help of gold and magnetic nanoparticles. The flexible polymeric materials, poly (p-xylylene) (Parylene) and polyethylene naphtholate (PEN), were used as substrates to replace the conventional rigid substrates such as glass and silicon wafers. The multilayered polymeric RF biosensor, including the two polymer layers and two copper transmission structure layers, was developed to reduce the total sensor size and further enhance the sensitivity of the biochip in the RF DNA detection. Thioglycolic acid (TGA) was used on the surface of the proposed biochip to form a thiolate-modified sensing surface for DNA hybridization. Gold nanoparticles (AuNPs) and magnetic nanoparticles (MNPs) were used to immobilize on the surface of the biosensor to enhance overall detection sensitivity. In addition to gold nanoparticles, the magnetic nanoparticles has been demonstrated the applicability for RF DNA detection. The performance of the proposed biosensor was evaluated by the shift of the center frequency of the RF biosensor because the electromagnetic characteristic of the biosensors can be altered by the immobilized multilayer nanoparticles on the biosensor. The experimental results show that the detection limit of the DNA concentration can reach as low as 10 pM, and the largest shift of the center frequency with triple-layer AuNPs and MNPs can approach 0.9 and 0.7 GHz, respectively. Such the achievement implies that the developed biosensor can offer an alternative inexpensive, disposable, and highly sensitive option for application in biomedicine diagnostic systems because the price and size of each biochip can be effectively reduced by using fully polymeric materials and multilayer-detecting structures. Copyright © 2011 Elsevier B.V. All rights reserved.

RF Single Electron Transistor Readout Amplifiers for Superconducting Astronomical Detectors for X-Ray to Sub-mm Wavelengths

NASA Technical Reports Server (NTRS)

Stevenson, Thomas; Aassime, Abdelhanin; Delsing, Per; Frunzio, Luigi; Li, Li-Qun; Prober, Daniel; Schoelkopf, Robert; Segall, Ken; Wilson, Chris; Stahle, Carl

2000-01-01

We report progress on using a new type of amplifier, the Radio-Frequency Single-Electron Transistor (RF-SET), to develop multi-channel sensor readout systems for fast and sensitive readout of high impedance cryogenic photodetectors such as Superconducting Tunnel Junctions and Single Quasiparticle Photon Counters. Although cryogenic, these detectors are desirable because of capabilities not other-wise attainable. However, high impedances and low output levels make low-noise, high-speed readouts challenging, and large format arrays would be facilitated by compact, low-power, on-chip integrated amplifiers. Well-suited for this application are RF-SETs, very high performance electrometers which use an rf readout technique to provide 100 MHz bandwidth. Small size, low power, and cryogenic operation allow direct integration with detectors, and using multiple rf carrier frequencies permits simultaneous readout of 20-50 amplifiers with a common electrical connection. We describe both the first 2-channel demonstration of this wavelength division multiplexing technique for RF-SETs, and Charge-Locked-Loop operation with 100 kHz of closed-loop bandwidth.

Analytical & Experimental Study of Radio Frequency Cavity Beam Profile Monitor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balcazar, Mario D.; Yonehara, Katsuya

The purpose of this analytical and experimental study is multifold: 1) To explore a new, radiation-robust, hadron beam profile monitor for intense neutrino beam applications; 2) To test, demonstrate, and develop a novel gas-filled Radio-Frequency (RF) cavity to use in this monitoring system. Within this context, the first section of the study analyzes the beam distribution across the hadron monitor as well as the ion-production rate inside the RF cavity. Furthermore a more effecient pixel configuration across the hadron monitor is proposed to provide higher sensitivity to changes in beam displacement. Finally, the results of a benchtop test of themore » tunable quality factor RF cavity will be presented. The proposed hadron monitor configuration consists of a circular array of RF cavities located at a radial distance of 7cm { corresponding to the standard deviation of the beam due to scatering { and a gas-filled RF cavity with a quality factor in the range 400 - 800.« less

Low-voltage high-reliability MEMS switch for millimeter wave 5G applications

NASA Astrophysics Data System (ADS)

Shekhar, Sudhanshu; Vinoy, K. J.; Ananthasuresh, G. K.

2018-07-01

Lack of reliability of radio-frequency microelectromechanical systems (RF MEMS) switches has inhibited their commercial success. Dielectric stiction/breakdown and mechanical shock due to high actuation voltage are common impediments in capacitive MEMS switches. In this work, we report low-actuation voltage RF MEMS switch and its reliability test. Experimental characterization of fabricated devices demonstrate that proposed MEMS switch topology needs very low voltage (4.8 V) for actuation. The mechanical resonant frequency, f 0, quality factor, Q, and switching time are measured to be 8.35 kHz, 1.2, and 33 microsecond, respectively. These MEMS switches have high reliability in terms of switching cycles. Measurements are performed using pulse waveform of magnitude of 6 V under hot-switching condition. Temperature measurement results confirm that the reported switch topology has good thermal stability. The robustness in terms of the measured pull-in voltage shows a variation of 0.08 V °C‑1. Lifetime measurement results after 10 million switching cycles demonstrate insignificant change in the RF performance without any failure. Experimental results show that low voltage improves the lifetime. Low insertion loss (less than 0.6 dB) and improved isolation (above 40 dB) in the frequency range up to 60 GHz have been reported. Measured RF characteristics in the frequency range from 10 MHz to 60 GHz support that these MEMS switches are favorable choice for mm-wave 5G applications.

Directions for rf-controlled intelligent microvalve

NASA Astrophysics Data System (ADS)

Enderling, Stefan; Varadan, Vijay K.; Abbott, Derek

2001-03-01

In this paper, we consider the novel concept of a Radio Frequency (RF) controllable microvalve for different medical applications. Wireless communication via a Surface Acoustic Wave Identification-mark (SAW ID-tag) is used to control, drive and locate the microvalve inside the human body. The energy required for these functions is provided by RF pulses, which are transmitted to the valve and back by a reader/transmitter system outside of the body. These RF bursts are converted into Surface Acoustic Waves (SAWs), which propagate along the piezoelectric actuator material of the microvalve. These waves cause deflections, which are employed to open and close the microvalve. We identified five important areas of application of the microvalve in biomedicine: 1) fertility control; 2) artificial venous valves; 3) flow cytometry; 4) drug delivery and 5) DNA mapping.

New Methods of Low-Field Magnetic Resonance Imaging for Application to Traumatic Brain Injury

DTIC Science & Technology

2016-04-01

the need for high power radio - frequency (RF) to saturate the electron spins. Addition- ally, as EPR frequencies are two orders of magnitude higher...Crozier S. Electromechanical design and construction of a rotating radio - frequency coil system for applications in magnetic resonance. IEEE Trans Biomed...1 Award Number: W81XWH- 11 -2-0076 TITLE: New Methods of Low-Field Magnetic Resonance Imaging for Application to Traumatic Brain Injury PRINCIPAL

Atmospheric-pressure diffuse dielectric barrier discharges in Ar/O2 gas mixture using 200 kHz/13.56 MHz dual frequency excitation

NASA Astrophysics Data System (ADS)

Liu, Y.; Starostin, S. A.; Peeters, F. J. J.; van de Sanden, M. C. M.; de Vries, H. W.

2018-03-01

Atmospheric-pressure diffuse dielectric barrier discharges (DBDs) were obtained in Ar/O2 gas mixture using dual-frequency (DF) excitation at 200 kHz low frequency (LF) and 13.56 MHz radio frequency (RF). The excitation dynamics and the plasma generation mechanism were studied by means of electrical characterization and phase resolved optical emission spectroscopy (PROES). The DF excitation results in a time-varying electric field which is determined by the total LF and RF gas voltage and the spatial ion distribution which only responds to the LF component. By tuning the amplitude ratio of the superimposed LF and RF signals, the effect of each frequency component on the DF discharge mechanism was analysed. The LF excitation results in a transient plasma with the formation of an electrode sheath and therefore a pronounced excitation near the substrate. The RF oscillation allows the electron trapping in the gas gap and helps to improve the plasma uniformity by contributing to the pre-ionization and by controlling the discharge development. The possibility of temporally modifying the electric field and thus the plasma generation mechanism in the DF discharge exhibits potential applications in plasma-assisted surface processing and plasma-assisted gas phase chemical conversion.

Power supply and impedance matching to drive technological radio-frequency plasmas with customized voltage waveforms.

PubMed

Franek, James; Brandt, Steven; Berger, Birk; Liese, Martin; Barthel, Matthias; Schüngel, Edmund; Schulze, Julian

2015-05-01

We present a novel radio-frequency (RF) power supply and impedance matching to drive technological plasmas with customized voltage waveforms. It is based on a system of phase-locked RF generators that output single frequency voltage waveforms corresponding to multiple consecutive harmonics of a fundamental frequency. These signals are matched individually and combined to drive a RF plasma. Electrical filters are used to prevent parasitic interactions between the matching branches. By adjusting the harmonics' phases and voltage amplitudes individually, any voltage waveform can be approximated as a customized finite Fourier series. This RF supply system is easily adaptable to any technological plasma for industrial applications and allows the commercial utilization of process optimization based on voltage waveform tailoring for the first time. Here, this system is tested on a capacitive discharge based on three consecutive harmonics of 13.56 MHz. According to the Electrical Asymmetry Effect, tuning the phases between the applied harmonics results in an electrical control of the DC self-bias and the mean ion energy at almost constant ion flux. A comparison with the reference case of an electrically asymmetric dual-frequency discharge reveals that the control range of the mean ion energy can be significantly enlarged by using more than two consecutive harmonics.

High frequency optical communications; Proceedings of the Meeting, Cambridge, MA, Sept. 23, 24, 1986

NASA Astrophysics Data System (ADS)

Ramer, O. Glenn; Sierak, Paul

Topics discussed in this volume include systems and applications, detectors, sources, and coherent communications. Papers are presented on RF fiber optic links for avionics applications, fiber optics and optoelectronics for radar and electronic warfare applications, symmetric coplanar electrodes for high-speed Ti:LiNbO3 devices, and surface wave electrooptic modulator. Attention is given to X-band RF fiber-optic links, fiber-optic links for microwave signal transmission, GaAs monolithic receiver and laser driver for GHz transmission rates, and monolithically integrable high-speed photodetectors. Additional papers are on irregular and chaotic behavior of semiconductor lasers under modulation, high-frequency laser package for microwave optical communications, receiver modeling for coherent light wave communications, and polarization sensors and controllers for coherent optical communication systems.

RF to millimeter wave integration and module technologies

NASA Astrophysics Data System (ADS)

Vähä-Heikkilä, T.

2015-04-01

Radio Frequency (RF) consumer applications have boosted silicon integrated circuits (IC) and corresponding technologies. More and more functions are integrated to ICs and their performance is also increasing. However, RF front-end modules with filters and switches as well as antennas still need other way of integration. This paper focuses to RF front-end module and antenna developments as well as to the integration of millimeter wave radios. VTT Technical Research Centre of Finland has developed both Low Temperature Co-fired Ceramics (LTCC) and Integrated Passive Devices (IPD) integration platforms for RF and millimeter wave integrated modules. In addition to in-house technologies, VTT is using module and component technologies from other commercial sources.

Wideband aperture array using RF channelizers and massively parallel digital 2D IIR filterbank

NASA Astrophysics Data System (ADS)

Sengupta, Arindam; Madanayake, Arjuna; Gómez-García, Roberto; Engeberg, Erik D.

2014-05-01

Wideband receive-mode beamforming applications in wireless location, electronically-scanned antennas for radar, RF sensing, microwave imaging and wireless communications require digital aperture arrays that offer a relatively constant far-field beam over several octaves of bandwidth. Several beamforming schemes including the well-known true time-delay and the phased array beamformers have been realized using either finite impulse response (FIR) or fast Fourier transform (FFT) digital filter-sum based techniques. These beamforming algorithms offer the desired selectivity at the cost of a high computational complexity and frequency-dependant far-field array patterns. A novel approach to receiver beamforming is the use of massively parallel 2-D infinite impulse response (IIR) fan filterbanks for the synthesis of relatively frequency independent RF beams at an order of magnitude lower multiplier complexity compared to FFT or FIR filter based conventional algorithms. The 2-D IIR filterbanks demand fast digital processing that can support several octaves of RF bandwidth, fast analog-to-digital converters (ADCs) for RF-to-bits type direct conversion of wideband antenna element signals. Fast digital implementation platforms that can realize high-precision recursive filter structures necessary for real-time beamforming, at RF radio bandwidths, are also desired. We propose a novel technique that combines a passive RF channelizer, multichannel ADC technology, and single-phase massively parallel 2-D IIR digital fan filterbanks, realized at low complexity using FPGA and/or ASIC technology. There exists native support for a larger bandwidth than the maximum clock frequency of the digital implementation technology. We also strive to achieve More-than-Moore throughput by processing a wideband RF signal having content with N-fold (B = N Fclk/2) bandwidth compared to the maximum clock frequency Fclk Hz of the digital VLSI platform under consideration. Such increase in bandwidth is achieved without use of polyphase signal processing or time-interleaved ADC methods. That is, all digital processors operate at the same Fclk clock frequency without phasing, while wideband operation is achieved by sub-sampling of narrower sub-bands at the the RF channelizer outputs.

Spin-torque resonant expulsion of the vortex core for an efficient radiofrequency detection scheme.

PubMed

Jenkins, A S; Lebrun, R; Grimaldi, E; Tsunegi, S; Bortolotti, P; Kubota, H; Yakushiji, K; Fukushima, A; de Loubens, G; Klein, O; Yuasa, S; Cros, V

2016-04-01

It has been proposed that high-frequency detectors based on the so-called spin-torque diode effect in spin transfer oscillators could eventually replace conventional Schottky diodes due to their nanoscale size, frequency tunability and large output sensitivity. Although a promising candidate for information and communications technology applications, the output voltage generated from this effect has still to be improved and, more pertinently, reduces drastically with decreasing radiofrequency (RF) current. Here we present a scheme for a new type of spintronics-based high-frequency detector based on the expulsion of the vortex core in a magnetic tunnel junction (MTJ). The resonant expulsion of the core leads to a large and sharp change in resistance associated with the difference in magnetoresistance between the vortex ground state and the final C-state configuration. Interestingly, this reversible effect is independent of the incoming RF current amplitude, offering a fast real-time RF threshold detector.

Silicon Carbide (SiC) MOSFET-based Full-Bridge for Fusion Science Applications

NASA Astrophysics Data System (ADS)

Ziemba, Timothy; Miller, Kenneth; Prager, James; Picard, Julian; Hashim, Akel

2014-10-01

Switching power amplifiers (SPAs) have a wide variety of applications within the fusion science community, including feedback and control systems for dynamic plasma stabilization in tokamaks, inductive and arc plasma sources, Radio Frequency (RF) helicity and flux injection, RF plasma heating and current drive schemes, ion beam generation, and RF pre-ionizer systems. SiC MOSFETs offer many advantages over IGBTs including lower drive energy requirements, lower conduction and switching losses, and higher switching frequency capabilities. When comparing SiC and traditional silicon-based MOSFETs, SiC MOSFETs provide higher current carrying capability allowing for smaller package weights and sizes and lower operating temperature. Eagle Harbor Technologies (EHT) is designing, constructing, and testing a SiC MOSFET-based full-bridge SPA. EHT will leverage the proprietary gate drive technology previously developed with the support of a DOE SBIR, which will enable fast, efficient switching in a small form factor. The primary goal is to develop a SiC MOSFET-based SPA for fusion science applications. Work supported in part by the DOE under Contract Number DE-SC0011907.

On the Application of Inverse-Mode SiGe HBTs in RF Receivers for the Mitigation of Single-Event Transients

NASA Astrophysics Data System (ADS)

Song, Ickhyun; Cho, Moon-Kyu; Oakley, Michael A.; Ildefonso, Adrian; Ju, Inchan; Buchner, Stephen P.; McMorrow, Dale; Paki, Pauline; Cressler, John. D.

2017-05-01

Best practice in mitigation strategies for single-event transients (SETs) in radio-frequency (RF) receiver modules is investigated using a variety of integrated receivers utilizing inverse-mode silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs). The receivers were designed and implemented in a 130-nm SiGe BiCMOS technology platform. In general, RF switches, low-noise amplifiers (LNAs), and downconversion mixers utilizing inverse-mode SiGe HBTs exhibit less susceptibility to SETs than conventional RF designs, in terms of transient peaks and duration, at the cost of RF performance. Under normal RF operation, the SET-hardened switch is mainly effective in peak reduction, while the LNA and the mixer exhibit reductions in transient peaks as well as transient duration.

A YBCO RF-squid variable temperature susceptometer and its applications

NASA Technical Reports Server (NTRS)

Zhou, Luwei; Qiu, Jinwu; Zhang, Xianfeng; Tang, Zhimin; Cai, Yimin; Qian, Yongjia

1991-01-01

The Superconducting QUantum Interference Device (SQUID) susceptibility using a high-temperature radio-frequency (rf) SQUID and a normal metal pick-up coil is employed in testing weak magnetization of the sample. The magnetic moment resolution of the device is 1 x 10(exp -6) emu, and that of the susceptibility is 5 x 10(exp -6) emu/cu cm.

Use of real-time GNSS-RF data to characterize the swing movements of forestry equipment

Treesearch

Ryer M. Becker; Robert F. Keefe; Nathaniel M. Anderson

2017-01-01

The western United States faces significant forest management challenges after severe bark beetle infestations have led to substantial mortality. Minimizing costs is vital for increasing the feasibility of management operations in affected forests. Multi‐transmitter Global Navigation Satellite System (GNSS)‐radio frequencies (RF) technology has applications in the...

Improved Drain Current Saturation and Voltage Gain in Graphene-on-Silicon Field Effect Transistors.

PubMed

Song, Seung Min; Bong, Jae Hoon; Hwang, Wan Sik; Cho, Byung Jin

2016-05-04

Graphene devices for radio frequency (RF) applications are of great interest due to their excellent carrier mobility and saturation velocity. However, the insufficient current saturation in graphene field effect transistors (FETs) is a barrier preventing enhancements of the maximum oscillation frequency and voltage gain, both of which should be improved for RF transistors. Achieving a high output resistance is therefore a crucial step for graphene to be utilized in RF applications. In the present study, we report high output resistances and voltage gains in graphene-on-silicon (GoS) FETs. This is achieved by utilizing bare silicon as a supporting substrate without an insulating layer under the graphene. The GoSFETs exhibit a maximum output resistance of 2.5 MΩ∙μm, maximum intrinsic voltage gain of 28 dB, and maximum voltage gain of 9 dB. This method opens a new route to overcome the limitations of conventional graphene-on-insulator (GoI) FETs and subsequently brings graphene electronics closer to practical usage.

Properties of radio-frequency heated argon confined uranium plasmas

NASA Technical Reports Server (NTRS)

1976-01-01

Pure uranium hexafluoride (UF6) was injected into an argon confined, steady state, rf-heated plasma within a fused silica peripheral wall test chamber. Exploratory tests conducted using an 80 kW rf facility and different test chamber flow configurations permitted selection of the configuration demonstrating the best confinement characteristics and minimum uranium compound wall coating. The overall test results demonstrated applicable flow schemes and associated diagnostic techniques were developed for the fluid mechanical confinement and characterization of uranium within an rf plasma discharge when pure UF6 is injected for long test times into an argon-confined, high-temperature, high-pressure, rf-heated plasma.

Electron current extraction from radio frequency excited micro-dielectric barrier discharges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jun-Chieh; Kushner, Mark J.; Leoni, Napoleon

Micro dielectric barrier discharges (mDBDs) consist of micro-plasma devices (10-100 {mu}m diameter) in which the electrodes are fully or partially covered by dielectrics, and often operate at atmospheric pressure driven with radio frequency (rf) waveforms. In certain applications, it may be desirable to extract electron current out of the mDBD plasma, which necessitates a third electrode. As a result, the physical structure of the m-DBD and the electron emitting properties of its materials are important to its operation. In this paper, results from a two-dimensional computer simulation of current extraction from mDBDs sustained in atmospheric pressure N{sub 2} will bemore » discussed. The mDBDs are sandwich structures with an opening of tens-of-microns excited with rf voltage waveforms of up to 25 MHz. Following avalanche by electron impact ionization in the mDBD cavity, the plasma can be expelled from the cavity towards the extraction electrode during the part of the rf cycle when the extraction electrode appears anodic. The electron current extraction can be enhanced by biasing this electrode. The charge collection can be controlled by choice of rf frequency, rf driving voltage, and permittivity of the dielectric barrier.« less

New Methods of Low-Field MRI for Application to Traumatic Brain Injury

DTIC Science & Technology

2014-04-01

resonance, and the sequences must be modified to allow for EPR saturation pulses. A difficulty of OMRI is the need for high power radio - frequency (RF...sign and construction of a rotating radio - frequency coil system for applications in magnetic reso- nance. IEEE transactions on bio-medical...1 AD_________________ Award Number: W81XWH- 11 -2-0076

Investigation of Helicon discharges as RF coupling concept of negative hydrogen ion sources

NASA Astrophysics Data System (ADS)

Briefi, S.; Fantz, U.

2013-02-01

The ITER reference source for H- and D- requires a high RF input power (up to 90 kW per driver). To reduce the demands on the RF circuit, it is highly desirable to reduce the power consumption while retaining the values of the relevant plasma parameters namely the positive ion density and the atomic hydrogen density. Helicon plasmas are a promising alternative RF coupling concept but they are typically generated in long thin discharge tubes using rare gases and an RF frequency of 13.56 MHz. Hence the applicability to the ITER reference source geometry, frequency and the utilization of hydrogen/deuterium has to be proved. In this paper the strategy of the approach for using Helicon discharges for ITER reference source parameters is introduced and the first promising measurements which were carried out at a small laboratory experiment are presented. With increasing RF power a mode transition to the Helicon regime was observed for argon and argon/hydrogen mixtures. In pure hydrogen/deuterium the mode transition could not yet be achieved as the available RF power is too low. In deuterium a special feature of Helicon discharges, the socalled low field peak, could be observed at a moderate B-field of 3 mT.

Verification of radio frequency pasteurization treatment for controlling Aspergillus parasiticus on corn grains.

PubMed

Zheng, Ajuan; Zhang, Lihui; Wang, Shaojin

2017-05-16

Radio frequency (RF) heating has been proposed and tested to achieve a required anti-fungal efficacy on various food samples due to its advantage of deeper penetration depth and better heating uniformity. The purpose of this study was to validate applications of RF treatments for controlling Aspergillus parasiticus in corn while maintaining product quality. A pilot-scale, 27.12MHz, 6kW RF heating system together with hot air heating was used to rapidly pasteurize 3.0kg corn samples. Results showed that the pasteurizing effect of RF heating on Aspergillus parasiticus increased with increasing heating temperature and holding time, and RF heating at 70°C holding in hot air for at least 12min resulted in 5-6 log reduction of Aspergillus parasiticus in corn samples with the moisture content of 15.0% w.b. Furthermore, thermal resistance of Aspergillus parasiticus decreased with increasing moisture content (MC) of corn samples. Quality (MC, water activity - a w , protein, starch, ash, fat, fatty acid, color, electrical conductivity and germination rate) of RF treated corn met the required quality standard used in cereal industry. Therefore, RF treatments can provide an effective and rapid heating method to control Aspergillus parasiticus and maintain acceptable corn quality. Copyright © 2017 Elsevier B.V. All rights reserved.

Study of Pulsed vs. RF Plasma Properties for Surface Processing Applications

NASA Astrophysics Data System (ADS)

Tang, Ricky; Hopkins, Matthew; Barnat, Edward; Miller, Paul

2015-09-01

The ability to manipulate the plasma parameters (density, E/N) was previously demonstrated using a double-pulsed column discharge. Experiments extending this to large-surface plasmas of interest to the plasma processing community were conducted. Differences between an audio-frequency pulsed plasma and a radio-frequency (rf) discharge, both prevalent in plasma processing applications, were studied. Optical emission spectroscopy shows higher-intensity emission in the UV/visible range for the pulsed plasma comparing to the rf plasma at comparable powers. Data suggest that the electron energy is higher for the pulsed plasma leading to higher ionization, resulting in increased ion density and ion flux. Diode laser absorption measurements of the concentration of the 1S5 metastable and 1S4 resonance states of argon (correlated with the plasma E/N) provide comparisons between the excitation/ionization states of the two plasmas. Preliminary modeling efforts suggest that the low-frequency polarity switch causes a much more abrupt potential variation to support interesting transport phenomena, generating a ``wave'' of higher temperature electrons leading to more ionization, as well as ``sheath capture'' of a higher density bolus of ions that are then accelerated during polarity switch.

Frequency stabilization for mobile satellite terminals via LORAN

NASA Technical Reports Server (NTRS)

Ernst, Gregory J.; Kee, Steven M.; Marquart, Robert C.

1990-01-01

Digital satellite communication systems require careful management of frequency stability. Historically, frequency stability has been accomplished by continuously powered, high cost, high performance reference oscillators. Today's low cost mobile satellite communication equipment must operate under wide ranging environmental conditions, stabilize quickly after application of power, and provide adequate performance margin to overcome RF link impairments unique to the land mobile environment. Methods for frequency stabilization in land mobile applications must meet these objectives without incurring excessive performance degradation. A frequency stabilization scheme utilizing the LORAN (Long Range Navigation) system is presented.

Radio Frequency Transistors Using Aligned Semiconducting Carbon Nanotubes with Current-Gain Cutoff Frequency and Maximum Oscillation Frequency Simultaneously Greater than 70 GHz.

PubMed

Cao, Yu; Brady, Gerald J; Gui, Hui; Rutherglen, Chris; Arnold, Michael S; Zhou, Chongwu

2016-07-26

In this paper, we report record radio frequency (RF) performance of carbon nanotube transistors based on combined use of a self-aligned T-shape gate structure, and well-aligned, high-semiconducting-purity, high-density polyfluorene-sorted semiconducting carbon nanotubes, which were deposited using dose-controlled, floating evaporative self-assembly method. These transistors show outstanding direct current (DC) performance with on-current density of 350 μA/μm, transconductance as high as 310 μS/μm, and superior current saturation with normalized output resistance greater than 100 kΩ·μm. These transistors create a record as carbon nanotube RF transistors that demonstrate both the current-gain cutoff frequency (ft) and the maximum oscillation frequency (fmax) greater than 70 GHz. Furthermore, these transistors exhibit good linearity performance with 1 dB gain compression point (P1dB) of 14 dBm and input third-order intercept point (IIP3) of 22 dBm. Our study advances state-of-the-art of carbon nanotube RF electronics, which have the potential to be made flexible and may find broad applications for signal amplification, wireless communication, and wearable/flexible electronics.

Highly Sensitive Electro-Optic Modulators

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeVore, Peter S

2015-10-26

There are very important diagnostic and communication applications that receive faint electrical signals to be transmitted over long distances for capture. Optical links reduce bandwidth and distance restrictions of metal transmission lines; however, such signals are only weakly imprinted onto the optical carrier, resulting in low fidelity transmission. Increasing signal fidelity often necessitates insertion of radio-frequency (RF) amplifiers before the electro-optic modulator, but (especially at high frequencies) RF amplification results in large irreversible distortions. We have investigated the feasibility of a Sensitive and Linear Modulation by Optical Nonlinearity (SALMON) modulator to supersede RF-amplified modulators. SALMON uses cross-phase modulation, a manifestationmore » of the Kerr effect, to enhance the modulation depth of an RF-modulated optical wave. This ultrafast process has the potential to result in less irreversible distortions as compared to a RF-amplified modulator due to the broadband nature of the Kerr effect. Here, we prove that a SALMON modulator is a feasible alternative to an RFamplified modulator, by demonstrating a sensitivity enhancement factor greater than 20 and significantly reduced distortion.« less

A 2×1 Coplanar Monopole Antenna Structure for Wireless RF Energy Harvesting

NASA Astrophysics Data System (ADS)

Mathur, Monika; Agarwal, Ankit; Singh, Ghanshyam; Bhatnagar, S. K.

2018-03-01

The objective of this paper is to design an efcient wireless energy harvesting (WEH) system to eliminate the problem to continuous charging of a battery operated electronics devices. Most of the devices are battery operated so charging of a battery time to time is serious issue. This WEH system receives the Radio Frequency (RF) and Microwave frequency signals present in the atmosphere and converting it into DC signal so that it can stores in Capacitor or charges a battery for utilize the power. For this RF energy harvesting purposes 21 antenna array structure of the coplanar monopole antenna is presented. This structure shows the gain of 10.2 dBi and 83% efciency. This structure is designed for resonating on multiple bands (Radio, GSM, ISM, and UWB). It is useful for this application because it covers almost all useful bands in the maximum capturing area. The antenna can be connected directly to an RF-DC converter module and it uses about 60% of the total PCB area. And RF to DC convertor circuit can be implemented in that remaining 40% area on the same substrate so it eliminates the need of port connectors and impedance matching circuit between them. This design is worked in receiving mode only when used for energy harvesting purposes. This may be useful for the biomedical and satellite applications.

An adjustable RF tuning element for microwave, millimeter wave, and submillimeter wave integrated circuits

NASA Technical Reports Server (NTRS)

Lubecke, Victor M.; Mcgrath, William R.; Rutledge, David B.

1991-01-01

Planar RF circuits are used in a wide range of applications from 1 GHz to 300 GHz, including radar, communications, commercial RF test instruments, and remote sensing radiometers. These circuits, however, provide only fixed tuning elements. This lack of adjustability puts severe demands on circuit design procedures and materials parameters. We have developed a novel tuning element which can be incorporated into the design of a planar circuit in order to allow active, post-fabrication tuning by varying the electrical length of a coplanar strip transmission line. It consists of a series of thin plates which can slide in unison along the transmission line, and the size and spacing of the plates are designed to provide a large reflection of RF power over a useful frequency bandwidth. Tests of this structure at 1 GHz to 3 Ghz showed that it produced a reflection coefficient greater than 0.90 over a 20 percent bandwidth. A 2 GHz circuit incorporating this tuning element was also tested to demonstrate practical tuning ranges. This structure can be fabricated for frequencies as high as 1000 GHz using existing micromachining techniques. Many commercial applications can benefit from this micromechanical RF tuning element, as it will aid in extending microwave integrated circuit technology into the high millimeter wave and submillimeter wave bands by easing constraints on circuit technology.

Bridging the Gap between RF and Optical Patch Antenna Analysis via the Cavity Model.

PubMed

Unal, G S; Aksun, M I

2015-11-02

Although optical antennas with a variety of shapes and for a variety of applications have been proposed and studied, they are still in their infancy compared to their radio frequency (rf) counterparts. Optical antennas have mainly utilized the geometrical attributes of rf antennas rather than the analysis tools that have been the source of intuition for antenna engineers in rf. This study intends to narrow the gap of experience and intuition in the design of optical patch antennas by introducing an easy-to-understand and easy-to-implement analysis tool in rf, namely, the cavity model, into the optical regime. The importance of this approach is not only its simplicity in understanding and implementation but also its applicability to a broad class of patch antennas and, more importantly, its ability to provide the intuition needed to predict the outcome without going through the trial-and-error simulations with no or little intuitive guidance by the user.

Active control of the spatial MRI phase distribution with optimal control theory

NASA Astrophysics Data System (ADS)

Lefebvre, Pauline M.; Van Reeth, Eric; Ratiney, Hélène; Beuf, Olivier; Brusseau, Elisabeth; Lambert, Simon A.; Glaser, Steffen J.; Sugny, Dominique; Grenier, Denis; Tse Ve Koon, Kevin

2017-08-01

This paper investigates the use of Optimal Control (OC) theory to design Radio-Frequency (RF) pulses that actively control the spatial distribution of the MRI magnetization phase. The RF pulses are generated through the application of the Pontryagin Maximum Principle and optimized so that the resulting transverse magnetization reproduces various non-trivial and spatial phase patterns. Two different phase patterns are defined and the resulting optimal pulses are tested both numerically with the ODIN MRI simulator and experimentally with an agar gel phantom on a 4.7 T small-animal MR scanner. Phase images obtained in simulations and experiments are both consistent with the defined phase patterns. A practical application of phase control with OC-designed pulses is also presented, with the generation of RF pulses adapted for a Magnetic Resonance Elastography experiment. This study demonstrates the possibility to use OC-designed RF pulses to encode information in the magnetization phase and could have applications in MRI sequences using phase images.

Resonance of magnetization excited by voltage in magnetoelectric heterostructures

NASA Astrophysics Data System (ADS)

Yu, Guoliang; Zhang, Huaiwu; Li, Yuanxun; Li, Jie; Zhang, Dainan; Sun, Nian

2018-04-01

Manipulation of magnetization dynamics is critical for spin-based devices. Voltage driven magnetization resonance is promising for realizing low-power information processing systems. Here, we show through Finite Element Method (FEM) simulations that magnetization resonance in nanoscale magnetic elements can be generated by a radio frequency (rf) voltage via the converse magnetoelectric (ME) effect. The magnetization dynamics induced by voltage in a ME heterostructures is simulated by taking into account the magnetoelastic and piezoelectric coupling mechanisms among magnetization, strain and voltage. The frequency of the excited magnetization resonance is equal to the driving rf voltage frequency. The proposed voltage driven magnetization resonance excitation mechanism opens a way toward energy-efficient spin based device applications.

The development of data acquisition and processing application system for RF ion source

NASA Astrophysics Data System (ADS)

Zhang, Xiaodan; Wang, Xiaoying; Hu, Chundong; Jiang, Caichao; Xie, Yahong; Zhao, Yuanzhe

2017-07-01

As the key ion source component of nuclear fusion auxiliary heating devices, the radio frequency (RF) ion source is developed and applied gradually to offer a source plasma with the advantages of ease of control and high reliability. In addition, it easily achieves long-pulse steady-state operation. During the process of the development and testing of the RF ion source, a lot of original experimental data will be generated. Therefore, it is necessary to develop a stable and reliable computer data acquisition and processing application system for realizing the functions of data acquisition, storage, access, and real-time monitoring. In this paper, the development of a data acquisition and processing application system for the RF ion source is presented. The hardware platform is based on the PXI system and the software is programmed on the LabVIEW development environment. The key technologies that are used for the implementation of this software programming mainly include the long-pulse data acquisition technology, multi-threading processing technology, transmission control communication protocol, and the Lempel-Ziv-Oberhumer data compression algorithm. Now, this design has been tested and applied on the RF ion source. The test results show that it can work reliably and steadily. With the help of this design, the stable plasma discharge data of the RF ion source are collected, stored, accessed, and monitored in real-time. It is shown that it has a very practical application significance for the RF experiments.

Airborne RF Measurement System and Analysis of Representative Flight RF Environment

NASA Technical Reports Server (NTRS)

Koppen, Sandra V.; Ely, Jay J.; Smith, Laura J.; Jones, Richard A.; Fleck, Vincent J.; Salud, Maria Theresa; Mielnik, John

2007-01-01

Environmental radio frequency (RF) data over a broad band of frequencies were needed to evaluate the airspace around several airports. An RF signal measurement system was designed using a spectrum analyzer connected to an aircraft VHF/UHF navigation antenna installed on a small aircraft. This paper presents an overview of the RF measurement system and provides analysis of a sample of RF signal measurement data over a frequency range of 30 MHz to 1000 MHz.

Implanted Miniaturized Antenna for Brain Computer Interface Applications: Analysis and Design

PubMed Central

Zhao, Yujuan; Rennaker, Robert L.; Hutchens, Chris; Ibrahim, Tamer S.

2014-01-01

Implantable Brain Computer Interfaces (BCIs) are designed to provide real-time control signals for prosthetic devices, study brain function, and/or restore sensory information lost as a result of injury or disease. Using Radio Frequency (RF) to wirelessly power a BCI could widely extend the number of applications and increase chronic in-vivo viability. However, due to the limited size and the electromagnetic loss of human brain tissues, implanted miniaturized antennas suffer low radiation efficiency. This work presents simulations, analysis and designs of implanted antennas for a wireless implantable RF-powered brain computer interface application. The results show that thin (on the order of 100 micrometers thickness) biocompatible insulating layers can significantly impact the antenna performance. The proper selection of the dielectric properties of the biocompatible insulating layers and the implantation position inside human brain tissues can facilitate efficient RF power reception by the implanted antenna. While the results show that the effects of the human head shape on implanted antenna performance is somewhat negligible, the constitutive properties of the brain tissues surrounding the implanted antenna can significantly impact the electrical characteristics (input impedance, and operational frequency) of the implanted antenna. Three miniaturized antenna designs are simulated and demonstrate that maximum RF power of up to 1.8 milli-Watts can be received at 2 GHz when the antenna implanted around the dura, without violating the Specific Absorption Rate (SAR) limits. PMID:25079941

Solid-state Terahertz Sources for Space Applications

NASA Technical Reports Server (NTRS)

Maiwald, Frank; Pearson, John C.; Ward, John S.; Schlecht, Erich; Chattopadhyay, Goutam; Gill, John J.; Ferber, R.; Tsang, Raymond; Lin, Robert H.; Peralta, Alejandro;

MIT Lincoln Laboratory Facts 2013

DTIC Science & Technology

2012-12-01

efforts span all network layers (from physical to application), with primary focuses on radio - frequency (RF) military satellite communications (MILSATCOM...upgrade, Kwajalein Atoll ■■ Extremely high- frequency submarine communications demonstrated ■■ Lincoln Experimental Satellites 8 and 9 Overview 5...Immersive Surveillance ■■ Lincoln Adaptable Real-time Information Assurance Testbed ■■ Graph detection algorithms ■■ Miniaturized radio - frequency

Variable slew-rate spiral design: theory and application to peak B(1) amplitude reduction in 2D RF pulse design.

PubMed

Xu, Dan; King, Kevin F; Liang, Zhi-Pei

2007-10-01

A new class of spiral trajectories called variable slew-rate spirals is proposed. The governing differential equations for a variable slew-rate spiral are derived, and both numeric and analytic solutions to the equations are given. The primary application of variable slew-rate spirals is peak B(1) amplitude reduction in 2D RF pulse design. The reduction of peak B(1) amplitude is achieved by changing the gradient slew-rate profile, and gradient amplitude and slew-rate constraints are inherently satisfied by the design of variable slew-rate spiral gradient waveforms. A design example of 2D RF pulses is given, which shows that under the same hardware constraints the RF pulse using a properly chosen variable slew-rate spiral trajectory can be much shorter than that using a conventional constant slew-rate spiral trajectory, thus having greater immunity to resonance frequency offsets.

Multi-level RF identification system

DOEpatents

Steele, Kerry D.; Anderson, Gordon A.; Gilbert, Ronald W.

2004-07-20

A radio frequency identification system having a radio frequency transceiver for generating a continuous wave RF interrogation signal that impinges upon an RF identification tag. An oscillation circuit in the RF identification tag modulates the interrogation signal with a subcarrier of a predetermined frequency and modulates the frequency-modulated signal back to the transmitting interrogator. The interrogator recovers and analyzes the subcarrier signal and determines its frequency. The interrogator generates an output indicative of the frequency of the subcarrier frequency, thereby identifying the responding RFID tag as one of a "class" of RFID tags configured to respond with a subcarrier signal of a predetermined frequency.

Digitally synthesized high purity, high-voltage radio frequency drive electronics for mass spectrometry.

PubMed

Schaefer, R T; MacAskill, J A; Mojarradi, M; Chutjian, A; Darrach, M R; Madzunkov, S M; Shortt, B J

2008-09-01

Reported herein is development of a quadrupole mass spectrometer controller (MSC) with integrated radio frequency (rf) power supply and mass spectrometer drive electronics. Advances have been made in terms of the physical size and power consumption of the MSC, while simultaneously making improvements in frequency stability, total harmonic distortion, and spectral purity. The rf power supply portion of the MSC is based on a series-resonant LC tank, where the capacitive load is the mass spectrometer itself, and the inductor is a solenoid or toroid, with various core materials. The MSC drive electronics is based on a field programmable gate array (FPGA), with serial peripheral interface for analog-to-digital and digital-to-analog converter support, and RS232/RS422 communications interfaces. The MSC offers spectral quality comparable to, or exceeding, that of conventional rf power supplies used in commercially available mass spectrometers; and as well an inherent flexibility, via the FPGA implementation, for a variety of tasks that includes proportional-integral derivative closed-loop feedback and control of rf, rf amplitude, and mass spectrometer sensitivity. Also provided are dc offsets and resonant dipole excitation for mass selective accumulation in applications involving quadrupole ion traps; rf phase locking and phase shifting for external loading of a quadrupole ion trap; and multichannel scaling of acquired mass spectra. The functionality of the MSC is task specific, and is easily modified by simply loading FPGA registers or reprogramming FPGA firmware.

System-Level Integrated Circuit (SLIC) development for phased array antenna applications

NASA Technical Reports Server (NTRS)

Shalkhauser, K. A.; Raquet, C. A.

1991-01-01

A microwave/millimeter wave system-level integrated circuit (SLIC) being developed for use in phased array antenna applications is described. The program goal is to design, fabricate, test, and deliver an advanced integrated circuit that merges radio frequency (RF) monolithic microwave integrated circuit (MMIC) technologies with digital, photonic, and analog circuitry that provide control, support, and interface functions. As a whole, the SLIC will offer improvements in RF device performance, uniformity, and stability while enabling accurate, rapid, repeatable control of the RF signal. Furthermore, the SLIC program addresses issues relating to insertion of solid state devices into antenna systems, such as the reduction in number of bias, control, and signal lines. Program goals, approach, and status are discussed.

System-level integrated circuit (SLIC) development for phased array antenna applications

NASA Technical Reports Server (NTRS)

Shalkhauser, K. A.; Raquet, C. A.

1991-01-01

A microwave/millimeter wave system-level integrated circuit (SLIC) being developed for use in phased array antenna applications is described. The program goal is to design, fabricate, test, and deliver an advanced integrated circuit that merges radio frequency (RF) monolithic microwave integrated circuit (MMIC) technologies with digital, photonic, and analog circuitry that provide control, support, and interface functions. As a whole, the SLIC will offer improvements in RF device performance, uniformity, and stability while enabling accurate, rapid, repeatable control of the RF signal. Furthermore, the SLIC program addresses issues relating to insertion of solid state devices into antenna systems, such as the reduction in number of bias, control, and signal lines. Program goals, approach, and status are discussed.

RF MEMS and Their Applications in NASA's Space Communication Systems

NASA Technical Reports Server (NTRS)

Williams, W. Daniel; Ponchak, George E.; Simons, Rainee N.; Zaman, Afroz; Kory, Carol; Wintucky, Edwin; Wilson, Jeffrey D.; Scardelletti, Maximilian; Lee, Richard; Nguyen, Hung

2001-01-01

Radio frequency (RF) and microwave communication systems rely on frequency, amplitude, and phase control circuits to efficiently use the available spectrum. Phase control circuits are required for electronically scanning phase array antennas that enable radiation pattern shaping, scanning, and hopping. Two types of phase shifters, which are the phase control circuits, are most often used. The first is comprised of two circuits with different phase characteristics such as two transmission lines of different lengths or a high pass and low pass filter and a switch that directs the RF power through one of the two circuits. Alternatively, a variable capacitor, or varactor, is used to change the effective electrical path length of a transmission line, which changes the phase characteristics. Filter banks are required for the diplexer at the front end of wide band communication satellites. These filters greatly increase the size and mass of the RF/microwave systems, but smaller diplexers may be made with a low loss varactor or a group of capacitors, a switch and an inductor.

47 CFR 24.51 - Equipment authorization.

Code of Federal Regulations, 2010 CFR

2010-10-01

..., “IEEE Standards for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic... for the Measurement of Potentially Hazardous Electromagnetic Fields—RF and Microwave.” The applicant...

47 CFR 24.51 - Equipment authorization.

Code of Federal Regulations, 2014 CFR

2014-10-01

..., “IEEE Standards for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic... for the Measurement of Potentially Hazardous Electromagnetic Fields—RF and Microwave.” The applicant...

47 CFR 24.51 - Equipment authorization.

Code of Federal Regulations, 2011 CFR

2011-10-01

..., “IEEE Standards for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic... for the Measurement of Potentially Hazardous Electromagnetic Fields—RF and Microwave.” The applicant...

47 CFR 24.51 - Equipment authorization.

Code of Federal Regulations, 2012 CFR

2012-10-01

..., “IEEE Standards for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic... for the Measurement of Potentially Hazardous Electromagnetic Fields—RF and Microwave.” The applicant...

47 CFR 24.51 - Equipment authorization.

Code of Federal Regulations, 2013 CFR

2013-10-01

..., “IEEE Standards for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic... for the Measurement of Potentially Hazardous Electromagnetic Fields—RF and Microwave.” The applicant...

Fast numerical design of spatial-selective rf pulses in MRI using Krotov and quasi-Newton based optimal control methods

NASA Astrophysics Data System (ADS)

Vinding, Mads S.; Maximov, Ivan I.; Tošner, Zdeněk; Nielsen, Niels Chr.

2012-08-01

The use of increasingly strong magnetic fields in magnetic resonance imaging (MRI) improves sensitivity, susceptibility contrast, and spatial or spectral resolution for functional and localized spectroscopic imaging applications. However, along with these benefits come the challenges of increasing static field (B0) and rf field (B1) inhomogeneities induced by radial field susceptibility differences and poorer dielectric properties of objects in the scanner. Increasing fields also impose the need for rf irradiation at higher frequencies which may lead to elevated patient energy absorption, eventually posing a safety risk. These reasons have motivated the use of multidimensional rf pulses and parallel rf transmission, and their combination with tailoring of rf pulses for fast and low-power rf performance. For the latter application, analytical and approximate solutions are well-established in linear regimes, however, with increasing nonlinearities and constraints on the rf pulses, numerical iterative methods become attractive. Among such procedures, optimal control methods have recently demonstrated great potential. Here, we present a Krotov-based optimal control approach which as compared to earlier approaches provides very fast, monotonic convergence even without educated initial guesses. This is essential for in vivo MRI applications. The method is compared to a second-order gradient ascent method relying on the Broyden-Fletcher-Goldfarb-Shanno (BFGS) quasi-Newton method, and a hybrid scheme Krotov-BFGS is also introduced in this study. These optimal control approaches are demonstrated by the design of a 2D spatial selective rf pulse exciting the letters "JCP" in a water phantom.

Response of a SET to large rf interference signals

NASA Astrophysics Data System (ADS)

Lewis, Rupert; Harris, C. Thomas; Shaner, Eric

Single electron transistors (SETs) fabricated from aluminum thin films and Al/AlOx Josephson tunnel junctions can be added to other structures as charge sensors with large intrinsic bandwidth-for example, the charge sensing corral of an electrons on helium quantum chip. We characterized a SET at temperature T =40 mk for its ability to tolerate extraneous radio frequency (rf) interference in such applications at frequencies from 10 kHz to 50 MHz. Our SET, with charging energy, Ec 1 K, normal resistance Rn 600 k Ω, and peak measured charge sensitivity of Sp = 5 × 10-5electrons/ √Hz maintained usable sensitivity (S <1 × 10-3electrons/ √Hz) when subjected to rf signals of strength greater than +/- 9 electrons. This suggests for frequencies well below fc 1/2 πRnCj where Cj is the junction capacitance, that SETs respond nearly instantaneously even to large rf signals. Exploiting this knowledge, we were able to cancel a known rf signal at 1 MHz nearly recovering the charge sensitivity in the absence of rf signals-a result we expect will hold to higher frequencies. Work performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Los Alamos National Laboratory (Contract DE-AC52-06NA25396) and Sandia National Laboratories (Contract DE-AC04-94AL85000). Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Zero-static power radio-frequency switches based on MoS2 atomristors.

PubMed

Kim, Myungsoo; Ge, Ruijing; Wu, Xiaohan; Lan, Xing; Tice, Jesse; Lee, Jack C; Akinwande, Deji

2018-06-28

Recently, non-volatile resistance switching or memristor (equivalently, atomristor in atomic layers) effect was discovered in transitional metal dichalcogenides (TMD) vertical devices. Owing to the monolayer-thin transport and high crystalline quality, ON-state resistances below 10 Ω are achievable, making MoS 2 atomristors suitable as energy-efficient radio-frequency (RF) switches. MoS 2 RF switches afford zero-hold voltage, hence, zero-static power dissipation, overcoming the limitation of transistor and mechanical switches. Furthermore, MoS 2 switches are fully electronic and can be integrated on arbitrary substrates unlike phase-change RF switches. High-frequency results reveal that a key figure of merit, the cutoff frequency (f c ), is about 10 THz for sub-μm 2 switches with favorable scaling that can afford f c above 100 THz for nanoscale devices, exceeding the performance of contemporary switches that suffer from an area-invariant scaling. These results indicate a new electronic application of TMDs as non-volatile switches for communication platforms, including mobile systems, low-power internet-of-things, and THz beam steering.

Exploring Sedimentary Basins with High Frequency Receiver Function: the Dublin Basin Case Study

NASA Astrophysics Data System (ADS)

Licciardi, A.; Piana Agostinetti, N.

2015-12-01

The Receiver Function (RF) method is a widely applied seismological tool for the imaging of crustal and lithospheric structures beneath a single seismic station with one to tens kilometers of vertical resolution. However, detailed information about the upper crust (0-10 km depth) can also be retrieved by increasing the frequency content of the analyzed RF data-set (with a vertical resolution lower than 0.5km). This information includes depth of velocity contrasts, S-wave velocities within layers, as well as presence and location of seismic anisotropy or dipping interfaces (e.g., induced by faulting) at depth. These observables provides valuable constraints on the structural settings and properties of sedimentary basins both for scientific and industrial applications. To test the RF capabilities for this high resolution application, six broadband seismic stations have been deployed across the southwestern margin of the Dublin Basin (DB), Ireland, whose geothermal potential has been investigated in the last few years. With an inter-station distance of about 1km, this closely spaced array has been designed to provide a clear picture of the structural transition between the margin and the inner portion of the basin. In this study, a Bayesian approach is used to retrieve the posterior probability distributions of S-wave velocity at depth beneath each seismic station. A multi-frequency RF data-set is analyzed and RF and curves of apparent velocity are jointly inverted to better constrain absolute velocity variations. A pseudo 2D section is built to observe the lateral changes in elastic properties across the margin of the basin with a focus in the shallow portion of the crust. Moreover, by means of the harmonic decomposition technique, the azimuthal variations in the RF data-set are isolated and interpreted in terms of anisotropy and dipping interfaces associated with the major fault system in the area. These results are compared with the available information from previous seismic active surveys in the area, including boreholes data.

FAST TRACK COMMUNICATION: Asymmetric surface barrier discharge plasma driven by pulsed 13.56 MHz power in atmospheric pressure air

NASA Astrophysics Data System (ADS)

Dedrick, J.; Boswell, R. W.; Charles, C.

2010-09-01

Barrier discharges are a proven method of generating plasmas at high pressures, having applications in industrial processing, materials science and aerodynamics. In this paper, we present new measurements of an asymmetric surface barrier discharge plasma driven by pulsed radio frequency (rf 13.56 MHz) power in atmospheric pressure air. The voltage, current and optical emission of the discharge are measured temporally using 2.4 kVp-p (peak to peak) 13.56 MHz rf pulses, 20 µs in duration. The results exhibit different characteristics to plasma actuators, which have similar discharge geometry but are typically driven at frequencies of up to about 10 kHz. However, the electrical measurements are similar to some other atmospheric pressure, rf capacitively coupled discharge systems with symmetric electrode configurations and different feed gases.

Recombination Processes on Low Bandgap Antimonides for Thermophotovoltaic Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saroop, Sudesh

1999-09-01

Recombination processes in antimonide-based (TPV) devices have been investigated using a technique, in which a Nd-YAG pulsed laser is materials for thermophotovoltaic radio-frequency (RF) photoreflectance used to excite excess carriers and the short-pulse response and photoconductivity decay are monitored with an inductively-coupled non-contacting RF probe. The system has been used to characterize surface and bulk recombination mechanisms in Sb-based materials.

High Current Density Scandate Cathodes for Future Vacuum Electronics Applications

DTIC Science & Technology

2008-05-30

of Technology HFSS Ansoft Corporation’s High Frequency Structure Simulator TWT Traveling Wave Tube - device for generating high levels of RF power ...cathodes are practical for high power RF sources. Typical thermi- onic cathodes consists of a tungsten matrix impregnated with a mixture of barium oxide...electron beam with the largest possible diameter, consistent with high gain, bandwidth, and efficiency at W- Band . The research concentrated on photonic

Synthesis of a fiber-optic magnetostrictive sensor (FOMS) pixel for RF magnetic field imaging

NASA Astrophysics Data System (ADS)

Rengarajan, Suraj

The principal objective of this dissertation was to synthesize a sensor element with properties specifically optimized for integration into arrays capable of imaging RF magnetic fields. The dissertation problem was motivated by applications in nondestructive eddy current testing, smart skins, etc., requiring sensor elements that non-invasively detect millimeter-scale variations over several square meters, in low level magnetic fields varying at frequencies in the 100 kHz-1 GHz range. The poor spatial and temporal resolution of FOMS elements available prior to this dissertation research, precluded their use in non-invasive large area mapping applications. Prior research had been focused on large, discrete devices for detecting extremely low level magnetic fields varying at a few kHz. These devices are incompatible with array integration and imaging applications. The dissertation research sought to overcome the limitations of current technology by utilizing three new approaches; synthesizing magnetostrictive thin films and optimizing their properties for sensor applications, integrating small sensor elements into an array compatible fiber optic interferometer, and devising a RF mixing approach to measure high frequency magnetic fields using the integrated sensor element. Multilayer thin films were used to optimize the magnetic properties of the magnetostrictive elements. Alternating soft (Nisb{80}Fesb{20}) and hard (Cosb{50}Fesb{50}) magnetic alloy layers were selected for the multilayer and the layer thicknesses were varied to obtain films with a combination of large magnetization, high frequency permeability and large magnetostrictivity. X-Ray data and measurement of the variations in the magnetization, resistivity and magnetostriction with layer thicknesses, indicated that an interfacial layer was responsible for enhancing the sensing performance of the multilayers. A FOMS pixel was patterned directly onto the sensing arm of a fiber-optic interferometer, by sputtering a multilayer film with favorable sensor properties. After calibrating the interferometer response with a piezo, the mechanical and magnetic responses of the FOMS element were evaluated for various test fields. High frequency magnetic fields were detected using a local oscillator field to downconvert the RF signal fields to the lower mechanical resonant frequency of the element. A field sensitivity of 0.3 Oe/cm sensor element length was demonstrated at 1 MHz. A coherent magnetization rotation model was developed to predict the magnetostrictive response of the element, and identify approaches for optimizing its performance. This model predicts that an optimized element could resolve ˜1 mm variations in fields varying at frequencies >10 MHz with a sensitivity of ˜10sp{-3} Oe/mm. The results demonstrate the potential utility of integrating this device as a FOMS pixel in RF magnetic field imaging arrays.

Improved nuclear magnetic resonance apparatus having semitoroidal rf coil for use in topical NMR and NMR imaging

DOEpatents

Fukushima, E.; Roeder, S.B.W.; Assink, R.A.; Gibson, A.A.V.

1984-01-01

An improved nuclear magnetic resonance (NMR) apparatus for use in topical magnetic resonance (TMR) spectroscopy and other remote sensing NMR applications includes a semitoroidal radio frequency (rf) coil. The semitoroidal rf coil produces an effective alternating magnetic field at a distance from the poles of the coil, so as to enable NMR measurements to be taken from selected regions inside an object, particularly including human and other living subjects. The semitoroidal rf coil is relatively insensitive to magnetic interference from metallic objects located behind the coil, thereby rendering the coil particularly suited for use in both conventional and superconducting NMR magnets. The semitoroidal NMR coil can be constructed so that it emits little or no excess rf electric field associated with the rf magnetic field, thus avoiding adverse effects due to dielectric heating of the sample or to any other interaction of the electric field with the sample.

Nuclear magnetic resonance apparatus having semitoroidal rf coil for use in topical NMR and NMR imaging

DOEpatents

Fukushima, Eiichi; Roeder, Stephen B. W.; Assink, Roger A.; Gibson, Atholl A. V.

1986-01-01

An improved nuclear magnetic resonance (NMR) apparatus for use in topical magnetic resonance (TMR) spectroscopy and other remote sensing NMR applications includes a semitoroidal radio-frequency (rf) coil. The semitoroidal rf coil produces an effective alternating magnetic field at a distance from the poles of the coil, so as to enable NMR measurements to be taken from selected regions inside an object, particularly including human and other living subjects. The semitoroidal rf coil is relatively insensitive to magnetic interference from metallic objects located behind the coil, thereby rendering the coil particularly suited for use in both conventional and superconducting NMR magnets. The semitoroidal NMR coil can be constructed so that it emits little or no excess rf electric field associated with the rf magnetic field, thus avoiding adverse effects due to dielectric heating of the sample or to any other interaction of the electric field with the sample.

Microwave vs optical crosslink study

NASA Technical Reports Server (NTRS)

Kwong, Paulman W.; Bruno, Ronald C.; Marshalek, Robert G.

1992-01-01

The intersatellite links (ISL's) at geostationary orbit is currently a missing link in commercial satellite services. Prior studies have found that potential application of ISL's to domestic, regional, and global satellites will provide more cost-effective services than the non-ISL's systems (i.e., multiple-hop systems). In addition, ISL's can improve and expand the existing satellite services in several aspects. For example, ISL's can conserve the scarce spectrum allocated for fixed satellite services (FSS) by avoiding multiple hopping of the relay stations. ISL's can also conserve prime orbit slot by effectively expanding the geostationary arc. As a result of the coverage extension by using ISL's more users will have direct access to the satellite network, thus providing reduced signal propagation delay and improved signal quality. Given the potential benefits of ISL's system, it is of interest to determine the appropriate implementations for some potential ISL architectures. Summary of the selected ISL network architecture as supplied by NASA are listed. The projected high data rate requirements (greater than 400 Mbps) suggest that high frequency RF or optical implementations are natural approaches. Both RF and optical systems have their own merits and weaknesses which make the choice between them dependent on the specific application. Due to its relatively mature technology base, the implementation risk associated with RF (at least 32 GHz) is lower than that of the optical ISL's. However, the relatively large antenna size required by RF ISL's payload may cause real-estate problems on the host spacecraft. In addition, because of the frequency sharing (for duplex multiple channels communications) within the limited bandwidth allocated, RF ISL's are more susceptible to inter-system and inter-channel interferences. On the other hand, optical ISL's can offer interference-free transmission and compact sized payload. However, the extremely narrow beam widths (on the order of 10 micro-rad) associated with optical ISL's impose very stringent pointing, acquisition, and tracking requirements on the system. Even if the RF and optical systems are considered separately, questions still remain as to selection of RF frequency, direct versus coherent optical detection, etc. in implementing an ISL for a particular network architecture. These and other issues are studied.

Additive manufacturing of RF absorbers

NASA Astrophysics Data System (ADS)

Mills, Matthew S.

The ability of additive manufacturing techniques to fabricate integrated electromagnetic absorbers tuned for specific radio frequency bands within structural composites allows for unique combinations of mechanical and electromagnetic properties. These composites and films can be used for RF shielding of sensitive electromagnetic components through in-plane and out-of-plane RF absorption. Structural composites are a common building block of many commercial platforms. These platforms may be placed in situations in which there is a need for embedded RF absorbing properties along with structural properties. Instead of adding radar absorbing treatments to the external surface of existing structures, which adds increased size, weight and cost; it could prove to be advantageous to integrate the microwave absorbing properties directly into the composite during the fabrication process. In this thesis, a method based on additive manufacturing techniques of composites structures with prescribed electromagnetic loss, within the frequency range 1 to 26GHz, is presented. This method utilizes screen printing and nScrypt micro dispensing to pattern a carbon based ink onto low loss substrates. The materials chosen for this study will be presented, and the fabrication technique that these materials went through to create RF absorbing structures will be described. The calibration methods used, the modeling of the RF structures, and the applications in which this technology can be utilized will also be presented.

Frequency-agile wireless sensor networks

NASA Astrophysics Data System (ADS)

Arms, Steven W.; Townsend, Christopher P.; Churchill, David L.; Hamel, Michael J.; Galbreath, Jacob H.; Mundell, Steven W.

2004-07-01

Our goal was to demonstrate a wireless communications system capable of simultaneous, high speed data communications from a variety of sensors. We have previously reported on the design and application of 2 KHz data logging transceiver nodes, however, only one node may stream data at a time, since all nodes on the network use the same communications frequency. To overcome these limitations, second generation data logging transceivers were developed with software programmable radio frequency (RF) communications. Each node contains on-board memory (2 Mbytes), sensor excitation, instrumentation amplifiers with programmable gains & offsets, multiplexer, 16 bit A/D converter, microcontroller, and frequency agile, bi-directional, frequency shift keyed (FSK) RF serial data link. These systems are capable of continuous data transmission from 26 distinct nodes (902-928 MHz band, 75 kbaud). The system was demonstrated in a compelling structural monitoring application. The National Parks Service requested a means for continual monitoring and recording of sensor data from the Liberty Bell during a move to a new location (Philadelphia, October 2003). Three distinct, frequency agile, wireless sensing nodes were used to detect visible crack shear/opening micromotions, triaxial accelerations, and hairline crack tip strains. The wireless sensors proved to be useful in protecting the Liberty Bell.

Fabrication and RF characterization of zinc oxide based Film Bulk Acoustic Resonator

NASA Astrophysics Data System (ADS)

Patel, Raju; Bansal, Deepak; Agrawal, Vimal Kumar; Rangra, Kamaljit; Boolchandani, Dharmendar

2018-06-01

This work reports fabrication and characterization of Film Bulk Acoustic Resonator (FBAR) to improve the performance characteristics for RF filter and sensing application. Zinc oxide as a piezoelectric (PZE) material was deposited on an aluminum bottom electrode using an RF magnetron sputtering, at room temperature, and gold as top electrode for the resonator. Tetramethyl ammonium hydroxide (TMAH) setup was used for bulk silicon etching to make back side cavity to confine the acoustic signals. The transmission characteristics show that the FBARs have a central frequency at 1.77 GHz with a return loss of -10.7 dB.

30 nm T-gate enhancement-mode InAlN/AlN/GaN HEMT on SiC substrates for future high power RF applications

NASA Astrophysics Data System (ADS)

Murugapandiyan, P.; Ravimaran, S.; William, J.

2017-08-01

The DC and RF performance of 30 nm gate length enhancement mode (E-mode) InAlN/AlN/GaN high electron mobility transistor (HEMT) on SiC substrate with heavily doped source and drain region have been investigated using the Synopsys TCAD tool. The proposed device has the features of a recessed T-gate structure, InGaN back barrier and Al2O3 passivated device surface. The proposed HEMT exhibits a maximum drain current density of 2.1 A/mm, transconductance {g}{{m}} of 1050 mS/mm, current gain cut-off frequency {f}{{t}} of 350 GHz and power gain cut-off frequency {f}\\max of 340 GHz. At room temperature the measured carrier mobility (μ), sheet charge carrier density ({n}{{s}}) and breakdown voltage are 1580 cm2/(V \\cdot s), 1.9× {10}13 {{cm}}-2, and 10.7 V respectively. The superlatives of the proposed HEMTs are bewitching competitor or future sub-millimeter wave high power RF VLSI circuit applications.

Improved Drain Current Saturation and Voltage Gain in Graphene–on–Silicon Field Effect Transistors

PubMed Central

Song, Seung Min; Bong, Jae Hoon; Hwang, Wan Sik; Cho, Byung Jin

2016-01-01

Graphene devices for radio frequency (RF) applications are of great interest due to their excellent carrier mobility and saturation velocity. However, the insufficient current saturation in graphene field effect transistors (FETs) is a barrier preventing enhancements of the maximum oscillation frequency and voltage gain, both of which should be improved for RF transistors. Achieving a high output resistance is therefore a crucial step for graphene to be utilized in RF applications. In the present study, we report high output resistances and voltage gains in graphene-on-silicon (GoS) FETs. This is achieved by utilizing bare silicon as a supporting substrate without an insulating layer under the graphene. The GoSFETs exhibit a maximum output resistance of 2.5 MΩ∙μm, maximum intrinsic voltage gain of 28 dB, and maximum voltage gain of 9 dB. This method opens a new route to overcome the limitations of conventional graphene-on-insulator (GoI) FETs and subsequently brings graphene electronics closer to practical usage. PMID:27142861

On-Board Fiber-Optic Network Architectures for Radar and Avionics Signal Distribution

NASA Technical Reports Server (NTRS)

Alam, Mohammad F.; Atiquzzaman, Mohammed; Duncan, Bradley B.; Nguyen, Hung; Kunath, Richard

2000-01-01

Continued progress in both civil and military avionics applications is overstressing the capabilities of existing radio-frequency (RF) communication networks based on coaxial cables on board modem aircrafts. Future avionics systems will require high-bandwidth on- board communication links that are lightweight, immune to electromagnetic interference, and highly reliable. Fiber optic communication technology can meet all these challenges in a cost-effective manner. Recently, digital fiber-optic communication systems, where a fiber-optic network acts like a local area network (LAN) for digital data communications, have become a topic of extensive research and development. Although a fiber-optic system can be designed to transport radio-frequency (RF) signals, the digital fiber-optic systems under development today are not capable of transporting microwave and millimeter-wave RF signals used in radar and avionics systems on board an aircraft. Recent advances in fiber optic technology, especially wavelength division multiplexing (WDM), has opened a number of possibilities for designing on-board fiber optic networks, including all-optical networks for radar and avionics RF signal distribution. In this paper, we investigate a number of different novel approaches for fiber-optic transmission of on-board VHF and UHF RF signals using commercial off-the-shelf (COTS) components. The relative merits and demerits of each architecture are discussed, and the suitability of each architecture for particular applications is pointed out. All-optical approaches show better performance than other traditional approaches in terms of signal-to-noise ratio, power consumption, and weight requirements.

Real-time cavity simulator-based low-level radio-frequency test bench and applications for accelerators

NASA Astrophysics Data System (ADS)

Qiu, Feng; Michizono, Shinichiro; Miura, Takako; Matsumoto, Toshihiro; Liu, Na; Wibowo, Sigit Basuki

2018-03-01

A Low-level radio-frequency (LLRF) control systems is required to regulate the rf field in the rf cavity used for beam acceleration. As the LLRF system is usually complex, testing of the basic functions or control algorithms of this system in real time and in advance of beam commissioning is strongly recommended. However, the equipment necessary to test the LLRF system, such as superconducting cavities and high-power rf sources, is very expensive; therefore, we have developed a field-programmable gate array (FPGA)-based cavity simulator as a substitute for real rf cavities. Digital models of the cavity and other rf systems are implemented in the FPGA. The main components include cavity baseband models for the fundamental and parasitic modes, a mechanical model of the Lorentz force detuning, and a model of the beam current. Furthermore, in our simulator, the disturbance model used to simulate the power-supply ripples and microphonics is also carefully considered. Based on the presented cavity simulator, we have established an LLRF system test bench that can be applied to different cavity operational conditions. The simulator performance has been verified by comparison with real cavities in KEK accelerators. In this paper, the development and implementation of this cavity simulator is presented first, and the LLRF test bench based on the presented simulator is constructed. The results are then compared with those for KEK accelerators. Finally, several LLRF applications of the cavity simulator are illustrated.

Performance of a laser frequency comb calibration system with a high-resolution solar echelle spectrograph

NASA Astrophysics Data System (ADS)

Doerr, H.-P.; Kentischer, T. J.; Steinmetz, T.; Probst, R. A.; Franz, M.; Holzwarth, R.; Udem, Th.; Hänsch, T. W.; Schmidt, W.

2012-09-01

Laser frequency combs (LFC) provide a direct link between the radio frequency (RF) and the optical frequency regime. The comb-like spectrum of an LFC is formed by exact equidistant laser modes, whose absolute optical frequencies are controlled by RF-references such as atomic clocks or GPS receivers. While nowadays LFCs are routinely used in metrological and spectroscopic fields, their application in astronomy was delayed until recently when systems became available with a mode spacing and wavelength coverage suitable for calibration of astronomical spectrographs. We developed a LFC based calibration system for the high-resolution echelle spectrograph at the German Vacuum Tower Telescope (VTT), located at the Teide observatory, Tenerife, Canary Islands. To characterize the calibration performance of the instrument, we use an all-fiber setup where sunlight and calibration light are fed to the spectrograph by the same single-mode fiber, eliminating systematic effects related to variable grating illumination.

Black Phosphorus Flexible Thin Film Transistors at Gighertz Frequencies.

PubMed

Zhu, Weinan; Park, Saungeun; Yogeesh, Maruthi N; McNicholas, Kyle M; Bank, Seth R; Akinwande, Deji

2016-04-13

Black phosphorus (BP) has attracted rapidly growing attention for high speed and low power nanoelectronics owing to its compelling combination of tunable bandgap (0.3 to 2 eV) and high carrier mobility (up to ∼1000 cm(2)/V·s) at room temperature. In this work, we report the first radio frequency (RF) flexible top-gated (TG) BP thin-film transistors on highly bendable polyimide substrate for GHz nanoelectronic applications. Enhanced p-type charge transport with low-field mobility ∼233 cm(2)/V·s and current density of ∼100 μA/μm at VDS = -2 V were obtained from flexible BP transistor at a channel length L = 0.5 μm. Importantly, with optimized dielectric coating for air-stability during microfabrication, flexible BP RF transistors afforded intrinsic maximum oscillation frequency fMAX ∼ 14.5 GHz and unity current gain cutoff frequency fT ∼ 17.5 GHz at a channel length of 0.5 μm. Notably, the experimental fT achieved here is at least 45% higher than prior results on rigid substrate, which is attributed to the improved air-stability of fabricated BP devices. In addition, the high-frequency performance was investigated through mechanical bending test up to ∼1.5% tensile strain, which is ultimately limited by the inorganic dielectric film rather than the 2D material. Comparison of BP RF devices to other 2D semiconductors clearly indicates that BP offers the highest saturation velocity, an important metric for high-speed and RF flexible nanosystems.

Emerging and potential opportunities for 2D flexible nanoelectronics

NASA Astrophysics Data System (ADS)

Zhu, Weinan; Park, Saungeun; Akinwande, Deji

2016-05-01

The last 10 years have seen the emergence of two-dimensional (2D) nanomaterials such as graphene, transition metal dichalcogenides (TMDs), and black phosphorus (BP) among the growing portfolio of layered van der Waals thin films. Graphene, the prototypical 2D material has advanced rapidly in device, circuit and system studies that has resulted in commercial large-area applications. In this work, we provide a perspective of the emerging and potential translational applications of 2D materials including semiconductors, semimetals, and insulators that comprise the basic material set for diverse nanosystems. Applications include RF transceivers, smart systems, the so-called internet of things, and neurotechnology. We will review the DC and RF electronic performance of graphene and BP thin film transistors. 2D materials at sub-um channel length have so far enabled cut-off frequencies from baseband to 100GHz suitable for low-power RF and sub-THz concepts.

Numerical Study of HHFW Heating in FRC Plasmas

NASA Astrophysics Data System (ADS)

Ceccherini, Francesco; Galeotti, Laura; Brambilla, Marco; Dettrick, Sean; Yang, Xiaokang; TAE Team

2017-10-01

The TriAlpha Energy (TAE) code RF-Pisa is a Finite Larmor Radius (FLR) full wave code developed over the years to study RF heating in the Field Reversed Configuration (FRC) in both the ion and electron cyclotron regimes. The FLR approximation is perfectly adequate to address RF propagation and absorption at the fundamental and second harmonic frequencies (as in the minority heating scheme), but it is not able to describe higher order processes such as high-harmonic fast waves (HHFW). The latter ones have frequencies lying between the ion cyclotron and lower hybrid resonances and they may represent a viable path to develop an efficient method to deposit energy inside the FRC separatrix, as suggested by recent results obtained at NSTX. A significant upgrade of RF-Pisa to include HHFW has been undertaken. In particular, the so-called ``quasi local approximation'' originally proposed for toroidal geometries has been re-derived for the cylindrical geometry and a new HHFW version of RF-Pisa concurrent to the FLR version has been developed. Here we present the first results of the application of the new code to FRC equilibria and we discuss the features of the dispersion relations and the absorption processes which characterize this novel regime.

Impact of device engineering on analog/RF performances of tunnel field effect transistors

NASA Astrophysics Data System (ADS)

Vijayvargiya, V.; Reniwal, B. S.; Singh, P.; Vishvakarma, S. K.

2017-06-01

The tunnel field effect transistor (TFET) and its analog/RF performance is being aggressively studied at device architecture level for low power SoC design. Therefore, in this paper we have investigated the influence of the gate-drain underlap (UL) and different dielectric materials for the spacer and gate oxide on DG-TFET (double gate TFET) and its analog/RF performance for low power applications. Here, it is found that the drive current behavior in DG-TFET with a UL feature while implementing dielectric material for the spacer is different in comparison to that of DG-FET. Further, hetero gate dielectric-based DG-TFET (HGDG-TFET) is more resistive against drain-induced barrier lowering (DIBL) as compared to DG-TFET with high-k (HK) gate dielectric. Along with that, as compared to DG-FET, this paper also analyses the attributes of UL and dielectric material on analog/RF performance of DG-TFET in terms of transconductance (gm ), transconductance generation factor (TGF), capacitance, intrinsic resistance (Rdcr), cut-off frequency (F T), and maximum oscillation frequency (F max). The LK spacer-based HGDG-TFET with a gate-drain UL has the potential to improve the RF performance of device.

Radio Frequency Ultrasound Time Series Signal Analysis to Evaluate High-intensity Focused Ultrasound Lesion Formation Status in Tissue.

PubMed

Mobasheri, Saeedeh; Behnam, Hamid; Rangraz, Parisa; Tavakkoli, Jahan

2016-01-01

High-intensity focused ultrasound (HIFU) is a novel treatment modality used by scientists and clinicians in the recent decades. This modality has had a great and significant success as a noninvasive surgery technique applicable in tissue ablation therapy and cancer treatment. In this study, radio frequency (RF) ultrasound signals were acquired and registered in three stages of before, during, and after HIFU exposures. Different features of RF time series signals including the sum of amplitude spectrum in the four quarters of the frequency range, the slope, and intercept of the best-fit line to the entire power spectrum and the Shannon entropy were utilized to distinguish between the HIFU-induced thermal lesion and the normal tissue. We also examined the RF data, frame by frame to identify exposure effects on the formation and characteristics of a HIFU thermal lesion at different time steps throughout the treatment. The results obtained showed that the spectrum frequency quarters and the slope and intercept of the best fit line to the entire power spectrum both increased two times during the HIFU exposures. The Shannon entropy, however, decreased after the exposures. In conclusion, different characteristics of RF time series signal possess promising features that can be used to characterize ablated and nonablated tissues and to distinguish them from each other in a quasi-quantitative fashion.

Bragg-cell receiver study

NASA Technical Reports Server (NTRS)

Wilson, Lonnie A.

1987-01-01

Bragg-cell receivers are employed in specialized Electronic Warfare (EW) applications for the measurement of frequency. Bragg-cell receiver characteristics are fully characterized for simple RF emitter signals. This receiver is early in its development cycle when compared to the IFM receiver. Functional mathematical models are derived and presented in this report for the Bragg-cell receiver. Theoretical analysis is presented and digital computer signal processing results are presented for the Bragg-cell receiver. Probability density function analysis are performed for output frequency. Probability density function distributions are observed to depart from assumed distributions for wideband and complex RF signals. This analysis is significant for high resolution and fine grain EW Bragg-cell receiver systems.

RF Frequency Oscillations in the Early Stages of Vacuum Arc Collapse

NASA Technical Reports Server (NTRS)

Griffin, Steven T.; Thio, Y. C. Francis

2003-01-01

RF frequency oscillations may be produced in a typical capacitive charging / discharging pulsed power system. These oscillations may be benign, parasitic, destructive or crucial to energy deposition. In some applications, proper damping of oscillations may be critical to proper plasma formation. Because the energy deposited into the plasma is a function of plasma and circuit conditions, the entire plasma / circuit system needs to be considered as a unit To accomplish this, the initiation of plasma is modeled as a time-varying, non-linear element in a circuit analysis model. The predicted spectra are compared to empirical power density spectra including those obtained from vacuum arcs.

The Effects of Postprocessing on Physical and Solution Deposition of Complex Oxide Thin Films for Tunable Applications

DTIC Science & Technology

2016-02-01

BST barium strontium titanate εr dielectric constant MIM metal /insulator/ metal MOSD metal organic spin deposition PtSi platinum silicide RF...improvement. In addition, BST films processed via solution metal organic spin deposition, which yield a lower dielectric range of 150–335, also...layers. This report details how we used solution and physical deposition to fabricate thin films via radio frequency (RF) sputtering and metal

Frequency mixer having ferromagnetic film

DOEpatents

Khitun, Alexander; Roshchin, Igor V.; Galatsis, Kosmas; Bao, Mingqiang; Wang, Kang L.

2016-03-29

A frequency conversion device, which may include a radiofrequency (RF) mixer device, includes a substrate and a ferromagnetic film disposed over a surface of the substrate. An insulator is disposed over the ferromagnetic film and at least one microstrip antenna is disposed over the insulator. The ferromagnetic film provides a non-linear response to the frequency conversion device. The frequency conversion device may be used for signal mixing and amplification. The frequency conversion device may also be used in data encryption applications.

Towards 5G: A Photonic Based Millimeter Wave Signal Generation for Applying in 5G Access Fronthaul.

PubMed

Alavi, S E; Soltanian, M R K; Amiri, I S; Khalily, M; Supa'at, A S M; Ahmad, H

2016-01-27

5G communications require a multi Gb/s data transmission in its small cells. For this purpose millimeter wave (mm-wave) RF signals are the best solutions to be utilized for high speed data transmission. Generation of these high frequency RF signals is challenging in electrical domain therefore photonic generation of these signals is more studied. In this work, a photonic based simple and robust method for generating millimeter waves applicable in 5G access fronthaul is presented. Besides generating of the mm-wave signal in the 60 GHz frequency band the radio over fiber (RoF) system for transmission of orthogonal frequency division multiplexing (OFDM) with 5 GHz bandwidth is presented. For the purpose of wireless transmission for 5G application the required antenna is designed and developed. The total system performance in one small cell was studied and the error vector magnitude (EVM) of the system was evaluated.

Towards 5G: A Photonic Based Millimeter Wave Signal Generation for Applying in 5G Access Fronthaul

PubMed Central

Alavi, S. E.; Soltanian, M. R. K.; Amiri, I. S.; Khalily, M.; Supa’at, A. S. M.; Ahmad, H.

2016-01-01

5G communications require a multi Gb/s data transmission in its small cells. For this purpose millimeter wave (mm-wave) RF signals are the best solutions to be utilized for high speed data transmission. Generation of these high frequency RF signals is challenging in electrical domain therefore photonic generation of these signals is more studied. In this work, a photonic based simple and robust method for generating millimeter waves applicable in 5G access fronthaul is presented. Besides generating of the mm-wave signal in the 60 GHz frequency band the radio over fiber (RoF) system for transmission of orthogonal frequency division multiplexing (OFDM) with 5 GHz bandwidth is presented. For the purpose of wireless transmission for 5G application the required antenna is designed and developed. The total system performance in one small cell was studied and the error vector magnitude (EVM) of the system was evaluated. PMID:26814621

Towards 5G: A Photonic Based Millimeter Wave Signal Generation for Applying in 5G Access Fronthaul

NASA Astrophysics Data System (ADS)

Alavi, S. E.; Soltanian, M. R. K.; Amiri, I. S.; Khalily, M.; Supa'At, A. S. M.; Ahmad, H.

2016-01-01

5G communications require a multi Gb/s data transmission in its small cells. For this purpose millimeter wave (mm-wave) RF signals are the best solutions to be utilized for high speed data transmission. Generation of these high frequency RF signals is challenging in electrical domain therefore photonic generation of these signals is more studied. In this work, a photonic based simple and robust method for generating millimeter waves applicable in 5G access fronthaul is presented. Besides generating of the mm-wave signal in the 60 GHz frequency band the radio over fiber (RoF) system for transmission of orthogonal frequency division multiplexing (OFDM) with 5 GHz bandwidth is presented. For the purpose of wireless transmission for 5G application the required antenna is designed and developed. The total system performance in one small cell was studied and the error vector magnitude (EVM) of the system was evaluated.

Optimizing electrical conductivity and optical transparency of IZO thin film deposited by radio frequency (RF) magnetron sputtering

NASA Astrophysics Data System (ADS)

Zhang, Lei

Transparent conducting oxide (TCO) thin films of In2O3, SnO2, ZnO, and their mixtures have been extensively used in optoelectronic applications such as transparent electrodes in solar photovoltaic devices. In this project I deposited amorphous indium-zinc oxide (IZO) thin films by radio frequency (RF) magnetron sputtering from a In2O3-10 wt.% ZnO sintered ceramic target to optimize the RF power, argon gas flowing rate, and the thickness of film to reach the maximum conductivity and transparency in visible spectrum. The results indicated optimized conductivity and transparency of IZO thin film is closer to ITO's conductivity and transparency, and is even better when the film was deposited with one specific tilted angle. National Science Foundation (NSF) MRSEC program at University of Nebraska Lincoln, and was hosted by Professor Jeff Shields lab.

Broadening the optical bandwidth of quantum cascade lasers using RF noise current perturbations.

PubMed

Pinto, Tomás H P; Kirkbride, James M R; Ritchie, Grant A D

2018-04-15

We report on the broadening of the optical bandwidth of a distributed feedback quantum cascade laser (QCL) caused by the application of radio frequency (RF) noise to the injection current. The broadening is quantified both via Lamb-dip spectroscopy and the frequency noise power spectral density (PSD). The linewidth of the unperturbed QCL (emitting at ∼5.3  μm) determined by Lamb-dip spectroscopy is 680±170  kHz, and is in reasonable agreement with the linewidth of 460±40  kHz estimated by integrating the PSD measured under the same laser operating conditions. Measurements with both techniques reveal that by mixing the driving current with broadband RF noise the laser lineshape was reproducibly broadened up to ca 6 MHz with an increasing Gaussian contribution. The effects of linewidth broadening are then demonstrated in the two-color coherent transient spectra of nitric oxide.

Mixed-signal 0.18μm CMOS and SiGe BiCMOS foundry technologies for ROIC applications

NASA Astrophysics Data System (ADS)

Kar-Roy, Arjun; Howard, David; Racanelli, Marco; Scott, Mike; Hurwitz, Paul; Zwingman, Robert; Chaudhry, Samir; Jordan, Scott

2010-10-01

Today's readout integrated-circuits (ROICs) require a high level of integration of high performance analog and low power digital logic. TowerJazz offers a commercial 0.18μm CMOS technology platform for mixed-signal, RF, and high performance analog applications which can be used for ROIC applications. The commercial CA18HD dual gate oxide 1.8V/3.3V and CA18HA dual gate oxide 1.8V/5V RF/mixed signal processes, consisting of six layers of metallization, have high density stacked linear MIM capacitors, high-value resistors, triple-well isolation and thick top aluminum metal. The CA18HA process also has scalable drain extended LDMOS devices, up to 40V Vds, for high-voltage sensor applications, and high-performance bipolars for low noise requirements in ROICs. Also discussed are the available features of the commercial SBC18 SiGe BiCMOS platform with SiGe NPNs operating up to 200/200GHz (fT/fMAX frequencies in manufacturing and demonstrated to 270 GHz fT, for reduced noise and integrated RF capabilities which could be used in ROICs. Implementation of these technologies in a thick film SOI process for integrated RF switch and power management and the availability of high fT vertical PNPs to enable complementary BiCMOS (CBiCMOS), for RF enabled ROICs, are also described in this paper.

Demonstration of Space Optical Transmitter Development for Multiple High Frequency Bands

NASA Technical Reports Server (NTRS)

Nguyen, Hung; Simons, Rainee; Wintucky, Edwin; Freeman, Jon

2013-01-01

As the demand for multiple radio frequency carrier bands continues to grow in space communication systems, the design of a cost-effective compact optical transmitter that is capable of transmitting selective multiple RF bands is of great interest, particularly for NASA Space Communications Network Programs. This paper presents experimental results that demonstrate the feasibility of a concept based on an optical wavelength division multiplexing (WDM) technique that enables multiple microwave bands with different modulation formats and bandwidths to be combined and transmitted all in one unit, resulting in many benefits to space communication systems including reduced size, weight and complexity with corresponding savings in cost. Experimental results will be presented including the individual received RF signal power spectra for the L, C, X, Ku, Ka, and Q frequency bands, and measurements of the phase noise associated with each RF frequency. Also to be presented is a swept RF frequency power spectrum showing simultaneous multiple RF frequency bands transmission. The RF frequency bands in this experiment are among those most commonly used in NASA space environment communications.

rf measurements and tuning of the 750 MHz radio frequency quadrupole

NASA Astrophysics Data System (ADS)

Koubek, Benjamin; Grudiev, Alexej; Timmins, Marc

2017-08-01

In the framework of the program on medical applications a compact 750 MHz RFQ has been designed and built to be used as an injector for a hadron therapy linac. This RFQ was designed to accelerate protons to an energy of 5 MeV within only 2 m length. It is divided into four segments and equipped with 32 tuners in total. The length of the RFQ corresponds to 5 λ which is considered to be close to the limit for field adjustment using only piston tuners. Moreover the high frequency, which is about double the frequency of existing RFQs, results in a sensitive structure and requires careful tuning. In this paper we present the tuning algorithm, the tuning procedure and rf measurements of the RFQ.

Acoustic Wave Filter Technology-A Review.

PubMed

Ruppel, Clemens C W

2017-09-01

Today, acoustic filters are the filter technology to meet the requirements with respect to performance dictated by the cellular phone standards and their form factor. Around two billion cellular phones are sold every year, and smart phones are of a very high percentage of approximately two-thirds. Smart phones require a very high number of filter functions ranging from the low double-digit range up to almost triple digit numbers in the near future. In the frequency range up to 1 GHz, surface acoustic wave (SAW) filters are almost exclusively employed, while in the higher frequency range, bulk acoustic wave (BAW) and SAW filters are competing for their shares. Prerequisites for the success of acoustic filters were the availability of high-quality substrates, advanced and highly reproducible fabrication technologies, optimum filter techniques, precise simulation software, and advanced design tools that allow the fast and efficient design according to customer specifications. This paper will try to focus on innovations leading to high volume applications of intermediate frequency (IF) and radio frequency (RF) acoustic filters, e.g., TV IF filters, IF filters for cellular phones, and SAW/BAW RF filters for the RF front-end of cellular phones.

The electromagnetic environment of Magnetic Resonance Imaging systems. Occupational exposure assessment reveals RF harmonics

NASA Astrophysics Data System (ADS)

Gourzoulidis, G.; Karabetsos, E.; Skamnakis, N.; Kappas, C.; Theodorou, K.; Tsougos, I.; Maris, T. G.

2015-09-01

Magnetic Resonance Imaging (MRI) systems played a crucial role in the postponement of the former occupational electromagnetic fields (EMF) European Directive (2004/40/EC) and in the formation of the latest exposure limits adopted in the new one (2013/35/EU). Moreover, the complex MRI environment will be finally excluded from the implementation of the new occupational limits, leading to an increased demand for Occupational Health and Safety (OHS) surveillance. The gradient function of MRI systems and the application of the RF excitation frequency result in low and high frequency exposures, respectively. This electromagnetic field exposure, in combination with the increased static magnetic field exposure, makes the MRI environment a unique case of combined EMF exposure. The electromagnetic field levels in close proximity of different MRI systems have been assessed at various frequencies. Quality Assurance (QA) & safety issues were also faced. Preliminary results show initial compliance with the forthcoming limits in each different frequency band, but also revealed peculiar RF harmonic components, of no safety concern, to the whole range detected (20-1000MHz). Further work is needed in order to clarify their origin and characteristics.

Optimization of L-shaped tunneling field-effect transistor for ambipolar current suppression and Analog/RF performance enhancement

NASA Astrophysics Data System (ADS)

Li, Cong; Zhao, Xiaolong; Zhuang, Yiqi; Yan, Zhirui; Guo, Jiaming; Han, Ru

2018-03-01

L-shaped tunneling field-effect transistor (LTFET) has larger tunnel area than planar TFET, which leads to enhanced on-current ION . However, LTFET suffers from severe ambipolar behavior, which needs to be further optimized for low power and high-frequency applications. In this paper, both hetero-gate-dielectric (HGD) and lightly doped drain (LDD) structures are introduced into LTFET for suppression of ambipolarity and improvement of analog/RF performance of LTFET. Current-voltage characteristics, the variation of energy band diagrams, distribution of band-to-band tunneling (BTBT) generation and distribution of electric field are analyzed for our proposed HGD-LDD-LTFET. In addition, the effect of LDD on the ambipolar behavior of LTFET is investigated, the length and doping concentration of LDD is also optimized for better suppression of ambipolar current. Finally, analog/RF performance of HGD-LDD-LTFET are studied in terms of gate-source capacitance, gate-drain capacitance, cut-off frequency, and gain bandwidth production. TCAD simulation results show that HGD-LDD-LTFET not only drastically suppresses ambipolar current but also improves analog/RF performance compared with conventional LTFET.

Near field magnetic communications for helmet-mounted display applications

NASA Astrophysics Data System (ADS)

Field, Mark; Sailer, Alan

2005-05-01

Helmet-mounted displays need a data feed that is typically provided by a cable or RF wireless data link to an external computer. In defense applications these solutions are problematic: a cable gets in the way and restricts use and emergency egress, while an RF wireless link can be detected at some distance giving away position and is susceptible to jamming. What is required is an alternative wireless technology that is low power, extremely localized and difficult to detect or jam. Near field magnetic communications is one possible alternative to RF communications that may fulfill these needs. This technology uses a time varying magnetic field to carry information, and is only useable over small distances of order six feet. This is expected to have significant advantages for particular applications: notably power requirements and security compared with RF wireless links. The power stored in a magnetic field falls off as 1/r6, compared with 1/r2 for RF, which means that all the power is localized around the transmitter. By having a physically small communications region around each platform or user, a large bandwidth can be guaranteed by allowing the reuse of the frequency spectrum outside the immediate vicinity. It also confers security on the data-link, as the signal is undetectable beyond the short range of the system.

The RF-powered surface wave sensor oscillator--a successful alternative to passive wireless sensing.

PubMed

Avramov, Ivan D

2004-09-01

A novel, passive wireless surface acoustic wave (SAW) sensor providing a highly coherent measurand proportional frequency, frequency modulated (FM) with identification (ID) data and immune to interference with multiple-path signals is described. The sensor is appropriate for bandwidth-limited applications requiring high-frequency accuracy. It comprises a low-power oscillator, stabilized with the sensing SAW resonator and powered by the rectified radio frequency (RF) power of the interrogating signal received by an antenna on the sensor part. A few hundred microwatts of direct current (DC) power are enough to power the sensor oscillator and ID modulation circuit and achieve stable operation at 1.0 and 2.49 GHz. Reliable sensor interrogation was achieved over a distance of 0.45 m from a SAW-based interrogation unit providing 50 mW of continuous RF power at 915 MHz. The -30 to -35 dBm of returned sensor power was enough to receive the sensor signal over a long distance and through several walls with a simple superheterodyne FM receiver converting the sensor signal to a low measurand proportional intermediate frequency and retrieving the ID data through FM detection. Different sensor implementations, including continuous and pulsed power versions and the possibility of transmitting data from several measurands with a single sensor, are discussed.

Biasable, Balanced, Fundamental Submillimeter Monolithic Membrane Mixer

NASA Technical Reports Server (NTRS)

Siegel, Peter; Schlecht, Erich; Mehdi, Imran; Gill, John; Velebir, James; Tsang, Raymond; Dengler, Robert; Lin, Robert

2010-01-01

This device is a biasable, submillimeter-wave, balanced mixer fabricated using JPL s monolithic membrane process a simplified version of planar membrane technology. The primary target application is instrumentation used for analysis of atmospheric constituents, pressure, temperature, winds, and other physical and chemical properties of the atmospheres of planets and comets. Other applications include high-sensitivity gas detection and analysis. This innovation uses a balanced configuration of two diodes allowing the radio frequency (RF) signal and local oscillator (LO) inputs to be separated. This removes the need for external diplexers that are inherently narrowband, bulky, and require mechanical tuning to change frequency. Additionally, this mixer uses DC bias-ability to improve its performance and versatility. In order to solve problems relating to circuit size, the GaAs membrane process was created. As much of the circuitry as possible is fabricated on-chip, making the circuit monolithic. The remainder of the circuitry is precision-machined into a waveguide block that holds the GaAs circuit. The most critical alignments are performed using micron-scale semiconductor technology, enabling wide bandwidth and high operating frequencies. The balanced mixer gets superior performance with less than 2 mW of LO power. This can be provided by a simple two-stage multiplier chain following an amplifier at around 90 GHz. Further, the diodes are arranged so that they can be biased. Biasing pushes the diodes closer to their switching voltage, so that less LO power is required to switch the diodes on and off. In the photo, the diodes are at the right end of the circuit. The LO comes from the waveguide at the right into a reduced-height section containing the diodes. Because the diodes are in series to the LO signal, they are both turned on and off simultaneously once per LO cycle. Conversely, the RF signal is picked up from the RF waveguide by the probe at the left, and flows rightward to the diodes. Because the RF is in a quasi- TEM (suspended, microstrip-like) mode, it impinges on the diodes in an anti-parallel mode that does not couple to the waveguide mode. This isolates the LO and RF signals. This operation is similar to a cross-bar mixer used at low frequencies, except the RF signal enters through the back-short end of the waveguide rather than through the side. The RF probe also conveys the down-converted intermediate frequency (IF) signal out to an off-chip circuit board through a simple LC low-pass filter to the left as indicated. The bias is brought to the diodes through a bypass capacitor at the top.

Multi-Channel RF System for MRI-Guided Transurethral Ultrasound Thermal Therapy

NASA Astrophysics Data System (ADS)

Yak, Nicolas; Asselin, Matthew; Chopra, Rajiv; Bronskill, Michael

2009-04-01

MRI-guided transurethral ultrasound thermal therapy is an approach to treating localized prostate cancer which targets precise deposition of thermal energy within a confined region of the gland. This treatment requires a system incorporating a heating applicator with multiple planar ultrasound transducers and associated RF electronics to control individual elements independently in order to achieve accurate 3D treatment. We report the design, construction, and characterization of a prototype multi-channel system capable of controlling 16 independent RF signals for a 16-element heating applicator. The main components are a control computer, microcontroller, and a 16-channel signal generator with 16 amplifiers, each incorporating a low-pass filter and transmitted/reflected power detection circuit. Each channel can deliver from 0.5 to 10 W of electrical power and good linearity from 3 to 12 MHz. Harmonic RF signals near the Larmor frequency of a 1.5 T MRI were measured to be below -30 dBm and heating experiments within the 1.5 T MR system showed no significant decrease in SNR of the temperature images. The frequency and power for all 16 channels could be changed in less than 250 ms, which was sufficiently rapid for proper performance of the control algorithms. A common backplane design was chosen which enabled an inexpensive, modular approach for each channel resulting in an overall system with minimal footprint.

Multipactor susceptibility on a dielectric with two carrier frequencies

NASA Astrophysics Data System (ADS)

Iqbal, Asif; Verboncoeur, John; Zhang, Peng

2018-04-01

This work investigates multipactor discharge on a single dielectric surface with two carrier frequencies of an rf electric field. We use Monte Carlo simulations and analytical calculations to obtain susceptibility diagrams in terms of the rf electric field and normal electric field due to the residual charge on the dielectric. It is found that in contrast to the single frequency case, in general, the presence of a second carrier frequency of the rf electric field increases the threshold of the magnitude of the rf electric field to initiate multipactor. The effects of the relative strength and phase, and the frequency separation of the two carrier frequencies are examined. The conditions to minimize mulitpactor are derived.

Effects of BOX engineering on analogue/RF and circuit performance of InGaAs-OI-Si MOSFET

NASA Astrophysics Data System (ADS)

Maity, Subir Kr.; Pandit, Soumya

2017-11-01

InGaAs is an attractive choice as alternate channel material in n-channel metal oxide semiconductor transistor for high-performance applications. However, electrostatic integrity of such device is poor. In this paper, we present a comprehensive technology computer-aided design simulation-based study of the effect of scaling the thickness of the buried oxide (BOX) region and varying the dielectric constant of BOX material on the electrostatic integrity, analogue/radio frequency (RF) performance and circuit performance of InGaAs-on-Insulator device. Device with thin BOX layer gives better drain-induced barrier lowering performance which enhances output resistance. The carrier mobility remains almost constant with thinning of BOX layer up to certain value. By lowering the dielectric constant of the BOX material, it is further possible to improve the analogue and RF performance. Effect of BOX thickness scaling and role of BOX dielectric material on gain-frequency response of common source amplifier is also studied. It is observed that frequency response of the amplifier improves for thin BOX and with low dielectric constant-based material.

High output lamp with high brightness

DOEpatents

Kirkpatrick, Douglas A.; Bass, Gary K.; Copsey, Jesse F.; Garber, Jr., William E.; Kwong, Vincent H.; Levin, Izrail; MacLennan, Donald A.; Roy, Robert J.; Steiner, Paul E.; Tsai, Peter; Turner, Brian P.

2002-01-01

An ultra bright, low wattage inductively coupled electrodeless aperture lamp is powered by a solid state RF source in the range of several tens to several hundreds of watts at various frequencies in the range of 400 to 900 MHz. Numerous novel lamp circuits and components are disclosed including a wedding ring shaped coil having one axial and one radial lead, a high accuracy capacitor stack, a high thermal conductivity aperture cup and various other aperture bulb configurations, a coaxial capacitor arrangement, and an integrated coil and capacitor assembly. Numerous novel RF circuits are also disclosed including a high power oscillator circuit with reduced complexity resonant pole configuration, parallel RF power FET transistors with soft gate switching, a continuously variable frequency tuning circuit, a six port directional coupler, an impedance switching RF source, and an RF source with controlled frequency-load characteristics. Numerous novel RF control methods are disclosed including controlled adjustment of the operating frequency to find a resonant frequency and reduce reflected RF power, controlled switching of an impedance switched lamp system, active power control and active gate bias control.

Low voltage driven RF MEMS capacitive switch using reinforcement for reduced buckling

NASA Astrophysics Data System (ADS)

Bansal, Deepak; Bajpai, Anuroop; Kumar, Prem; Kaur, Maninder; Kumar, Amit; Chandran, Achu; Rangra, Kamaljit

2017-02-01

Variation in actuation voltage for RF MEMS switches is observed as a result of stress-generated buckling of MEMS structures. Large voltage driven RF-MEMS switches are a major concern in space bound communication applications. In this paper, we propose a low voltage driven RF MEMS capacitive switch with the introduction of perforations and reinforcement. The performance of the fabricated switch is compared with conventional capacitive RF MEMS switches. The pull-in voltage of the switch is reduced from 70 V to 16.2 V and the magnitude of deformation is reduced from 8 µm to 1 µm. The design of the reinforcement frame enhances the structural stiffness by 46 % without affecting the high frequency response of the switch. The measured isolation and insertion loss of the reinforced switch is more than 20 dB and 0.4 dB over the X band range.

Radiofrequency Heating Pathways for Gold Nanoparticles

PubMed Central

Collins, C. B.; McCoy, R. S.; Ackerson, B. J.; Collins, G. J.

2015-01-01

This feature article reviews the thermal dissipation of nanoscopic gold under radiofrequency (RF) irradiation. It also presents previously unpublished data addressing obscure aspects of this phenomenon. While applications in biology motivated initial investigation of RF heating of gold nanoparticles, recent controversy concerning whether thermal effects can be attributed to nanoscopic gold highlight the need to understand the involved mechanism or mechanisms of heating. Both the nature of the particle and the nature of the RF field influence heating. Aspects of nanoparticle chemistry and physics, including the hydrodynamic diameter of the particle, the oxidation state and related magnetism of the core, and the chemical nature of the ligand shell may all strongly influence to what extent a nanoparticle heats in an RF field. Aspects of RF include: power, frequency and antenna designs that emphasize relative strength of magnetic or electric fields, and also influence the extent to which a gold nanoparticle heats in RF. These nanoparticle and RF properties are analysed in the context of three heating mechanisms proposed to explain gold nanoparticle heating in an RF field. This article also makes a critical analysis of the existing literature in the context of the nanoparticle preparations, RF structure, and suggested mechanisms in previously reported experiments. PMID:24962620

Radiofrequency heating of nanomaterials for cancer treatment: Progress, controversies, and future development

NASA Astrophysics Data System (ADS)

Liu, Xiaoming; Chen, Hui-jiuan; Chen, Xiaodong; Alfadhl, Yasir; Yu, Junsheng; Wen, Dongsheng

2015-03-01

In recent years, the application of nanomaterials to biological and biomedicine areas has attracted intensive interest. One of the hot topics is the nanomaterial mediated radiofrequency (RF) hyperthermia or ablation, i.e., using RF fields/waves to heat tumor tissues treated with nanomaterials to destroy cancerous cells while minimizing the side-heating effect. However, there are currently many contradictive results reported concerning the heating effect of nanomaterials under a RF field. This paper provided a comprehensive review to nanomaterial mediated RF ablation from both experimental and theoretical aspects. Three heating mechanisms were discussed, i.e., laser heating, magnetic field heating, and electric field heating in RF spectrum, with the focus on the last one. The results showed that while diluted pure metallic nanoparticles could be heated significantly by a laser through the surface plasmon resonance, they cannot be easily heated by a RF electric field. Further studies are proposed focusing on nanoparticle structure and morphology, electromagnetic frequency and localized heating effect to pave the way for future development.

The Value Estimation of an HFGW Frequency Time Standard for Telecommunications Network Optimization

NASA Astrophysics Data System (ADS)

Harper, Colby; Stephenson, Gary

2007-01-01

The emerging technology of gravitational wave control is used to augment a communication system using a development roadmap suggested in Stephenson (2003) for applications emphasized in Baker (2005). In the present paper consideration is given to the value of a High Frequency Gravitational Wave (HFGW) channel purely as providing a method of frequency and time reference distribution for use within conventional Radio Frequency (RF) telecommunications networks. Specifically, the native value of conventional telecommunications networks may be optimized by using an unperturbed frequency time standard (FTS) to (1) improve terminal navigation and Doppler estimation performance via improved time difference of arrival (TDOA) from a universal time reference, and (2) improve acquisition speed, coding efficiency, and dynamic bandwidth efficiency through the use of a universal frequency reference. A model utilizing a discounted cash flow technique provides an estimation of the additional value using HFGW FTS technology could bring to a mixed technology HFGW/RF network. By applying a simple net present value analysis with supporting reference valuations to such a network, it is demonstrated that an HFGW FTS could create a sizable improvement within an otherwise conventional RF telecommunications network. Our conservative model establishes a low-side value estimate of approximately 50B USD Net Present Value for an HFGW FTS service, with reasonable potential high-side values to significant multiples of this low-side value floor.

TDR method for determine IC's parameters

NASA Astrophysics Data System (ADS)

Timoshenkov, V.; Rodionov, D.; Khlybov, A.

2016-12-01

Frequency domain simulation is a widely used approach for determine integrated circuits parameters. This approach can be found in most of software tools used in IC industry. Time domain simulation approach shows intensive usage last years due to some advantages. In particular it applicable for analysis of nonlinear and nonstationary systems where frequency domain is inapplicable. Resolution of time domain systems allow see heterogeneities on distance 1mm, determine it parameters and properties. Authors used approach based on detecting reflected signals from heterogeneities - time domain reflectometry (TDR). Field effect transistor technology scaling up to 30-60nm gate length and 10nm gate dielectric, heterojunction bi-polar transistors with 10-30nm base width allows fabricate digital IC's with 20GHz clock frequency and RF-IC's with tens GHz bandwidth. Such devices and operation speed suppose transit signal by use microwave lines. There are local heterogeneities can be found inside of the signal path due to connections between different parts of signal lines (stripe line-RF-connector pin, stripe line - IC package pin). These heterogeneities distort signals that cause bandwidth decrease for RF-devices. Time domain research methods of transmission and reflected signals give the opportunities to determine heterogeneities, it properties, parameters and built up equivalent circuits. Experimental results are provided and show possibility for inductance and capacitance measurement up to 25GHz. Measurements contains result of signal path research on IC and printed circuit board (PCB) used for 12GHz RF chips. Also dielectric constant versus frequency was measured up to 35GHz.

[Development of RF coil of permanent magnet mini-magnetic resonance imager and mouse imaging experiments].

PubMed

Hou, Shulian; Xie, Huantong; Chen, Wei; Wang, Guangxin; Zhao, Qiang; Li, Shiyu

2014-10-01

In the development of radio frequency (RF) coils for better quality of the mini-type permanent magnetic resonance imager for using in the small animal imaging, the solenoid RF coil has a special advantage for permanent magnetic system based on analyses of various types.of RF coils. However, it is not satisfied for imaging if the RF coils are directly used. By theoretical analyses of the magnetic field properties produced from the solenoid coil, the research direction was determined by careful studies to raise further the uniformity of the magnetic field coil, receiving coil sensitivity for signals and signal-to-noise ratio (SNR). The method had certain advantages and avoided some shortcomings of the other different coil types, such as, birdcage coil, saddle shaped coil and phased array coil by using the alloy materials (from our own patent). The RF coils were designed, developed and made for keeled applicable to permanent magnet-type magnetic resonance imager, multi-coil combination-type, single-channel overall RF receiving coil, and applied for a patent. Mounted on three instruments (25 mm aperture, with main magnetic field strength of 0.5 T or 1.5 T, and 50 mm aperture, with main magnetic field strength of 0.48 T), we performed experiments with mice, rats, and nude mice bearing tumors. The experimental results indicated that the RF receiving coil was fully applicable to the permanent magnet-type imaging system.

Flexible diodes for radio frequency (RF) electronics: a materials perspective

NASA Astrophysics Data System (ADS)

Semple, James; Georgiadou, Dimitra G.; Wyatt-Moon, Gwenhivir; Gelinck, Gerwin; Anthopoulos, Thomas D.

2017-12-01

Over the last decade, there has been increasing interest in transferring the research advances in radiofrequency (RF) rectifiers, the quintessential element of the chip in the RF identification (RFID) tags, obtained on rigid substrates onto plastic (flexible) substrates. The growing demand for flexible RFID tags, wireless communications applications and wireless energy harvesting systems that can be produced at a low-cost is a key driver for this technology push. In this topical review, we summarise recent progress and status of flexible RF diodes and rectifying circuits, with specific focus on materials and device processing aspects. To this end, different families of materials (e.g. flexible silicon, metal oxides, organic and carbon nanomaterials), manufacturing processes (e.g. vacuum and solution processing) and device architectures (diodes and transistors) are compared. Although emphasis is placed on performance, functionality, mechanical flexibility and operating stability, the various bottlenecks associated with each technology are also addressed. Finally, we present our outlook on the commercialisation potential and on the positioning of each material class in the RF electronics landscape based on the findings summarised herein. It is beyond doubt that the field of flexible high and ultra-high frequency rectifiers and electronics as a whole will continue to be an active area of research over the coming years.

Investigations and Applications of Field- and Photo-emitted Electron Beams from a Radio Frequency Gun

DOE Office of Scientific and Technical Information (OSTI.GOV)

Panuganti, SriHarsha

Production of quality electron bunches using e cient ways of generation is a crucial aspect of accelerator technology. Radio frequency electron guns are widely used to generate and rapidly accelerate electron beams to relativistic energies. In the current work, we primarily study the charge generation processes of photoemission and eld emission inside an RF gun installed at Fermilab's High Brightness Electron Source Laboratory (HBESL). Speci cally, we study and characterize second-order nonlinear photoemission from a Cesium Telluride (Cs 2Te) semiconductor photocathode, and eld emission from carbon based cathodes including diamond eld emission array (DFEA) and carbon nanotube (CNT) cathodes locatedmore » in the RF gun's cavity. Finally, we discuss the application experiments conducted at the facility to produce soft x-rays via inverse Compton scattering (ICS), and to generate uniformly lled ellipsoidal bunches and temporally shaped electron beams from the Cs 2Te photocathode.« less

Radiofrequency heating pathways for gold nanoparticles.

PubMed

Collins, C B; McCoy, R S; Ackerson, B J; Collins, G J; Ackerson, C J

2014-08-07

This feature article reviews the thermal dissipation of nanoscopic gold under radiofrequency (RF) irradiation. It also presents previously unpublished data addressing obscure aspects of this phenomenon. While applications in biology motivated initial investigation of RF heating of gold nanoparticles, recent controversy concerning whether thermal effects can be attributed to nanoscopic gold highlight the need to understand the involved mechanism or mechanisms of heating. Both the nature of the particle and the nature of the RF field influence heating. Aspects of nanoparticle chemistry which may affect thermal dissipation include the hydrodynamic diameter of the particle, the oxidation state and related magnetism of the core, and the chemical nature of the ligand shell. Aspects of RF which may affect thermal dissipation include power, frequency and antenna designs that emphasize relative strength of magnetic or electric fields. These nanoparticle and RF properties are analysed in the context of three heating mechanisms proposed to explain gold nanoparticle heating in an RF field. This article also makes a critical analysis of the existing literature in the context of the nanoparticle preparations, RF structure, and suggested mechanisms in previously reported experiments.

Photonic chirped radio-frequency generator with ultra-fast sweeping rate and ultra-wide sweeping range.

PubMed

Wun, Jhih-Min; Wei, Chia-Chien; Chen, Jyehong; Goh, Chee Seong; Set, S Y; Shi, Jin-Wei

2013-05-06

A high-performance photonic sweeping-frequency (chirped) radio-frequency (RF) generator has been demonstrated. By use of a novel wavelength sweeping distributed-feedback (DFB) laser, which is operated based on the linewidth enhancement effect, a fixed wavelength narrow-linewidth DFB laser, and a wideband (dc to 50 GHz) photodiode module for the hetero-dyne beating RF signal generation, a very clear chirped RF waveform can be captured by a fast real-time scope. A very-high frequency sweeping rate (10.3 GHz/μs) with an ultra-wide RF frequency sweeping range (~40 GHz) have been demonstrated. The high-repeatability (~97%) in sweeping frequency has been verified by analyzing tens of repetitive chirped waveforms.

3C-SiC microdisk mechanical resonators with multimode resonances at radio frequencies

NASA Astrophysics Data System (ADS)

Lee, Jaesung; Zamani, Hamidrera; Rajgopal, Srihari; Zorman, Christian A.; X-L Feng, Philip

2017-07-01

We report on the design, modeling, fabrication and measurement of single-crystal 3C-silicon carbide (SiC) microdisk mechanical resonators with multimode resonances operating at radio frequencies (RF). These microdisk resonators (center-clamped on a vertical stem pedestal) offer multiple flexural-mode resonances with frequencies dependent on both disk and anchor dimensions. The resonators are made using a novel fabrication method comprised of focused ion beam nanomachining and hydroflouic : nitric : acetic (HNA) acid etching. Resonance peaks (in the frequency spectrum) are detected through laser-interferometry measurements. Resonators with different dimensions are tested, and multimode resonances, mode splitting, energy dissipation (in the form of quality factor measurement) are investigated. Further, we demonstrate a feedback oscillator based on a passive 3C-SiC resonator. This investigation provides important guidelines for microdisk resonator development, ranging from an analytical prediction of frequency scaling law to fabrication, suggesting RF microdisk resonators can be good candidates for future sensing applications in harsh environments.

Design of High Efficiency High Power Electron Accelerator Systems Based on Normal Conducting RF Technology for Energy and Environmental Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dolgashev, Valery; Tantawi, Sami

The goal of this project was to perform engineering design studies of three extremely high efficiency electron accelerators with the following parameters [1]: 2 MeV output beam energy and 1 MW average beam power; 10 MeV output energy and 10 MW; 10 MeV output energy and 1 MW. These linacs are intended for energy and environmental applications [2]. We based our designs on normal conducting radio-frequency technology. We have successfully reached this goal where we show rf-to-beam efficiency of 96.7 %, 97.2 %, and 79.6 % for these linacs.

Advances in simulation of wave interactions with extended MHD phenomena

NASA Astrophysics Data System (ADS)

Batchelor, D.; Abla, G.; D'Azevedo, E.; Bateman, G.; Bernholdt, D. E.; Berry, L.; Bonoli, P.; Bramley, R.; Breslau, J.; Chance, M.; Chen, J.; Choi, M.; Elwasif, W.; Foley, S.; Fu, G.; Harvey, R.; Jaeger, E.; Jardin, S.; Jenkins, T.; Keyes, D.; Klasky, S.; Kruger, S.; Ku, L.; Lynch, V.; McCune, D.; Ramos, J.; Schissel, D.; Schnack, D.; Wright, J.

2009-07-01

The Integrated Plasma Simulator (IPS) provides a framework within which some of the most advanced, massively-parallel fusion modeling codes can be interoperated to provide a detailed picture of the multi-physics processes involved in fusion experiments. The presentation will cover four topics: 1) recent improvements to the IPS, 2) application of the IPS for very high resolution simulations of ITER scenarios, 3) studies of resistive and ideal MHD stability in tokamk discharges using IPS facilities, and 4) the application of RF power in the electron cyclotron range of frequencies to control slowly growing MHD modes in tokamaks and initial evaluations of optimized location for RF power deposition.

Commissioning of two RF operation modes for RF negative ion source experimental setup at HUST

NASA Astrophysics Data System (ADS)

Li, D.; Chen, D.; Liu, K.; Zhao, P.; Zuo, C.; Wang, X.; Wang, H.; Zhang, L.

2017-08-01

An RF-driven negative ion source experimental setup, without a cesium oven and an extraction system, has been built at Huazhong University of Science and Technology (HUST). The working gas is hydrogen, and the typical operational gas pressure is 0.3 Pa. The RF generator is capable of delivering up to 20 kW at 0.9 - 1.1 MHz, and has two operation modes, the fixed-frequency mode and auto-tuning mode. In the fixed-frequency mode, it outputs a steady RF forward power (Pf) at a fixed frequency. In the auto-tuning mode, it adjusts the operating frequency to seek and track the minimum standing wave ratio (SWR) during plasma discharge. To achieve fast frequency tuning, the RF signal source adopts a direct digital synthesizer (DDS). To withstand high SWR during the discharge, a tetrode amplifier is chosen as the final stage amplifier. The trend of maximum power reflection coefficient |ρ|2 at plasma ignition is presented at the fixed frequency of 1.02 MHz with the Pf increasing from 5 kW to 20 kW, which shows the maximum |ρ|2 tends to be "steady" under high RF power. The experiments in auto-tuning mode fail due to over-current protection of screen grid. The possible reason is the relatively large equivalent anode impedance caused by the frequency tuning. The corresponding analysis and possible solution are presented.

Large Area CVD MoS2 RF transistors with GHz performance

NASA Astrophysics Data System (ADS)

Nagavalli Yogeesh, Maruthi; Sanne, Atresh; Park, Saungeun; Akinwade, Deji; Banerjee, Sanjay

Molybdenum disulfide (MoS2) is a 2D semiconductor in the family of transition metal dichalcogenides (TMDs). Its single layer direct bandgap of 1.8 eV allows for high ION/IOFF metal-oxide semiconducting field-effect transistors (FETs). More relevant for radio frequency (RF) wireless applications, theoretical studies predict MoS2 to have saturation velocities, vsat >3×106 cm/s. Facilitated by cm-scale CVD MoS2, here we design and fabricate both top-gated and embedded gate short channel MoS2 RF transistors, and provide a systematic comparison of channel length scaling, extrinsic doping from oxygen-deficient dielectrics, and a gate-first gate-last process flow. The intrinsic fT (fmax) obtained from the embedded gate transistors shows 3X (2X) improvement over top-gated CVD MoS2 RF FETs, and the largest high-field saturation velocity, vsat = 1.88 ×106 cm/s, in MoS2 reported so far. The gate-first approach, offers enhancement mode operation, ION/IOFF ratio of 10, 8< and the highest reported transconductance (gm) of 70 μS/ μm. By manipulating the interfacial oxygen vacancies in atomic layer deposited (ALD) HfO2-x we are able to achieve 2X current density over stoichiometric Al2O3. We demonstrate a common-source (CS) amplifier with voltage gain of 14 dB and an active frequency mixer with conversion gain of -15 dB. Our results of gigahertz frequency performance as well as analog circuit operation show that large area CVD MoS2 may be suitable for industrial-scale electronic applications.

Analysis of an Optical Channelization Technique for Microwave Applications

DTIC Science & Technology

2007-06-27

optical heterodyne RF signal generation using a mode- locked - laser frequency comb: theory and experiments,” in... optical carrier where +5 dBm RF tones at 9 GHz and 12 GHz were applied to the MZM biased at quadrature. The labels applied to this plot correspond to...Fig. 2 and Table I assuming ω1=2π· 9 GHz and ω2=2π·12 GHz . The laser -only spectrum illustrates the limitation set by the OSA. 7 -80 -60 -40 -20

RF Modal Quantity Gaging

NASA Technical Reports Server (NTRS)

Vanleuven, K.

1989-01-01

The primary objective is to provide a concept of a radio frequency (RF) modal resonance technique which is being investigated as a method for gaging the quantities of subcritical cryogenic propellants in metallic tanks. Of special interest are the potential applications of the technique to microgravity propellant gaging situations. The results of concept testing using cryogenic oxygen, hydrogen, and nitrogen, as well as paraffin simulations of microgravity fluid orientations, are reported. These test results were positive and showed that the gaging concept was viable.

Silicon Micromachining in RF and Photonic Applications

NASA Technical Reports Server (NTRS)

Lin, Tsen-Hwang; Congdon, Phil; Magel, Gregory; Pang, Lily; Goldsmith, Chuck; Randall, John; Ho, Nguyen

1995-01-01

Texas Instruments (TI) has developed membrane and micromirror devices since the late 1970s. An eggcrate space membrane was used as the spatial light modulator in the early years. Discrete micromirrors supported by cantilever beams created a new era for micromirror devices. Torsional micromirror and flexure-beam micromirror devices were promising for mass production because of their stable supports. TI's digital torsional micromirror device is an amplitude modulator (known as the digital micromirror device (DMD) and is in production development, discussed elsewhere. We also use a torsional device for a 4 x 4 fiber-optic crossbar switch in a 2 cm x 2 cm package. The flexure-beam micromirror device is an analog phase modulator and is considered more efficient than amplitude modulators for use in optical processing systems. TI also developed millimeter-sized membranes for integrated optical switches for telecommunication and network applications. Using a member in radio frequency (RF) switch applications is a rapidly growing area because of the micromechanical device performance in microsecond-switching characteristics. Our preliminary membrane RF switch test structure results indicate promising speed and RF switching performance. TI collaborated with MIT for modeling of metal-based micromachining.

Microwave fiber optics delay line

NASA Astrophysics Data System (ADS)

Slayman, C.; Yen, H. W.

1980-01-01

A microwave delay line is one of the devices used in EW systems for preserving the frequency and phase contents of RF signals. For such applications, delay lines are required to have large dynamic range, wide bandwidth, low insertion loss, and a linear response. The basic components of a fiber-optics delay line are: an optical source, a wideband optical modulator, a spool of single-mode fiber with appropriate length to provide a given microwave signal delay, and a high-speed photodetector with an RF amplifier. This contract program is to study the feasibility of such a fiber-optic delay line in the frequency range of 4.0 to 6.5 GHz. The modulation scheme studied is the direct modulation of injection lasers. The most important issue identified is the frequency response of the injection laser and the photodetector.

Experimental investigation of mode transitions in asymmetric capacitively coupled radio-frequency Ne and CF4 plasmas

NASA Astrophysics Data System (ADS)

Liu, Gang-Hu; Liu, Yong-Xin; Bai, Li-Shui; Zhao, Kai; Wang, You-Nian

2018-02-01

The dependence of the electron density and the emission intensity on external parameters during the transitions of the electron power absorption mode is experimentally studied in asymmetric electropositive (neon) and electronegative (CF4) capacitively coupled radio-frequency plasmas. The spatio-temporal distribution of the emission intensity is measured with phase resolved optical emission spectroscopy and the electron density at the discharge center is measured by utilizing a floating hairpin probe. In neon discharge, the emission intensity increases almost linearly with the rf voltage at all driving frequencies covered here, while the variation of the electron density with the rf voltage behaves differently at different driving frequencies. In particular, the electron density increases linearly with the rf voltage at high driving frequencies, while at low driving frequencies the electron density increases slowly at the low-voltage side and, however, grows rapidly, when the rf voltage is higher than a certain value, indicating a transition from α to γ mode. The rf voltage, at which the mode transition occurs, increases with the decrease of the driving frequency/the working pressure. By contrast, in CF4 discharge, three different electron power absorption modes can be observed and the electron density and emission intensity do not exhibit a simple dependence on the rf voltage. In particular, the electron density exhibits a minimum at a certain rf voltage when the electron power absorption mode is switching from drift-ambipolar to the α/γ mode. A minimum can also be found in the emission intensity at a higher rf voltage when a discharge is switching into the γ mode.

An analytical model for floating probes in AC plasma and its application to double probes for high density, high power RF discharges

NASA Astrophysics Data System (ADS)

Caneses, Juan Francisco; Blackwell, Boyd; Plasma Research Laboratory Team

2013-10-01

In this work we provide an analytical model that allows one to quantitatively assess the RF compensation performance and suitability of the double probe technique for use in RF generated plasma. The model is based in the theory of the self-bias effect as described in Braithwaite's work, which we extend to include the time resolved behavior of floating probes. We provide experimental verification for this model and show that the theory of transient RF self-bias probes and harmonic current detection probes are limiting cases of this extended model. Furthermore, the model shows that the RF compensation is solely dependent on the sheath impedance, the probe's stray capacitance to ground and RF frequency. In addition, we use these results to implement a double probe system for use in high density helicon plasma where heat loads could potentially damage the intricate components in an RF compensating circuit. Finally we use this model to (1) recommend ways to extend the operational regime of double probes where the plasma conditions would render them unsuitable and to (2) comment on the use of this model to aid design of RF compensated Langmuir probes.

Investigation and Prediction of RF Window Performance in APT Accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Humphries, S. Jr.

1997-05-01

The work described in this report was performed between November 1996 and May 1997 in support of the APT (Accelerator Production of Tritium) Program at Los Alamos National Laboratory. The goal was to write and to test computer programs for charged particle orbits in RF fields. The well-documented programs were written in portable form and compiled for standard personal computers for easy distribution to LANL researchers. They will be used in several APT applications including the following. Minimization of multipactor effects in the moderate {beta} superconducting linac cavities under design for the APT accelerator. Investigation of suppression techniques for electronmore » multipactoring in high-power RF feedthroughs. Modeling of the response of electron detectors for the protection of high power RF vacuum windows. In the contract period two new codes, Trak{_}RF and WaveSim, were completed and several critical benchmark etests were carried out. Trak{_}RF numerically tracks charged particle orbits in combined electrostatic, magnetostatic and electromagnetic fields. WaveSim determines frequency-domain RF field solutions and provides a key input to Trak{_}RF. The two-dimensional programs handle planar or cylindrical geometries. They have several unique characteristics.« less

An RF dosimeter for independent SAR measurement in MRI scanners

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qian, Di; Bottomley, Paul A.; El-Sharkawy, AbdEl-Monem M.

2013-12-15

Purpose: The monitoring and management of radio frequency (RF) exposure is critical for ensuring magnetic resonance imaging (MRI) safety. Commercial MRI scanners can overestimate specific absorption rates (SAR) and improperly restrict clinical MRI scans or the application of new MRI sequences, while underestimation of SAR can lead to tissue heating and thermal injury. Accurate scanner-independent RF dosimetry is essential for measuring actual exposure when SAR is critical for ensuring regulatory compliance and MRI safety, for establishing RF exposure while evaluating interventional leads and devices, and for routine MRI quality assessment by medical physicists. However, at present there are no scanner-independentmore » SAR dosimeters. Methods: An SAR dosimeter with an RF transducer comprises two orthogonal, rectangular copper loops and a spherical MRI phantom. The transducer is placed in the magnet bore and calibrated to approximate the resistive loading of the scanner's whole-body birdcage RF coil for human subjects in Philips, GE and Siemens 3 tesla (3T) MRI scanners. The transducer loop reactances are adjusted to minimize interference with the transmit RF field (B{sub 1}) at the MRI frequency. Power from the RF transducer is sampled with a high dynamic range power monitor and recorded on a computer. The deposited power is calibrated and tested on eight different MRI scanners. Whole-body absorbed power vs weight and body mass index (BMI) is measured directly on 26 subjects. Results: A single linear calibration curve sufficed for RF dosimetry at 127.8 MHz on three different Philips and three GE 3T MRI scanners. An RF dosimeter operating at 123.2 MHz on two Siemens 3T scanners required a separate transducer and a slightly different calibration curve. Measurement accuracy was ∼3%. With the torso landmarked at the xiphoid, human adult whole‑body absorbed power varied approximately linearly with patient weight and BMI. This indicates that whole-body torso SAR is on average independent of the imaging subject, albeit with fluctuations. Conclusions: Our 3T RF dosimeter and transducers accurately measure RF exposure in body-equivalent loads and provide scanner-independent assessments of whole-body RF power deposition for establishing safety compliance useful for MRI sequence and device testing.« less

NASA Radio Frequency Spectrum Management Manual

NASA Technical Reports Server (NTRS)

1989-01-01

The Radio Frequency (RF) Spectrum Management Manual sets forth procedures and guidelines for the management requirements for controlling the use of radio frequencies by the National Aeronautics and Space Administration. It is applicable to NASA Headquarters and field installations. NASA Management Instruction 1102.3 assigns the authority for management of radio frequencies for the National Aeronautics and Space Administration to the Associate Administrator for Space Operations, NASA Headquarters. This manual is issued in loose-leaf form and will be revised by page changes.

1997 Technology Applications Report,

DTIC Science & Technology

1997-01-01

handle high -power loads at microwave radio frequencies , microwave vacuum tubes remain the chosen technology to amplify high power. Aria Microwave...structure called the active RF cavity amplifier (ARFCA). With this design , the amplifier handles high -power loads at radio and microwave frequencies ...developed this technology using BMDO-funded modeling methods designed to simulate the dynamics of large space-based structures. Because it increases

Densities of Active species in N2/H2 RF and HF afterglows: application to surface nitriding of TiO2 nanocrystals

NASA Astrophysics Data System (ADS)

Ricard, André; Sarrette, Jean-Philippe; Wang, Yunfei; Kim, Yu-Kwon

2017-10-01

N2/0-5% H2 flowing afterglows from Radio Frequency (RF) and High Frequency (HF) sources have been analyzed by optical emission spectroscopy. In similar conditions (pressure 5-6 Torr, flow rate 0.5 slm and power 100 W), it is found in pure N2 a nearly constant N-atom density from the pink to the late afterglow, which is higher in HF than in RF: (1-2) and 0.4 × 1015 cm-3, respectively. With a N2/2% H2 gas mixture, the early afterglows is changed to a late afterglow with about the same N-atom density for both RF and HF cases: (8-9) × 1014 cm-3. Anatase TiO2 nanocrystals and Atomic Layer Deposition-grown films were exposed to the RF afterglows at room temperature. XPS analysis of the samples has shown that the highest N/Ti ratio of 0.24 can be achieved with the pure N2 late afterglow. In the HF pure N2 late afterglow, however, the N/Ti coverage was limited to 0.04 in spite of higher N-atom density. Such differences in the N content between the two RF and HF cases are attributed to the presence of a high O-atom impurity of 2 × 1013 cm-3 in HF as compared to that (8 × 1011 cm-3) in RF. Contribution to the topical issue "Plasma Sources and Plasma Processes (PSPP)", edited by Luis Lemos Alves, Thierry Belmonte and Tiberiu Minea

Negative ion kinetics in RF glow discharges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gottscho, R.A.; Gacbe, C.E.

1986-04-01

Using temporally and spatially resolved laser spectroscopy, the authors have determined the identities, approximate concentrations, effects on the local field, and kinetics of formation and loss of negative ions in RF discharges. CI/sup -/ and BCI/sub 3//sup -/ are the dominant negative ions found in low-frequency discharges through CI/sub 2/ and BCI/sub 3/, respectively. The electron affinity for CI is measured to be 3.6118 +- 0.0005 eV. Negative ion kinetics are strongly affected by application of the RF field. Formation of negative ions by attachment of slow electrons in RF discharges is governed by the extent and duration of electronmore » energy relaxation. Similarly, destruction of negative ions by collisional detachment and field extraction is dependent upon ion energy modulation. Thus, at low frequency, the anion density peaks at the beginning of the anodic and cathodic half-cycles after electrons have attached but before detachment and extraction have had time to occur. At higher frequencies, electrons have insufficient time to attach before they are reheated and the instantaneous anion density in the sheath is greatly reduced. When the negative ion density is comparable to the positive ion density, the plasma potential is observed to lie below the anode potential, double layers form between sheath and plasma, and anions and electrons are accelerated by large sheath fields to electrode surfaces.« less

Scaling laws for AC gas breakdown and implications for universality

NASA Astrophysics Data System (ADS)

Loveless, Amanda M.; Garner, Allen L.

2017-10-01

The reduced dependence on secondary electron emission and electrode surface properties makes radiofrequency (RF) and microwave (MW) plasmas advantageous over direct current (DC) plasmas for various applications, such as microthrusters. Theoretical models relating molecular constants to alternating current (AC) breakdown often fail due to incomplete understanding of both the constants and the mechanisms involved. This work derives simple analytic expressions for RF and MW breakdown, demonstrating the transition between these regimes at their high and low frequency limits, respectively. We further show that the limiting expressions for DC, RF, and MW breakdown voltage all have the same universal scaling dependence on pressure and gap distance at high pressure, agreeing with experiment.

Novel Low Loss Wide-Band Multi-Port Integrated Circuit Technology for RF/Microwave Applications

NASA Technical Reports Server (NTRS)

Simons, Rainee N.; Goverdhanam, Kavita; Katehi, Linda P. B.; Burke, Thomas P. (Technical Monitor)

2001-01-01

In this paper, novel low loss, wide-band coplanar stripline technology for radio frequency (RF)/microwave integrated circuits is demonstrated on high resistivity silicon wafer. In particular, the fabrication process for the deposition of spin-on-glass (SOG) as a dielectric layer, the etching of microvias for the vertical interconnects, the design methodology for the multiport circuits and their measured/simulated characteristics are graphically illustrated. The study shows that circuits with very low loss, large bandwidth, and compact size are feasible using this technology. This multilayer planar technology has potential to significantly enhance RF/microwave IC performance when combined with semi-conductor devices and microelectromechanical systems (MEMS).

SIDON: A simulator of radio-frequency networks. Application to WEST ICRF launchers

NASA Astrophysics Data System (ADS)

Helou, Walid; Dumortier, Pierre; Durodié, Frédéric; Goniche, Marc; Hillairet, Julien; Mollard, Patrick; Berger-By, Gilles; Bernard, Jean-Michel; Colas, Laurent; Lombard, Gilles; Maggiora, Riccardo; Magne, Roland; Milanesio, Daniele; Moreau, Didier

2015-12-01

SIDON (SImulator of raDiO-frequency Networks) is an in-house developed Radio-Frequency (RF) network solver that has been implemented to cross-validate the design of WEST ICRF launchers and simulate their impedance matching algorithm while considering all mutual couplings and asymmetries. In this paper, the authors illustrate the theory of SIDON as well as results of its calculations. The authors have built time-varying plasma scenarios (a sequence of launchers front-faces L-mode and H-mode Z-matrices), where at each time step (1 millisecond here), SIDON solves the RF network. At the same time, when activated, the impedance matching algorithm controls the matching elements (vacuum capacitors) and thus their corresponding S-matrices. Typically a 1-second pulse requires around 10 seconds of computational time on a desktop computer. These tasks can be hardly handled by commercial RF software. This innovative work allows identifying strategies for the launchers future operation while insuring the limitations on the currents, voltages and electric fields, matching and Load-Resilience, as well as the required straps voltage amplitude/phase balance. In this paper, a particular attention is paid to the simulation of the launchers behavior when arcs appear at several locations of their circuits using SIDON calculator. This latter work shall confirm or identify strategies for the arc detection using various RF electrical signals. One shall note that the use of such solvers in not limited to ICRF launchers simulations but can be employed, in principle, to any linear or linearized RF problem.

Single-chip fully integrated direct-modulation CMOS RF transmitters for short-range wireless applications.

PubMed

El-Desouki, Munir M; Qasim, Syed Manzoor; BenSaleh, Mohammed; Deen, M Jamal

2013-08-02

Ultra-low power radio frequency (RF) transceivers used in short-range application such as wireless sensor networks (WSNs) require efficient, reliable and fully integrated transmitter architectures with minimal building blocks. This paper presents the design, implementation and performance evaluation of single-chip, fully integrated 2.4 GHz and 433 MHz RF transmitters using direct-modulation power voltage-controlled oscillators (PVCOs) in addition to a 2.0 GHz phase-locked loop (PLL) based transmitter. All three RF transmitters have been fabricated in a standard mixed-signal CMOS 0.18 µm technology. Measurement results of the 2.4 GHz transmitter show an improvement in drain efficiency from 27% to 36%. The 2.4 GHz and 433 MHz transmitters deliver an output power of 8 dBm with a phase noise of -122 dBc/Hz at 1 MHz offset, while drawing 15.4 mA of current and an output power of 6.5 dBm with a phase noise of -120 dBc/Hz at 1 MHz offset, while drawing 20.8 mA of current from 1.5 V power supplies, respectively. The PLL transmitter delivers an output power of 9 mW with a locking range of 128 MHz and consumes 26 mA from 1.8 V power supply. The experimental results demonstrate that the RF transmitters can be efficiently used in low power WSN applications.

Enhanced dynamical stability with harmonic slip stacking

DOE PAGES

Eldred, Jeffrey; Zwaska, Robert

2016-10-26

We develop a configuration of radio-frequency (rf) cavities to dramatically improve the performance of slip-stacking. Slip-stacking is an accumulation technique used at Fermilab to nearly double proton intensity by maintaining two beams of different momenta in the same storage ring. The two particle beams are longitudinally focused in the Recycler by two 53 MHz 100 kV rf cavities with a small frequency difference between them. We propose an additional 106 MHz 20 kV rf cavity with a frequency at the double the average of the upper and lower main rf frequencies. We show the harmonic rf cavity cancels out themore » resonances generated between the two main rf cavities and we derive the relationship between the harmonic rf voltage and the main rf voltage. We find the area factors that can be used to calculate the available phase space area for any set of beam parameters without individual simulation. We establish Booster beam quality requirements to achieve 99\\% slip-stacking efficiency. We measure the longitudinal distribution of the Booster beam and use it to generate a realistic beam model for slip-stacking simulation. In conclusion, we demonstrate that the harmonic rf cavity can not only reduce particle loss during slip-stacking, but also reduce the final longitudinal emittance.« less

Enhanced dynamical stability with harmonic slip stacking

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eldred, Jeffrey; Zwaska, Robert

We develop a configuration of radio-frequency (rf) cavities to dramatically improve the performance of slip-stacking. Slip-stacking is an accumulation technique used at Fermilab to nearly double proton intensity by maintaining two beams of different momenta in the same storage ring. The two particle beams are longitudinally focused in the Recycler by two 53 MHz 100 kV rf cavities with a small frequency difference between them. We propose an additional 106 MHz 20 kV rf cavity with a frequency at the double the average of the upper and lower main rf frequencies. We show the harmonic rf cavity cancels out themore » resonances generated between the two main rf cavities and we derive the relationship between the harmonic rf voltage and the main rf voltage. We find the area factors that can be used to calculate the available phase space area for any set of beam parameters without individual simulation. We establish Booster beam quality requirements to achieve 99\\% slip-stacking efficiency. We measure the longitudinal distribution of the Booster beam and use it to generate a realistic beam model for slip-stacking simulation. In conclusion, we demonstrate that the harmonic rf cavity can not only reduce particle loss during slip-stacking, but also reduce the final longitudinal emittance.« less

Transmit-reference methods in software defined radio platforms for communication in harsh propagation environments and systems thereof

DOEpatents

Dowla, Farid U; Nekoogar, Faranak

2015-03-03

A method for adaptive Radio Frequency (RF) jamming according to one embodiment includes dynamically monitoring a RF spectrum; detecting any undesired signals in real time from the RF spectrum; and sending a directional countermeasure signal to jam the undesired signals. A method for adaptive Radio Frequency (RF) communications according to another embodiment includes transmitting a data pulse in a RF spectrum; and transmitting a reference pulse separated by a predetermined period of time from the data pulse; wherein the data pulse is modulated with data, wherein the reference pulse is unmodulated. A method for adaptive Radio Frequency (RF) communications according to yet another embodiment includes receiving a data pulse in a RF spectrum; and receiving a reference pulse separated in time from the data pulse, wherein the data pulse is modulated with data, wherein the reference pulse is unmodulated; and demodulating the pulses.

Transmit-reference methods in software defined radio platforms for communication in harsh propagation environments and systems thereof

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dowla, Farid; Nekoogar, Faranak

A method for adaptive Radio Frequency (RF) jamming according to one embodiment includes dynamically monitoring a RF spectrum; detecting any undesired signals in real time from the RF spectrum; and sending a directional countermeasure signal to jam the undesired signals. A method for adaptive Radio Frequency (RF) communications according to another embodiment includes transmitting a data pulse in a RF spectrum; and transmitting a reference pulse separated by a predetermined period of time from the data pulse; wherein the data pulse is modulated with data, wherein the reference pulse is unmodulated. A method for adaptive Radio Frequency (RF) communications accordingmore » to yet another embodiment includes receiving a data pulse in a RF spectrum; and receiving a reference pulse separated in time from the data pulse, wherein the data pulse is modulated with data, wherein the reference pulse is unmodulated; and demodulating the pulses.« less

Resonance properties of the biological objects in the RF field

NASA Astrophysics Data System (ADS)

Cocherova, E.; Kupec, P.; Stofanik, V.

2011-12-01

Irradiation of people with electromagnetic fields emitted from miscellaneous devices working in the radio-frequency (RF) range may have influence, for example may affect brain processes. The question of health impact of RF electromagnetic fields on population is still not closed. This article is devoted to an investigation of resonance phenomena of RF field absorption in the models of whole human body and body parts (a head) of different size and shape. The values of specific absorption rate (SAR) are evaluated for models of the different shapes: spherical, cylindrical, realistic shape and for different size of the model, that represents the case of new-born, child and adult person. In the RF frequency region, absorption depends nonlinearly on frequency. Under certain conditions (E-polarization), absorption reaches maximum at frequency, that is called "resonance frequency". The whole body absorption and the resonance frequency depends on many further parameters, that are not comprehensively clarified. The simulation results showed the dependence of the whole-body average SAR and resonance frequency on the body dimensions, as well as the influence of the body shape.

Radio-frequency plasma transducer for use in harsh environments.

PubMed

May, Andrew; Andarawis, Emad

2007-10-01

We describe a compact transducer used to generate and modulate low-intensity radio-frequency atmospheric pressure plasma (RF-APP) for high temperature gap measurement and generation of air-coupled ultrasound. The new transducer consists of a quarter-wave transmission line where the ground return path is a coaxial solenoid winding. The RF-APP is initiated at the open end of the transmission line and stabilized by passive negative feedback between the electrical impedance of the plasma and the energy stored in the solenoid. The electrical impedance of the plasma was measured at the lower-voltage source end of the transducer, eliminating the need to measure kilovolt-level voltages near the discharge. We describe the use of a 7 MHz RF-APP prototype as a harsh-environment clearance sensor to demonstrate the suitability of plasma discharges for a common nondestructive inspection application. Clearance measurements of 0-5 mm were performed on a rotating calibration target with a measurement precision of 0.1 mm and a 20 kHz sampling rate.

Radio frequency magnetic field limits of Nb and Nb 3Sn

DOE PAGES

Posen, S.; Valles, N.; Liepe, M.

2015-07-21

Superconducting radio frequency (srf) cavities, essential components of many large particle accelerators, rely on the metastable flux-free state of superconducting materials. In this Letter, we present results of experiments measuring the magnetic field limits of two srf materials, Nb and Nb 3Sn. Resonators made using these materials were probed using both high power rf pulses and dc magnetic fields. Nb, which is the current standard material for srf cavities in applications, was found to be limited by the superheating field H sh when prepared using methods to avoid excessive rf dissipation at high fields. Nb 3Sn, which is a promisingmore » alternative material that is still in the early stages of development for srf purposes, was found to be limited between the onset field of metastability H c1 and H sh. Furthermore, analysis of the results shows that the limitation is consistent with nucleation of flux penetration at defects in the rf layer.« less

RF Design of a Wideband CMOS Integrated Receiver for Phased Array Applications

NASA Astrophysics Data System (ADS)

Jackson, Suzy A.

2004-06-01

New silicon CMOS processes developed primarily for the burgeoning wireless networking market offer significant promise as a vehicle for the implementation of highly integrated receivers, especially at the lower end of the frequency range proposed for the Square Kilometre Array (SKA). An RF-CMOS ‘Receiver-on-a-Chip’ is being developed as part of an Australia Telescope program looking at technologies associated with the SKA. The receiver covers the frequency range 500 1700 MHz, with instantaneous IF bandwidth of 500 MHz and, on simulation, yields an input noise temperature of < 50 K at mid-band. The receiver will contain all active circuitry (LNA, bandpass filter, quadrature mixer, anti-aliasing filter, digitiser and serialiser) on one 0.18 μm RF-CMOS integrated circuit. This paper outlines receiver front-end development work undertaken to date, including design and simulation of an LNA using noise cancelling techniques to achieve a wideband input-power-match with little noise penalty.

Airborne RF Measurement System (ARMS) and Analysis of Representative Flight RF Environment

NASA Technical Reports Server (NTRS)

Koppen, Sandra V.; Ely, Jay J.; Smith, Laura J.; Jones, Richard A.; Fleck, Vincent J.; Salud, Maria Theresa; Mielnik, John J.

2007-01-01

Environmental radio frequency (RF) data over a broad band of frequencies (30 MHz to 1000 MHz) were obtained to evaluate the electromagnetic environment in airspace around several airports. An RF signal measurement system was designed utilizing a spectrum analyzer connected to the NASA Lancair Columbia 300 aircraft's VHF/UHF navigation antenna. This paper presents an overview of the RF measurement system and provides analysis of sample RF signal measurement data. This aircraft installation package and measurement system can be quickly returned to service if needed by future projects requiring measurement of an RF signal environment or exploration of suspected interference situations.

Application of Au-Sn eutectic bonding in hermetic radio-frequency microelectromechanical system wafer level packaging

NASA Astrophysics Data System (ADS)

Wang, Qian; Choa, Sung-Hoon; Kim, Woonbae; Hwang, Junsik; Ham, Sukjin; Moon, Changyoul

2006-03-01

Development of packaging is one of the critical issues toward realizing commercialization of radio-frequency-microelectromechanical system (RF-MEMS) devices. The RF-MEMS package should be designed to have small size, hermetic protection, good RF performance, and high reliability. In addition, packaging should be conducted at sufficiently low temperature. In this paper, a low-temperature hermetic wafer level packaging scheme for the RF-MEMS devices is presented. For hermetic sealing, Au-Sn eutectic bonding technology at temperatures below 300°C is used. Au-Sn multilayer metallization with a square loop of 70 µm in width is performed. The electrical feed-through is achieved by the vertical through-hole via filling with electroplated Cu. The size of the MEMS package is 1 mm × 1 mm × 700 µm. The shear strength and hermeticity of the package satisfies the requirements of MIL-STD-883F. Any organic gases or contamination are not observed inside the package. The total insertion loss for the packaging is 0.075 dB at 2 GHz. Furthermore, the robustness of the package is demonstrated by observing no performance degradation and physical damage of the package after several reliability tests.

RF-to-DC Characteristics of Direct Irradiated On-Chip Gallium Arsenide Schottky Diode and Antenna for Application in Proximity Communication System

PubMed Central

Mustafa, Farahiyah; Hashim, Abdul Manaf

2014-01-01

We report the RF-to-DC characteristics of the integrated AlGaAs/GaAs Schottky diode and antenna under the direct injection and irradiation condition. The conversion efficiency up to 80% under direct injection of 1 GHz signal to the diode was achieved. It was found that the reduction of series resistance and parallel connection of diode and load tend to lead to the improvement of RF-to-DC conversion efficiency. Under direct irradiation from antenna-to-antenna method, the output voltage of 35 mV was still obtainable for the distance of 8 cm between both antennas in spite of large mismatch in the resonant frequency between the diode and the connected antenna. Higher output voltage in volt range is expected to be achievable for the well-matching condition. The proposed on-chip AlGaAs/GaAs HEMT Schottky diode and antenna seems to be a promising candidate to be used for application in proximity communication system as a wireless low power source as well as a highly sensitive RF detector. PMID:24561400

FAST TRACK COMMUNICATION: Ferroelectric properties and dielectric responses of multiferroic BiFeO3 films grown by RF magnetron sputtering

NASA Astrophysics Data System (ADS)

Qi, Xiaoding; Tsai, Po-Chou; Chen, Yi-Chun; Ko, Cheng-Hung; Huang, Jung-Chun-Andrew; Chen, In-Gann

2008-12-01

Multiferroic BiFeO3 films have been grown on LaNiO3-x/SrTiO3 and Pt/Si substrates by RF magnetron sputtering. The films showed fully saturated ferroelectric hysteresis loops with large remanent polarization of 64 µC cm-2, suitable for most device applications. Piezoresponse force microscopy confirmed that the films were electrically writable. In addition to the high-frequency intrinsic dielectric loss of epitaxial films, the Argand diagram also revealed low-frequency contributions from both dc conductivity and interfacial polarization at electrodes. For polycrystalline films on Pt/Si, the dominant contribution to dielectric loss was space charge polarization at grain boundaries.

Infrared Avionics Signal Distribution using Wavelength Division Multiplexing

NASA Technical Reports Server (NTRS)

Atiquzzaman, Mohammed; Sluss, Jim; Nguyen, Hung; Ngo, Duc

2003-01-01

Pilots in the cockpits of aircrafts currently communicate with ground stations using Radio Frequency (RF) signals. Antennas mounted outside the aircraft receive and transmit RF signals from and to the ground stations. The RF signals received at the antennas are sent to the cockpit using coaxial cables. As the number of antennas needed to provide more than one frequency band in aircrafts increases, RF distribution media (such as coaxial cable) adds to the complexity and weight of the cockpit wiring. Concomitantly, the safety and signal to noise ratio also decreases due to the use of RF signals. The University of Oklahoma is collaborating with the National Aeronautics and Space Administration to develop optical fiber based schemes to replace the coaxial cable used for RF signal distribution within an aircraft. The project aims at exploiting emerging Wavelength Division Multiplexing (WDM) techniques to reduce the weight of cabling, and increase the signal to noise ratio and reliability. This will be achieved by wavelength division multiplexing the signals from the various antennas and then demultiplexing the signals to recover the original signals at the cockpit. This paper will show that (i) RF signals can not only be wavelength multiplexed at the end of a fiber, but additional signals can be inserted into the middle of the fiber using WDM technology, and (ii) the signals can also be successfully extracted by tapping into the middle of the fiber. We are currently extending our previous laboratory prototype (which could multiplex signals only at the end of the fiber) to include additional multiplexing and demultiplexing of RF signals from the middle of the optical backbone with a view to validating the proof of concept, and carrying out measurements to determine the effectiveness of Wavelength Division Multiplexing for avionics applications. A test bed to perform measurements of several relevant parameters for various modulation schemes and frequencies (such as VHF, UHF, and L-Band) has been implemented. In particular, results of transmitter and receiver noise, bit-error-rate (BER), effect of cross talk on the quality of the multiplexed signals, and Signal to Noise ratio and Carrier to Noise ratio, obtained using the aforementioned test bed, will be presented.

Characterization of an Outdoor Ambient Radio Frequency Environment

DTIC Science & Technology

2016-02-16

radio frequency noise ”) prior to testing of a specific system under test (SUT). With this characterization, locations can be selected to avoid RF...spectrum analyzer, ambient RF noise floor, RF interference 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18...environment (sometimes referred to as “radio frequency noise ”) prior to testing of a specific system under test (SUT). With this characterization

Broadband photonic single sideband frequency up-converter based on the cross polarization modulation effect in a semiconductor optical amplifier for radio-over-fiber systems.

PubMed

Lee, Seung-Hun; Kim, Hyoung-Jun; Song, Jong-In

2014-01-13

A broadband photonic single sideband (SSB) frequency up-converter based on the cross polarization modulation (XPolM) effect in a semiconductor optical amplifier (SOA) is proposed and experimentally demonstrated. An optical radio frequency (RF) signal in the form of an optical single sideband (OSSB) is generated by the photonic SSB frequency up-converter to solve the power fading problem caused by fiber chromatic dispersion. The generated OSSB RF signal has almost identical optical carrier power and optical sideband power. This SSB frequency up-conversion scheme shows an almost flat electrical RF power response as a function of the RF frequency in a range from 31 GHz to 75 GHz after 40 km single mode fiber (SMF) transmission. The photonic SSB frequency up-conversion technique shows negligible phase noise degradation. The phase noise of the up-converted RF signal at 49 GHz for an offset of 10 kHz is -93.17 dBc/Hz. Linearity analysis shows that the photonic SSB frequency up-converter has a spurious free dynamic range (SFDR) value of 79.51 dB · Hz(2/3).

Investigation of analog/RF performance of staggered heterojunctions based nanowire tunneling field-effect transistors

NASA Astrophysics Data System (ADS)

Chakraborty, Avik; Sarkar, Angsuman

2015-04-01

In this paper, the analog/RF performance of an III-V semiconductor based staggered hetero-tunnel-junction (HETJ) n-type nanowire (NW) tunneling FET (n-TFET) is investigated, for the first time. The device performance figure-of-merits governing the analog/RF performance such as transconductance (gm), transconductance-to-drive current ratio (gm/IDS), output resistance (Rout), intrinsic gain and unity-gain cutoff frequency (fT) have been studied. The analog/RF performance parameters is compared between HETJ NW TFET and a homojunction (HJ) NW n-type TFET of similar dimensions. In addition to enhanced ION and subthreshold swing, a significant improvement in the analog/RF performance parameters obtained by the HETJ n-TFET over HJ counterpart for use in analog/mixed signal System-on-Chip (SoC) applications is reported. Moreover, the analog/RF performance parameters of a III-V based staggered HETJ NW TFET is also compared with a heterojunction (HETJ) NW n-type MOSFET having same material as HETJ n-TFET and equal dimension in order to provide a systematic comparison between HETJ-TFET and HETJ-MOSFET for use in analog/mixed-signal applications. The results reveal that HETJ n-TFET provides higher Rout and hence, a higher intrinsic gain, an improved gm/IDS ratio, and reasonable fT at lower values of gate-overdrive voltage as compared to the HETJ NW n-MOSFET.

Determination of Atomic and Molecular Excited-State Lifetimes Using an Opto-electronic Cross-Correlation Method.

DTIC Science & Technology

1981-10-07

new instrument (cf. Fig. 1) is simply a four - quadrant ring-diode multi- 5 plier (Fig. 2). The reference frequency (RF) and local oscillator (LO) inputs...movement, and scan speed of the corner-cube. Other Components. A rotating-sector chopper modulates the laser pulse train at a frequency of approximately 50...the cross-correlation experiment. In this application, the detection bandpass is simply displaced from DC to the chopper frequency; problems arising

A novel scaling law relating the geometrical dimensions of a photocathode radio frequency gun to its radio frequency properties

NASA Astrophysics Data System (ADS)

Lal, Shankar; Pant, K. K.; Krishnagopal, S.

2011-12-01

Developing a photocathode RF gun with the desired RF properties of the π-mode, such as field balance (eb) ˜1, resonant frequency fπ = 2856 MHz, and waveguide-to-cavity coupling coefficient βπ ˜1, requires precise tuning of the resonant frequencies of the independent full- and half-cells (ff and fh), and of the waveguide-to-full-cell coupling coefficient (βf). While contemporary electromagnetic codes and precision machining capability have made it possible to design and tune independent cells of a photocathode RF gun for desired RF properties, thereby eliminating the need for tuning, access to such computational resources and quality of machining is not very widespread. Therefore, many such structures require tuning after machining by employing conventional tuning techniques that are iterative in nature. Any procedure that improves understanding of the tuning process and consequently reduces the number of iterations and the associated risks in tuning a photocathode gun would, therefore, be useful. In this paper, we discuss a method devised by us to tune a photocathode RF gun for desired RF properties under operating conditions. We develop and employ a simple scaling law that accounts for inter-dependence between frequency of independent cells and waveguide-to-cavity coupling coefficient, and the effect of brazing clearance for joining of the two cells. The method has been employed to successfully develop multiple 1.6 cell BNL/SLAC/UCLA type S-band photocathode RF guns with the desired RF properties, without the need to tune them by a tiresome cut-and-measure process. Our analysis also provides a physical insight into how the geometrical dimensions affect the RF properties of the photo-cathode RF gun.

Lightning detection from Space Science and Applications Team review. [optical and radio frequency sensors

NASA Technical Reports Server (NTRS)

Few, A. A., Jr.

1981-01-01

The various needs for lightning data that exist among potential users of satellite lightning data were identified and systems were defined which utilize the optical and radio frequency radiations from lightning to serve as the satellite based lightning mapper. Three teams worked interactively with NASA to develop a system concept. An assessment of the results may be summarized as follows: (1) a small sensor system can be easily designed to operate on a geostationary satellite that can provide the bulk of the real time user requirements; (2) radio frequency systems in space may be feasible but would be much larger and more costly; RF technology for this problem lags the optical technology by years; and (3) a hybrid approach (optical in space and RF on the ground) would provide the most complete information but is probably unreasonably complex and costly at this time.

Reducing flicker noise in chemical vapor deposition graphene field-effect transistors

NASA Astrophysics Data System (ADS)

Arnold, Heather N.; Sangwan, Vinod K.; Schmucker, Scott W.; Cress, Cory D.; Luck, Kyle A.; Friedman, Adam L.; Robinson, Jeremy T.; Marks, Tobin J.; Hersam, Mark C.

2016-02-01

Single-layer graphene derived from chemical vapor deposition (CVD) holds promise for scalable radio frequency (RF) electronic applications. However, prevalent low-frequency flicker noise (1/f noise) in CVD graphene field-effect transistors is often up-converted to higher frequencies, thus limiting RF device performance. Here, we achieve an order of magnitude reduction in 1/f noise in field-effect transistors based on CVD graphene transferred onto silicon oxide substrates by utilizing a processing protocol that avoids aqueous chemistry after graphene transfer. Correspondingly, the normalized noise spectral density (10-7-10-8 μm2 Hz-1) and noise amplitude (4 × 10-8-10-7) in these devices are comparable to those of exfoliated and suspended graphene. We attribute the reduction in 1/f noise to a decrease in the contribution of fluctuations in the scattering cross-sections of carriers arising from dynamic redistribution of interfacial disorder.

Multipole and field uniformity tailoring of a 750 MHz rf dipole

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delayen, Jean R.; Castillo, Alejandro

2014-12-01

In recent years great interest has been shown in developing rf structures for beam separation, correction of geometrical degradation on luminosity, and diagnostic applications in both lepton and hadron machines. The rf dipole being a very promising one among all of them. The rf dipole has been tested and proven to have attractive properties that include high shunt impedance, low and balance surface fields, absence of lower order modes and far-spaced higher order modes that simplify their damping scheme. As well as to be a compact and versatile design in a considerable range of frequencies, its fairly simple geometry dependencymore » is suitable both for fabrication and surface treatment. The rf dipole geometry can also be optimized for lowering multipacting risk and multipole tailoring to meet machine specific field uniformity tolerances. In the present work a survey of field uniformities, and multipole contents for a set of 750 MHz rf dipole designs is presented as both a qualitative and quantitative analysis of the inherent flexibility of the structure and its limitations.« less

Toward a Mobility-Driven Architecture for Multimodal Underwater Networking

DTIC Science & Technology

2017-02-01

applications. By equipping AUVs with short-range, high -bandwidth underwater wireless communications , which feature lower energy-per-bit cost than acoustic...protocols. They suffer from significant transmission path losses at high frequencies , long propagation delays, low and distance-dependent bandwidth, time...of data preprocessing, data compression, and either tethering to a surface buoy able to use radio frequency (RF) communications or using undersea

Injection-locking of terahertz quantum cascade lasers up to 35GHz using RF amplitude modulation.

PubMed

Gellie, Pierre; Barbieri, Stefano; Lampin, Jean-François; Filloux, Pascal; Manquest, Christophe; Sirtori, Carlo; Sagnes, Isabelle; Khanna, Suraj P; Linfield, Edmund H; Davies, A Giles; Beere, Harvey; Ritchie, David

2010-09-27

We demonstrate that the cavity resonance frequency - the round-trip frequency - of Terahertz quantum cascade lasers can be injection-locked by direct modulation of the bias current using an RF source. Metal-metal and single-plasmon waveguide devices with roundtrip frequencies up to 35GHz have been studied, and show locking ranges above 200MHz. Inside this locking range the laser round-trip frequency is phase-locked, with a phase noise determined by the RF-synthesizer. We find a square-root dependence of the locking range with RF-power in agreement with classical injection-locking theory. These results are discussed in the context of mode-locking operation.

Frequency-locked chaotic opto-RF oscillator.

PubMed

Thorette, Aurélien; Romanelli, Marco; Brunel, Marc; Vallet, Marc

2016-06-15

A driven opto-RF oscillator, consisting of a dual-frequency laser (DFL) submitted to frequency-shifted feedback, is experimentally and numerically studied in a chaotic regime. Precise control of the reinjection strength and detuning permits isolation of a parameter region of bounded-phase chaos, where the opto-RF oscillator is frequency-locked to the master oscillator, in spite of chaotic phase and intensity oscillations. Robust experimental evidence of this synchronization regime is found, and phase noise spectra allow us to compare phase-locking and bounded-phase chaos regimes. In particular, it is found that the long-term phase stability of the master oscillator is well transferred to the opto-RF oscillator, even in the chaotic regime.

Improving uniformity of atmospheric-pressure dielectric barrier discharges using dual frequency excitation

NASA Astrophysics Data System (ADS)

Liu, Y.; Peeters, F. J. J.; Starostin, S. A.; van de Sanden, M. C. M.; de Vries, H. W.

2018-01-01

This letter reports a novel approach to improve the uniformity of atmospheric-pressure dielectric barrier discharges using a dual-frequency excitation consisting of a low frequency (LF) at 200 kHz and a radio frequency (RF) at 13.56 MHz. It is shown that due to the periodic oscillation of the RF electric field, the electron acceleration and thus the gas ionization is temporally modulated, i.e. enhanced and suppressed during each RF cycle. As a result, the discharge development is slowed down with a lower amplitude and a longer duration of the LF discharge current. Hence, the RF electric field facilitates improved stability and uniformity simultaneously allowing a higher input power.

Marking multi-channel silicon-substrate electrode recording sites using radiofrequency lesions.

PubMed

Brozoski, Thomas J; Caspary, Donald M; Bauer, Carol A

2006-01-30

Silicon-substrate multi-channel electrodes (multiprobes) have proven useful in a variety of electrophysiological tasks. When using multiprobes it is often useful to identify the site of each channel, e.g., when recording single-unit activity from a heterogeneous structure. Lesion marking of electrode sites has been used for many years. Electrolytic, or direct current (DC) lesions, have been used successfully to mark multiprobe sites in rat hippocampus [Townsend G, Peloquin P, Kloosterman F, Hetke JF, Leung LS. Recording and marking with silicon multichannel electrodes. Brain Res Brain Res Protoc 2002;9:122-9]. The present method used radio-frequency (rf) lesions to distinctly mark each of the 16 recording sites of 16-channel linear array multiprobes, in chinchilla inferior colliculus. A commercial radio-frequency lesioner was used as the current source, in conjunction with custom connectors adapted to the multiprobe configuration. In vitro bench testing was used to establish current-voltage-time parameters, as well as to check multiprobe integrity and radio-frequency performance. In in vivo application, visualization of individual-channel multiprobe recording sites was clear in 21 out of 33 sets of collicular serial-sections (i.e., probe tracks) obtained from acute experimental subjects, i.e., maximum post-lesion survival time of 2h. Advantages of the rf method include well-documented methods of in vitro calibration as well as low impact on probe integrity. The rf method of marking individual-channel sites should be useful in a variety of applications.

FBG wavelength demodulation based on a radio frequency optical true time delay method.

PubMed

Wang, Jin; Zhu, Wanshan; Ma, Chenyuan; Xu, Tong

2018-06-01

A new fiber Bragg grating (FBG) wavelength shift demodulation method based on optical true time delay microwave phase detection is proposed. We used a microwave photonic link (MPL) to transport a radio frequency (RF) signal over a dispersion compensation fiber (DCF). The wavelength shift of the FBG will cause the time delay change of the optical carrier that propagates in an optical fiber with chromatic dispersion, which will result in the variation of the RF signal phase. A long DCF was adopted to enlarge the RF signal phase variation. An IQ mixer was used to measure the RF phase variation of the RF signal propagating in the MPL, and the wavelength shift of the FBG can be obtained by the measured RF signal phase variation. The experimental results showed that the wavelength shift measurement resolution is 2 pm when the group velocity dispersion of the DCF is 79.5 ps/nm and the frequency of the RF signal is 18 GHz. The demodulation time is as short as 0.1 ms. The measurement resolution can be improved simply by using a higher frequency of the RF signal and a longer DCF or larger chromatic dispersion value of the DCF.

Efficient Radio Frequency Inductive Discharges in Near Atmospheric Pressure Using Immittance Conversion Topology

NASA Astrophysics Data System (ADS)

Razzak, M. Abdur; Takamura, Shuichi; Uesugi, Yoshihiko; Ohno, Noriyasu

A radio frequency (rf) inductive discharge in atmospheric pressure range requires high voltage in the initial startup phase and high power during the steady state sustainment phase. It is, therefore, necessary to inject high rf power into the plasma ensuring the maximum use of the power source, especially where the rf power is limited. In order to inject the maximum possible rf power into the plasma with a moderate rf power source of few kilowatts range, we employ the immittance conversion topology by converting a constant voltage source into a constant current source to generate efficient rf discharge by inductively coupled plasma (ICP) technique at a gas pressure with up to one atmosphere in argon. A novel T-LCL immittance circuit is designed for constant-current high-power operation, which is practically very important in the high-frequency range, to provide high effective rf power to the plasma. The immittance conversion system combines the static induction transistor (SIT)-based radio frequency (rf) high-power inverter circuit and the immittance conversion elements including the rf induction coil. The basic properties of the immittance circuit are studied by numerical analysis and verified the results by experimental measurements with the inductive plasma as a load at a relatively high rf power of about 4 kW. The performances of the immittance circuit are also evaluated and compared with that of the conventional series resonance circuit in high-pressure induction plasma generation. The experimental results reveal that the immittance conversion circuit confirms injecting higher effective rf power into the plasma as much as three times than that of the series resonance circuit under the same operating conditions and same dc supply voltage to the inverter, thereby enhancing the plasma heating efficiency to generate efficient rf inductive discharges.

Development of an X-band 25 watt traveling-wave tube

NASA Technical Reports Server (NTRS)

Roberts, L. A.; Knight, R. I.

1972-01-01

The development of a 25 watt high efficiency travelingwave tube at 8.5 GHz for space communications and telemetry applications is reported. Described is the design basis for the tube, which is known as the WJ-3703. Because of the combined high efficiency and high frequency requirements, the helix and body dimensions are very small and require special techniques for various assembly and construction procedures. These are described in detail. Measurement results of focusing tests and RF operation are given, but only pulsed RF performance of the tubes was obtained.

Wireless-powered electroactive soft microgripper

NASA Astrophysics Data System (ADS)

Cheong, Hau Ran; Teo, Choon Yee; Leow, Pei Ling; Lai, Koon Chun; Chee, Pei Song

2018-05-01

This paper presents a wireless powered single active finger ionic polymer metal composite (IPMC) based microgripper that is operated using external radio-frequency (RF) magnetic field for biological cell manipulation application. A unimorph-like active finger is fabricated by integrating the IPMC actuator to the planar resonant LC receiver and DC rectifier circuits (made of flexible double-sided copper clad polyimide). The finger activated when the device is exposed to the external magnetic field generated by transmitter circuit that matches the resonant frequency of LC receiver circuit, ∼13.6 MHz in magnetic resonant coupling power transfer mechanism. The fabricated prototype shows a maximum IPMC deflection of 0.765 mm (activation force of 0.17 mN) at the RF power of 0.65 W with 3.5 VDC supplied from the LC receiver circuit. Three repeated ON-OFF wireless activation cycle was performed with the reported cumulative deflection of 0.57 mm. The cumulative deflection was increased to 1.17 mm, 1.19 mm and 1.24 mm for three different samples respectively at 5 VDC supplied. As a proof of concept, fish egg was used to represent the biological cell manipulation operation. The microgripper successfully gripped the fish egg sample without any damages. The experiments result validates the effectiveness of wireless RF soft microgripper towards the target application.

Acousto-optic modulation and opto-acoustic gating in piezo-optomechanical circuits

PubMed Central

Balram, Krishna C.; Davanço, Marcelo I.; Ilic, B. Robert; Kyhm, Ji-Hoon; Song, Jin Dong; Srinivasan, Kartik

2017-01-01

Acoustic wave devices provide a promising chip-scale platform for efficiently coupling radio frequency (RF) and optical fields. Here, we use an integrated piezo-optomechanical circuit platform that exploits both the piezoelectric and photoelastic coupling mechanisms to link 2.4 GHz RF waves to 194 THz (1550 nm) optical waves, through coupling to propagating and localized 2.4 GHz acoustic waves. We demonstrate acousto-optic modulation, resonant in both the optical and mechanical domains, in which waveforms encoded on the RF carrier are mapped to the optical field. We also show opto-acoustic gating, in which the application of modulated optical pulses interferometrically gates the transmission of propagating acoustic pulses. The time-domain characteristics of this system under both pulsed RF and pulsed optical excitation are considered in the context of the different physical pathways involved in driving the acoustic waves, and modelled through the coupled mode equations of cavity optomechanics. PMID:28580373

Ferroelectric Based High Power Components for L-Band Accelerator Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kanareykin, Alex; Jing, Chunguang; Kostin, Roman

2018-01-16

We are developing a new electronic device to control the power in particle accelerators. The key technology is a new nanostructured material developed by Euclid that changes its properties with an applied electric field. Both superconducting and conventional accelerating structures require fast electronic control of the input rf power. A fast controllable phase shifter would allow for example the control of the rf power delivered to multiple accelerating cavities from a single power amplifier. Nonlinear ferroelectric microwave components can control the tuning or the input power coupling for rf cavities. Applying a bias voltage across a nonlinear ferroelectric changes itsmore » permittivity. This effect can be used to cause a phase change of a propagating rf signal or change the resonant frequency of a cavity. The key is the development of a low loss highly tunable ferroelectric material.« less

Design of temperature detection device for drum of belt conveyor

NASA Astrophysics Data System (ADS)

Zhang, Li; He, Rongjun

2018-03-01

For difficult wiring and big measuring error existed in the traditional temperature detection method for drum of belt conveyor, a temperature detection device for drum of belt conveyor based on Radio Frequency(RF) communication is designed. In the device, detection terminal can collect temperature data through tire pressure sensor chip SP370 which integrates temperature detection and RF emission. The receiving terminal which is composed of RF receiver chip and microcontroller receives the temperature data and sends it to Controller Area Network(CAN) bus. The test results show that the device meets requirements of field application with measuring error ±3.73 ° and single button battery can provide continuous current for the detection terminal over 1.5 years.

Spontaneous Magnetic Alignment by Yearling Snapping Turtles: Rapid Association of Radio Frequency Dependent Pattern of Magnetic Input with Novel Surroundings

PubMed Central

Landler, Lukas; Painter, Michael S.; Youmans, Paul W.; Hopkins, William A.; Phillips, John B.

2015-01-01

We investigated spontaneous magnetic alignment (SMA) by juvenile snapping turtles using exposure to low-level radio frequency (RF) fields at the Larmor frequency to help characterize the underlying sensory mechanism. Turtles, first introduced to the testing environment without the presence of RF aligned consistently towards magnetic north when subsequent magnetic testing conditions were also free of RF (‘RF off → RF off’), but were disoriented when subsequently exposed to RF (‘RF off → RF on’). In contrast, animals initially introduced to the testing environment with RF present were disoriented when tested without RF (‘RF on → RF off’), but aligned towards magnetic south when tested with RF (‘RF on → RF on’). Sensitivity of the SMA response of yearling turtles to RF is consistent with the involvement of a radical pair mechanism. Furthermore, the effect of RF appears to result from a change in the pattern of magnetic input, rather than elimination of magnetic input altogether, as proposed to explain similar effects in other systems/organisms. The findings show that turtles first exposed to a novel environment form a lasting association between the pattern of magnetic input and their surroundings. However, under natural conditions turtles would never experience a change in the pattern of magnetic input. Therefore, if turtles form a similar association of magnetic cues with the surroundings each time they encounter unfamiliar habitat, as seems likely, the same pattern of magnetic input would be associated with multiple sites/localities. This would be expected from a sensory input that functions as a global reference frame, helping to place multiple locales (i.e., multiple local landmark arrays) into register to form a global map of familiar space. PMID:25978736

Spontaneous magnetic alignment by yearling snapping turtles: rapid association of radio frequency dependent pattern of magnetic input with novel surroundings.

PubMed

Landler, Lukas; Painter, Michael S; Youmans, Paul W; Hopkins, William A; Phillips, John B

2015-01-01

We investigated spontaneous magnetic alignment (SMA) by juvenile snapping turtles using exposure to low-level radio frequency (RF) fields at the Larmor frequency to help characterize the underlying sensory mechanism. Turtles, first introduced to the testing environment without the presence of RF aligned consistently towards magnetic north when subsequent magnetic testing conditions were also free of RF ('RF off → RF off'), but were disoriented when subsequently exposed to RF ('RF off → RF on'). In contrast, animals initially introduced to the testing environment with RF present were disoriented when tested without RF ('RF on → RF off'), but aligned towards magnetic south when tested with RF ('RF on → RF on'). Sensitivity of the SMA response of yearling turtles to RF is consistent with the involvement of a radical pair mechanism. Furthermore, the effect of RF appears to result from a change in the pattern of magnetic input, rather than elimination of magnetic input altogether, as proposed to explain similar effects in other systems/organisms. The findings show that turtles first exposed to a novel environment form a lasting association between the pattern of magnetic input and their surroundings. However, under natural conditions turtles would never experience a change in the pattern of magnetic input. Therefore, if turtles form a similar association of magnetic cues with the surroundings each time they encounter unfamiliar habitat, as seems likely, the same pattern of magnetic input would be associated with multiple sites/localities. This would be expected from a sensory input that functions as a global reference frame, helping to place multiple locales (i.e., multiple local landmark arrays) into register to form a global map of familiar space.

Microfluidic stretchable RF electronics.

PubMed

Cheng, Shi; Wu, Zhigang

2010-12-07

Stretchable electronics is a revolutionary technology that will potentially create a world of radically different electronic devices and systems that open up an entirely new spectrum of possibilities. This article proposes a microfluidic based solution for stretchable radio frequency (RF) electronics, using hybrid integration of active circuits assembled on flex foils and liquid alloy passive structures embedded in elastic substrates, e.g. polydimethylsiloxane (PDMS). This concept was employed to implement a 900 MHz stretchable RF radiation sensor, consisting of a large area elastic antenna and a cluster of conventional rigid components for RF power detection. The integrated radiation sensor except the power supply was fully embedded in a thin elastomeric substrate. Good electrical performance of the standalone stretchable antenna as well as the RF power detection sub-module was verified by experiments. The sensor successfully detected the RF radiation over 5 m distance in the system demonstration. Experiments on two-dimensional (2D) stretching up to 15%, folding and twisting of the demonstrated sensor were also carried out. Despite the integrated device was severely deformed, no failure in RF radiation sensing was observed in the tests. This technique illuminates a promising route of realizing stretchable and foldable large area integrated RF electronics that are of great interest to a variety of applications like wearable computing, health monitoring, medical diagnostics, and curvilinear electronics.

Challenges and opportunities for multi-functional oxide thin films for voltage tunable radio frequency/microwave components

NASA Astrophysics Data System (ADS)

Subramanyam, Guru; Cole, M. W.; Sun, Nian X.; Kalkur, Thottam S.; Sbrockey, Nick M.; Tompa, Gary S.; Guo, Xiaomei; Chen, Chonglin; Alpay, S. P.; Rossetti, G. A.; Dayal, Kaushik; Chen, Long-Qing; Schlom, Darrell G.

2013-11-01

There has been significant progress on the fundamental science and technological applications of complex oxides and multiferroics. Among complex oxide thin films, barium strontium titanate (BST) has become the material of choice for room-temperature-based voltage-tunable dielectric thin films, due to its large dielectric tunability and low microwave loss at room temperature. BST thin film varactor technology based reconfigurable radio frequency (RF)/microwave components have been demonstrated with the potential to lower the size, weight, and power needs of a future generation of communication and radar systems. Low-power multiferroic devices have also been recently demonstrated. Strong magneto-electric coupling has also been demonstrated in different multiferroic heterostructures, which show giant voltage control of the ferromagnetic resonance frequency of more than two octaves. This manuscript reviews recent advances in the processing, and application development for the complex oxides and multiferroics, with the focus on voltage tunable RF/microwave components. The over-arching goal of this review is to provide a synopsis of the current state-of the-art of complex oxide and multiferroic thin film materials and devices, identify technical issues and technical challenges that need to be overcome for successful insertion of the technology for both military and commercial applications, and provide mitigation strategies to address these technical challenges.

Nothing more than a pair of curvatures: A common mechanism for the detection of both radial and non-radial frequency patterns.

PubMed

Schmidtmann, Gunnar; Kingdom, Frederick A A

2017-05-01

Radial frequency (RF) patterns, which are sinusoidal modulations of a radius in polar coordinates, are commonly used to study shape perception. Previous studies have argued that the detection of RF patterns is either achieved globally by a specialized global shape mechanism, or locally using as cue the maximum tangent orientation difference between the RF pattern and the circle. Here we challenge both ideas and suggest instead a model that accounts not only for the detection of RF patterns but also for line frequency patterns (LF), i.e. contours sinusoidally modulated around a straight line. The model has two features. The first is that the detection of both RF and LF patterns is based on curvature differences along the contour. The second is that this curvature metric is subject to what we term the Curve Frequency Sensitivity Function, or CFSF, which is characterized by a flat followed by declining response to curvature as a function of modulation frequency, analogous to the modulation transfer function of the eye. The evidence that curvature forms the basis for detection is that at very low modulation frequencies (1-3 cycles for the RF pattern) there is a dramatic difference in thresholds between the RF and LF patterns, a difference however that disappears at medium and high modulation frequencies. The CFSF feature on the other hand explains why thresholds, rather than continuously declining with modulation frequency, asymptote at medium and high modulation frequencies. In summary, our analysis suggests that the detection of shape modulations is processed by a common curvature-sensitive mechanism that is subject to a shape-frequency-dependent transfer function. This mechanism is independent of whether the modulation is applied to a circle or a straight line. Copyright © 2017 Elsevier Ltd. All rights reserved.

Whistlers, Helicons, Lower Hybrid Waves: the Physics of RF Wave Absorption Without Cyclotron Resonances

NASA Astrophysics Data System (ADS)

Pinsker, R. I.

2014-10-01

In hot magnetized plasmas, two types of linear collisionless absorption processes are used to heat and drive noninductive current: absorption at ion or electron cyclotron resonances and their harmonics, and absorption by Landau damping and the transit-time-magnetic-pumping (TTMP) interactions. This tutorial discusses the latter process, i.e., parallel interactions between rf waves and electrons in which cyclotron resonance is not involved. Electron damping by the parallel interactions can be important in the ICRF, particularly in the higher harmonic region where competing ion cyclotron damping is weak, as well as in the Lower Hybrid Range of Frequencies (LHRF), which is in the neighborhood of the geometric mean of the ion and electron cyclotron frequencies. On the other hand, absorption by parallel processes is not significant in conventional ECRF schemes. Parallel interactions are especially important for the realization of high current drive efficiency with rf waves, and an application of particular recent interest is current drive with the whistler or helicon wave at high to very high (i.e., the LHRF) ion cyclotron harmonics. The scaling of absorption by parallel interactions with wave frequency is examined and the advantages and disadvantages of fast (helicons/whistlers) and slow (lower hybrid) waves in the LHRF in the context of reactor-grade tokamak plasmas are compared. In this frequency range, both wave modes can propagate in a significant fraction of the discharge volume; the ways in which the two waves can interact with each other are considered. The use of parallel interactions to heat and drive current in practice will be illustrated with examples from past experiments; also looking forward, this tutorial will provide an overview of potential applications in tokamak reactors. Supported by the US Department of Energy under DE-FC02-04ER54698.

The Impact of Emerging MEMS-Based Microsystems on US Defense Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

STAPLE,BEVAN D.; JAKUBCZAK II,JEROME F.

2000-01-20

This paper examines the impact of inserting Micro-Electro-Mechanical Systems (MEMS) into US defense applications. As specific examples, the impacts of micro Inertial Measurement Units (IMUs), radio frequency MEMS (RF MEMS), and Micro-Opto-Electro-Mechanical Systems (MOEMS) to provide integrated intelligence, communication, and control to the defense infrastructure with increased affordability, functionality, and performance are highlighted.

Studies on omnidirectional enhancement of giga-hertz radiation by sub-wavelength plasma modulation

NASA Astrophysics Data System (ADS)

Fanrong, KONG; Qiuyue, NIE; Shu, LIN; Zhibin, WANG; Bowen, LI; Shulei, ZHENG; Binhao, JIANG

2018-01-01

The technology of radio frequency (RF) radiation intensification for radio compact antennas based on modulation and enhancement effects of sub-wavelength plasma structures represents an innovative developing strategy. It exhibits important scientific significance and promising potential of broad applications in various areas of national strategic demands, such as electrical information network and microwave communication, detection and control technology. In this paper, laboratory experiments and corresponding analyses have been carried out to investigate the modulation and enhancement technology of sub-wavelength plasma structure on the RF electromagnetic radiation. An application focused sub-wavelength plasma-added intensification up to ∼7 dB higher than the free-space radiation is observed experimentally in giga-hertz (GHz) RF band. The effective radiation enhancement bandwidth covers from 0.85 to 1.17 GHz, while the enhanced electromagnetic signals transmitted by sub-wavelength plasma structures maintain good communication quality. Particularly, differing from the traditional RF electromagnetic radiation enhancement method characterized by focusing the radiation field of antenna in a specific direction, the sub-wavelength plasma-added intensification of the antenna radiation presents an omnidirectional enhancement, which is reported experimentally for the first time. Corresponding performance characteristics and enhancement mechanism analyses are also conducted in this paper. The results have demonstrated the feasibility and promising potential of sub-wavelength plasma modulation in application focused RF communication, and provided the scientific basis for further research and development of sub-wavelength plasma enhanced compact antennas with wide-range requests and good quality for communication.

An RF phased array applicator designed for hyperthermia breast cancer treatments

PubMed Central

Wu, Liyong; McGough, Robert J; Arabe, Omar Ali; Samulski, Thaddeus V

2007-01-01

An RF phased array applicator has been constructed for hyperthermia treatments in the intact breast. This RF phased array consists of four antennas mounted on a Lexan water tank, and geometric focusing is employed so that each antenna points in the direction of the intended target. The operating frequency for this phased array is 140 MHz. The RF array has been characterized both by electric field measurements in a water tank and by electric field simulations using the finite-element method. The finite-element simulations are performed with HFSS software, where the mesh defined for finite-element calculations includes the geometry of the tank enclosure and four end-loaded dipole antennas. The material properties of the water tank enclosure and the antennas are also included in each simulation. The results of the finite-element simulations are compared to the measured values for this configuration, and the results, which include the effects of amplitude shading and phase shifting, show that the electric field predicted by finite-element simulations is similar to the measured field. Simulations also show that the contributions from standing waves are significant, which is consistent with measurement results. Simulated electric field and bio-heat transfer results are also computed within a simple 3D breast model. Temperature simulations show that, although peak temperatures are generated outside the simulated tumour target, this RF phased array applicator is an effective device for regional hyperthermia in the intact breast. PMID:16357427

Titanium dioxide thin films deposited by pulsed laser deposition and integration in radio frequency devices: Study of structure, optical and dielectric properties

NASA Astrophysics Data System (ADS)

Orlianges, Jean-Christophe; Crunteanu, Aurelian; Pothier, Arnaud; Merle-Mejean, Therese; Blondy, Pierre; Champeaux, Corinne

2012-12-01

Titanium dioxide presents a wide range of technological application possibilities due to its dielectric, electrochemical, photocatalytic and optical properties. The three TiO2 allotropic forms: anatase, rutile and brookite are also interesting, since they exhibit different properties, stabilities and growth modes. For instance, rutile has a high dielectric permittivity, of particular interest for the integration as dielectric in components such as microelectromechanical systems (MEMS) for radio frequency (RF) devices. In this study, titanium dioxide thin films are deposited by pulsed laser deposition. Characterizations by Raman spectroscopy and X-ray diffraction show the evolution of the structural properties. Thin films optical properties are investigated using spectroscopic ellipsometry and transmission measurements from UV to IR range. Co-planar waveguide (CPW) devices are fabricated based on these films. Their performances are measured in the RF domain and compared to simulation, leading to relative permittivity values in the range 30-120, showing the potentialities of the deposited material for capacitive switches applications.

Measurements and modeling of radio frequency field structures in a helicon plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, C. A.; Chen, Guangye; Arefiev, A. V.

2011-01-01

Measurements of the radio frequency (rf) field structure, plasma density, and electron temperature are presented for a 1 kW argon helicon plasma source. The measured profiles change considerably when the equilibrium magnetic field is reversed. The measured rf fields are identified as fields of radially localized helicon waves, which propagate in the axial direction. The rf field structure is compared to the results of two-dimensional cold plasma full-wave simulations for the measured density profiles. Electron collision frequency is adjusted in the simulations to match the simulated and measured field profiles. The resulting frequency is anomalously high, which is attributed tomore » the excitation of an ion-acoustic instability. The calculated power deposition is insensitive to the collision frequency and accounts for most of the power supplied by the rf-generator.« less

Photocatalytic characteristic and photodegradation kinetics of toluene using N-doped TiO2 modified by radio frequency plasma.

PubMed

Shie, Je-Lueng; Lee, Chiu-Hsuan; Chiou, Chyow-San; Chen, Yi-Hung; Chang, Ching-Yuan

2014-01-01

This study investigates the feasibility of applications of the plasma surface modification of photocatalysts and the removal of toluene from indoor environments. N-doped TiO2 is prepared by precipitation methods and calcined using a muffle furnace (MF) and modified by radio frequency plasma (RF) at different temperatures with light sources from a visible light lamp (VLL), a white light-emitting diode (WLED) and an ultraviolet light-emitting diode (UVLED). The operation parameters and influential factors are addressed and prepared for characteristic analysis and photo-decomposition examination. Furthermore, related kinetic models are established and used to simulate the experimental data. The characteristic analysis results show that the RF plasma-calcination method enhanced the Brunauer Emmett Teller surface area of the modified photocatalysts effectively. For the elemental analysis, the mass percentages of N for the RF-modified photocatalyst are larger than those of MF by six times. The aerodynamic diameters of the RF-modifiedphotocatalyst are all smaller than those of MF. Photocatalytic decompositions of toluene are elucidated according to the Langmuir-Hinshelwood model. Decomposition efficiencies (eta) of toluene for RF-calcined methods are all higher than those of commercial TiO2 (P25). Reaction kinetics ofphoto-decomposition reactions using RF-calcined methods with WLED are proposed. A comparison of the simulation results with experimental data is also made and indicates good agreement. All the results provide useful information and design specifications. Thus, this study shows the feasibility and potential use of plasma modification via LED in photocatalysis.

An Energy-Efficient ASIC for Wireless Body Sensor Networks in Medical Applications.

PubMed

Xiaoyu Zhang; Hanjun Jiang; Lingwei Zhang; Chun Zhang; Zhihua Wang; Xinkai Chen

2010-02-01

An energy-efficient application-specific integrated circuit (ASIC) featured with a work-on-demand protocol is designed for wireless body sensor networks (WBSNs) in medical applications. Dedicated for ultra-low-power wireless sensor nodes, the ASIC consists of a low-power microcontroller unit (MCU), a power-management unit (PMU), reconfigurable sensor interfaces, communication ports controlling a wireless transceiver, and an integrated passive radio-frequency (RF) receiver with energy harvesting ability. The MCU, together with the PMU, provides quite flexible communication and power-control modes for energy-efficient operations. The always-on passive RF receiver with an RF energy harvesting block offers the sensor nodes the capability of work-on-demand with zero standby power. Fabricated in standard 0.18-¿m complementary metal-oxide semiconductor technology, the ASIC occupies a die area of 2 mm × 2.5 mm. A wireless body sensor network sensor-node prototype using this ASIC only consumes < 10-nA current under the passive standby mode, and < 10 ¿A under the active standby mode, when supplied by a 3-V battery.

An Rf Focused Interdigital Ion Accelerating Structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swenson, D.A.

2003-08-26

An Rf Focused Interdigital (RFI) ion accelerating structure will be described. It represents an effective combination of the Wideroee (or interdigital) linac structure, used for many low frequency, heavy ion applications, and the rf electric quadrupole focusing used in the RFQ and RFD linac structures. As in the RFD linac structure, rf focusing is introduced into the RFI linac structure by configuring the drift tubes as two independent pieces operating at different electrical potentials as determined by the rf fields of the linac structure. Each piece (or electrode) of the RFI drift tube supports two fingers pointed inwards towards themore » opposite end of the drift tube forming a four-finger geometry that produces an rf quadrupole field along the axis of the linac for focusing the beam. However, because of the differences in the rf field configuration along the axis, the scheme for introducing rf focusing into the interdigital linac structure is quite different from that adopted for the RFD linac structure. The RFI linac structure promises to have significant size, efficiency, performance, and cost advantages over existing linac structures for the acceleration of low energy ion beams of all masses (light to heavy). These advantages will be reviewed. A 'cold model' of this new linac structure has been fabricated and the results of rf cavity measurements on this cold model will be presented.« less

Inactivation of foodborne pathogens in ground beef by cooking with highly controlled radio frequency energy.

PubMed

Schlisselberg, Dov B; Kler, Edna; Kalily, Emmanuel; Kisluk, Guy; Karniel, Ohad; Yaron, Sima

2013-01-01

The consumer demand for fresh tasting, high quality, low salt, preservative-free meals which require minimal preparation time magnifies the safety concern and emphasizes the need to use innovative technologies for food processing. A modern technique to uniformly heat and cook foods is based on a combination of convection and controlled radio frequency (RF) energy. However any advantage conferred on meat cooked by this method would be lost if application of the technology results in decreased safety. Our main goal was to study the inactivation efficacy of this method of cooking against pathogens in ground meat in comparison to standard convection cooking. Meat balls were artificially inoculated with GFP expressing Escherichia coli, Salmonella Typhimurium and Listeria monocytogenes as well as spores of Bacillus cereus and Bacillus thuringiensis and cooked by convection heating (220°C, 40 min), by using energy generated from frequencies in the RF bandwidth (RF cooking, 7.5 min) or by combined heating (5.5 min), until the center temperature of each sample reached 73°C. The mean reductions in total indigenous bacteria obtained by RF and convection were 2.8 and 2.5 log CFU/g, respectively. Cooking of meat balls with convection reduced the E. coli population (8 log CFU/g) by 5.5 log CFU/g, whilst treatment with RF reduced E. coli population to undetectable levels. The mean reductions of S. Typhimurium obtained by RF and convection were 5.7 and 6.5 log CFU/g, respectively. The combined treatment reduced the Salmonella population to undetectable levels. In contrast, L. monocytogenes was poorly affected by RF cooking. The mean reduction of L. monocytogenes obtained by RF energy was 0.4 log CFU/g, while convection cooking resulted in undetectable levels. Interestingly, the combined treatment also resulted with undetectable levels of Listeria although time of cooking was reduced by 86%. One-step cooking had negligible effects on the Bacillus spores and therefore a 2-step treatment of RF or convection was applied. This 2-step treatment proved to be efficient with 4.5 log CFU/g reduction for both RF and convection. In conclusion, here we show that combination of RF with convection cooking resulted in similar or even better effects on selected foodborne pathogens compared to convection only, while the time required for safe cooking is cut down by up to 86%. The equal or better results in the levels of all investigated pathogens using RF with convection compared with convection only suggest that this technology looks promising and safe for ground beef cooking. Copyright © 2012 Elsevier B.V. All rights reserved.

Transition from Townsend to radio-frequency homogeneous dielectric barrier discharge in a roll-to-roll configuration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bazinette, R.; SIAME, Université de Pau et des Pays de l'Adour, Pau; Paillol, J.

The aim of this paper is to better understand the transition from Townsend to radio-frequency homogeneous dielectric barrier discharge (DBD) at atmospheric pressure. The study is done in an Ar/NH{sub 3} Penning mixture for an electrode configuration adapted to roll-to-roll plasma surface treatment. The study was led in a frequency range running from 50 kHz up to 8.3 MHz leading to different DBD modes with a 1 mm gas gap: Glow (GDBD), Townsend (TDBD), and Radio-frequency (RF-DBD). In the frequency range between TDBD and RF-DBD, from 250 kHz to 2.3 MHz, additional discharges are observed outside the inter-electrode gas gap. Because each high voltagemore » electrode are inside a dielectric barrel, these additional discharges occur on the side of the barrel where the gap is larger. They disappear when the RF-DBD mode is attained in the 1 mm inter-electrode gas gap, i.e., for frequencies equal or higher than 3 MHz. Fast imaging and optical emission spectroscopy show that the additional discharges are radio-frequency DBDs while the inter-electrode discharge is a TDBD. The RF-DBD discharge mode is attained when electrons drift becomes low enough compared to the voltage oscillation frequency to limit electron loss at the anode. To check that the additional discharges are due to a larger gas gap and a lower voltage amplitude, the TDBD/RF-DBD transition is investigated as a function of the gas gap and the applied voltage frequency and amplitude. Results show that the increase in the frequency at constant gas gap or in the gas gap at constant frequency allows to obtain RF-DBD instead of TDBD. At low frequency and large gap, the increase in the applied voltage allows RF-DBD/TDBD transition. As a consequence, an electrode configuration allowing different gap values is a solution to successively have different discharge modes with the same applied voltage.« less

Development of Wireless RFID Glove for Various Applications

NASA Astrophysics Data System (ADS)

Lee, Changwon; Kim, Minchul; Park, Jinwoo; Oh, Jeonghoon; Eom, Kihwan

Radio Frequency Identification is increasingly popular technology with many applications. The majority of applications of RFID are supply-chain management. In this paper, we proposed the development of wireless RFID Glove for various applications in real life. Proposed wireless RFID glove is composed of RFID reader of 13.56 MHz and RF wireless module. Proposed Gloves were applied to two applications. First is the interactive leaning and second is Meal aid system for blind people. The experimental results confirmed good performances.

Dual-functional on-chip AlGaAs/GaAs Schottky diode for RF power detection and low-power rectenna applications.

PubMed

Hashim, Abdul Manaf; Mustafa, Farahiyah; Rahman, Shaharin Fadzli Abd; Rahman, Abdul Rahim Abdul

2011-01-01

A Schottky diode has been designed and fabricated on an n-AlGaAs/GaAs high-electron-mobility-transistor (HEMT) structure. Current-voltage (I-V) measurements show good device rectification, with a Schottky barrier height of 0.4349 eV for Ni/Au metallization. The differences between the Schottky barrier height and the theoretical value (1.443 eV) are due to the fabrication process and smaller contact area. The RF signals up to 1 GHz are rectified well by the fabricated Schottky diode and a stable DC output voltage is obtained. The increment ratio of output voltage vs input power is 0.2 V/dBm for all tested frequencies, which is considered good enough for RF power detection. Power conversion efficiency up to 50% is obtained at frequency of 1 GHz and input power of 20 dBm with series connection between diode and load, which also shows the device's good potential as a rectenna device with further improvement. The fabricated n-AlGaAs/GaAs Schottky diode thus provides a conduit for breakthrough designs for RF power detectors, as well as ultra-low power on-chip rectenna device technology to be integrated in nanosystems.

Dual-Functional On-Chip AlGaAs/GaAs Schottky Diode for RF Power Detection and Low-Power Rectenna Applications

PubMed Central

Hashim, Abdul Manaf; Mustafa, Farahiyah; Rahman, Shaharin Fadzli Abd; Rahman, Abdul Rahim Abdul

2011-01-01

A Schottky diode has been designed and fabricated on an n-AlGaAs/GaAs high-electron-mobility-transistor (HEMT) structure. Current-voltage (I–V) measurements show good device rectification, with a Schottky barrier height of 0.4349 eV for Ni/Au metallization. The differences between the Schottky barrier height and the theoretical value (1.443 eV) are due to the fabrication process and smaller contact area. The RF signals up to 1 GHz are rectified well by the fabricated Schottky diode and a stable DC output voltage is obtained. The increment ratio of output voltage vs input power is 0.2 V/dBm for all tested frequencies, which is considered good enough for RF power detection. Power conversion efficiency up to 50% is obtained at frequency of 1 GHz and input power of 20 dBm with series connection between diode and load, which also shows the device’s good potential as a rectenna device with further improvement. The fabricated n-AlGaAs/GaAs Schottky diode thus provides a conduit for breakthrough designs for RF power detectors, as well as ultra-low power on-chip rectenna device technology to be integrated in nanosystems. PMID:22164066

A home-built digital optical MRI console using high-speed serial links.

PubMed

Tang, Weinan; Wang, Weimin; Liu, Wentao; Ma, Yajun; Tang, Xin; Xiao, Liang; Gao, Jia-Hong

2015-08-01

To develop a high performance, cost-effective digital optical console for scalable multichannel MRI. The console system was implemented with flexibility and efficiency based on a modular architecture with distributed pulse sequencers. High-speed serial links were optimally utilized to interconnect the system, providing fast digital communication with a multi-gigabit data rate. The conventional analog radio frequency (RF) chain was replaced with a digital RF manipulation. The acquisition electronics were designed in close proximity to RF coils and preamplifiers, using a digital optical link to transmit the MR signal. A prototype of the console was constructed with a broad frequency range from direct current to 100 MHz. A temporal resolution of 1 μs was achieved for both the RF and gradient operations. The MR signal was digitized in the scanner room with an overall dynamic range between 16 and 24 bits and was transmitted to a master controller over a duplex optic fiber with a high data rate of 3.125 gigabits per second. High-quality phantom and human images were obtained using the prototype on both 0.36T and 1.5T clinical MRI scanners. A homemade digital optical MRI console with high-speed serial interconnection has been developed to better serve imaging research and clinical applications. © 2014 Wiley Periodicals, Inc.

Precursor and Neutral Loss Scans in an RF Scanning Linear Quadrupole Ion Trap

NASA Astrophysics Data System (ADS)

Snyder, Dalton T.; Szalwinski, Lucas J.; Schrader, Robert L.; Pirro, Valentina; Hilger, Ryan; Cooks, R. Graham

2018-03-01

Methodology for performing precursor and neutral loss scans in an RF scanning linear quadrupole ion trap is described and compared to the unconventional ac frequency scan technique. In the RF scanning variant, precursor ions are mass selectively excited by a fixed frequency resonance excitation signal at low Mathieu q while the RF amplitude is ramped linearly to pass ions through the point of excitation such that the excited ion's m/z varies linearly with time. Ironically, a nonlinear ac frequency scan is still required for ejection of the product ions since their frequencies vary nonlinearly with the linearly varying RF amplitude. In the case of the precursor scan, the ejection frequency must be scanned so that it is fixed on a product ion m/z throughout the RF scan, whereas in the neutral loss scan, it must be scanned to maintain a constant mass offset from the excited precursor ions. Both simultaneous and sequential permutation scans are possible; only the former are demonstrated here. The scans described are performed on a variety of samples using different ionization sources: protonated amphetamine ions generated by nanoelectrospray ionization (nESI), explosives ionized by low-temperature plasma (LTP), and chemical warfare agent simulants sampled from a surface and analyzed with swab touch spray (TS). We lastly conclude that the ac frequency scan variant of these MS/MS scans is preferred due to electronic simplicity. In an accompanying manuscript, we thus describe the implementation of orthogonal double resonance precursor and neutral loss scans on the Mini 12 using constant RF voltage. [Figure not available: see fulltext.

Magnetic Resonance Based Electrical Properties Tomography: A Review

PubMed Central

Zhang, Xiaotong; Liu, Jiaen

2014-01-01

Frequency-dependent electrical properties (EPs; conductivity and permittivity) of biological tissues provide important diagnostic information (e.g. tumor characterization), and also play an important role in quantifying radiofrequency (RF) coil induced Specific Absorption Rate (SAR) which is a major safety concern in high- and ultrahigh-field Magnetic Resonance Imaging (MRI) applications. Cross-sectional imaging of EPs has been pursued for decades. Recently introduced Electrical Properties Tomography (EPT) approaches utilize the measurable RF magnetic field induced by the RF coil in an MRI system to quantitatively reconstruct the EP distribution in vivo and non-invasively with a spatial resolution of a few millimeters or less. This paper reviews the Electrical Properties Tomography approach from its basic theory in electromagnetism to the state of the art research outcomes. Emphasizing on the imaging reconstruction methods rather than experimentation techniques, we review the developed imaging algorithms, validation results in physical phantoms and biological tissues, as well as their applications in in vivo tumor detection and subject-specific SAR prediction. Challenges for future research are also discussed. PMID:24803104

Conductor backed and shielded multi-layer coplanar waveguide designs on LTCC for RF carrier boards for packaging PICs

NASA Astrophysics Data System (ADS)

Marraccini, Philip J.; Jezzini, Moises A.; Peters, Frank H.

2016-05-01

Designing photonic integrated circuits (PICs) with packaging in mind is important since this impacts the performance of the final product. In coherent optical communication applications there are a large number of DC and RF lines that need routed to connect the PIC to the outer packaging. These RF lines should be impedance matched to the devices, isolated from each other, low loss and protected against electromagnetic interference (EMI) over the frequency range of interest to achieve the performance required for the application. Multilevel low temperature co-fired ceramic (LTCC) boards can be used as a carrier board connecting the PIC to the packaging due to its good RF performance, machinability, compatibility with hermetic sealing, and ability to integrate drivers into the board. Flexibility with layer numbers enables additional layers for shielding against electromagnetic interference or increased space for routing electrical connections. In this paper the design, simulations, and measured results for a set of 4 phase matched transmission lines in LTCC that would be used with an IQ MZM are presented. The measured 3dB bandwidth for a set of four phase matched transmission lines for an IQ MZM was measured to be 19.8 GHz.

Multiphysics Analysis of Frequency Detuning in Superconducting RF Cavities for Proton Particle Accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Awida, M. H.; Gonin, I.; Passarelli, D.

2016-01-22

Multiphysics analyses for superconducting cavities are essential in the course of cavity design to meet stringent requirements on cavity frequency detuning. Superconducting RF cavities are the core accelerating elements in modern particle accelerators whether it is proton or electron machine, as they offer extremely high quality factors thus reducing the RF losses per cavity. However, the superior quality factor comes with the challenge of controlling the resonance frequency of the cavity within few tens of hertz bandwidth. In this paper, we investigate how the multiphysics analysis plays a major role in proactively minimizing sources of frequency detuning, specifically; microphonics andmore » Lorentz Force Detuning (LFD) in the stage of RF design of the cavity and mechanical design of the niobium shell and the helium vessel.« less

Development of an automatic frequency control system for an X-band (=9300 MHz) RF electron linear accelerator

NASA Astrophysics Data System (ADS)

Cha, Sungsu; Kim, Yujong; Lee, Byung Cheol; Park, Hyung Dal; Lee, Seung Hyun; Buaphad, Pikad

2017-05-01

KAERI is developing a 6 MeV X-band radio frequency (RF) electron linear accelerator for medical purposes. The proposed X-band accelerator consists of an e-gun, an accelerating structure, two solenoid magnets, two steering magnets, a magnetron, a modulator, and an automatic frequency control (AFC) system. The accelerating structure of the component consists of oxygen-free high-conductivity copper (OFHC). Therefore, the ambient temperature changes the volume, and the resonance frequency of the accelerating structure also changes. If the RF frequency of a 9300 MHz magnetron and the resonance frequency of the accelerating structure do not match, it can degrade the performance. That is, it will decrease the output power, lower the beam current, decrease the X-ray dose rate, increase the reflection power, and result in unstable operation of the accelerator. Accelerator operation should be possible at any time during all four seasons. To prevent humans from being exposed to radiation when it is operated, the accelerator should also be operable through remote monitoring and remote control. Therefore, the AFC system is designed to meet these requirements; it is configured based on the concept of a phase-locked loop (PLL) model, which includes an RF section, an intermediate frequency (IF) [1-3] section, and a local oscillator (LO) section. Some resonance frequency controllers use a DC motor, chain, and potentiometer to store the position and tune the frequency [4,5]. Our AFC system uses a step motor to tune the RF frequency of the magnetron. The maximum tuning turn number of our magnetron frequency tuning shaft is ten. Since the RF frequency of our magnetron is 9300±25 MHz, it gives 5 MHz (∵±25 MHz/10 turns → 50 MHz/10 turns =5 MHz/turn) frequency tuning per turn. The rotation angle of our step motor is 0.72° per step and the total step number per one rotation is 360°/0.72°=500 steps. Therefore, the tuning range per step is 10 kHz/step (=5 MHz per turn/500 steps per turn). The developed system is a more compact new resonance frequency control system. In addition, a frequency measuring part is included and it can measure the real-time resonance frequency from the magnetron. We have succeeded in the stable provisioning of RF power by recording the results of a 0.01% frequency deviation in the AFC during an RF test. Accordingly, in this paper, the detailed design, fabrication, and a high power test of the AFC system for the X-band linac are presented.

670-GHz Down- and Up-Converting HEMT-Based Mixers

NASA Technical Reports Server (NTRS)

Schlecht, Enrich T.; Chattopadhyay, Goutam; Lin, Robert H.; Sin, Seth; Deal, William; Rodriquez, Bryan; Bayuk, Brian; Leong, Kevin; Mei, Gerry

2012-01-01

A large category of scientific investigation takes advantage of the interactions of signals in the frequency range from 300 to 1,000 GHz and higher. This includes astronomy and atmospheric science, where spectral observations in this frequency range give information about molecular abundances, pressures, and temperatures of small-sized molecules such as water. Additionally, there is a minimum in the atmospheric absorption at around 670 GHz that makes this frequency useful for terrestrial imaging, radar, and possibly communications purposes. This is because 670 GHz is a good compromise for imaging and radar applications between spatial resolution (for a given antenna size) that favors higher frequencies, and atmospheric losses that favor lower frequencies. A similar trade-off applies to communications link budgets: higher frequencies allow smaller antennas, but incur a higher loss. All of these applications usually require converting the RF (radio frequency) signal at 670 GHz to a lower IF (intermediate frequency) for processing. Further, transmitting for communication and radar generally requires up-conversion from IF to the RF. The current state-of-the-art device for performing the frequency conversion is based on Schottky diode mixers for both up and down conversion in this frequency range for room-temperature operation. Devices that can operate at room temperature are generally required for terrestrial, military, and planetary applications that cannot tolerate the mass, bulk, and power consumption of cryogenic cooling. The technology has recently advanced to the point that amplifiers in the region up to nearly 1,000 GHz are feasible. Almost all of these have been based on indium phosphide pseudomorphic high-electron mobility transistors (pHEMTs), in the form of monolithic microwave integrated circuits (MMICs). Since the processing of HEMT amplifiers is quite differ en t from that of Schottky diodes, use of Schottky mixers requires separate MMICs for the mixers and amplifiers. Fabrication of all the down-/up-conversion circuitry on single MMICs, using a ll-HEMT circuits, would constitute a major advance in circuit simplicity.

Enhanced soil vapor extraction with radio frequency heating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bowders, J.J.; Daniel, D.E.

1997-12-31

A field demonstration of enhanced soil vapor extraction using radio frequency (RF) heating to remove semi-volatiles from the subsurface is nearing completion. The site, a fire training area consisting of a well-graded sand with silt, had initial petroleum hydrocarbon concentrations up to 22,000 mg/kg. The treatment volume contained approximately 80 kg of diesel range organics (DRO, C-12 to C-20). Vapors are extracted from a central well while RF energy is supplied by two applicators positioned in vertical wells on either side of the extraction well. Temperatures in the center of the treatment zone have reached 140{degrees}C and at the treatmentmore » perimeter (2m radius) have reached 100{degrees}C to 120{degrees}C. Analyses of the condensed offgas show the chromatogram matches that for DRO with constituents up to C-20. Preliminary mass balance indicates that more than 65 kg of DRO have been removed from the site. The first 77 days of RF heating operation are reported in this paper. The project is continuing and final results will be reported at a later time.« less

DC and analog/RF performance optimisation of source pocket dual work function TFET

NASA Astrophysics Data System (ADS)

Raad, Bhagwan Ram; Sharma, Dheeraj; Kondekar, Pravin; Nigam, Kaushal; Baronia, Sagar

2017-12-01

We investigate a systematic study of source pocket tunnel field-effect transistor (SP TFET) with dual work function of single gate material by using uniform and Gaussian doping profile in the drain region for ultra-low power high frequency high speed applications. For this, a n+ doped region is created near the source/channel junction to decrease the depletion width results in improvement of ON-state current. However, the dual work function of the double gate is used for enhancement of the device performance in terms of DC and analog/RF parameters. Further, to improve the high frequency performance of the device, Gaussian doping profile is considered in the drain region with different characteristic lengths which decreases the gate to drain capacitance and leads to drastic improvement in analog/RF figures of merit. Furthermore, the optimisation is performed with different concentrations for uniform and Gaussian drain doping profile and for various sectional length of lower work function of the gate electrode. Finally, the effect of temperature variation on the device performance is demonstrated.

History and Technology Developments of Radio Frequency (RF) Systems for Particle Accelerators

NASA Astrophysics Data System (ADS)

Nassiri, A.; Chase, B.; Craievich, P.; Fabris, A.; Frischholz, H.; Jacob, J.; Jensen, E.; Jensen, M.; Kustom, R.; Pasquinelli, R.

2016-04-01

This article attempts to give a historical account and review of technological developments and innovations in radio frequency (RF) systems for particle accelerators. The evolution from electrostatic field to the use of RF voltage suggested by R. Wideröe made it possible to overcome the shortcomings of electrostatic accelerators, which limited the maximum achievable electric field due to voltage breakdown. After an introduction, we will provide reviews of technological developments of RF systems for particle accelerators.

Recent progress on improving ICRF coupling and reducing RF-specific impurities in ASDEX Upgrade

NASA Astrophysics Data System (ADS)

Zhang, Wei; Bobkov, Volodymyr; Noterdaeme, Jean-Marie; Tierens, Wouter; Aguiam, Diogo; Bilato, Roberto; Coster, David; Colas, Laurent; Crombé, Kristel; Fuenfgelder, Helmut; Faugel, Helmut; Feng, Yuhe; Jacquot, Jonathan; Jacquet, Philippe; Kallenbach, Arne; Kostic, Ana; Lunt, Tilmann; Maggiora, Riccardo; Ochoukov, Roman; Silva, Antonio; Suárez, Guillermo; Tuccilo, Angelo A.; Tudisco, Onofrio; Usoltceva, Mariia; Van Eester, Dirk; Wang, Yongsheng; Yang, Qingxi

2017-10-01

The recent scientific research on ASDEX Upgrade (AUG) has greatly advanced solutions to two issues of Radio Frequency (RF) heating in the Ion Cyclotron Range of Frequencies (ICRF): (a) the coupling of ICRF power to the plasma is significantly improved by density tailoring with local gas puffing; (b) the release of RF-specific impurities is significantly reduced by minimizing the RF near field with 3-strap antennas. This paper summarizes the applied methods and reviews the associated achievements.

A 17 GHz molecular rectifier

PubMed Central

Trasobares, J.; Vuillaume, D.; Théron, D.; Clément, N.

2016-01-01

Molecular electronics originally proposed that small molecules sandwiched between electrodes would accomplish electronic functions and enable ultimate scaling to be reached. However, so far, functional molecular devices have only been demonstrated at low frequency. Here, we demonstrate molecular diodes operating up to 17.8 GHz. Direct current and radio frequency (RF) properties were simultaneously measured on a large array of molecular junctions composed of gold nanocrystal electrodes, ferrocenyl undecanethiol molecules and the tip of an interferometric scanning microwave microscope. The present nanometre-scale molecular diodes offer a current density increase by several orders of magnitude compared with that of micrometre-scale molecular diodes, allowing RF operation. The measured S11 parameters show a diode rectification ratio of 12 dB which is linked to the rectification behaviour of the direct current conductance. From the RF measurements, we extrapolate a cut-off frequency of 520 GHz. A comparison with the silicon RF-Schottky diodes, architecture suggests that the RF-molecular diodes are extremely attractive for scaling and high-frequency operation. PMID:27694833

UWB multi-burst transmit driver for averaging receivers

DOEpatents

Dallum, Gregory E

2012-11-20

A multi-burst transmitter for ultra-wideband (UWB) communication systems generates a sequence of precisely spaced RF bursts from a single trigger event. There are two oscillators in the transmitter circuit, a gated burst rate oscillator and a gated RF burst or RF power output oscillator. The burst rate oscillator produces a relatively low frequency, i.e., MHz, square wave output for a selected transmit cycle, and drives the RF burst oscillator, which produces RF bursts of much higher frequency, i.e., GHz, during the transmit cycle. The frequency of the burst rate oscillator sets the spacing of the RF burst packets. The first oscillator output passes through a bias driver to the second oscillator. The bias driver conditions, e.g., level shifts, the signal from the first oscillator for input into the second oscillator, and also controls the length of each RF burst. A trigger pulse actuates a timing circuit, formed of a flip-flop and associated reset time delay circuit, that controls the operation of the first oscillator, i.e., how long it oscillates (which defines the transmit cycle).

Miniature EVA Software Defined Radio

NASA Technical Reports Server (NTRS)

Pozhidaev, Aleksey

2012-01-01

As NASA embarks upon developing the Next-Generation Extra Vehicular Activity (EVA) Radio for deep space exploration, the demands on EVA battery life will substantially increase. The number of modes and frequency bands required will continue to grow in order to enable efficient and complex multi-mode operations including communications, navigation, and tracking applications. Whether conducting astronaut excursions, communicating to soldiers, or first responders responding to emergency hazards, NASA has developed an innovative, affordable, miniaturized, power-efficient software defined radio that offers unprecedented power-efficient flexibility. This lightweight, programmable, S-band, multi-service, frequency- agile EVA software defined radio (SDR) supports data, telemetry, voice, and both standard and high-definition video. Features include a modular design, an easily scalable architecture, and the EVA SDR allows for both stationary and mobile battery powered handheld operations. Currently, the radio is equipped with an S-band RF section. However, its scalable architecture can accommodate multiple RF sections simultaneously to cover multiple frequency bands. The EVA SDR also supports multiple network protocols. It currently implements a Hybrid Mesh Network based on the 802.11s open standard protocol. The radio targets RF channel data rates up to 20 Mbps and can be equipped with a real-time operating system (RTOS) that can be switched off for power-aware applications. The EVA SDR's modular design permits implementation of the same hardware at all Network Nodes concept. This approach assures the portability of the same software into any radio in the system. It also brings several benefits to the entire system including reducing system maintenance, system complexity, and development cost.

Influences of the shielding cylinder on the length of radio-frequency cold atmospheric plasma jets

NASA Astrophysics Data System (ADS)

Li, He-Ping; Li, Jing; Zhang, Xiao-Fei; Guo, Heng; Chen, Jian; Department of Engineering Physics Team

2017-10-01

Cold atmospheric plasma jets driven by a radio frequency power supply contain abundant species and complex chemical reactions, which have wide applications in the fields of materials processing and modifications, food engineering, bio-medical science, etc. Our previous experiments have shown that the total length of a radio-frequency cold atmospheric plasma (RF-CAP) jet can exceed 1 meter with the shielding of a quartz tube. However, the shielding mechanisms of the solid cylinder has not been studied systematically. In this study, a two-dimensional, quasi-steady fluid model is used to investigate the influences of the shielding tube on the length of the RF-CAP jets under different conditions. The simulation results show that the total jet length grows monotonously; while simultaneously, the jet length out of the tube shows a non-monotonic variation trend, with the increase of the tube length, which is in good agreement with the experimental observations. The shielding mechanisms of the solid cylinder on the RF-CAP jet is also discussed in detail based on the modeling results. This work was supported by the National Natural Science Foundation of China (11475103, 21627812), the National Key Research and Development Program of China (2016YFD0102106) and Tsinghua University Initiative Scientific Program (20161080108).

The effect of MRET polymer compound on SAR values of RF phones.

PubMed

Smirnov, Igor

2008-01-01

This article is related to the proposed hypothesis and experimental data regarding the ability of defined polar polymer compound (MRET polymer) applied to RF phones to increase the dielectric permittivity of water based solutions and to reduce the SAR (Specific Absorption Rate) values inside the "phantom head" filled with the jelly simulating muscle and brain tissues. Due to the high organizational state of fractal structures of MRET polymer compounds and the phenomenon of piezoelectricity, this polymer generates specific subtle, low frequency, non-coherent electromagnetic oscillations (optimal random field) that can affect the hydrogen lattice of the molecular structure of water and subsequently modify the electrodynamic properties of water. The increase of dielectric permittivity of water finally leads to the reduction of the absorption rate of the electromagnetic field by living tissue. The reduction of SAR values is confirmed by the research conducted in June - July of 2006 at RF Exposure Laboratory in Escondido, California. This test also confirmed that the application of MRET polymer to RF phones does not significantly affect the air measurements of RF phone signals, and subsequently does not lead to any significant distortion of transmitted RF signals.

Miniature lowpass filters in low loss 9k7 LTCC

DOE PAGES

Dai, Steve; Hsieh, Lung -Hwa

2015-07-01

DuPont 9k7 low temperature cofired ceramic (LTCC) is a low loss, or high quality factor Q, tape system targeting at radio frequency (RF) applications. This paper reports the effect of a critical process parameter, heating rate, on the densification and dielectric properties of the 9k7 LTCC. The role of competing densification and crystallization during the sintering of 9k7 is discussed. The high Q of DuPont 9K7 can be used to improve RF system performance, for example a better receiver noise figure, by designing embedded passive RF components such as inductors, capacitors and filters. As a result, miniaturized multilayer low passmore » filters (LPF) with a wide stopband were fabricated to showcase the technology.« less

Miniature lowpass filters in low loss 9k7 LTCC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dai, Steve; Hsieh, Lung -Hwa

DuPont 9k7 low temperature cofired ceramic (LTCC) is a low loss, or high quality factor Q, tape system targeting at radio frequency (RF) applications. This paper reports the effect of a critical process parameter, heating rate, on the densification and dielectric properties of the 9k7 LTCC. The role of competing densification and crystallization during the sintering of 9k7 is discussed. The high Q of DuPont 9K7 can be used to improve RF system performance, for example a better receiver noise figure, by designing embedded passive RF components such as inductors, capacitors and filters. As a result, miniaturized multilayer low passmore » filters (LPF) with a wide stopband were fabricated to showcase the technology.« less

Miniature low-pass filter in low-loss 9k7 LTCC

DOE PAGES

Dai, Steve Xunhu; Hsieh, Lung -Hwa

2015-09-30

DuPont 9k7 low-temperature cofired ceramic (LTCC) is a low-loss, or high-quality-factor Q, tape system targeting at radio frequency (RF) applications. This paper reports on the effect of a critical process parameter, the heating rate, on the densification and dielectric properties of the 9k7 LTCC. The role of competing densification and crystallization during the sintering of 9k7 is discussed. The high Q of DuPont 9K7 can be used to improve RF system performance, for example a better receiver noise figure, by designing embedded passive RF components such as inductors, capacitors and filters. Furthermore, miniaturized multilayer low-pass filters (LPF) with a widemore » stopband were fabricated to showcase the technology.« less

Single frequency RF powered ECG telemetry system

NASA Technical Reports Server (NTRS)

Ko, W. H.; Hynecek, J.; Homa, J.

1979-01-01

It has been demonstrated that a radio frequency magnetic field can be used to power implanted electronic circuitry for short range telemetry to replace batteries. A substantial reduction in implanted volume can be achieved by using only one RF tank circuit for receiving the RF power and transmitting the telemetered information. A single channel telemetry system of this type, using time sharing techniques, was developed and employed to transmit the ECG signal from Rhesus monkeys in primate chairs. The signal from the implant is received during the period when the RF powering radiation is interrupted. The ECG signal is carried by 20-microsec pulse position modulated pulses, referred to the trailing edge of the RF powering pulse. Satisfactory results have been obtained with this single frequency system. The concept and the design presented may be useful for short-range long-term implant telemetry systems.

47 CFR 90.1217 - RF Hazards.

Code of Federal Regulations, 2010 CFR

2010-10-01

... MOBILE RADIO SERVICES Regulations Governing Licensing and Use of Frequencies in the 4940-4990 MHz Band... requirements specified in §§ 1.1307(b), 2.1091 and 2.1093 of this chapter, as appropriate. Applications for equipment authorization of mobile or portable devices operating under this section must contain a statement...

Teaching Management System with Applications of RFID and IoT Technology

ERIC Educational Resources Information Center

Tan, Ping; Wu, Han; Li, Peng; Xu, He

2018-01-01

Currently, Internet of Things (IoT) technologies are used in many areas, such as intelligent transportation, smart city, hospital, games, education. Earlier interactive response system uses infrared or radio frequency (RF) wireless communication technologies to transmit the students' answer to teachers' management system, where there exists high…

Electrical and Structural Properties Study of Layered Dielectric and Magnetic Composites and Blends Structures for RF and Microwave Applications

DTIC Science & Technology

2014-06-12

Graduação em Engenharia de Teleinformática (2012) 3- STUDY of THERMAL STABILITY of microwave Resonant frequency of (τf) of DIELETRICS and...SYNTHESIS of CERAMIC MATERIALS with NEAR-ZERO τf Marcelo Antonio Santos da Silva, Programa de Pós Graduação em Quimica (2012) 4- STUDY OF DIELECTRIC...PROPERTIES OF CERAMIC MATRIX SrBi2Nb2O9 (SBN) FOR USE IN RF AND MICROWAVE DEVICES, EMMANUELLE DE OLIVEIRA SANCHO PROGRAMA DE PÓS-GRADUAÇÃO EM ENGENHARIA

ICRH system performance during ITER-Like Wall operations at JET and the outlook for DT campaign

NASA Astrophysics Data System (ADS)

Monakhov, Igor; Blackman, Trevor; Dumortier, Pierre; Durodié, Frederic; Jacquet, Philippe; Lerche, Ernesto; Noble, Craig

2017-10-01

Performance of JET ICRH system since installation of the metal ITER-Like Wall (ILW) has been assessed statistically. The data demonstrate steady increase of the RF power coupled to plasmas over recent years with the maximum pulse-average and peak values exceeding respectively 6MW and 8MW in 2016. Analysis and extrapolation of power capabilities of conventional JET ICRH antennas is provided and key performance-limiting factors are discussed. The RF plant operational frequency options are presented highlighting the issues of efficient ICRH application within a foreseeable range of DT plasma scenarios.

High power tests of an electroforming cavity operating at 11.424 GHz

NASA Astrophysics Data System (ADS)

Dolgashev, V. A.; Gatti, G.; Higashi, Y.; Leonardi, O.; Lewandowski, J. R.; Marcelli, A.; Rosenzweig, J.; Spataro, B.; Tantawi, S. G.; Yeremian, D. A.

2016-03-01

The achievement of ultra high accelerating gradients is mandatory in order to fabricate compact accelerators at 11.424 GHz for scientific and industrial applications. An extensive experimental and theoretical program to determine a reliable ultra high gradient operation of the future linear accelerators is under way in many laboratories. In particular, systematic studies on the 11.424 GHz frequency accelerator structures, R&D on new materials and the associated microwave technology are in progress to achieve accelerating gradients well above 120 MeV/m. Among the many, the electroforming procedure is a promising approach to manufacture high performance RF devices in order to avoid the high temperature brazing and to produce precise RF structures. We report here the characterization of a hard high gradient RF accelerating structure at 11.424 GHz fabricated using the electroforming technique. Low-level RF measurements and high power RF tests carried out at the SLAC National Accelerator Laboratory on this prototype are presented and discussed. In addition, we present also a possible layout where the water-cooling of irises based on the electroforming process has been considered for the first time.

Ultra High-Speed Radio Frequency Switch Based on Photonics.

PubMed

Ge, Jia; Fok, Mable P

2015-11-26

Microwave switches, or Radio Frequency (RF) switches have been intensively used in microwave systems for signal routing. Compared with the fast development of microwave and wireless systems, RF switches have been underdeveloped particularly in terms of switching speed and operating bandwidth. In this paper, we propose a photonics based RF switch that is capable of switching at tens of picoseconds speed, which is hundreds of times faster than any existing RF switch technologies. The high-speed switching property is achieved with the use of a rapidly tunable microwave photonic filter with tens of gigahertz frequency tuning speed, where the tuning mechanism is based on the ultra-fast electro-optics Pockels effect. The RF switch has a wide operation bandwidth of 12 GHz and can go up to 40 GHz, depending on the bandwidth of the modulator used in the scheme. The proposed RF switch can either work as an ON/OFF switch or a two-channel switch, tens of picoseconds switching speed is experimentally observed for both type of switches.

[Percutaneous radiofrequency ablation of osteoid osteomas: technique and results].

PubMed

Bruners, P; Penzkofer, T; Günther, R W; Mahnken, A

2009-08-01

Osteoid osteoma is a benign primary bone tumor that typically occurs in children and young adults. Besides local pain, which is often worse at night, prompt relief due to medication with acetylsalicylic acid (ASS) is characteristic for this bone lesion. Because long-term medication with ASS does not represent an alternative treatment strategy due to its potentially severe side effects, different minimally invasive image-guided techniques for the therapy of osteoid osteoma have been developed. In this context radiofrequency (RF) ablation in particular has become part of the clinical routine. The technique and results of image-guided RF ablation are compared to alternative treatment strategies. Using this technique, an often needle-shaped RF applicator is percutaneously placed into the tumor under image guidance. Then a high-frequency alternating current is applied by the tip of the applicator which leads to ionic motion within the tissue resulting in local heat development and thus in thermal destruction of the surrounding tissue including the tumor. The published primary and secondary success rates of this technique are 87 and 83 %, respectively. Surgical resection and open curettage show comparable success rates but are associated with higher complication rates. In addition image-guided RF ablation of osteoid osteomas is associated with low costs. In conclusion image-guided RF ablation can be considered the gold standard for the treatment of osteoid osteoma.

THz in biology and medicine: toward quantifying and understanding the interaction of millimeter- and submillimeter-waves with cells and cell processes

NASA Astrophysics Data System (ADS)

Siegel, Peter H.; Pikov, Victor

2010-02-01

As the application and commercial use of millimeter- and submillimeter-wavelength radiation become more widespread, there is a growing need to understand and quantify both the coupling mechanisms and the impact of this long wavelength energy on biological function. Independent of the health impact of high doses of radio frequency (RF) energy on full organisms, which has been extensively investigated, there exists the potential for more subtle effects, which can best be quantified in studies which examine real-time changes in cellular functions as RF energy is applied. In this paper we present the first real time examination of RF induced changes in cellular activity at absorbed power levels well below the existing safe exposure limits. Fluorescence microscopy imaging of immortalized epithelial and neuronal cells in vitro indicate increased cellular membrane permeability and nanoporation after short term exposure to modest levels (10-50 mW/cm2) of RF power at 60 GHz. Sensitive patch clamp measurements on pyramidal neurons in cortical slices of neonatal rats showed a dramatic increase in cellular membrane permeability resulting either in suppression or facilitation of neuronal activity during exposure to sub-μW/cm2 of RF power at 60 GHz. Non-invasive modulation of neuronal activity could prove useful in a variety of health applications from suppression of peripheral neuropathic pain to treatment of central neurological disorders.

Multi-carrier transmission for hybrid radio frequency with optical wireless communications

NASA Astrophysics Data System (ADS)

Wang, Gang; Chen, Genshe; Shen, Dan; Pham, Khanh; Blasch, Erik; Nguyen, Tien M.

2015-05-01

Radio frequency (RF) wireless communication is reaching its capacity to support large data rate transmissions due to hardware constraints (e.g., silicon processes), software strategies (e.g., information theory), and consumer desire for timely large file exchanges (e.g., big data and mobile cloud computing). A high transmission rate performance must keep pace with the generated huge volumes of data for real-time processing. Integrated RF and optical wireless communications (RF/OWC) could be the next generation transmission technology to satisfy both the increased data rate exchange and the communications constraints. However, with the promising benefits of RF/OWC, challenges remain to fully develop hybrid RF with wireless optical communications such as uniform waveform design for information transmission and detection. In this paper, an orthogonal frequency division multiplexing (OFDM) transmission scheme, which widely employed in RF communications, is developed for optical communications. The traditional high peak-to-average power ratio (PAPR) in OFDM is reduced to improve system performance. The proposed multi-carrier waveform is evaluated with a frequency-selective fading channel. The results demonstrate that bit error rate (BER) performance of our proposed optical OFDM transmission technique outperforms the traditional OWC on-off keying (OOK) transmission scheme.

Evaluation of power transfer efficiency for a high power inductively coupled radio-frequency hydrogen ion source

NASA Astrophysics Data System (ADS)

Jain, P.; Recchia, M.; Cavenago, M.; Fantz, U.; Gaio, E.; Kraus, W.; Maistrello, A.; Veltri, P.

2018-04-01

Neutral beam injection (NBI) for plasma heating and current drive is necessary for International Thermonuclear Experimental reactor (ITER) tokamak. Due to its various advantages, a radio frequency (RF) driven plasma source type was selected as a reference ion source for the ITER heating NBI. The ITER relevant RF negative ion sources are inductively coupled (IC) devices whose operational working frequency has been chosen to be 1 MHz and are characterized by high RF power density (˜9.4 W cm-3) and low operational pressure (around 0.3 Pa). The RF field is produced by a coil in a cylindrical chamber leading to a plasma generation followed by its expansion inside the chamber. This paper recalls different concepts based on which a methodology is developed to evaluate the efficiency of the RF power transfer to hydrogen plasma. This efficiency is then analyzed as a function of the working frequency and in dependence of other operating source and plasma parameters. The study is applied to a high power IC RF hydrogen ion source which is similar to one simplified driver of the ELISE source (half the size of the ITER NBI source).

Monitoring radio-frequency thermal ablation with ultrasound by low frequency acoustic emissions--in vitro and in vivo study.

PubMed

Winkler, Itai; Adam, Dan

2011-05-01

The object of this study was to evaluate the monitoring of thermal ablation therapy by measuring the nonlinear response to ultrasound insonation at the region being treated. Previous reports have shown that during tissue heating, microbubbles are formed. Under the application of ultrasound, these microbubbles may be driven into nonlinear motion that produces acoustic emissions at sub-harmonic frequencies and a general increase of emissions at low frequencies. These low frequency emissions may be used to monitor ablation surgery. In this study, a modified commercial ultrasound system was used for transmitting ultrasound pulses and for recording raw RF-lines from a scan plane in porcine (in vitro) and rabbit (in vivo) livers during radio-frequency ablation (RFA). The transmission pulse was 15 cycles in length at 4 MHz (in vitro) and 3.6 MHz (in vivo). Thermocouples were used for monitoring temperatures during the RFA treatment.In the in vitro experiments, recorded RF signals (A-lines) were segmented, and the total energy was measured at two different frequency bands: at a low frequency band (LFB) of 1-2.5 MHz and at the transmission frequency band (TFB) of 3.5-4.5 MHz. The mean energy at the LFB and at the TFB increased substantially in areas adjacent to the RF needle. These energies also changed abruptly at higher temperatures, thus, producing great variance in the received energy. Mean energies in areas distant from RF needle showed little change and variation during treatment. It was also shown that a 3 dB increase of energy at the low frequency band was typically obtained in regions in which temperature was above 53.3 ± 5° C. Thus, this may help in evaluating regions undergoing hyperthermia. In the in vivo experiments, an imaging algorithm based on measuring the LFB energy was used. The algorithm performs a moving average of the LFB energies measured at segments within the scan plane.Results show that a colored region is formed on the image and that it is similar in size to a measurement of the lesion from gross pathology, with a correlation coefficient of 0.743. Copyright © 2011. Published by Elsevier Inc.

Overview of the High Performance Antiproton Trap (HiPAT) Experiment

NASA Technical Reports Server (NTRS)

Martin, James; Chakrabarti, Suman; Pearson, Boise; Sims, W. Herbert; Lewis, Raymond; Fant, Wallace; Rodgers, Stephen (Technical Monitor)

2002-01-01

A general overview of the High Performance Antiproton Trap (HiPAT) Experiment is presented. The topics include: 1) Why Antimatter? 2) HiPAT Applicability; 3) Approach-Goals; 4) HiPAT General Layout; 5) Sizing For Containment; 6) Laboratory Operations; 7) Vacuum System Cleaning; 8) Ion Production Via Electron Gun; 9) Particle Capture Via Ion Sources; 10) Ion Beam Steering/Focusing; 11) Ideal Ion Stacking Sequence; 12) Setup For Dynamic Capture; 13) Dynamic Capture of H(+) Ions; 14) Dynamic Capture; 15) Radio Frequency Particle Detection; 16) Radio Frequency Antenna Modeling; and 17) R.F. Stabilization-Low Frequencies. A short presentation of propulsion applications of Antimatter is also given. This paper is in viewgraph form.

Technique for Predicting the RF Field Strength Inside an Enclosure

NASA Technical Reports Server (NTRS)

Hallett, M.; Reddell, J.

1998-01-01

This Memorandum presents a simple analytical technique for predicting the RF electric field strength inside an enclosed volume in which radio frequency radiation occurs. The technique was developed to predict the radio frequency (RF) field strength within a launch vehicle's fairing from payloads launched with their telemetry transmitters radiating and to the impact of the radiation on the vehicle and payload. The RF field strength is shown to be a function of the surface materials and surface areas. The method accounts for RF energy losses within exposed surfaces, through RF windows, and within multiple layers of dielectric materials which may cover the surfaces. This Memorandum includes the rigorous derivation of all equations and presents examples and data to support the validity of the technique.

Radio-frequency power-assisted performance improvement of a magnetohydrodynamic power generator

NASA Astrophysics Data System (ADS)

Murakami, Tomoyuki; Okuno, Yoshihiro; Yamasaki, Hiroyuki

2005-12-01

We describe a radio-frequency (rf) electromagnetic-field-assisted magnetohydrodynamic power generation experiment, where an inductively coupled rf field (13.56MHz, 5.2kW) is continuously supplied to the disk generator. The rf power assists the precise plasma ignition, by which the otherwise irregular plasma behavior was stabilized. The rf heating suppresses the ionization instability in the plasma behavior and homogenizes the nonuniformity of the plasma structures. The power-generating performance is significantly improved with the aid of the rf power under wide seeding conditions: insufficient, optimum, and excessive seed fractions. The increment of the enthalpy extraction ratio of around 2% is significantly greater than the fraction of the net rf power, that is, 0.16%, to the thermal input.

Selective RF pulses in NMR and their effect on coupled and uncoupled spin systems

NASA Astrophysics Data System (ADS)

Slotboom, J.

1993-10-01

This thesis describes various aspects of the usage of shaped RF-pulses for volume selection and spectral editing. Contents: Introduction--The History of Magnetic Resonance in a Nutshell, and The Usage of RF Pulses in Contemporary MRS and MRI; Theoretical and Practical Aspects of Localized NMR Spectroscopy; The Effects of RF Pulse Shape Discretization on the Spatially Selective Performance; Design of Frequency-Selective RF Pulses by Optimizing a Small Number of Pulse Parameters; A Single-Shot Localization Pulse Sequence Suited for Coils with Inhomogeneous RF Fields Using Adiabatic Slice-Selective RF Pulses; The Bloch Equations for an AB System and the Design of Spin State Selective RF Pulses for Coupled Spin Systems; The Effects of Frequency Selective RF Pulses on J Coupled Spin-1/2 Systems; A Quantitative (1)H MRS in vivo Study of the Effects of L-Ornithine-L-Aspartate on the Development of Mild Encephalopathy Using a Single Shot Localization Technique Based on SAR Reduced Adiabatic 2(pi) Pulses.

Ultra-High Accelerating Gradients in Radio-Frequency Cryogenic Copper Structures

NASA Astrophysics Data System (ADS)

Cahill, Alexander David

Normal conducting radio-frequency (rf) particle accelerators have many applications, including colliders for high energy physics, high-intensity synchrotron light sources, non-destructive testing for security, and medical radiation therapy. In these applications, the accelerating gradient is an important parameter. Specifically for high energy physics, increasing the accelerating gradient extends the potential energy reach and is viewed as a way to mitigate their considerable cost. Furthermore, a gradient increase will enable for more compact and thus accessible free electron lasers (FELs). The major factor limiting larger accelerating gradients is vacuum rf breakdown. Basic physics of this phenomenon has been extensively studied over the last few decades. During which, the occurrence of rf breakdowns was shown to be probabilistic, and can be characterized by a breakdown rate. The current consensus is that vacuum rf breakdowns are caused by movements of crystal defects induced by periodic mechanical stress. The stress may be caused by pulsed surface heating and large electric fields. A compelling piece of evidence that supports this hypothesis is that accelerating structures constructed from harder materials exhibit larger accelerating gradients for similar breakdown rates. One possible method to increase sustained electric fields in copper cavities is to cool them to temperatures below 77 K, where the rf surface resistance and coefficient of thermal expansion decrease, while the yield strength (which correlates with hardness) and thermal conductivity increase. These changes in material properties at low temperature increases metal hardness and decreases the mechanical stress from exposure to rf electromagnetic fields. To test the validity of the improvement in breakdown rate, experiments were conducted with cryogenic accelerating cavities in the Accelerator Structure Test Area (ASTA) at SLAC National Accelerator Laboratory. A short 11.4 GHz standing wave accelerating structure was conditioned to an accelerating gradient of 250 MV/m at 45 K with 108 rf pulses. At gradients greater than 150 MV/m I observed a degradation in the intrinsic quality factor of the cavity, Q0. I developed a model for the change in Q0 using measured field emission currents and rf signals. I found that the Q 0 degradation is consistent with the rf power being absorbed by strong field emission currents accelerated inside the cavity. I measured rf breakdown rates for 45 K and found 2*10-4/pulse/meter when accounting for any change in Q0. These are the largest accelerating gradients for a structure with similar breakdown rates. The final chapter presents the design of an rf photoinjector electron source that uses the cryogenic normal conducting accelerator technology: the TOPGUN. With this cryogenic rf photoinjector, the beam brightness will increase by over an order of a magnitude when compared to the current photoinjector for the Linac Coherent Light Source (LCLS). When using the TOPGUN as the source for an X-ray Free Electron Laser, the higher brightness would allow for a decrease in the required length of the LCLS undulator by more than a factor of two.

Dynamic Metasurface Aperture as Smart Around-the-Corner Motion Detector.

PubMed

Del Hougne, Philipp; F Imani, Mohammadreza; Sleasman, Timothy; Gollub, Jonah N; Fink, Mathias; Lerosey, Geoffroy; Smith, David R

2018-04-25

Detecting and analysing motion is a key feature of Smart Homes and the connected sensor vision they embrace. At present, most motion sensors operate in line-of-sight Doppler shift schemes. Here, we propose an alternative approach suitable for indoor environments, which effectively constitute disordered cavities for radio frequency (RF) waves; we exploit the fundamental sensitivity of modes of such cavities to perturbations, caused here by moving objects. We establish experimentally three key features of our proposed system: (i) ability to capture the temporal variations of motion and discern information such as periodicity ("smart"), (ii) non line-of-sight motion detection, and (iii) single-frequency operation. Moreover, we explain theoretically and demonstrate experimentally that the use of dynamic metasurface apertures can substantially enhance the performance of RF motion detection. Potential applications include accurately detecting human presence and monitoring inhabitants' vital signs.

A high sensitivity ultralow temperature RF conductance and noise measurement setup.

PubMed

Parmentier, F D; Mahé, A; Denis, A; Berroir, J-M; Glattli, D C; Plaçais, B; Fève, G

2011-01-01

We report on the realization of a high sensitivity RF noise measurement scheme to study small current fluctuations of mesoscopic systems at milli-Kelvin temperatures. The setup relies on the combination of an interferometric amplification scheme and a quarter-wave impedance transformer, allowing the measurement of noise power spectral densities with gigahertz bandwidth up to five orders of magnitude below the amplifier noise floor. We simultaneously measure the high frequency conductance of the sample by derivating a portion of the signal to a microwave homodyne detection. We describe the principle of the setup, as well as its implementation and calibration. Finally, we show that our setup allows to fully characterize a subnanosecond on-demand single electron source. More generally, its sensitivity and bandwidth make it suitable for applications manipulating single charges at GHz frequencies.

Design of catheter radio frequency coils using coaxial transmission line resonators for interventional neurovascular MR imaging.

PubMed

Zhang, Xiaoliang; Martin, Alastair; Jordan, Caroline; Lillaney, Prasheel; Losey, Aaron; Pang, Yong; Hu, Jeffrey; Wilson, Mark; Cooke, Daniel; Hetts, Steven W

2017-04-01

It is technically challenging to design compact yet sensitive miniature catheter radio frequency (RF) coils for endovascular interventional MR imaging. In this work, a new design method for catheter RF coils is proposed based on the coaxial transmission line resonator (TLR) technique. Due to its distributed circuit, the TLR catheter coil does not need any lumped capacitors to support its resonance, which simplifies the practical design and construction and provides a straightforward technique for designing miniature catheter-mounted imaging coils that are appropriate for interventional neurovascular procedures. The outer conductor of the TLR serves as an RF shield, which prevents electromagnetic energy loss, and improves coil Q factors. It also minimizes interaction with surrounding tissues and signal losses along the catheter coil. To investigate the technique, a prototype catheter coil was built using the proposed coaxial TLR technique and evaluated with standard RF testing and measurement methods and MR imaging experiments. Numerical simulation was carried out to assess the RF electromagnetic field behavior of the proposed TLR catheter coil and the conventional lumped-element catheter coil. The proposed TLR catheter coil was successfully tuned to 64 MHz for proton imaging at 1.5 T. B 1 fields were numerically calculated, showing improved magnetic field intensity of the TLR catheter coil over the conventional lumped-element catheter coil. MR images were acquired from a dedicated vascular phantom using the TLR catheter coil and also the system body coil. The TLR catheter coil is able to provide a significant signal-to-noise ratio (SNR) increase (a factor of 200 to 300) over its imaging volume relative to the body coil. Catheter imaging RF coil design using the proposed coaxial TLR technique is feasible and advantageous in endovascular interventional MR imaging applications.

A fractional-N frequency synthesizer for WCDMA/Bluetooth/ZigBee applications

NASA Astrophysics Data System (ADS)

Chunyuan, Zhou; Guolin, Li; Chun, Zhang; Baoyong, Chi; Dongmei, Li; Zhihua, Wang

2009-07-01

A triple-mode fractional-N frequency synthesizer with a noise-filter voltage controlled oscillator (VCO) for WCDMA/Bluetooth/ZigBee applications has been implemented in 0.18-μm RF-CMOS technology. The proposed synthesizer achieves a good phase noise lower than -80 dBc/Hz in band and -115 dBc/Hz@1 MHz for the three modes, and only draws 21 mA from a 1.8 V supply. It has a high hardware sharing and a small size, only 1.5 × 1.4 mm2. The system architecture, circuit design, and measured results are also presented.

Plasma production by helicon and slow waves.

PubMed

Sakawa, Youichi; Kunimatsu, Hiroyuki; Kikuchi, Hideki; Fukui, Yasuaki; Shoji, Tatsuo

2003-03-14

The observation of slow-wave sustained (SW) discharge in a whistler- or helicon-wave range of frequency is made using high-frequency and very-high-frequency bands of rf. The SW discharge occurs at an extremely low rf power and plasma density, which are lower than a capacitive-coupling discharge region.

Frequency-tuning radiofrequency plasma source operated in inductively-coupled mode under a low magnetic field

NASA Astrophysics Data System (ADS)

Takahashi, Kazunori; Nakano, Yudai; Ando, Akira

2017-07-01

A radiofrequency (rf) inductively-coupled plasma source is operated with a frequency-tuning impedance matching system, where the rf frequency is variable in the range of 20-50 MHz and the maximum power is 100 W. The source consists of a 45 mm-diameter pyrex glass tube wound by an rf antenna and a solenoid providing a magnetic field strength in the range of 0-200 Gauss. A reflected rf power for no plasma case is minimized at the frequency of ˜25 MHz, whereas the frequency giving the minimum reflection with the high density plasma is about 28 MHz, where the density jump is observed when minimizing the reflection. A high density argon plasma above 1× {{10}12} cm-3 is successfully obtained in the source for the rf power of 50-100 W, where it is observed that an external magnetic field of a few tens of Gauss yields the highest plasma density in the present configuration. The frequency-tuning plasma source is applied to a compact and high-speed silicon etcher in an Ar-SF6 plasma; then the etching rate of 8~μ m min-1 is obtained for no bias voltage to the silicon wafer, i.e. for the case that a physical ion etching process is eliminated.

Monitoring and localization of buried plastic natural gas pipes using passive RF tags

NASA Astrophysics Data System (ADS)

Mondal, Saikat; Kumar, Deepak; Ghazali, Mohd. Ifwat; Chahal, Prem; Udpa, Lalita; Deng, Yiming

2018-04-01

A passive harmonic radio frequency (RF) tag on the pipe with added sensing capabilities is proposed in this paper. Radio frequency identification (RFID) based tagging has already emerged as a potential solution for chemical sensing, location detection, animal tagging, etc. Harmonic transponders are already quite popular compared to conventional RFIDs due to their improved signal to noise ratio (SNR). However, the operating frequency, transmitted power and tag efficiency become critical issues for underground RFIDs. In this paper, a comprehensive on-tag sensing, power budget and frequency analyses is performed for buried harmonic tag design. Accurate tracking of infrastructure burial depth is proposed to reduce the probability of failure of underground pipelines. Burial depth is estimated using phase information of received signals at different frequencies calculated using genetic algorithm (GA) based optimization for post processing. Suitable frequency range is determined for a variety of soil with different moisture content for small tag-antenna size. Different types of harmonic tags such as 1) Schottky diode, 2) Non-linear Transmission Line (NLTL) were compared for underground applications. In this study, the power, frequency and tag design have been optimized to achieve small antenna size, minimum signal loss and simple reader circuit for underground detection at up to 5 feet depth in different soil medium and moisture contents.

Challenges and opportunities for multi-functional oxide thin films for voltage tunable radio frequency/microwave components

DOE Office of Scientific and Technical Information (OSTI.GOV)

Subramanyam, Guru, E-mail: gsubramanyam1@udayton.edu; Cole, M. W., E-mail: melanie.w.cole.civ@mail.mil; Sun, Nian X.

2013-11-21

There has been significant progress on the fundamental science and technological applications of complex oxides and multiferroics. Among complex oxide thin films, barium strontium titanate (BST) has become the material of choice for room-temperature-based voltage-tunable dielectric thin films, due to its large dielectric tunability and low microwave loss at room temperature. BST thin film varactor technology based reconfigurable radio frequency (RF)/microwave components have been demonstrated with the potential to lower the size, weight, and power needs of a future generation of communication and radar systems. Low-power multiferroic devices have also been recently demonstrated. Strong magneto-electric coupling has also been demonstratedmore » in different multiferroic heterostructures, which show giant voltage control of the ferromagnetic resonance frequency of more than two octaves. This manuscript reviews recent advances in the processing, and application development for the complex oxides and multiferroics, with the focus on voltage tunable RF/microwave components. The over-arching goal of this review is to provide a synopsis of the current state-of the-art of complex oxide and multiferroic thin film materials and devices, identify technical issues and technical challenges that need to be overcome for successful insertion of the technology for both military and commercial applications, and provide mitigation strategies to address these technical challenges.« less

Estimation of RF energy absorbed in the brain from mobile phones in the Interphone Study.

PubMed

Cardis, E; Varsier, N; Bowman, J D; Deltour, I; Figuerola, J; Mann, S; Moissonnier, M; Taki, M; Vecchia, P; Villegas, R; Vrijheid, M; Wake, K; Wiart, J

2011-09-01

The objective of this study was to develop an estimate of a radio frequency (RF) dose as the amount of mobile phone RF energy absorbed at the location of a brain tumour, for use in the Interphone Epidemiological Study. We systematically evaluated and quantified all the main parameters thought to influence the amount of specific RF energy absorbed in the brain from mobile telephone use. For this, we identified the likely important determinants of RF specific energy absorption rate during protocol and questionnaire design, we collected information from study subjects, network operators and laboratories involved in specific energy absorption rate measurements and we studied potential modifiers of phone output through the use of software-modified phones. Data collected were analysed to assess the relative importance of the different factors, leading to the development of an algorithm to evaluate the total cumulative specific RF energy (in joules per kilogram), or dose, absorbed at a particular location in the brain. This algorithm was applied to Interphone Study subjects in five countries. The main determinants of total cumulative specific RF energy from mobile phones were communication system and frequency band, location in the brain and amount and duration of mobile phone use. Though there was substantial agreement between categorisation of subjects by cumulative specific RF energy and cumulative call time, misclassification was non-negligible, particularly at higher frequency bands. Factors such as adaptive power control (except in Code Division Multiple Access networks), discontinuous transmission and conditions of phone use were found to have a relatively minor influence on total cumulative specific RF energy. While amount and duration of use are important determinants of RF dose in the brain, their impact can be substantially modified by communication system, frequency band and location in the brain. It is important to take these into account in analyses of risk of brain tumours from RF exposure from mobile phones.

Estimation of RF energy absorbed in the brain from mobile phones in the Interphone Study

PubMed Central

Varsier, N; Bowman, J D; Deltour, I; Figuerola, J; Mann, S; Moissonnier, M; Taki, M; Vecchia, P; Villegas, R; Vrijheid, M; Wake, K; Wiart, J

2011-01-01

Objectives The objective of this study was to develop an estimate of a radio frequency (RF) dose as the amount of mobile phone RF energy absorbed at the location of a brain tumour, for use in the Interphone Epidemiological Study. Methods We systematically evaluated and quantified all the main parameters thought to influence the amount of specific RF energy absorbed in the brain from mobile telephone use. For this, we identified the likely important determinants of RF specific energy absorption rate during protocol and questionnaire design, we collected information from study subjects, network operators and laboratories involved in specific energy absorption rate measurements and we studied potential modifiers of phone output through the use of software-modified phones. Data collected were analysed to assess the relative importance of the different factors, leading to the development of an algorithm to evaluate the total cumulative specific RF energy (in joules per kilogram), or dose, absorbed at a particular location in the brain. This algorithm was applied to Interphone Study subjects in five countries. Results The main determinants of total cumulative specific RF energy from mobile phones were communication system and frequency band, location in the brain and amount and duration of mobile phone use. Though there was substantial agreement between categorisation of subjects by cumulative specific RF energy and cumulative call time, misclassification was non-negligible, particularly at higher frequency bands. Factors such as adaptive power control (except in Code Division Multiple Access networks), discontinuous transmission and conditions of phone use were found to have a relatively minor influence on total cumulative specific RF energy. Conclusions While amount and duration of use are important determinants of RF dose in the brain, their impact can be substantially modified by communication system, frequency band and location in the brain. It is important to take these into account in analyses of risk of brain tumours from RF exposure from mobile phones. PMID:21659468

Relative acoustic frequency response of induced methane, carbon dioxide and air gas bubble plumes, observed laterally.

PubMed

Kubilius, Rokas; Pedersen, Geir

2016-10-01

There is an increased need to detect, identify, and monitor natural and manmade seabed gas leaks. Fisheries echosounders are well suited to monitor large volumes of water and acoustic frequency response [normalized acoustic backscatter, when a measure at one selected frequency is used as a denominator, r(f)] is commonly used to identify echoes from fish and zooplankton species. Information on gas plume r(f) would be valuable for automatic detection of subsea leaks and for separating bubble plumes from natural targets such as swimbladder-bearing fish. Controlled leaks were produced with a specially designed instrument frame suspended in mid-water in a sheltered fjord. The frame was equipped with echosounders, stereo-camera, and gas-release nozzles. The r(f) of laterally observed methane, carbon dioxide, and air plumes (0.040-29 l/min) were measured at 70, 120, 200, and 333 kHz, with bubble sizes determined optically. The observed bubble size range (1-25 mm) was comparable to that reported in the literature for natural cold seeps of methane. A negative r(f) with increasing frequency was observed, namely, r(f) of about 0.7, 0.6, and 0.5 at 120, 200, and 333 kHz when normalized to 70 kHz. Measured plume r(f) is also compared to resolved, single bubble target strength-based, and modeled r(f).

Proposed Cavity for Reduced Slip-Stacking Loss

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eldred, J.; Zwaska, R.

This paper employs a novel dynamical mechanism to improve the performance of slip-stacking. Slip-stacking in an accumulation technique used at Fermilab since 2004 which nearly double the proton intensity. During slip-stacking, the Recycler or the Main Injector stores two particles beams that spatially overlap but have different momenta. The two particle beams are longitudinally focused by two 53 MHz 100 kV RF cavities with a small frequency difference between them. We propose an additional 106 MHz 20 kV RF cavity, with a frequency at the double the average of the upper and lower main RF frequencies. In simulation, we findmore » the proposed RF cavity significantly enhances the stable bucket area and reduces slip-stacking losses under reasonable injection scenarios. We quantify and map the stability of the parameter space for any accelerator implementing slip-stacking with the addition of a harmonic RF cavity.« less

Photonically enabled Ka-band radar and infrared sensor subscale testbed

NASA Astrophysics Data System (ADS)

Lohr, Michele B.; Sova, Raymond M.; Funk, Kevin B.; Airola, Marc B.; Dennis, Michael L.; Pavek, Richard E.; Hollenbeck, Jennifer S.; Garrison, Sean K.; Conard, Steven J.; Terry, David H.

2014-10-01

A subscale radio frequency (RF) and infrared (IR) testbed using novel RF-photonics techniques for generating radar waveforms is currently under development at The Johns Hopkins University Applied Physics Laboratory (JHU/APL) to study target scenarios in a laboratory setting. The linearity of Maxwell's equations allows the use of millimeter wavelengths and scaled-down target models to emulate full-scale RF scene effects. Coupled with passive IR and visible sensors, target motions and heating, and a processing and algorithm development environment, this testbed provides a means to flexibly and cost-effectively generate and analyze multi-modal data for a variety of applications, including verification of digital model hypotheses, investigation of correlated phenomenology, and aiding system capabilities assessment. In this work, concept feasibility is demonstrated for simultaneous RF, IR, and visible sensor measurements of heated, precessing, conical targets and of a calibration cylinder. Initial proof-of-principle results are shown of the Ka-band subscale radar, which models S-band for 1/10th scale targets, using stretch processing and Xpatch models.

A 1.2-V CMOS front-end for LTE direct conversion SAW-less receiver

NASA Astrophysics Data System (ADS)

Riyan, Wang; Jiwei, Huang; Zhengping, Li; Weifeng, Zhang; Longyue, Zeng

2012-03-01

A CMOS RF front-end for the long-term evolution (LTE) direct conversion receiver is presented. With a low noise transconductance amplifier (LNA), current commutating passive mixer and transimpedance operational amplifier (TIA), the RF front-end structure enables high-integration, high linearity and simple frequency planning for LTE multi-band applications. Large variable gain is achieved using current-steering transconductance stages. A current commutating passive mixer with 25% duty-cycle LO improves gain, noise and linearity. A direct coupled current-input filter (DCF) is employed to suppress the out-of-band interferer. Fabricated in a 0.13-μm CMOS process, the RF front-end achieves a 45 dB conversion voltage gain, 2.7 dB NF, -7 dBm IIP3, and +60 dBm IIP2 with calibration from 2.3 to 2.7 GHz. The total RF front end with divider draws 40 mA from a single 1.2-V supply.

UHF front-end feeding RFID-based body sensor networks by exploiting the reader signal

NASA Astrophysics Data System (ADS)

Pasca, M.; Colella, R.; Catarinucci, L.; Tarricone, L.; D'Amico, S.; Baschirotto, A.

2016-05-01

This paper presents an integrated, high-sensitivity UHF radio frequency identification (RFID) power management circuit for body sensor network applications. The circuit consists of a two-stage RF-DC Dickson's rectifier followed by an integrated five-stage DC-DC Pelliconi's charge pump driven by an ultralow start-up voltage LC oscillator. The DC-DC charge pump interposed between the RF-DC rectifier and the output load provides the RF to load isolation avoiding losses due to the diodes reverse saturation current. The RF-DC rectifier has been realized on FR4 substrate, while the charge pump and the oscillator have been realized in 180 nm complementary metal oxide semiconductor (CMOS) technology. Outdoor measurements demonstrate the ability of the power management circuit to provide 400 mV output voltage at 14 m distance from the UHF reader, in correspondence of -25 dBm input signal power. As demonstrated in the literature, such output voltage level is suitable to supply body sensor network nodes.

Anthropogenic Radio-Frequency Electromagnetic Fields Elicit Neuropathic Pain in an Amputation Model

PubMed Central

Jones, Erick; Romero-Ortega, Mario

2016-01-01

Anecdotal and clinical reports have suggested that radio-frequency electromagnetic fields (RF EMFs) may serve as a trigger for neuropathic pain. However, these reports have been widely disregarded, as the epidemiological effects of electromagnetic fields have not been systematically proven, and are highly controversial. Here, we demonstrate that anthropogenic RF EMFs elicit post-neurotomy pain in a tibial neuroma transposition model. Behavioral assays indicate a persistent and significant pain response to RF EMFs when compared to SHAM surgery groups. Laser thermometry revealed a transient skin temperature increase during stimulation. Furthermore, immunofluorescence revealed an increased expression of temperature sensitive cation channels (TRPV4) in the neuroma bulb, suggesting that RF EMF-induced pain may be due to cytokine-mediated channel dysregulation and hypersensitization, leading to thermal allodynia. Additional behavioral assays were performed using an infrared heating lamp in place of the RF stimulus. While thermally-induced pain responses were observed, the response frequency and progression did not recapitulate the RF EMF effects. In vitro calcium imaging experiments demonstrated that our RF EMF stimulus is sufficient to directly contribute to the depolarization of dissociated sensory neurons. Furthermore, the perfusion of inflammatory cytokine TNF-α resulted in a significantly higher percentage of active sensory neurons during RF EMF stimulation. These results substantiate patient reports of RF EMF-pain, in the case of peripheral nerve injury, while confirming the public and scientific consensus that anthropogenic RF EMFs engender no adverse sensory effects in the general population. PMID:26760033

FPGA-based RF interference reduction techniques for simultaneous PET–MRI

PubMed Central

Gebhardt, P; Wehner, J; Weissler, B; Botnar, R; Marsden, P K; Schulz, V

2016-01-01

Abstract The combination of positron emission tomography (PET) and magnetic resonance imaging (MRI) as a multi-modal imaging technique is considered very promising and powerful with regard to in vivo disease progression examination, therapy response monitoring and drug development. However, PET–MRI system design enabling simultaneous operation with unaffected intrinsic performance of both modalities is challenging. As one of the major issues, both the PET detectors and the MRI radio-frequency (RF) subsystem are exposed to electromagnetic (EM) interference, which may lead to PET and MRI signal-to-noise ratio (SNR) deteriorations. Early digitization of electronic PET signals within the MRI bore helps to preserve PET SNR, but occurs at the expense of increased amount of PET electronics inside the MRI and associated RF field emissions. This raises the likelihood of PET-related MRI interference by coupling into the MRI RF coil unwanted spurious signals considered as RF noise, as it degrades MRI SNR and results in MR image artefacts. RF shielding of PET detectors is a commonly used technique to reduce PET-related RF interferences, but can introduce eddy-current-related MRI disturbances and hinder the highest system integration. In this paper, we present RF interference reduction methods which rely on EM field coupling–decoupling principles of RF receive coils rather than suppressing emitted fields. By modifying clock frequencies and changing clock phase relations of digital circuits, the resulting RF field emission is optimised with regard to a lower field coupling into the MRI RF coil, thereby increasing the RF silence of PET detectors. Our methods are demonstrated by performing FPGA-based clock frequency and phase shifting of digital silicon photo-multipliers (dSiPMs) used in the PET modules of our MR-compatible Hyperion IID PET insert. We present simulations and magnetic-field map scans visualising the impact of altered clock phase pattern on the spatial RF field distribution, followed by MRI noise and SNR scans performed with an operating PET module using different clock frequencies and phase patterns. The methods were implemented via firmware design changes without any hardware modifications. This introduces new means of flexibility by enabling adaptive RF interference reduction optimisations in the field, e.g. when using a PET insert with different MRI systems or when different MRI RF coil types are to be operated with the same PET detector. PMID:27049898

FPGA-based RF interference reduction techniques for simultaneous PET-MRI.

PubMed

Gebhardt, P; Wehner, J; Weissler, B; Botnar, R; Marsden, P K; Schulz, V

2016-05-07

The combination of positron emission tomography (PET) and magnetic resonance imaging (MRI) as a multi-modal imaging technique is considered very promising and powerful with regard to in vivo disease progression examination, therapy response monitoring and drug development. However, PET-MRI system design enabling simultaneous operation with unaffected intrinsic performance of both modalities is challenging. As one of the major issues, both the PET detectors and the MRI radio-frequency (RF) subsystem are exposed to electromagnetic (EM) interference, which may lead to PET and MRI signal-to-noise ratio (SNR) deteriorations. Early digitization of electronic PET signals within the MRI bore helps to preserve PET SNR, but occurs at the expense of increased amount of PET electronics inside the MRI and associated RF field emissions. This raises the likelihood of PET-related MRI interference by coupling into the MRI RF coil unwanted spurious signals considered as RF noise, as it degrades MRI SNR and results in MR image artefacts. RF shielding of PET detectors is a commonly used technique to reduce PET-related RF interferences, but can introduce eddy-current-related MRI disturbances and hinder the highest system integration. In this paper, we present RF interference reduction methods which rely on EM field coupling-decoupling principles of RF receive coils rather than suppressing emitted fields. By modifying clock frequencies and changing clock phase relations of digital circuits, the resulting RF field emission is optimised with regard to a lower field coupling into the MRI RF coil, thereby increasing the RF silence of PET detectors. Our methods are demonstrated by performing FPGA-based clock frequency and phase shifting of digital silicon photo-multipliers (dSiPMs) used in the PET modules of our MR-compatible Hyperion II (D) PET insert. We present simulations and magnetic-field map scans visualising the impact of altered clock phase pattern on the spatial RF field distribution, followed by MRI noise and SNR scans performed with an operating PET module using different clock frequencies and phase patterns. The methods were implemented via firmware design changes without any hardware modifications. This introduces new means of flexibility by enabling adaptive RF interference reduction optimisations in the field, e.g. when using a PET insert with different MRI systems or when different MRI RF coil types are to be operated with the same PET detector.

FPGA-based RF interference reduction techniques for simultaneous PET-MRI

NASA Astrophysics Data System (ADS)

Gebhardt, P.; Wehner, J.; Weissler, B.; Botnar, R.; Marsden, P. K.; Schulz, V.

2016-05-01

The combination of positron emission tomography (PET) and magnetic resonance imaging (MRI) as a multi-modal imaging technique is considered very promising and powerful with regard to in vivo disease progression examination, therapy response monitoring and drug development. However, PET-MRI system design enabling simultaneous operation with unaffected intrinsic performance of both modalities is challenging. As one of the major issues, both the PET detectors and the MRI radio-frequency (RF) subsystem are exposed to electromagnetic (EM) interference, which may lead to PET and MRI signal-to-noise ratio (SNR) deteriorations. Early digitization of electronic PET signals within the MRI bore helps to preserve PET SNR, but occurs at the expense of increased amount of PET electronics inside the MRI and associated RF field emissions. This raises the likelihood of PET-related MRI interference by coupling into the MRI RF coil unwanted spurious signals considered as RF noise, as it degrades MRI SNR and results in MR image artefacts. RF shielding of PET detectors is a commonly used technique to reduce PET-related RF interferences, but can introduce eddy-current-related MRI disturbances and hinder the highest system integration. In this paper, we present RF interference reduction methods which rely on EM field coupling-decoupling principles of RF receive coils rather than suppressing emitted fields. By modifying clock frequencies and changing clock phase relations of digital circuits, the resulting RF field emission is optimised with regard to a lower field coupling into the MRI RF coil, thereby increasing the RF silence of PET detectors. Our methods are demonstrated by performing FPGA-based clock frequency and phase shifting of digital silicon photo-multipliers (dSiPMs) used in the PET modules of our MR-compatible Hyperion II D PET insert. We present simulations and magnetic-field map scans visualising the impact of altered clock phase pattern on the spatial RF field distribution, followed by MRI noise and SNR scans performed with an operating PET module using different clock frequencies and phase patterns. The methods were implemented via firmware design changes without any hardware modifications. This introduces new means of flexibility by enabling adaptive RF interference reduction optimisations in the field, e.g. when using a PET insert with different MRI systems or when different MRI RF coil types are to be operated with the same PET detector.

The Design and Operation of Ultra-Sensitive and Tunable Radio-Frequency Interferometers.

PubMed

Cui, Yan; Wang, Pingshan

2014-12-01

Dielectric spectroscopy (DS) is an important technique for scientific and technological investigations in various areas. DS sensitivity and operating frequency ranges are critical for many applications, including lab-on-chip development where sample volumes are small with a wide range of dynamic processes to probe. In this work, we present the design and operation considerations of radio-frequency (RF) interferometers that are based on power-dividers (PDs) and quadrature-hybrids (QHs). Such interferometers are proposed to address the sensitivity and frequency tuning challenges of current DS techniques. Verified algorithms together with mathematical models are presented to quantify material properties from scattering parameters for three common transmission line sensing structures, i.e., coplanar waveguides (CPWs), conductor-backed CPWs, and microstrip lines. A high-sensitivity and stable QH-based interferometer is demonstrated by measuring glucose-water solution at a concentration level that is ten times lower than some recent RF sensors while our sample volume is ~1 nL. Composition analysis of ternary mixture solutions are also demonstrated with a PD-based interferometer. Further work is needed to address issues like system automation, model improvement at high frequencies, and interferometer scaling.

Rare-earth-doped materials with application to optical signal processing, quantum information science, and medical imaging technology

NASA Astrophysics Data System (ADS)

Cone, R. L.; Thiel, C. W.; Sun, Y.; Böttger, Thomas; Macfarlane, R. M.

2012-02-01

Unique spectroscopic properties of isolated rare earth ions in solids offer optical linewidths rivaling those of trapped single atoms and enable a variety of recent applications. We design rare-earth-doped crystals, ceramics, and fibers with persistent or transient "spectral hole" recording properties for applications including high-bandwidth optical signal processing where light and our solids replace the high-bandwidth portion of the electronics; quantum cryptography and information science including the goal of storage and recall of single photons; and medical imaging technology for the 700-900 nm therapeutic window. Ease of optically manipulating rare-earth ions in solids enables capturing complex spectral information in 105 to 108 frequency bins. Combining spatial holography and spectral hole burning provides a capability for processing high-bandwidth RF and optical signals with sub-MHz spectral resolution and bandwidths of tens to hundreds of GHz for applications including range-Doppler radar and high bandwidth RF spectral analysis. Simply stated, one can think of these crystals as holographic recording media capable of distinguishing up to 108 different colors. Ultra-narrow spectral holes also serve as a vibration-insensitive sub-kHz frequency reference for laser frequency stabilization to a part in 1013 over tens of milliseconds. The unusual properties and applications of spectral hole burning of rare earth ions in optical materials are reviewed. Experimental results on the promising Tm3+:LiNbO3 material system are presented and discussed for medical imaging applications. Finally, a new application of these materials as dynamic optical filters for laser noise suppression is discussed along with experimental demonstrations and theoretical modeling of the process.

A sensor-type application of a self-oscillating dynamic system with a fiber optic feedback line, including chemical sensors and biosensors

NASA Astrophysics Data System (ADS)

Rabinovich, Emmanuel M.

2004-05-01

We present an overview of research, conducted and published by the author and colleagues during the preceding decade, with self-oscillating dynamic systems. Special attention has been addressed to sensor type applications that allow one to design a new type of sensors of different physical parameters as well as using system for chemical and biosensors. Many detection methods exploit self-oscillating systems, such as lasers and RF or microwave oscillators, and use changes introduced into a feedback mechanism (for instance laser inter-cavity spectroscopy) for evaluation of different physical parameters such as refractive indices or absorption coefficients. Typically, that approach is very efficient, is easy to implement, and gives high sensitivity. We have demonstrated that a similar method can be used in the case of an RF optoelectronic self-oscillating system (OSOS) with a fiber-optic feedback line. Using fiber as an element of a positive feedback line allows one to design a new family of fiber-optic sensors each of which can be integrated into a fiber-optic feedback line. Changes introduced into the feedback line of an OSOS typically cause an RF frequency shift that can be measured very precisely with an RF frequency counter or spectrum analyzer. For some types of sensors an OSOS can easily incorporate and utilize advantages of well-developed modern inexpensive light sources (VCSELs, LEDs) and opto-electronic components that have been designed for communication purposes. A single closed loop OSOS can be easily duplicated for sensor array measurement via the use of parallel fiber-optics (for example VCSEL arrays and fiber ribbon cables) that have been well developed for telecommunication systems.

Graphene Quantum Capacitors for High Frequency Tunable Analog Applications.

PubMed

Moldovan, Clara F; Vitale, Wolfgang A; Sharma, Pankaj; Tamagnone, Michele; Mosig, Juan R; Ionescu, Adrian M

2016-08-10

Graphene quantum capacitors (GQC) are demonstrated to be enablers of radio-frequency (RF) functions through voltage-tuning of their capacitance. We show that GQC complements MEMS and MOSFETs in terms of performance for high frequency analog applications and tunability. We propose a CMOS compatible fabrication process and report the first experimental assessment of their performance at microwaves frequencies (up to 10 GHz), demonstrating experimental GQCs in the pF range with a tuning ratio of 1.34:1 within 1.25 V, and Q-factors up to 12 at 1 GHz. The figures of merit of graphene variable capacitors are studied in detail from 150 to 350 K. Furthermore, we describe a systematic, graphene specific approach to optimize their performance and predict the figures of merit achieved if such a methodology is applied.

Secure free-space communication, turbulence mitigation, and other applications using acousto-optic chaos.

PubMed

Chatterjee, Monish R; Mohamed, Ali; Almehmadi, Fares S

2018-04-01

Use of acousto-optic (A-O) chaos via the feedback loop in a Bragg cell for signal encryption began as a conceptual demonstration around 2008. Radio frequency (RF) chaos from a hybrid A-O feedback device may be used for secure communications of analog and digital signals. In this paper, modulation of RF chaos via first-order feedback is discussed with results corroborated by nonlinear dynamics, bifurcation maps, and Lyapunov analyses. Applications based on encryption with profiled optical beams, and extended to medical and embedded steganographic data, and video signals are discussed. It is shown that the resulting encryption is significantly robust with key tolerances potentially less than 0.1%. Results are also presented for the use of chaotic encryption for image restoration during propagation through atmospheric turbulence.

Microwave thermal radiation effects on skin tissues

NASA Astrophysics Data System (ADS)

Yoon, Hargsoon; Song, Kyo D.; Lee, Uhn; Choi, Sang H.

2012-10-01

Microwave/RF energy has been used for wireless power transmission including many therapeutic applications, such as transurethral microwave therapy (TUMT). For safe uses of RF power, it is important to know how to deliver microwave energy on focused area and control the temperature changes not to drastically increase on adjacent areas. Graphical analysis of thermal loading factor is important to understand how to achieve effective transmission of microwave through the tissue. The loss mechanism while transmission often appears as thermal effects due to absorption of microwave, especially for materials such as human skin, muscles, and other organic parts including brain. In this paper, microwave thermal effects are investigated to measure temperatures, penetration depth through animal skins in terms of input power and various frequencies. This result will be compare with the case of human applications.

Study of RF breakdown and multipacting in accelerator components

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pande, Manjiri; Singh, P., E-mail: manjiri@barc.gov.in, E-mail: psingh@barc.gov.in

2014-07-01

Radio frequency (RF) structures that are part of accelerators and energy sources, operate with sinusoidally varying electromagnetic fields under high RF energy. Here, RF breakdown and multipacting take place in RF structures and limit their performance. Electron field emission processes in a RF structure are precursors for breakdown processes. RF breakdown is a major phenomena affecting and causing the irreversible damage to RF structures. Breakdown rate and the damage induced by the breakdowns are its important properties. The damage is related to power absorbed during breakdown, while the breakdown rate is determined by the amplitudes of surface electric and magneticmore » fields, geometry, metal surface preparation and conditioning history. It limits working power and produces irreversible surface damage. The breakdown limit depends on the RF circuit, structure geometry, RF frequency, input RF power, pulse width, materials used, surface processing technique and surface electric and magnetic fields. Multipactor (MP) is a low power, electron multiplication based resonance breakdown phenomenon in vacuum and is often observed in RF structures. A multipactor discharge is undesirable, as it can create a reactive component that detunes the resonant cavities and components, generates noise in communication system and induces gas desorption from the conductor surfaces. In RF structures, certain conditions are required to generate multipacting. (author)« less

Interaction between pulsed discharge and radio frequency discharge burst at atmospheric pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jie; College of Science, Donghua University, Shanghai 201620; Guo, Ying

The atmospheric pressure glow discharges (APGD) with dual excitations in terms of pulsed voltage and pulse-modulation radio frequency (rf) power are studied experimentally between two parallel plates electrodes. Pulse-modulation applied in rf APGD temporally separates the discharge into repetitive discharge bursts, between which the high voltage pulses are introduced to ignite sub-microsecond pulsed discharge. The discharge characteristics and spatio-temporal evolution are investigated by means of current voltage characteristics and time resolved imaging, which suggests that the introduced pulsed discharge assists the ignition of rf discharge burst and reduces the maintain voltage of rf discharge burst. Furtherly, the time instant ofmore » pulsed discharge between rf discharge bursts is manipulated to study the ignition dynamics of rf discharge burst.« less

Frequency, moisture content, and temperature dependent dielectric properties of potato starch related to drying with radio-frequency/microwave energy.

PubMed

Zhu, Zhuozhuo; Guo, Wenchuan

2017-08-24

To develop advanced drying methods using radio-frequency (RF) or microwave (MW) energy, dielectric properties of potato starch were determined using an open-ended coaxial-line probe and network analyzer at frequencies between 20 and 4,500 MHz, moisture contents between 15.1% and 43.1% wet basis (w.b.), and temperatures between 25 and 75 °C. The results showed that both dielectric constant (ε') and loss factor (ε″) were dependent on frequency, moisture content, and temperature. ε' decreased with increasing frequency at a given moisture content or temperature. At low moisture contents (≤25.4% w.b.) or low temperatures (≤45 °C), ε″ increased with increasing frequency. However, ε″ changed from decrease to increase with increasing frequency at high moisture contents or temperatures. At low temperatures (25-35 °C), both ε' and ε″ increased with increasing moisture content. At low moisture contents (15.1-19.5% w.b.), they increased with increasing temperature. The change trends of ε' and ε″ were different and dependent on temperature and moisture content at their high levels. The penetration depth (d p ) decreased with increasing frequency. RF treatments may provide potential large-scale industrial drying application for potato starch. This research offers useful information on dielectric properties of potato starch related to drying with electromagnetic energy.

Gamma-ray irradiation of ohmic MEMS switches

NASA Astrophysics Data System (ADS)

Maciel, John J.; Lampen, James L.; Taylor, Edward W.

2012-10-01

Radio Frequency (RF) Microelectromechanical System (MEMS) switches are becoming important building blocks for a variety of military and commercial applications including switch matrices, phase shifters, electronically scanned antennas, switched filters, Automatic Test Equipment, instrumentation, cell phones and smart antennas. Low power consumption, large ratio of off-impedance to on-impedance, extreme linearity, low mass, small volume and the ability to be integrated with other electronics makes MEMS switches an attractive alternative to other mechanical and solid-state switches for a variety of space applications. Radant MEMS, Inc. has developed an electrostatically actuated broadband ohmic microswitch that has applications from DC through the microwave region. Despite the extensive earth based testing, little is known about the performance and reliability of these devices in space environments. To help fill this void, we have irradiated our commercial-off-the-shelf SPST, DC to 40 GHz MEMS switches with gamma-rays as an initial step to assessing static impact on RF performance. Results of Co-60 gamma-ray irradiation of the MEMS switches at photon energies ≥ 1.0 MeV to a total dose of ~ 118 krad(Si) did not show a statistically significant post-irradiation change in measured broadband, RF insertion loss, insertion phase, return loss and isolation.

Design and Implementation of RF Energy Harvesting System for Low-Power Electronic Devices

NASA Astrophysics Data System (ADS)

Uzun, Yunus

2016-08-01

Radio frequency (RF) energy harvester systems are a good alternative for energizing of low-power electronics devices. In this work, an RF energy harvester is presented to obtain energy from Global System for Mobile Communications (GSM) 900 MHz signals. The energy harvester, consisting of a two-stage Dickson voltage multiplier circuit and L-type impedance matching circuits, was designed, simulated, fabricated and tested experimentally in terms of its performance. Simulation and experimental works were carried out for various input power levels, load resistances and input frequencies. Both simulation and experimental works have been carried out for this frequency band. An efficiency of 45% is obtained from the system at 0 dBm input power level using the impedance matching circuit. This corresponds to the power of 450 μW and this value is sufficient for many low-power devices. The most important parameters affecting the efficiency of the RF energy harvester are the input power level, frequency band, impedance matching and voltage multiplier circuits, load resistance and the selection of diodes. RF energy harvester designs should be optimized in terms of these parameters.

ISM band to U-NII band frequency transverter and method of frequency transversion

DOEpatents

Stepp, Jeffrey David [Grandview, MO; Hensley, Dale [Grandview, MO

2006-04-04

A frequency transverter (10) and method for enabling bi-frequency dual-directional transfer of digitally encoded data on an RF carrier by translating between a crowded or otherwise undesirable first frequency band, such as the 2.4 GHz ISM band, and a less-crowded or otherwise desirable second frequency band, such as the 5.0 GHz-6.0 GHz U-NII band. In a preferred embodiment, the transverter (10) connects between an existing data radio (11) and its existing antenna (30), and comprises a bandswitch (12); an input RF isolating device (14); a transmuter (16); a converter (18); a dual output local oscillator (20); an output RF isolating device (22); and an antenna (24) tuned to the second frequency band. The bandswitch (12) allows for bypassing the transverter (10), thereby facilitating its use with legacy systems. The transmuter (14) and converter (16) are adapted to convert to and from, respectively, the second frequency band.

ISM band to U-NII band frequency transverter and method of frequency transversion

DOEpatents

Stepp, Jeffrey David [Grandview, MO; Hensley, Dale [Grandview, MO

2006-09-12

A frequency transverter (10) and method for enabling bi-frequency dual-directional transfer of digitally encoded data on an RF carrier by translating between a crowded or otherwise undesirable first frequency band, such as the 2.4 GHz ISM band, and a less-crowded or otherwise desirable second frequency band, such as the 5.0 GHz 6.0 GHz U-NII band. In a preferred embodiment, the transverter (10) connects between an existing data radio (11) and its existing antenna (30), and comprises a bandswitch (12); an input RF isolating device (14); a transmuter (16); a converter (18); a dual output local oscillator (20); an output RF isolating device (22); and an antenna (24) tuned to the second frequency band. The bandswitch (12) allows for bypassing the transverter (10), thereby facilitating its use with legacy systems. The transmuter (14) and converter (16) are adapted to convert to and from, respectively, the second frequency band.

Recent research trends of radio-frequency biosensors for biomolecular detection.

PubMed

Lee, Hee-Jo; Yook, Jong-Gwan

2014-11-15

This article reviews radio-frequency (RF) biosensors based on passive and/or active devices and circuits. In particular, we focus on RF biosensors designed for detection of various biomolecules such as biotin-streptavidin, DNA hybridization, IgG, and glucose. The performance of these biosensors has been enhanced by the introduction of various sensing schemes with diverse nanomaterials (e.g., carbon nanotubes, graphene oxide, magnetic and gold nanoparticles, etc.). In addition, the RF biosensing platforms that can be associated with an RF active system are discussed. Finally, the challenges of RF biosensors are presented and suggestions are made for their future direction and prospects. Copyright © 2014 Elsevier B.V. All rights reserved.

All-optical single-sideband frequency upconversion utilizing the XPM effect in an SOA-MZI.

PubMed

Kim, Doo-Ho; Lee, Joo-Young; Choi, Hyung-June; Song, Jong-In

2016-09-05

An all-optical single sideband (OSSB) frequency upconverter based on the cross-phase modulation (XPM) effect is proposed and experimentally demonstrated to overcome the power fading problem caused by the chromatic dispersion of fiber in radio-over-fiber systems. The OSSB frequency upconverter consists of an arrayed waveguide grating (AWG) and a semiconductor optical amplifier Mach-Zehnder interferometer (SOA-MZI) and does not require an extra delay line used for phase noise compensation. The generated OSSB radio frequency (RF) signal transmitted over single-mode fibers up to 20 km shows a flat electrical RF power response as a function of the fiber length. The upconverted electrical RF signal at 48 GHz shows negligible degradation of the phase noise even without an extra delay line. The measured phase noise of the upconverted RF signal (48 GHz) is -74.72 dBc/Hz at an offset frequency of 10 kHz. The spurious free dynamic range (SFDR) measured by a two-tone test to estimate the linearity of the OSSB frequency upconverter is 72.5 dB·Hz^2/3.

Real-time digital signal processing for live electro-optic imaging.

PubMed

Sasagawa, Kiyotaka; Kanno, Atsushi; Tsuchiya, Masahiro

2009-08-31

We present an imaging system that enables real-time magnitude and phase detection of modulated signals and its application to a Live Electro-optic Imaging (LEI) system, which realizes instantaneous visualization of RF electric fields. The real-time acquisition of magnitude and phase images of a modulated optical signal at 5 kHz is demonstrated by imaging with a Si-based high-speed CMOS image sensor and real-time signal processing with a digital signal processor. In the LEI system, RF electric fields are probed with light via an electro-optic crystal plate and downconverted to an intermediate frequency by parallel optical heterodyning, which can be detected with the image sensor. The artifacts caused by the optics and the image sensor characteristics are corrected by image processing. As examples, we demonstrate real-time visualization of electric fields from RF circuits.

A proposed adjustable RF cable connector

NASA Technical Reports Server (NTRS)

Stringer, E. J.; Doyle, J. D.

1973-01-01

In system that requires negligible loss, it may be necessary to adjust cable length to exact multiple of transmitted wavelength. Adjustable cable connector saves time and cost by eliminating need to add to or cut from cable. Device was especially designed for use with high frequencies. For particular application, connector of suitable dimensions should be used.

Measurement of dielectric properties of whole and ground chicken breast meat over the frequency range from 500 MHz to 50 GHz

USDA-ARS?s Scientific Manuscript database

The dielectric properties of food greatly influence its interaction with RF and MW electromagnetic fields and subsequently determine the absorption of microwave energy and consequent heating behavior of food materials in microwave heating and processing applications. Microwave heating is usually re...

Noninvasive radio frequency for skin tightening and body contouring.

PubMed

Weiss, Robert A

2013-03-01

The medical use of radio frequency (RF) is based on an oscillating electrical current forcing collisions between charged molecules and ions, which are then transformed into heat. RF heating occurs irrespective of chromophore or skin type and is not dependent on selective photothermolysis. RF can be delivered using monopolar, bipolar, and unipolar devices, and each method has theoretical limits of depth penetration. A variant of bipolar delivery is fractional RF delivery. In monopolar configurations, RF will penetrate deeply and return via a grounding electrode. Multiple devices are available and are detailed later in the text. RF thermal stimulation is believed to result in a microinflammatory process that promotes new collagen. By manipulating skin cooling, RF can also be used for heating and reduction of fat. Currently, the most common uses of RF-based devices are to noninvasively manage and treat skin tightening of lax skin (including sagging jowls, abdomen, thighs, and arms), as well as wrinkle reduction, cellulite improvement, and body contouring.

Radio-frequency response of single pores and artificial ion channels

NASA Astrophysics Data System (ADS)

Kim, H. S.; Ramachandran, S.; Stava, E.; van der Weide, D. W.; Blick, R. H.

2011-09-01

Intercellular communication relies on ion channels and pores in cell membranes. These protein-formed channels enable the exchange of ions and small molecules to electrically and/or chemically interact with the cells. Traditionally, recordings on single-ion channels and pores are performed in the dc regime, due to the extremely high impedance of these molecular junctions. This paper is intended as an introduction to radio-frequency (RF) recordings of single-molecule junctions in bilipid membranes. First, we demonstrate how early approaches to using microwave circuitry as readout devices for ion channel formation were realized. The second step will then focus on how to engineer microwave coupling into the high-impedance channel by making use of bio-compatible micro-coaxial lines. We then demonstrate integration of an ultra-broadband microwave circuit for the direct sampling of single α-hemolysin pores in a suspended bilipid membrane. Simultaneous direct current recordings reveal that we can monitor and correlate the RF transmission signal. This enables us to relate the open-close states of the direct current to the RF signal. Altogether, our experiments lay the ground for an RF-readout technique to perform real-time in vitro recordings of pores. The technique thus holds great promise for research and drug screening applications. The possible enhancement of sampling rates of single channels and pores by the large recording bandwidth will allow us to track the passage of single ions.

Spin dynamics in the modulation frame: application to homonuclear recoupling in magic angle spinning solid-state NMR.

PubMed

De Paëpe, Gaël; Lewandowski, Józef R; Griffin, Robert G

2008-03-28

We introduce a family of solid-state NMR pulse sequences that generalizes the concept of second averaging in the modulation frame and therefore provides a new approach to perform magic angle spinning dipolar recoupling experiments. Here, we focus on two particular recoupling mechanisms-cosine modulated rotary resonance (CMpRR) and cosine modulated recoupling with isotropic chemical shift reintroduction (COMICS). The first technique, CMpRR, is based on a cosine modulation of the rf phase and yields broadband double-quantum (DQ) (13)C recoupling using >70 kHz omega(1,C)/2pi rf field for the spinning frequency omega(r)/2=10-30 kHz and (1)H Larmor frequency omega(0,H)/2pi up to 900 MHz. Importantly, for p>or=5, CMpRR recouples efficiently in the absence of (1)H decoupling. Extension to lower p values (3.5

Slow wave structures integrated with ferromagnetic and ferro-electric thin films for smart RF applications

NASA Astrophysics Data System (ADS)

Rahman, B. M. Farid

Modern communications systems are following a common trend to increase the operational frequency, level of integration and number of frequency bands. Although 90-95% components in a cell phone are passives which take 80% of the total board area. High performance RF passive components play limited role and are desired towards this technological advancement. Slow wave structure is one of the most promising candidates to design compact RF and mm-Wave passive components. Slow wave structures are the specially designed transmission line realized by placing the alternate narrow and wide signal conductors in order to reduce the physical size of the components. This dissertation reports multiband slow wave structures integrated with ferromagnetic and ferroelectric thin films and their RF applications. A comparative study on different types of coplanar wave-guide (CPW) slow wave structures (SWS) has been demonstrated for the first time. Slow wave structures with various shapes have been investigated and optimized with various signal conductor shapes, ground conductor shapes and pitch of the sections. Novel techniques i.e. the use of the defected ground structure and the different signal conductor length has been implemented to achieve higher slow wave effect with minimum loss. The measured results have shown the reduction of size over 43.47% and 37.54% in the expense of only 0.27dB and 0.102dB insertion loss respectively which can reduce the area of a designed branch line coupler by 68% and 61% accordingly. Permalloy (Py) is patterned on top of the developed SWS for the first time to further increase the slow wave effect and provide tunable inductance value. High frequency applications of Py are limited by its ferro-magnetic resonance frequency since the inductance value decreases beyond that. Sub-micrometer patterning of Py has increased FMR frequency until 6.3GHz and 3.2GHz by introducing the shape anisotropy. For the SWS with patterned Py, the size of the quarter wavelength has been reduced from 14.86mm to 4.7mm at 2GHz. DC current which is the most convenient and available tuning parameter in a practical circuit board has been used, the developed SWS can function as quarter wave transmission line from 2GHz to 1.80GHz (i.e. 10%). Lead Zirconium Titanate (PZT) is grown and patterned on top of the section with standard sol-gel method to increase capacitance value. The inter digit capacitor type structure along with PZT thin film has been adopted and results showed capacitance value increment by 36%. An electric field between signal and ground has been applied to change the polarization of the thin film which resulted in a tuning of center frequency by 15% (1.75GHz to 2GHz). In addition, a novel approach has been implemented by integrating both the ferromagnetic and the ferroelectric thin films simultaneously to achieve higher slow wave effect, wider tuning range and smaller variation in Characteristics Impedance. The size of the final structure for a quarter wavelengths has been reduced from 14.86mm to 3.98mm while the center frequency has been tuned from 2GHz to 1.5GHz (i.e. 25%). Tunable RF applications of the ferro-magnetic thin films are also demonstrated as a DC current band pass filter, tunable noise suppressor and meander line inductor. A well designed frequency tunable band pass filter (BPF) is implemented at 4GHz with patterned Permalloy. The pass band frequency of a band pass filter has been tuned from 4GHz to 4.02GHz by applying a DC current. The suppression frequency of the developed noise suppressor is tuned from 4.8GHz to 6GHz and 4GHz to 6GHz by changing the aspect ratio of the Py bars and the gap in between them. Moreover, a novel way of tuning the stop band frequency of the noise suppressor by using an external direct current changed the suppression frequency from 6GHz to 4.3GHz. A pass band loss of 1.5%, less than 2° transmitted signal phase distortion, and 3 dB extra return loss of the designed noise suppressor showed the promise the noise suppressors. The increase in the number of turns of a meander line inductor has increased the inductance density from 2565nH/m to 3396nH/m while application of the patterned Py has increased the inductance density from 2565nH/m to 3060nH/m. The tuning of the meander line inductor has been performed by applying DC current until the FMR frequency 4.51GHz.

A Tightly Coupled Non-Equilibrium Magneto-Hydrodynamic Model for Inductively Coupled RF Plasmas

DTIC Science & Technology

2016-02-29

development a tightly coupled magneto-hydrodynamic model for Inductively Coupled Radio- Frequency (RF) Plasmas. Non Local Thermodynamic Equilibrium (NLTE...for Inductively Coupled Radio-Frequency (RF) Plasmas. Non Local Thermodynamic Equilibrium (NLTE) effects are described based on a hybrid State-to-State... thermodynamic variable. This choice allows one to hide the non-linearity of the gas (total) thermal conductivity κ and can partially alle- 2 viate numerical

Quantitative evaluations of mechanisms of radiofrequency interactions with biological molecules and processes.

PubMed

Sheppard, Asher R; Swicord, Mays L; Balzano, Quirino

2008-10-01

The complexity of interactions of electromagnetic fields up to 10(12) Hz with the ions, atoms, and molecules of biological systems has given rise to a large number of established and proposed biophysical mechanisms applicable over a wide range of time and distance scales, field amplitudes, frequencies, and waveforms. This review focuses on the physical principles that guide quantitative assessment of mechanisms applicable for exposures at or below the level of endogenous electric fields associated with development, wound healing, and excitation of muscles and the nervous system (generally, 1 to 10(2) V m(-1)), with emphasis on conditions where temperature increases are insignificant (<1 K). Experiment and theory demonstrate possible demodulation at membrane barriers for frequencies < or =10 MHz, but not at higher frequencies. Although signal levels somewhat below system noise can be detected, signal-to-noise ratios substantially less than 0.1 cannot be overcome by cooperativity, signal averaging, coherent detection, or by nonlinear dynamical systems. Sensory systems and possible effects on biological magnetite suggest paradigms for extreme sensitivity at lower frequencies, but there are no known radiofrequency (RF) analogues. At the molecular level, vibrational modes are so overdamped by water molecules that excitation of molecular modes below the far infrared cannot occur. Two RF mechanisms plausibly may affect biological matter under common exposure conditions. For frequencies below approximately 150 MHz, shifts in the rate of chemical reactions can be mediated by radical pairs and, at all frequencies, dielectric and resistive heating can raise temperature and increase the entropy of the affected biological system.

Causes and mitigation of radio frequency (RF) blackout during reentry of reusable launch vehicles

DOT National Transportation Integrated Search

2007-01-26

The Aerospace Corporation was tasked to assess radio frequency (RF) blackout phenomena caused by plasma generation around vehicles during reentry and presently known methodologies for mitigation of this condition inhibiting communications. The purpos...

An experimental performance evaluation of the hybrid FSO/RF

NASA Astrophysics Data System (ADS)

Touati, Abir; Touati, Farid; Abdaoui, Abderrazak; Khandakar, Amith; Hussain, Syed Jawad; Bouallegue, Ammar

2017-02-01

This paper is a first attempt to study the effects of atmospheric turbulences on hybrid free space optics/ radio frequency (FSO/RF) transmission system in Doha, Qatar. The state of Qatar is characterized by a Mediterranean climate with hot and dry summers with modest cloud coverage highly affected by airborne dust. Due to its sensitivity to atmospheric turbulences, throughout this study, we try to demonstrate the working capabilities of FSO technology as well as to promote an understanding of this technology amongst the countries of the gulf cooperation council (GCC). Moreover, we studied the behavior of RF link during the same period. In order to analyze the transport media, two transmitting subsystems are employed and installed at Qatar University (QU) at two different buildings separated by a distance of 600 m. Each system is composed of a FSO and RF terminal. We have ported an Embedded Linux kernel on Micro-blaze processor build in Field Programmable Gate Array (FPGA). Then, we have designed a network sniffer application that can run on the FPGA board. The measurements from the network sniffer applications were carried out during summer season from June up to September 2015. The relation between the measurements and the atmospheric factors, taken from a weather station installed at QU, were also found.

RF low-level control for the Linac4 H{sup −} source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Butterworth, A., E-mail: andrew.butterworth@cern.ch; Grudiev, A.; Lettry, J.

2015-04-08

The H{sup −} source for the Linac4 accelerator at CERN uses an RF driven plasma for the production of H{sup −}. The RF is supplied by a 2 MHz RF tube amplifier with a maximum power output of 100 kW and a pulse duration of up to 2 ms. The low-level RF signal generation and measurement system has been developed using standard CERN controls electronics in the VME form factor. The RF frequency and amplitude reference signals are generated using separate arbitrary waveform generator channels. The frequency and amplitude are both freely programmable over the duration of the RF pulse, which allowsmore » fine-tuning of the excitation. Measurements of the forward and reverse RF power signals are performed via directional couplers using high-speed digitizers, and permit the estimation of the plasma impedance and deposited power via an equivalent circuit model. The low-level RF hardware and software implementations are described, and experimental results obtained with the Linac4 ion sources in the test stand are presented.« less

Spatial Power Combining Amplifier for Ground and Flight Applications

NASA Astrophysics Data System (ADS)

Velazco, J. E.; Taylor, M.

2016-11-01

Vacuum-tube amplifiers such as klystrons and traveling-wave tubes are the workhorses of high-power microwave radiation generation. At JPL, vacuum tubes are extensively used in ground and flight missions for radar and communications. Vacuum tubes use electron beams as the source of energy to achieve microwave power amplification. Such electron beams operate at high kinetic energies and thus require high voltages to function. In addition, vacuum tubes use compact cavity and waveguide structures that hold very intense radio frequency (RF) fields inside. As the operational frequency is increased, the dimensions of these RF structures become increasingly smaller. As power levels and operational frequencies are increased, the highly intense RF fields inside of the tubes' structures tend to arc and create RF breakdown. In the case of very high-power klystrons, electron interception - also known as body current - can produce thermal runaway of the cavities that could lead to the destruction of the tube. The high voltages needed to power vacuum tubes tend to require complicated and cumbersome power supplies. Consequently, although vacuum tubes provide unmatched high-power microwaves, they tend to arc, suffer from thermal issues, and require failure-prone high-voltage power supplies. In this article, we present a new concept for generating high-power microwaves that we refer to as the Spatial Power Combining Amplifier (SPCA). The SPCA is very compact, requires simpler, lower-voltage power supplies, and uses a unique power-combining scheme wherein power from solid-state amplifiers is coherently combined. It is a two-port amplifier and can be used inline as any conventional two-port amplifier. It can deliver its output power to a coaxial line, a waveguide, a feed, or to any microwave load. A key feature of this new scheme is the use of higher-order-mode microwave structures to spatially divide and combine power. Such higher-order-mode structures have considerably larger cross-sections than comparable klystrons and traveling-wave tube counterparts and thus avoid RF breakdown and thermal issues common to vacuum tubes. We present a basic description of the SPCA mechanism and initial results of an S-band (2.4 GHz) 100-W, 45-dB gain SPCA prototype. We also discuss future X-band (8.4 GHz), Ka-band (32 GHz), and W-band (94 GHz) SPCA designs for both radar and communications applications.

Ion energy distributions in a pulsed dual frequency inductively coupled discharge of Ar/CF{sub 4} and effect of duty ratio

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishra, Anurag; Seo, Jin Seok; Kim, Tae Hyung

2015-08-15

Controlling time averaged ion energy distribution (IED) is becoming increasingly important in many plasma material processing applications for plasma etching and deposition. The present study reports the evolution of ion energy distributions with radio frequency (RF) powers in a pulsed dual frequency inductively discharge and also investigates the effect of duty ratio. The discharge has been sustained using two radio frequency, low (P{sub 2 MHz} = 2 MHz) and high (P{sub 13.56 MHz} = 13.56 MHz) at a pressure of 10 mTorr in argon (90%) and CF{sub 4} (10%) environment. The low frequency RF powers have been varied from 100 to 600 W, whereas the high frequency powers frommore » 200 to 1200 W. Typically, IEDs show bimodal structure and energy width (energy separation between the high and low energy peaks) increases with increasing P{sub 13.56 MHz}; however, it shows opposite trends with P{sub 2 MHz}. It has been observed that IEDs bimodal structure tends to mono-modal structure and energy peaks shift towards low energy side as duty ratio increases, keeping pulse power owing to mode transition (capacitive to inductive) constant.« less

Effect of source frequency and pulsing on the SiO2 etching characteristics of dual-frequency capacitive coupled plasma

NASA Astrophysics Data System (ADS)

Kim, Hoe Jun; Jeon, Min Hwan; Mishra, Anurag Kumar; Kim, In Jun; Sin, Tae Ho; Yeom, Geun Young

2015-01-01

A SiO2 layer masked with an amorphous carbon layer (ACL) has been etched in an Ar/C4F8 gas mixture with dual frequency capacitively coupled plasmas under variable frequency (13.56-60 MHz)/pulsed rf source power and 2 MHz continuous wave (CW) rf bias power, the effects of the frequency and pulsing of the source rf power on the SiO2 etch characteristics were investigated. By pulsing the rf power, an increased SiO2 etch selectivity was observed with decreasing SiO2 etch rate. However, when the rf power frequency was increased, not only a higher SiO2 etch rate but also higher SiO2 etch selectivity was observed for both CW and pulse modes. A higher CF2/F ratio and lower electron temperature were observed for both a higher source frequency mode and a pulsed plasma mode. Therefore, when the C 1s binding states of the etched SiO2 surfaces were investigated using X-ray photoelectron spectroscopy (XPS), the increase of C-Fx bonding on the SiO2 surface was observed for a higher source frequency operation similar to a pulsed plasma condition indicating the increase of SiO2 etch selectivity over the ACL. The increase of the SiO2 etch rate with increasing etch selectivity for the higher source frequency operation appears to be related to the increase of the total plasma density with increasing CF2/F ratio in the plasma. The SiO2 etch profile was also improved not only by using the pulsed plasma but also by increasing the source frequency.

Optically controlled switch-mode current-source amplifiers for on-coil implementation in high field parallel transmission

PubMed Central

Gudino, Natalia; Duan, Qi; de Zwart, Jacco A; Murphy-Boesch, Joe; Dodd, Stephen J; Merkle, Hellmut; van Gelderen, Peter; Duyn, Jeff H

2015-01-01

Purpose We tested the feasibility of implementing parallel transmission (pTX) for high field MRI using a radiofrequency (RF) amplifier design to be located on or in the immediate vicinity of a RF transmit coil. Method We designed a current-source switch-mode amplifier based on miniaturized, non-magnetic electronics. Optical RF carrier and envelope signals to control the amplifier were derived, through a custom-built interface, from the RF source accessible in the scanner control. Amplifier performance was tested by benchtop measurements as well as with imaging at 7 T (300 MHz) and 11.7 T (500 MHz). The ability to perform pTX was evaluated by measuring inter-channel coupling and phase adjustment in a 2-channel setup. Results The amplifier delivered in excess of 44 W RF power and caused minimal interference with MRI. The interface derived accurate optical control signals with carrier frequencies ranging from 64 to 750 MHz. Decoupling better than 14 dB was obtained between 2 coil loops separated by only 1 cm. Application to MRI was demonstrated by acquiring artifact-free images at 7 T and 11.7 T. Conclusion An optically controlled miniaturized RF amplifier for on-coil implementation at high field is demonstrated that should facilitate implementation of high-density pTX arrays. PMID:26256671

Methods and devices based on brillouin selective sideband amplification

NASA Technical Reports Server (NTRS)

Yao, X. Steve (Inventor)

2003-01-01

Opto-electronic devices and techniques using Brillouin scattering to select a sideband in a modulated optical carrier signal for amplification. Two lasers respectively provide a carrier signal beam and a Brillouin pump beam which are fed into an Brillouin optical medium in opposite directions. The relative frequency separation between the lasers is adjusted to align the frequency of the backscattered Brillouin signal with a desired sideband in the carrier signal to effect a Brillouin gain on the sideband. This effect can be used to implement photonic RF signal mixing and conversion with gain, conversion from phase modulation to amplitude modulation, photonic RF frequency multiplication, optical and RF pulse generation and manipulation, and frequency-locking of lasers.

NMR imaging of cell phone radiation absorption in brain tissue

PubMed Central

Gultekin, David H.; Moeller, Lothar

2013-01-01

A method is described for measuring absorbed electromagnetic energy radiated from cell phone antennae into ex vivo brain tissue. NMR images the 3D thermal dynamics inside ex vivo bovine brain tissue and equivalent gel under exposure to power and irradiation time-varying radio frequency (RF) fields. The absorbed RF energy in brain tissue converts into Joule heat and affects the nuclear magnetic shielding and the Larmor precession. The resultant temperature increase is measured by the resonance frequency shift of hydrogen protons in brain tissue. This proposed application of NMR thermometry offers sufficient spatial and temporal resolution to characterize the hot spots from absorbed cell phone radiation in aqueous media and biological tissues. Specific absorption rate measurements averaged over 1 mg and 10 s in the brain tissue cover the total absorption volume. Reference measurements with fiber optic temperature sensors confirm the accuracy of the NMR thermometry. PMID:23248293

Study on the steady operating state of a micro-pulse electron gun.

PubMed

Kui, Zhou; Xiangyang, Lu; Shengwen, Quan; Jifei, Zhao; Xing, Luo; Ziqin, Yang

2014-09-01

Micro-pulse electron gun (MPG) employs the basic concept of multipacting to produce high-current and short-pulse electron beams from a radio-frequency (RF) cavity. The concept of MPG has been proposed for more than two decades. However, the unstable operating state of MPG vastly obstructs its practical applications. This paper presents a study on the steady operating state of a micro-pulse electron gun with theory and experiments. The requirements for the steady operating state are proposed through the analysis of the interaction between the RF cavity and the beam load. Accordingly, a MPG cavity with the frequency of 2856 MHz has been designed, constructed, and tested. Some primary experiments have been finished. Both the unstable and stable operating states of the MPG have been observed. The stable output beam current has been detected at about 3.8 mA. Further experimental study is under way now.

NMR imaging of cell phone radiation absorption in brain tissue.

PubMed

Gultekin, David H; Moeller, Lothar

2013-01-02

A method is described for measuring absorbed electromagnetic energy radiated from cell phone antennae into ex vivo brain tissue. NMR images the 3D thermal dynamics inside ex vivo bovine brain tissue and equivalent gel under exposure to power and irradiation time-varying radio frequency (RF) fields. The absorbed RF energy in brain tissue converts into Joule heat and affects the nuclear magnetic shielding and the Larmor precession. The resultant temperature increase is measured by the resonance frequency shift of hydrogen protons in brain tissue. This proposed application of NMR thermometry offers sufficient spatial and temporal resolution to characterize the hot spots from absorbed cell phone radiation in aqueous media and biological tissues. Specific absorption rate measurements averaged over 1 mg and 10 s in the brain tissue cover the total absorption volume. Reference measurements with fiber optic temperature sensors confirm the accuracy of the NMR thermometry.

RF Stabilization for Storage of Antiprotons

NASA Technical Reports Server (NTRS)

Pearson, J. Boise; Lewis, Raymond A.

2005-01-01

Portable storage of antimatter is an important step in the experimental exploration of antimatter in propulsion applications. The High Performance Antiproton Trap (HiPAT) at NASA Marshall Space Flight Center is a Penning-Malmberg ion trap being developed to trap and store low energy antiprotons for a period of weeks. The antiprotons can then be transported for use in experiments. HiPAT is being developed and evaluated using normal matter, before an attempt is made to store and transport antiprotons. Stortd ions have inherent instabilities that limit the storage lifetime. RF stabilization at cyclotron resonance frequencies is demonstrated over a period of 6 days for normal matter ion clouds. A variety of particles have been stored, including protons, C+ ions, and H2+ ions. Cyclotron resonance frequencies are defined and experimental evidence presented to demonstrate excitation of cyclotron waves in the plasma for all three species of ions.

Pancreatic adenocarcinoma response to chemotherapy enhanced with non-invasive radio frequency evaluated via an integrated experimental/computational approach.

PubMed

Ware, Matthew J; Curtis, Louis T; Wu, Min; Ho, Jason C; Corr, Stuart J; Curley, Steven A; Godin, Biana; Frieboes, Hermann B

2017-06-13

Although chemotherapy combined with radiofrequency exposure has shown promise in cancer treatment by coupling drug cytotoxicity with thermal ablation or thermally-induced cytotoxicity, limited access of the drug to tumor loci in hypo-vascularized lesions has hampered clinical application. We recently showed that high-intensity short-wave capacitively coupled radiofrequency (RF) electric-fields may reach inaccessible targets in vivo. This non-invasive RF combined with gemcitabine (Gem) chemotherapy enhanced drug uptake and effect in pancreatic adenocarcinoma (PDAC), notorious for having poor response and limited therapeutic options, but without inducing thermal injury. We hypothesize that the enhanced cytotoxicity derives from RF-facilitated drug transport in the tumor microenvironment. We propose an integrated experimental/computational approach to evaluate chemotherapeutic response combined with RF-induced phenotypic changes in tissue with impaired transport. Results show that RF facilitates diffusive transport in 3D cell cultures representing hypo-vascularized lesions, enhancing drug uptake and effect. Computational modeling evaluates drug vascular extravasation and diffusive transport as key RF-modulated parameters, with transport being dominant. Assessment of hypothetical schedules following current clinical protocol for Stage-IV PDAC suggests that unresponsive lesions may be growth-restrained when exposed to Gem plus RF. Comparison of these projections to experiments in vivo indicates that synergy may result from RF-induced cell phenotypic changes enhancing drug transport and cytotoxicity, thus providing a potential baseline for clinically-focused evaluation.

Analysis of emotionality and locomotion in radio-frequency electromagnetic radiation exposed rats.

PubMed

Narayanan, Sareesh Naduvil; Kumar, Raju Suresh; Paval, Jaijesh; Kedage, Vivekananda; Bhat, M Shankaranarayana; Nayak, Satheesha; Bhat, P Gopalakrishna

2013-07-01

In the current study the modulatory role of mobile phone radio-frequency electromagnetic radiation (RF-EMR) on emotionality and locomotion was evaluated in adolescent rats. Male albino Wistar rats (6-8 weeks old) were randomly assigned into the following groups having 12 animals in each group. Group I (Control): they remained in the home cage throughout the experimental period. Group II (Sham exposed): they were exposed to mobile phone in switch-off mode for 28 days, and Group III (RF-EMR exposed): they were exposed to RF-EMR (900 MHz) from an active GSM (Global system for mobile communications) mobile phone with a peak power density of 146.60 μW/cm(2) for 28 days. On 29th day, the animals were tested for emotionality and locomotion. Elevated plus maze (EPM) test revealed that, percentage of entries into the open arm, percentage of time spent on the open arm and distance travelled on the open arm were significantly reduced in the RF-EMR exposed rats. Rearing frequency and grooming frequency were also decreased in the RF-EMR exposed rats. Defecation boli count during the EPM test was more with the RF-EMR group. No statistically significant difference was found in total distance travelled, total arm entries, percentage of closed arm entries and parallelism index in the RF-EMR exposed rats compared to controls. Results indicate that mobile phone radiation could affect the emotionality of rats without affecting the general locomotion.

Breakdown-Resistant RF Connectors for Vacuum

NASA Technical Reports Server (NTRS)

Caro, Edward R.; Bonazza, Walter J.

1987-01-01

Resilient inserts compensate for insulation shrinkage. Coaxial-cable connector for radio-frequency (RF) energy resists electrical breakdown in vacuum. Used on RF equipment in vacuum chambers as well as in spaceborne radar and communication gear.

Impact of underlap and mole-fraction on RF performance of strained-Si/Si1-xGex/strained-Si DG MOSFETs

NASA Astrophysics Data System (ADS)

Dutta, Arka; Koley, Kalyan; Sarkar, Chandan K.

2014-11-01

In this paper, a systematic RF performance analysis of double-gate strained silicon (DGSS) nMOSFETs is presented. The analysis is focused upon impact of Germanium mole-fraction variation on RF performance of underlap engineered DGSS nMOSFET. The RF performance of the device is analysed as a function of intrinsic RF figure of merits (FOMs) including non-quasi static effects (NQS). The RF FOMs are represented by the intrinsic gate to source/drain capacitance (Cgs and Cgd) and resistance (Rgs and Rgd), the transport delay (τm), the intrinsic inductance (Lsd), the cut-off frequency (fT), and the maximum oscillation frequency (fMAX). The results of the study suggested a significant improvement in the device performance, up to 40% increase in Germanium mole fraction (χ).

Pneumothorax as a complication of percutaneous radiofrequency ablation for lung neoplasms.

PubMed

Yamagami, Takuji; Kato, Takeharu; Hirota, Tatsuya; Yoshimatsu, Rika; Matsumoto, Tomohiro; Nishimura, Tsunehiko

2006-10-01

The present study was performed to determine the frequency of the complication of pneumothorax after radiofrequency (RF) ablation for lung neoplasms and risk factors affecting such pneumothoraces. The study was based on 129 consecutive sessions of percutaneous RF ablation of lung neoplasms under real-time computed tomographic fluoroscopic guidance performed in a single institution between May 2003 and November 2005 in 41 patients (17 women, 24 men; mean age, 63 years; age range, 29-82 y). Correlation was determined between the incidence of pneumothorax after RF ablation and multiple factors: sex, age, presence of emphysema, lesion size, lesion depth, contact of tumor with pleura, number of punctures, maximum power of RF generator, period of ablation, tissue temperature at the end of the RF ablation session, and patient position during the procedure. Management of each case of iatrogenic pneumothorax was reviewed. Pneumothorax after RF ablation occurred in 38 of 129 RF ablation sessions (29.5%). Fourteen of the 38 cases were treated by manual aspiration, and 24 were simply observed. In five cases (3.9%), chest tube placement was required as therapy for pneumothorax. The risk of pneumothorax was significantly increased in patients with pulmonary emphysema. The frequency of pneumothorax after RF ablation in our experience is similar to the frequency of pneumothorax after lung biopsy reported in the literature. Various conditions for RF ablation did not influence the incidence of pneumothorax. Emphysema was the only individual factor that correlated significantly with the development of iatrogenic pneumothorax.

Standards-Based Wireless Sensor Networking Protocols for Spaceflight Applications

NASA Technical Reports Server (NTRS)

Barton, Richard J.; Wagner, Raymond S.

2009-01-01

Wireless sensor networks (WSNs) have the capacity to revolutionize data gathering in both spaceflight and terrestrial applications. WSNs provide a huge advantage over traditional, wired instrumentation since they do not require wiring trunks to connect sensors to a central hub. This allows for easy sensor installation in hard to reach locations, easy expansion of the number of sensors or sensing modalities, and reduction in both system cost and weight. While this technology offers unprecedented flexibility and adaptability, implementing it in practice is not without its difficulties. Any practical WSN deployment must contend with a number of difficulties in its radio frequency (RF) environment. Multi-path reflections can distort signals, limit data rates, and cause signal fades that prevent nodes from having clear access to channels, especially in a closed environment such as a spacecraft. Other RF signal sources, such as wireless internet, voice, and data systems may contend with the sensor nodes for bandwidth. Finally, RF noise from electrical systems and periodic scattering from moving objects such as crew members will all combine to give an incredibly unpredictable, time-varying communication environment.

New Digisonde for research and monitoring applications

NASA Astrophysics Data System (ADS)

Reinisch, B. W.; Galkin, I. A.; Khmyrov, G. M.; Kozlov, A. V.; Bibl, K.; Lisysyan, I. A.; Cheney, G. P.; Huang, X.; Kitrosser, D. F.; Paznukhov, V. V.; Luo, Y.; Jones, W.; Stelmash, S.; Hamel, R.; Grochmal, J.

2009-02-01

The new Digisonde-4D, while preserving the basic principles of the Digisonde family, introduces important hardware and software changes that implement the latest capabilities of new digital radio frequency (RF) circuitry and embedded computers. The "D" refers to digital transmitters and receivers in which no analog circuitry is used for conversion between the baseband and the RF. In conjunction with the new hardware design, new software solutions offer significantly enhanced measurement flexibility, enhanced signal selectivity, and new types of data, e.g., the complete set of time domain samples of all four antenna signals suitable for independent scientific analysis. With the new method of mitigating in-band RF interference, the ionogram running time can be made as short as a couple of seconds. The h'(f) precision ranging technique with an accuracy of better than 1 km can be used on a routine basis. The 4D model runs the new ARTIST-5 ionogram autoscaling software which reports in real time the required data for assimilation in ionospheric models. The paper highlights technical advances of the new Digisonde for research and monitoring applications.

Using antennas separated in flight direction to avoid effect of emitter clock drift in geolocation

DOEpatents

Ormesher, Richard C.; Bickel, Douglas L

2012-10-23

The location of a land-based radio frequency (RF) emitter is determined from an airborne platform. RF signaling is received from the RF emitter via first and second antennas. In response to the received RF signaling, signal samples for both antennas are produced and processed to determine the location of the RF emitter.

Digital processing of RF signals from optical frequency combs

NASA Astrophysics Data System (ADS)

Cizek, Martin; Smid, Radek; Buchta, Zdeněk.; Mikel, Břetislav; Lazar, Josef; Cip, Ondřej

2013-01-01

The presented work is focused on digital processing of beat note signals from a femtosecond optical frequency comb. The levels of mixing products of single spectral components of the comb with CW laser sources are usually very low compared to products of mixing all the comb components together. RF counters are more likely to measure the frequency of the strongest spectral component rather than a weak beat note. Proposed experimental digital signal processing system solves this problem by analyzing the whole spectrum of the output RF signal and using software defined radio (SDR) algorithms. Our efforts concentrate in two main areas: Firstly, using digital servo-loop techniques for locking free running continuous laser sources on single components of the fs comb spectrum. Secondly, we are experimenting with digital signal processing of the RF beat note spectrum produced by f-2f 1 technique used for assessing the offset and repetition frequencies of the comb, resulting in digital servo-loop stabilization of the fs comb. Software capable of computing and analyzing the beat-note RF spectrums using FFT and peak detection was developed. A SDR algorithm performing phase demodulation on the f- 2f signal is used as a regulation error signal source for a digital phase-locked loop stabilizing the offset frequency of the fs comb.

Filterless frequency 12-tupling optical millimeter-wave generation using two cascaded dual-parallel Mach-Zehnder modulators.

PubMed

Zhu, Zihang; Zhao, Shanghong; Zheng, Wanze; Wang, Wei; Lin, Baoqin

2015-11-10

A novel frequency 12-tupling optical millimeter-wave (mm-wave) generation using two cascaded dual-parallel Mach-Zehnder modulators (DP-MZMs) without an optical filter is proposed and demonstrated by computer simulation. By properly adjusting the amplitude and phase of radio frequency (RF) driving signal and the direct current (DC) bias points of two DP-MZMs, a 120 GHz mm-wave with an optical sideband suppression ratio (OSSR) of 25.1 dB and a radio frequency spurious suppression ratio (RFSSR) of 19.1 dB is shown to be generated from a 10 GHz RF driving signal, which largely reduces the response frequency of electronic devices. Furthermore, it is also proved to be valid that even if the phase difference of RF driving signals, the RF driving voltage, and the DC bias voltage deviate from the ideal values to a certain degree, the performance is still acceptable. Since no optical filter is employed to suppress the undesired optical sidebands, a high-spectral-purity mm-wave signal tunable from 48 to 216 GHz can be obtained theoretically when a RF driving signal from 4 to 18 GHz is applied to the DP-MZMs, and the system can be readily implemented in wavelength-division-multiplexing upconversion systems to provide high-quality optical local oscillator signal.

Method for creating ideal tissue fusion in soft-tissue structures using radio frequency (RF) energy.

PubMed

Shields, Chelsea A; Schechter, David A; Tetzlaff, Phillip; Baily, Ali L; Dycus, Sean; Cosgriff, Ned

2004-01-01

Bipolar radiofrequency (RF) energy can successfully seal vascular structures up to 7 mm by fusing collagen and elastin in the lumen. Valleylab has created a system to expand this technology beyond vessel sealing with the development of a closed-loop, feedback-control RF generator that closely monitors tissue fusion. This generator, operating with a loop time of approximately 250 micros, continuously adjusts energy output, creating optimized soft-tissue fusion through structural protein amalgamation. In the first study, RF energy was applied to canine lung using the new-generation generator and lung-prototype device. A lobectomy was completed, sealing the lobar bronchus, parenchyma, and pulmonary vasculature. Chronic performance of the seals was evaluated at necropsy on postoperative days 7 and 14. In a second study, RF energy was applied to porcine small intestine using the same closed-loop generator and anastomosis prototype device. Acute tissue fusion was assessed qualitatively for hemostasis and seal quality. Terminal tissue evaluation was completed on postoperative day 7 and analyzed histopathologically. Histopathology confirmed acute and chronic tissue fusion in both the lung and intestine. Normal pathological healing was substantiated by angiogenesis, granulation, and proliferation of fibroblasts. Preliminary studies using canine lung and porcine small intestine demonstrate the potential of this closed-loop generator for soft-tissue amalgamation. Advanced monitoring capabilities make this fusion system applicable in many soft-tissue structures with adequate collagen and elastin. Further investigation of potential surgical applications needs to be completed.

Gate Drain Underlapped-PNIN-GAA-TFET for Comprehensively Upgraded Analog/RF Performance

NASA Astrophysics Data System (ADS)

Madan, Jaya; Chaujar, Rishu

2017-02-01

This work integrates the merits of gate-drain underlapping (GDU) and N+ source pocket on cylindrical gate all around tunnel FET (GAA-TFET) to form GDU-PNIN-GAA-TFET. It is analysed that the source pocket located at the source-channel junction narrows the tunneling barrier width at the tunneling junction and thereby enhances the ON-state current of GAA-TFET. Further, it is obtained that the GDU resists the extension of carrier density (built-up under the gated region) towards the drain side (under the underlapped length), thereby suppressing the ambipolar current and reducing the parasitic capacitances of GAA-TFET. Consequently, the amalgamated merits of both engineering schemes are obtained in GDU-PNIN-GAA-TFET that thus conquers the greatest challenges faced by TFET. Thus, GDU-PNIN-GAA-TFET results in an up-gradation in the overall performance of GAA-TFET. Moreover, it is realised that the RF figure of merits FOMs such as cut-off frequency (fT) and maximum oscillation frequency (fMAX) are also considerably improved with integration of source pocket on GAA-TFET. Thus, the improved analog and RF performance of GDU-PNIN-GAA-TFET makes it ideal for low power and high-speed applications.

The state of technology in electromagnetic (RF) sensors (for lightning detection)

NASA Technical Reports Server (NTRS)

Shumpert, T. H.; Honnell, M. A.

1979-01-01

A brief overview of the radio-frequency sensors which were applied to the detection, isolation, and/or identification of the transient electromagnetic energy (sferics) radiated from one or more lightning discharges in the atmosphere is presented. Radio frequency (RF) characteristics of lightning discharges, general RF sensor (antenna) characteristics, sensors and systems previously used for sferic detection, electromagnetic pulse sensors are discussed. References containing extensive bibliographies concerning lightning are presented.

Insight into RF power requirements and B1 field homogeneity for human MRI via rigorous FDTD approach.

PubMed

Ibrahim, Tamer S; Tang, Lin

2007-06-01

To study the dependence of radiofrequency (RF) power deposition on B(0) field strength for different loads and excitation mechanisms. Studies were performed utilizing a finite difference time domain (FDTD) model that treats the transmit array and the load as a single system. Since it was possible to achieve homogenous excitations across the human head model by varying the amplitudes/phases of the voltages driving the transmit array, studies of the RF power/B(0) field strength (frequency) dependence were achievable under well-defined/fixed/homogenous RF excitation. Analysis illustrating the regime in which the RF power is dependent on the square of the operating frequency is presented. Detailed studies focusing on the RF power requirements as a function of number of excitation ports, driving mechanism, and orientations/positioning within the load are presented. With variable phase/amplitude excitation, as a function of frequency, the peak-then-decrease relation observed in the upper axial slices of brain with quadrature excitation becomes more evident in the lower slices as well. Additionally, homogeneity optimization targeted at minimizing the ratio of maximum/minimum B(1) (+) field intensity within the region of interest, typically results in increased RF power requirements (standard deviation was not considered in this study). Increasing the number of excitation ports, however, can result in significant RF power reduction. (c) 2007 Wiley-Liss, Inc.

FIBER AND INTEGRATED OPTICS: Radio-frequency electrooptic modulation in optical fibers

NASA Astrophysics Data System (ADS)

Bulyuk, A. N.

1992-10-01

The electrooptic interaction in single-mode optical fibers with both linear and circular birefringe is analyzed. In most cases, a large interaction length imposes a limit on the modulation frequency. A circular birefringence in an optical fiber may lead to an effective coupling of polarization normal modes if a phase-matching condition is satisfied. Through an appropriate choice of polarization states of the light at the entrance and exit of the device, one can achieve a polarization modulation or a frequency shift of the light. There are possible applications in rf polarization modulators, devices for shifting the frequency of light, and detectors of electromagnetic fields.

Terahertz radiation mixer

DOEpatents

Wanke, Michael C [Albuquerque, NM; Allen, S James [Santa Barbara, CA; Lee, Mark [Albuquerque, NM

2008-05-20

A terahertz radiation mixer comprises a heterodyned field-effect transistor (FET) having a high electron mobility heterostructure that provides a gatable two-dimensional electron gas in the channel region of the FET. The mixer can operate in either a broadband pinch-off mode or a narrowband resonant plasmon mode by changing a grating gate bias of the FET. The mixer can beat an RF signal frequency against a local oscillator frequency to generate an intermediate frequency difference signal in the microwave region. The mixer can have a low local oscillator power requirement and a large intermediate frequency bandwidth. The terahertz radiation mixer is particularly useful for terahertz applications requiring high resolution.

FUSION++: A New Data Assimilative Model for Electron Density Forecasting

NASA Astrophysics Data System (ADS)

Bust, G. S.; Comberiate, J.; Paxton, L. J.; Kelly, M.; Datta-Barua, S.

2014-12-01

There is a continuing need within the operational space weather community, both civilian and military, for accurate, robust data assimilative specifications and forecasts of the global electron density field, as well as derived RF application product specifications and forecasts obtained from the electron density field. The spatial scales of interest range from a hundred to a few thousand kilometers horizontally (synoptic large scale structuring) and meters to kilometers (small scale structuring that cause scintillations). RF space weather applications affected by electron density variability on these scales include navigation, communication and geo-location of RF frequencies ranging from 100's of Hz to GHz. For many of these applications, the necessary forecast time periods range from nowcasts to 1-3 hours. For more "mission planning" applications, necessary forecast times can range from hours to days. In this paper we present a new ionosphere-thermosphere (IT) specification and forecast model being developed at JHU/APL based upon the well-known data assimilation algorithms Ionospheric Data Assimilation Four Dimensional (IDA4D) and Estimating Model Parameters from Ionospheric Reverse Engineering (EMPIRE). This new forecast model, "Forward Update Simple IONosphere model Plus IDA4D Plus EMPIRE (FUSION++), ingests data from observations related to electron density, winds, electric fields and neutral composition and provides improved specification and forecast of electron density. In addition, the new model provides improved specification of winds, electric fields and composition. We will present a short overview and derivation of the methodology behind FUSION++, some preliminary results using real observational sources, example derived RF application products such as HF bi-static propagation, and initial comparisons with independent data sources for validation.

High-Power Rf Load

DOEpatents

Tantawi, Sami G.; Vlieks, Arnold E.

1998-09-01

A compact high-power RF load comprises a series of very low Q resonators, or chokes [16], in a circular waveguide [10]. The sequence of chokes absorb the RF power gradually in a short distance while keeping the bandwidth relatively wide. A polarizer [12] at the input end of the load is provided to convert incoming TE.sub.10 mode signals to circularly polarized TE.sub.11 mode signals. Because the load operates in the circularly polarized mode, the energy is uniformly and efficiently absorbed and the load is more compact than a rectangular load. Using these techniques, a load having a bandwidth of 500 MHz can be produced with an average power dissipation level of 1.5 kW at X-band, and a peak power dissipation of 100 MW. The load can be made from common lossy materials, such as stainless steel, and is less than 15 cm in length. These techniques can also produce loads for use as an alternative to ordinary waveguide loads in small and medium RF accelerators, in radar systems, and in other microwave applications. The design is easily scalable to other RF frequencies and adaptable to the use of other lossy materials.

The 30-GHz monolithic receive module

NASA Technical Reports Server (NTRS)

Sokolov, V.; Geddes, J.; Bauhahn, P.

1983-01-01

Key requirements for a 30 GHz GaAs monolithic receive module for spaceborne communication antenna feed array applications include an overall receive module noise figure of 5 dB, a 30 dB RF to IF gain with six levels of intermediate gain control, a five-bit phase shifter, and a maximum power consumption of 250 mW. The RF designs for each of the four submodules (low noise amplifier, some gain control, phase shifter, and RF to IF sub-module) are presented. Except for the phase shifter, high frequency, low noise FETs with sub-half micron gate lengths are employed in the submodules. For the gain control, a two stage dual gate FET amplifier is used. The phase shifter is of the passive switched line type and consists of 5-bits. It uses relatively large gate width FETs (with zero drain to source bias) as the switching elements. A 20 GHz local oscillator buffer amplifier, a FET compatible balanced mixer, and a 5-8 GHz IF amplifier constitute the RF/IF sub-module. Phase shifter fabrication using ion implantation and a self-aligned gate technique is described. Preliminary RF results obtained on such phase shifters are included.

An optically coupled system for quantitative monitoring of MRI-induced RF currents into long conductors.

PubMed

Zanchi, Marta G; Venook, Ross; Pauly, John M; Scott, Greig C

2010-01-01

The currents induced in long conductors such as guidewires by the radio-frequency (RF) field in magnetic resonance imaging (MRI) are responsible for potentially dangerous heating of surrounding media, such as tissue. This paper presents an optically coupled system with the potential to quantitatively measure the RF currents induced on these conductors. The system uses a self shielded toroid transducer and active circuitry to modulate a high speed light-emitting-diode transmitter. Plastic fiber guides the light to a photodiode receiver and transimpedance amplifier. System validation included a series of experiments with bare wires that compared wire tip heating by fluoroptic thermometers with the RF current sensor response. Validations were performed on a custom whole body 64 MHz birdcage test platform and on a 1.5 T MRI scanner. With this system, a variety of phenomena were demonstrated including cable trap current attenuation, lossy dielectric Q-spoiling and even transverse electromagnetic wave node patterns. This system should find applications in studies of MRI RF safety for interventional devices such as pacemaker leads, and guidewires. In particular, variations of this device could potentially act as a realtime safety monitor during MRI guided interventions.

Higher-order mode rf guns

NASA Astrophysics Data System (ADS)

Lewellen, John W.

2001-04-01

Traditional photocathode rf gun design is based around the use of TM0,1,0-mode cavities. This is typically done in the interest of obtaining the highest possible gradient per unit supplied rf power and for historical reasons. In a multicell, aperture-coupled photoinjector, however, the gun as a whole is produced from strongly coupled cavities oscillating in a π mode. This design requires very careful preparation and tuning, as the field balance and resonant frequencies are easily disturbed. Side-coupled designs are often avoided because of the dipole modes introduced into the cavity fields. This paper proposes the use of a single higher-order mode rf cavity in order to generate the desired on-axis fields. It is shown that the field experienced by a beam in a higher-order mode rf gun is initially very similar to traditional 1.5- or 2.5-cell π-mode gun fields, and projected performance in terms of beam quality is also comparable. The new design has the advantages of much greater ease of fabrication, immunity from coupled-cell effects, and simpler tuning procedures. Because of the gun geometry, the possibility also exists for improved temperature stabilization and cooling for high duty-cycle applications.

Association of Exposure to Radio-Frequency Electromagnetic Field Radiation (RF-EMFR) Generated by Mobile Phone Base Stations with Glycated Hemoglobin (HbA1c) and Risk of Type 2 Diabetes Mellitus.

PubMed

Meo, Sultan Ayoub; Alsubaie, Yazeed; Almubarak, Zaid; Almutawa, Hisham; AlQasem, Yazeed; Hasanato, Rana Muhammed

2015-11-13

Installation of mobile phone base stations in residential areas has initiated public debate about possible adverse effects on human health. This study aimed to determine the association of exposure to radio frequency electromagnetic field radiation (RF-EMFR) generated by mobile phone base stations with glycated hemoglobin (HbA1c) and occurrence of type 2 diabetes mellitus. For this study, two different elementary schools (school-1 and school-2) were selected. We recruited 159 students in total; 96 male students from school-1, with age range 12-16 years, and 63 male students with age range 12-17 years from school-2. Mobile phone base stations with towers existed about 200 m away from the school buildings. RF-EMFR was measured inside both schools. In school-1, RF-EMFR was 9.601 nW/cm² at frequency of 925 MHz, and students had been exposed to RF-EMFR for a duration of 6 h daily, five days in a week. In school-2, RF-EMFR was 1.909 nW/cm² at frequency of 925 MHz and students had been exposed for 6 h daily, five days in a week. 5-6 mL blood was collected from all the students and HbA1c was measured by using a Dimension Xpand Plus Integrated Chemistry System, Siemens. The mean HbA1c for the students who were exposed to high RF-EMFR was significantly higher (5.44 ± 0.22) than the mean HbA1c for the students who were exposed to low RF-EMFR (5.32 ± 0.34) (p = 0.007). Moreover, students who were exposed to high RF-EMFR generated by MPBS had a significantly higher risk of type 2 diabetes mellitus (p = 0.016) relative to their counterparts who were exposed to low RF-EMFR. It is concluded that exposure to high RF-EMFR generated by MPBS is associated with elevated levels of HbA1c and risk of type 2 diabetes mellitus.

Compact Superconducting Radio-frequency Accelerators and Innovative RF Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kephart, Robert; Chattopadhyay, Swaapan; Milton, Stephen

2015-04-10

We will present several new technical and design breakthroughs that enable the creation of a new class of compact linear electron accelerators for industrial purposes. Use of Superconducting Radio-Frequency (SRF) cavities allow accelerators less than 1.5 M in length to create electron beams beyond 10 MeV and with average beam powers measured in 10’s of KW. These machines can have the capability to vary the output energy dynamically to produce brehmstrahlung x-rays of varying spectral coverage for applications such as rapid scanning of moving cargo for security purposes. Such compact accelerators will also be cost effective for many existing andmore » new industrial applications. Examples include radiation crosslinking of plastics and rubbers, creation of pure materials with surface properties radically altered from the bulk, modification of bulk or surface optical properties of materials, sterilization of medical instruments animal solid or liquid waste, and destruction of organic compounds in industrial waste water effluents. Small enough to be located on a mobile platform, such accelerators will enable new remediation methods for chemical and biological spills and/or in-situ crosslinking of materials. We will describe one current design under development at Fermilab including plans for prototype and value-engineering to reduce costs. We will also describe development of new nano-structured field-emitter arrays as sources of electrons, new methods for fabricating and cooling superconducting RF cavities, and a new novel RF power source based on magnetrons with full phase and amplitude control.« less

Controlling satellite communication system unwanted emissions in congested RF spectrum

NASA Astrophysics Data System (ADS)

Olsen, Donald; Heymann, Roger

2007-09-01

The International Telecommunication Union (ITU), a United Nations (UN) agency, is the agency that, under an international treaty, sets radio spectrum usage regulations among member nations. Within the United States of America (USA), the organization that sets regulations, coordinates an application for use, and provides authorization for federal government/agency use of the radio frequency (RF) spectrum is the National Telecommunications and Information Administration (NTIA). In this regard, the NTIA defines which RF spectrum is available for federal government use in the USA, and how it is to be used. The NTIA is a component of the United States (U.S.) Department of Commerce of the federal government. The significance of ITU regulations is that ITU approval is required for U.S. federal government/agency permission to use the RF spectrum outside of U.S. boundaries. All member nations have signed a treaty to do so. U.S. federal regulations for federal use of the RF spectrum are found in the Manual of Regulations and Procedures for Federal Radio Frequency Management, and extracts of the manual are found in what is known as the Table of Frequency Allocations. Nonfederal government and private sector use of the RF spectrum within the U.S. is regulated by the Federal Communications Commission (FCC). There is a need to control "unwanted emissions" (defined to include out-of-band emissions, which are those immediately adjacent to the necessary and allocated bandwidth, plus spurious emissions) to preclude interference to all other authorized users. This paper discusses the causes, effects, and mitigation of unwanted RF emissions to systems in adjacent spectra. Digital modulations are widely used in today's satellite communications. Commercial communications sector standards are covered for the most part worldwide by Digital Video Broadcast - Satellite (DVB-S) and digital satellite news gathering (DSNG) evolutions and the second generation of DVB-S (DVB-S2) standard, developed by the European Telecommunications Standards Institute (ETSI). In the USA, the Advanced Television Systems Committee (ATSC) has adopted Europe's DVB-S and DVB-S2 standards for satellite digital transmission. With today's digital modulations, RF spectral side lobes can extend out many times the modulating frequency on either side of the carrier at excessive power levels unless filtered. Higher-order digital modulations include quadrature phase shift keying (QPSK), 8 PSK (8-ary phase shift keying), 16 APSK (also called 12-4 APSK (amplitude phase shift keying)), and 16 QAM (quadrature amplitude modulation); they are key for higher spectrum efficiency to enable higher data rate transmissions in limited available bandwidths. Nonlinear high-power amplifiers (HPAs) can regenerate frequency spectral side lobes on input-filtered digital modulations. The paper discusses technologies and techniques for controlling these spectral side lobes, such as the use of square root raised cosine (SRRC) filtering before or during the modulation process, HPA output power back-off (OPBO), and RF filters after the HPA. Spectral mask specifications are a common method of the NTIA and ITU to define spectral occupancy power limits. They are intended to reduce interference among RF spectrum users by limiting excessive radiation at frequencies beyond the regulatory allocated bandwidth.The focus here is on the communication systems of U.S. government satellites used for space research, space operations, Earth exploration satellite services (EESS), meteorological satellite services (METSATS), and other government services. The 8025 to 8400 megahertz (MHz) X band can be used to illustrate the "unwanted emissions" issue. 8025 to 8400 MHz abuts the 8400 to 8450 MHz band allocated by the NTIA and ITU to space research for space-to-Earth transmissions such as receiving very weak Deep Space Network signals. The views and ideas expressed in this paper are those of the authors and do not necessarily reflect those of The Aerospace Corporation or The National Oceanic and Atmospheric Administration (NOAA) and its National Environmental Satellite Service (NESDIS).

Prediction of the Lorentz Force Detuning and pressure sensitivity for a Pillbox cavity

DOE PAGES

Parise, M.

2018-05-18

The Lorentz Force Detuning (LFD) and the pressure sensitivity are two critical concerns during the design of a Superconducting Radio Frequency (SRF) cavity resonator. The mechanical deformation of the bare Niobium cavity walls, due to the electromagnetic fields and fluctuation of the external pressure in the Helium bath, can dynamically and statically detune the frequency of the cavity and can cause beam phase errors. The frequency shift can be compensated by additional RF power, that is required to maintain the accelerating gradient, or by sophisticated tuning mechanisms and control-compensation algorithms. Passive stiffening is one of the simplest and most effectivemore » tools that can be used during the early design phase, capable of satisfying the Radio Frequency (RF) requisites. This approach requires several multiphysics simulations as well as a deep mechanical and RF knowledge of the phenomena involved. In this paper, is presented a new numerical model for a pillbox cavity that can predict the frequency shifts caused by the LFD and external pressure. This method allows to greatly reduce the computational effort, which is necessary to meet the RF requirements and to keep track of the frequency shifts without using the time consuming multiphysics simulations.« less

Prediction of the Lorentz Force Detuning and pressure sensitivity for a Pillbox cavity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parise, M.

The Lorentz Force Detuning (LFD) and the pressure sensitivity are two critical concerns during the design of a Superconducting Radio Frequency (SRF) cavity resonator. The mechanical deformation of the bare Niobium cavity walls, due to the electromagnetic fields and fluctuation of the external pressure in the Helium bath, can dynamically and statically detune the frequency of the cavity and can cause beam phase errors. The frequency shift can be compensated by additional RF power, that is required to maintain the accelerating gradient, or by sophisticated tuning mechanisms and control-compensation algorithms. Passive stiffening is one of the simplest and most effectivemore » tools that can be used during the early design phase, capable of satisfying the Radio Frequency (RF) requisites. This approach requires several multiphysics simulations as well as a deep mechanical and RF knowledge of the phenomena involved. In this paper, is presented a new numerical model for a pillbox cavity that can predict the frequency shifts caused by the LFD and external pressure. This method allows to greatly reduce the computational effort, which is necessary to meet the RF requirements and to keep track of the frequency shifts without using the time consuming multiphysics simulations.« less

Prediction of the Lorentz Force Detuning and pressure sensitivity for a Pillbox cavity

NASA Astrophysics Data System (ADS)

Parise, M.

2018-05-01

The Lorentz Force Detuning (LFD) and the pressure sensitivity are two critical concerns during the design of a Superconducting Radio Frequency (SRF) cavity resonator. The mechanical deformation of the bare Niobium cavity walls, due to the electromagnetic fields and fluctuation of the external pressure in the Helium bath, can dynamically and statically detune the frequency of the cavity and can cause beam phase errors. The frequency shift can be compensated by additional RF power, that is required to maintain the accelerating gradient, or by sophisticated tuning mechanisms and control-compensation algorithms. Passive stiffening is one of the simplest and most effective tools that can be used during the early design phase, capable of satisfying the Radio Frequency (RF) requisites. This approach requires several multiphysics simulations as well as a deep mechanical and RF knowledge of the phenomena involved. In this paper, is presented a new numerical model for a pillbox cavity that can predict the frequency shifts caused by the LFD and external pressure. This method allows to greatly reduce the computational effort, which is necessary to meet the RF requirements and to keep track of the frequency shifts without using the time consuming multiphysics simulations.

Prediction of the Lorentz Force Detuning and Pressure Sensitivity for a Pillbox Cavity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parise, M.

2018-04-23

The Lorentz Force Detuning (LFD) and the pressure sensitivity are two critical concerns during the design of a Superconducting Radio Frequency (SRF) cavity resonator. The mechanical deformation of the bare Niobium cavity walls, due to the electromagnetic fields and fluctuation of the external pressure in the Helium bath, can dynamically and statically detune the frequency of the cavity and can cause beam phase errors. The frequency shift can be compensated by additional RF power, that is required to maintain the accelerating gradient, or by sophisticated tuning mechanisms and control-compensation algorithms. Passive stiffening is one of the simplest and most effectivemore » tools that can be used during the early design phase, capable of satisfying the Radio Frequency (RF) requisites. This approach requires several multiphysics simulations as well as a deep mechanical and RF knowledge of the phenomena involved. In this paper, is presented a new numerical model for a pillbox cavity that can predict the frequency shifts caused by the LFD and external pressure. This method allows to greatly reduce the computational effort, which is necessary to meet the RF requirements and to keep track of the frequency shifts without using the time consuming multiphysics simulations.« less

Self-aligning LED-based optical link

NASA Astrophysics Data System (ADS)

Shen, Thomas C.; Drost, Robert J.; Rzasa, John R.; Sadler, Brian M.; Davis, Christopher C.

2016-09-01

The steady advances in light-emitting diode (LED) technology have motivated the use of LEDs in optical wireless communication (OWC) applications such as indoor local area networks (LANs) and communication between mobile platforms (e.g., robots, vehicles). In contrast to traditional radio frequency (RF) wireless communication, OWC utilizes electromagnetic spectrum that is largely unregulated and unrestricted. OWC communication may be especially useful in RF-denied environments, in which RF communication may be prohibited or undesirable. However, OWC does present some challenges, including the need to maintain alignment between potentially moving nodes. We describe a novel system for link alignment that is composed of a hyperboloidal mirror, camera, and gimbal. The experimental system is able to use the mirror and camera to detect an LED beacon of a neighboring node and estimate its bearing (azimuth and elevation), point the gimbal towards the beacon, and establish an optical link.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Read, Michael; Ives, Robert Lawrence; Marsden, David

The Phase II program developed an internal RF coupler that transforms the whispering gallery RF mode produced in gyrotron cavities to an HE11 waveguide mode propagating in corrugated waveguide. This power is extracted from the vacuum using a broadband, chemical vapor deposited (CVD) diamond, Brewster angle window capable of transmitting more than 1.5 MW CW of RF power over a broad range of frequencies. This coupling system eliminates the Mirror Optical Units now required to externally couple Gaussian output power into corrugated waveguide, significantly reducing system cost and increasing efficiency. The program simulated the performance using a broad range ofmore » advanced computer codes to optimize the design. Both a direct coupler and Brewster angle window were built and tested at low and high power. Test results confirmed the performance of both devices and demonstrated they are capable of achieving the required performance for scientific, defense, industrial, and medical applications.« less

High-power CO laser with RF discharge for isotope separation employing condensation repression

NASA Astrophysics Data System (ADS)

Baranov, I. Ya.; Koptev, A. V.

2008-10-01

High-power CO laser can be the effective tool in such applications as isotope separation using the free-jet CRISLA method. The way of transfer from CO small-scale experimental installation to industrial high-power CO lasers is proposed through the use of a low-current radio-frequency (RF) electric discharge in a supersonic stream without an electron gun. The calculation model of scaling CO laser with RF discharge in supersonic stream was developed. The developed model allows to calculate parameters of laser installation and optimize them with the purpose of reception of high efficiency and low cost of installation as a whole. The technical decision of industrial CO laser for isotope separation employing condensation repression is considered. The estimated cost of laser is some hundred thousand dollars USA and small sizes of laser head give possibility to install it in any place.

Non-Ionizing Radiation From Wireless Technology| RadTown ...

EPA Pesticide Factsheets

2017-10-31

Cell phones emit radio frequency (RF) energy. The Federal Communications Commission (FCC) sets safety guidelines to limit RF exposure from wireless devices. Scientists continue to study the effects of long-term exposure to low levels of RF.

Operational Parameters, Considerations, and Design Decisions for Resource-Constrained Ion Trap Mass Spectrometers

NASA Technical Reports Server (NTRS)

Danell, Ryan M.; VanAmerom, Friso H. W.; Pinnick, Veronica; Cotter, Robert J.; Brickerhoff, William; Mahaffy, Paul

2011-01-01

Mass spectrometers are increasingly finding applications in new and unique areas, often in situations where key operational resources (i.e. power, weight and size) are limited. One such example is the Mars Organic Molecule Analyzer (MOMA). This instrument is a joint venture between NASA and the European Space Agency (ESA) to develop an ion trap mass spectrometer for chemical analysis on Mars. The constraints on such an instrument are significant as are the performance requirements. While the ideal operating parameters for an ion trap are generally well characterized, methods to maintain analytical performance with limited power and system weight need to be investigated and tested. Methods Experiments have been performed on two custom ion trap mass spectrometers developed as prototypes for the MOMA instrument. This hardware consists of quadrupole ion trap electrodes that are 70% the size of common commercial instrumentation. The trapping RF voltage is created with a custom tank circuit that can be tuned over a range of RF frequencies and is driven using laboratory supplies and amplifiers. The entire instrument is controlled with custom Lab VIEW software that allows a high degree of flexibility in the definition of the scan function defining the ion trap experiment. Ions are typically generated via an internal electron ionization source, however, a laser desorption source is also in development for analysis of larger intact molecules. Preliminary Data The main goals in this work have been to reduce the power required to generate the radio frequency trapping field used in an ion trap mass spectrometer. Generally minimizing the power will also reduce the volume and mass of the electronics to support the instrument. In order to achieve optimum performance, commercial instruments typically utilize RF frequencies in the 1 MHz range. Without much concern for power usage, they simply generate the voltage required to access the mass range of interest. In order to reduce the required RF voltage (and power), operation of the ion trap at lower RF frequencies has been investigated. Surprisingly, the performance of the instrument has only been slightly degraded at RF frequencies all the way down to 500 kHz. Mass resolution is relatively stable to this point and depending on the resonant ejection point used, the peak intensity is also quite stable. To date only masses up to m/z 200 have been fully investigated, however, additional studies are planned to verify the performance with higher mass ions. The lower frequency and voltage should reduce the pseudo potential well depth, eventually affecting the trapping efficiency of the instrument -- effect that could manifest itself in significantly limiting the mass range of trapped ions. Other methods to reduce the RF power while maintaining analytical performance are also under investigation. This includes ion ejection at lower q(sub z) values to access a given mass with a lower RF voltage. The loss of mass resolution at lower q(sub eject) points has been measured and current work is underway to leverage scan speed and the use of non-linear resonances in order to counter this trend. The overall trap performance under this range of operating conditions will be presented with a goal of identifying what trade-offs are acceptable.

Hybrid Radio Frequency/Free-Space Optics (RF/FSO) Wireless Sensor Network: Security Concerns and Protective Measures

NASA Astrophysics Data System (ADS)

Banerjee, Koushik; Sharma, Hemant; Sengupta, Anasuya

Wireless sensor networks (WSNs) are ad hoc wireless networks that are written off as spread out structure and ad hoc deployment. Sensor networks have all the rudimentary features of ad hoc networks but to altered points—for instance, considerably lesser movement and far more energy necessities. Commonly used technology for communication is radio frequency (RF) communications. Free-space optics (FSO) is relatively new technology which has the prospective to deliver remarkable increases in network lifetime of WSN. Hybrid RF/FSO communications has been suggested to decrease power consumption by a single sensor node. It is observed that security plays a very important role for either RF WSN or hybrid RF/FSO WSN as those are vulnerable to numerous threats. In this paper, various possible attacks in RF/FSO WSN are discussed and aimed to propose some way out from those attacks.

RF radiation from lightning

NASA Technical Reports Server (NTRS)

Levine, D. M.

1978-01-01

Radiation from lightning in the RF band from 3-300 MHz were monitored. Radiation in this frequency range is of interest as a potential vehicle for monitoring severe storms and for studying the lightning itself. Simultaneous measurements were made of RF radiation and fast and slow field changes. Continuous analogue recordings with a system having 300 kHz of bandwidth were made together with digital records of selected events (principally return strokes) at greater temporal resolution. The data reveal patterns in the RF radiation for the entire flash which are characteristic of flash type and independent of the frequency of observation. Individual events within the flash also have characteristic RF patterns. Strong radiation occurs during the first return strokes, but delayed about 20 micron sec with respect to the begining of the return stroke; whereas, RF radiation from subsequent return strokes tends to be associated with cloud processes preceding the flash with comparatively little radiation occurring during the return stroke itself.

Physics-based parametrization of the surface impedance for radio frequency sheaths

DOE PAGES

Myra, J. R.

2017-07-07

The properties of sheaths near conducting surfaces are studied for the case where both magnetized plasma and intense radio frequency (rf) waves coexist. The work is motivated primarily by the need to understand, predict and control ion cyclotron range of frequency (ICRF) interactions with tokamak scrape-off layer plasmas, and is expected to be useful in modeling rf sheath interactions in global ICRF codes. Here, employing a previously developed model for oblique angle magnetized rf sheaths [J. R. Myra and D. A. D’Ippolito, Phys. Plasmas 22, 062507 (2015)], an investigation of the four-dimensional parameter space governing these sheath is carried out.more » By combining numerical and analytical results, a parametrization of the surface impedance and voltage rectification for rf sheaths in the entire four-dimensional space is obtained.« less

DESIGN AND INSTRUMENTATION OF A POUND-WATKINS NUCLEAR MAGNETIC-RESONANCE SPECTROMETER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geiger, F.E. Jr.

Problems of instrumentation of a Pound-Watkins nuclear magnetic- resonance spectrometer were investigated. Experimertal data were collected for the sensitivity of the os cillator to a signal from a Watkins calibrator as a function of modulation frequencies from 30 cps to 5 kc and rf tank voltsges from 0.05 to 0.7v/sub rms/. The results confirm Watkins" oscillator theory. An expression was derived for the amount of frequency modulation of the rf oscillator by the Watkins calibrator. For representative values of rf circuit components, this frequency modulation is roughly 0.5 cps at 10 Mc. The rf sample probes constructed for this projectmore » are almost free of modulation pickup in modulation fields as high as 23.5 oersteds (280 cps) and a steady field of 7000 oersteds. (auth)« less

Physics-based parametrization of the surface impedance for radio frequency sheaths

DOE Office of Scientific and Technical Information (OSTI.GOV)

Myra, J. R.

The properties of sheaths near conducting surfaces are studied for the case where both magnetized plasma and intense radio frequency (rf) waves coexist. The work is motivated primarily by the need to understand, predict and control ion cyclotron range of frequency (ICRF) interactions with tokamak scrape-off layer plasmas, and is expected to be useful in modeling rf sheath interactions in global ICRF codes. Here, employing a previously developed model for oblique angle magnetized rf sheaths [J. R. Myra and D. A. D’Ippolito, Phys. Plasmas 22, 062507 (2015)], an investigation of the four-dimensional parameter space governing these sheath is carried out.more » By combining numerical and analytical results, a parametrization of the surface impedance and voltage rectification for rf sheaths in the entire four-dimensional space is obtained.« less

Retarding field analyzer for ion energy distribution measurements at a radio-frequency biased electrode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gahan, D.; Hopkins, M. B.; Dolinaj, B.

2008-03-15

A retarding field energy analyzer designed to measure ion energy distributions impacting a radio-frequency biased electrode in a plasma discharge is examined. The analyzer is compact so that the need for differential pumping is avoided. The analyzer is designed to sit on the electrode surface, in place of the substrate, and the signal cables are fed out through the reactor side port. This prevents the need for modifications to the rf electrode--as is normally the case for analyzers built into such electrodes. The capabilities of the analyzer are demonstrated through experiments with various electrode bias conditions in an inductively coupledmore » plasma reactor. The electrode is initially grounded and the measured distributions are validated with the Langmuir probe measurements of the plasma potential. Ion energy distributions are then given for various rf bias voltage levels, discharge pressures, rf bias frequencies - 500 kHz to 30 MHz, and rf bias waveforms - sinusoidal, square, and dual frequency.« less

Monochromatic coherent transition and diffraction radiation from a relativistic electron bunch train

NASA Astrophysics Data System (ADS)

Naumenko, G.; Potylitsyn, A.; Shevelev, M.; Karataev, P.; Shipulya, M.; Bleko, V.

2018-04-01

Electron beams of most accelerators have a bunched structure and are synchronized with the accelerating RF field. Due to modulation of the electron beam with frequency ν RF one can expect to observe resonances with frequencies ν k=kṡ ν RF in radiation spectrum generated via any spontaneous emission mechanism (k is an integer and the resonance order). In this paper we present the results of spectral measurements of coherent transition radiation (CTR) generated by an electron bunch train from the Tomsk microtron with ν RF=2.63GHz in the spectral frequency range from 8 to 35 GHz. We also measured the spectrum of coherent diffraction radiation and demonstrated that the observed spectra in both cases consist of monochromatic lines. For spectral measurements the Martin-Puplett interferometer with spectral resolution of 800 MHz (FWMH) was employed. Using a waveguide frequency cut-off we were able to exclude several spectral lines to observe higher resonance orders of up to k =7.

Ion Emittance Growth Due to Focusing Modulation from Slipping Electron Bunch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, G.

2015-02-17

Low energy RHIC operation has to be operated at an energy ranging from γ = 4.1 to γ = 10. The energy variation causes the change of revolution frequency. While the rf system for the circulating ion will operate at an exact harmonic of the revolution frequency (h=60 for 4.5 MHz rf and h=360 for 28 MHz rf.), the superconducting rf system for the cooling electron beam does not have a frequency tuning range that is wide enough to cover the required changes of revolution frequency. As a result, electron bunches will sit at different locations along the ion bunchmore » from turn to turn, i.e. the slipping of the electron bunch with respect to the circulating ion bunch. At cooling section, ions see a coherent focusing force due to the electrons’ space charge, which differs from turn to turn due to the slipping. We will try to estimate how this irregular focusing affects the transverse emittance of the ion bunch.« less

Multiple-quantum spin counting in magic-angle-spinning NMR via low-power symmetry-based dipolar recoupling

NASA Astrophysics Data System (ADS)

Teymoori, Gholamhasan; Pahari, Bholanath; Viswanathan, Elumalai; Edén, Mattias

2013-11-01

By using a symmetry-based R281R28-1 double-quantum (2Q) dipolar recoupling sequence, we demonstrate high-order multiple-quantum coherence (MQC) excitation at fast magic-angle spinning (MAS) frequencies up to 34 kHz. This scheme combines several attractive features, such as a relatively high dipolar scaling factor, good compensation to rf-errors, isotropic and anisotropic chemical shifts, as well as an ultra-low radio-frequency (rf) power requirement. The latter translates into nutation frequencies below 30 kHz for MAS rates up to 60 kHz, thereby permitting rf application for very long excitation periods without risk of damaging the NMR probehead or sample, while the compensation to chemical shifts improves as the MAS rate increases. 31P MQC spin counting is demonstrated on powders of calcium hydroxyapatite (Ca5(PO4)3OH) and anhydrous sodium diphosphate (Na4P2O7), from which all even coherence orders up to 30 and 14 were detected, respectively, over the respective MAS ranges of 15-24 kHz and 20-34 kHz. The amplitude distributions among the 31P MQC orders depend on the precise nutation frequency during recoupling, despite that the highest detected order was relatively insensitive to this parameter. An observed gradual transition from a Gaussian to exponential functionality of the MQC amplitude-profile is discussed in relation to the prevailing approach to derive spin-cluster sizes by fitting the MQC amplitude-distribution to a Gaussian decay, where minor systematic deviations between the model and experimental data are frequently reported.

Novel radio-frequency gun structures for ultrafast relativistic electron diffraction.

PubMed

Musumeci, P; Faillace, L; Fukasawa, A; Moody, J T; O'Shea, B; Rosenzweig, J B; Scoby, C M

2009-08-01

Radio-frequency (RF) photoinjector-based relativistic ultrafast electron diffraction (UED) is a promising new technique that has the potential to probe structural changes at the atomic scale with sub-100 fs temporal resolution in a single shot. We analyze the limitations on the temporal and spatial resolution of this technique considering the operating parameters of a standard 1.6 cell RF gun (which is the RF photoinjector used for the first experimental tests of relativistic UED at Stanford Linear Accelerator Center; University of California, Los Angeles; Brookhaven National Laboratory), and study the possibility of employing novel RF structures to circumvent some of these limits.

Radio frequency-mediated local thermotherapy for destruction of pancreatic tumors using Ni-Au core-shell nanowires

NASA Astrophysics Data System (ADS)

Hopkins, Xiaoping; Gill, Waqas Amin; Kringel, Rosemarie; Wang, Guankui; Hass, Jamie; Acharya, Suresh; Park, Jungrae; Tak Jeon, In; An, Boo Hyun; Lee, Ji Sung; Ryu, Jong Eun; Hill, Rod; McIlroy, David; Kim, Young Keun; Choi, Daniel S.

2017-01-01

We present a novel method of radio frequency (RF)-mediated thermotherapy in tumors by remotely heating nickel (Ni)-gold (Au) core-shell nanowires (CSNWs). Ectopic pancreatic tumors were developed in nude mice to evaluate the thermotherapeutic effects on tumor progression. Tumor ablation was produced by RF-mediated thermotherapy via activation of the paramagnetic properties of the Ni-Au CSNWs. Histopathology demonstrated that heat generated by RF irradiation caused significant cellular death with pyknotic nuclei and nuclear fragmentation dispersed throughout the tumors. These preliminary results suggest that thermotherapy ablation induced via RF activation of nanowires provides a potential alternative therapy for cancer treatment.

Radio frequency switching network: a technique for infrared sensing

NASA Astrophysics Data System (ADS)

Mechtel, Deborah M.; Jenkins, R. Brian; Joyce, Peter J.; Nelson, Charles L.

2016-10-01

This paper describes a unique technique that implements photoconductive sensors in a radio frequency (RF) switching network designed to locate in real-time the position and intensity of IR radiation incident on a composite structure. In the implementation described here, photoconductive sensors act as rapid response switches in a two-layer RF network embedded in an FR-4 laminate. To detect radiation, phosphorous-doped silicon photoconductive sensors are inserted in GHz range RF transmission lines. By permitting signal propagation only when a sensor is illuminated, the RF signals are selectively routed from lower layer transmission lines to upper layer lines, thereby pinpointing the location and strength of incident radiation. Simulations based on a high frequency three-dimensional planar electromagnetics model are presented and compared to the experimental results. The experimental results are described for GHz range RF signal control for 300- and 180-mW incident energy from 975- to 1060-nm wavelength lasers, respectively, where upon illumination, RF transmission line signal output power doubled when compared to nonilluminated results. The experimental results are also reported for 100-W incident energy from a 1060-nm laser. Test results illustrate real-time signal processing would permit a structure to be controlled in response to incident radiation.

A bee-hive frequency selective surface for Wi-Max and GPS applications

NASA Astrophysics Data System (ADS)

Ray, A.; Kahar, M.; Sarkar, P. P.

2013-10-01

The paper presents investigations on a bee-hive cell, concentric aperture frequency selective surface (FSS) tuned to pass 1.5 GHz for global positioning system application and 3.5 GHz for worldwide interoperability for microwave access applications. The designed dual-band FSS screen is easy to fabricate with low cost materials, exhibiting low weight, with two broad transmission bands, where the maximum recorded -10 dB transmission percentage bandwidth is 68.67 %. Due to symmetrical nature of design, FSS is insensitive to variation of RF incidence angle for 60° rotations. A computationally efficient method for analysing this FSS is presented. Experimental investigation is performed using standard microwave test bench. It is observed that the computed and experimental results are in close agreement.

Agile Blocker and Clock Jitter Tolerant Low-Power Frequency Selective Receiver with Energy Harvesting Capability.

PubMed

Hasan, Abul; Helaoui, Mohamed; Ghannouchi, Fadhel M

2017-08-29

In this article, a novel tunable, blocker and clock jitter tolerant, low power, quadrature phase shift frequency selective (QPS-FS) receiver with energy harvesting capability is proposed. The receiver's design embraces and integrates (i) the baseband to radio frequency (RF) impedance translation concept to improve selectivity over that of conventional homodyne receiver topologies and (ii) broadband quadrature phase shift circuitry in the RF path to remove an active multi-phase clock generation circuit in passive mixer (PM) receivers. The use of a single local oscillator clock signal with a passive clock division network improves the receiver's robustness against clock jitter and reduces the source clock frequency by a factor of N, compared to PM receivers using N switches (N≥4). As a consequence, the frequency coverage of the QPS-FS receiver is improved by a factor of N, given a clock source of maximum frequency; and, the power consumption of the whole receiver system can eventually be reduced. The tunable QPS-FS receiver separates the wanted RF band signal from the unwanted blockers/interferers. The desired RF signal is frequency down-converted to baseband, while the undesired blocker/interferer signals are reflected by the receiver, collected and could be energy recycled using an auxiliary energy harvesting device.

Emission characteristics of 6.78-MHz radio-frequency glow discharge plasma in a pulsed mode

NASA Astrophysics Data System (ADS)

Zhang, Xinyue; Wagatsuma, Kazuaki

2017-07-01

This paper investigated Boltzmann plots for both atomic and ionic emission lines of iron in an argon glow discharge plasma driven by 6.78-MHz radio-frequency (RF) voltage in a pulsed operation, in order to discuss how the excitation/ionization process was affected by the pulsation. For this purpose, a pulse frequency as well as a duty ratio of the pulsed RF voltage was selected as the experimenter parameters. A Grimm-style radiation source was employed at a forward RF power of 70 W and at an argon pressures of 670 Pa. The Boltzmann plot for low-lying excited levels of iron atom was on a linear relationship, which was probably attributed to thermal collisions with ultimate electrons in the negative glow region; in this case, the excitation temperature was obtained in a narrow range of 3300-3400 K, which was hardly affected by the duty ratio as well as the pulse frequency of the pulsed RF glow discharge plasma. This observation suggested that the RF plasma could be supported by a self-stabilized negative glow region, where the kinetic energy distribution of the electrons would be changed to a lesser extent. Additional non-thermal excitation processes, such as a Penning-type collision and a charge-transfer collision, led to deviations (overpopulation) of particular energy levels of iron atom or iron ion from the normal Boltzmann distribution. However, their contributions to the overall excitation/ionization were not altered so greatly, when the pulse frequency or the duty ratio was varied in the pulsed RF glow discharge plasma.

A coherent fiber link for very long baseline interferometry.

PubMed

Clivati, Cecilia; Costanzo, Giovanni A; Frittelli, Matteo; Levi, Filippo; Mura, Alberto; Zucco, Massimo; Ambrosini, Roberto; Bortolotti, Claudio; Perini, Federico; Roma, Mauro; Calonico, Davide

2015-11-01

We realize a coherent fiber link for application in very long baseline interferometry (VLBI) for radio astronomy and geodesy. A 550-km optical fiber connects the Italian National Metrological Institute (INRIM) to a radio telescope in Italy and is used for the primary Cs fountain clock stability and accuracy dissemination. We use an ultrastable laser frequency- referenced to the primary standard as a transfer oscillator; at the radio telescope, an RF signal is generated from the laser by using an optical frequency comb. This scheme now provides the traceability of the local maser to the SI second, realized by the Cs fountain at the 1.7 × 10(-16) accuracy. The fiber link never limits the experiment and is robust enough to sustain radio astronomical campaigns. This experiment opens the possibility of replacing the local hydrogen masers at the VLBI sites with optically-synthesized RF signals. This could improve VLBI resolution by providing more accurate and stable frequency references and, in perspective, by enabling common- clock VLBI based on a network of telescopes connected by fiber links.

Feed-forward coherent link from a comb to a diode laser: Application to widely tunable cavity ring-down spectroscopy

NASA Astrophysics Data System (ADS)

Gotti, Riccardo; Prevedelli, Marco; Kassi, Samir; Marangoni, Marco; Romanini, Daniele

2018-02-01

We apply a feed-forward frequency control scheme to establish a phase-coherent link from an optical frequency comb to a distributed feedback (DFB) diode laser: This allows us to exploit the full laser tuning range (up to 1 THz) with the linewidth and frequency accuracy of the comb modes. The approach relies on the combination of an RF single-sideband modulator (SSM) and of an electro-optical SSM, providing a correction bandwidth in excess of 10 MHz and a comb-referenced RF-driven agile tuning over several GHz. As a demonstration, we obtain a 0.3 THz cavity ring-down scan of the low-pressure methane absorption spectrum. The spectral resolution is 100 kHz, limited by the self-referenced comb, starting from a DFB diode linewidth of 3 MHz. To illustrate the spectral resolution, we obtain saturation dips for the 2ν3 R(6) methane multiplet at μbar pressure. Repeated measurements of the Lamb-dip positions provide a statistical uncertainty in the kHz range.

Investigations on the effect of frequency and noise in a localization technique based on microwave imaging for an in-body RF source

NASA Astrophysics Data System (ADS)

Chandra, Rohit; Balasingham, Ilangko

2015-05-01

Localization of a wireless capsule endoscope finds many clinical applications from diagnostics to therapy. There are potentially two approaches of the electromagnetic waves based localization: a) signal propagation model based localization using a priori information about the persons dielectric channels, and b) recently developed microwave imaging based localization without using any a priori information about the persons dielectric channels. In this paper, we study the second approach in terms of a variety of frequencies and signal-to-noise ratios for localization accuracy. To this end, we select a 2-D anatomically realistic numerical phantom for microwave imaging at different frequencies. The selected frequencies are 13:56 MHz, 431:5 MHz, 920 MHz, and 2380 MHz that are typically considered for medical applications. Microwave imaging of a phantom will provide us with an electromagnetic model with electrical properties (relative permittivity and conductivity) of the internal parts of the body and can be useful as a foundation for localization of an in-body RF source. Low frequency imaging at 13:56 MHz provides a low resolution image with high contrast in the dielectric properties. However, at high frequencies, the imaging algorithm is able to image only the outer boundaries of the tissues due to low penetration depth as higher frequency means higher attenuation. Furthermore, recently developed localization method based on microwave imaging is used for estimating the localization accuracy at different frequencies and signal-to-noise ratios. Statistical evaluation of the localization error is performed using the cumulative distribution function (CDF). Based on our results, we conclude that the localization accuracy is minimally affected by the frequency or the noise. However, the choice of the frequency will become critical if the purpose of the method is to image the internal parts of the body for tumor and/or cancer detection.

Tuner design and RF test of a four-rod RFQ

NASA Astrophysics Data System (ADS)

Zhou, QuanFeng; Zhu, Kun; Guo, ZhiYu; Kang, MingLei; Gao, ShuLi; Lu, YuanRong; Chen, JiaEr

2011-12-01

A mini-vane four-rod radio frequency quadruple (RFQ) accelerator has been built for neutron imaging. The RFQ will operate at 201.5 MHz, and its length is 2.7 m. The original electric field distribution along the electrodes is not flat. The resonant frequency needs to be tuned to the operating value. And the frequency needs to be compensated for temperature change during high power RF test and beam test. As tuning such a RFQ is difficult, plate tuners and stick tuners are designed. This paper will present the tuners design, the tuning procedure, and the RF properties of the RFQ.

Design of 1 MHz Solid State High Frequency Power Supply

NASA Astrophysics Data System (ADS)

Parmar, Darshan; Singh, N. P.; Gajjar, Sandip; Thakar, Aruna; Patel, Amit; Raval, Bhavin; Dhola, Hitesh; Dave, Rasesh; Upadhay, Dishang; Gupta, Vikrant; Goswami, Niranjan; Mehta, Kush; Baruah, Ujjwal

2017-04-01

High Frequency Power supply (HFPS) is used for various applications like AM Transmitters, metallurgical applications, Wireless Power Transfer, RF Ion Sources etc. The Ion Source for a Neutral beam Injector at ITER-India uses inductively coupled power source at High Frequency (∼1 MHz). Switching converter based topology used to generate 1 MHz sinusoidal output is expected to have advantages on efficiency and reliability as compared to traditional RF Tetrode tubes based oscillators. In terms of Power Electronics, thermal and power coupling issues are major challenges at such a high frequency. A conceptual design for a 200 kW, 1 MHz power supply and a prototype design for a 600 W source been done. The prototype design is attempted with Class-E amplifier topology where a MOSFET is switched resonantly. The prototype uses two low power modules and a ferrite combiner to add the voltage and power at the output. Subsequently solution with Class-D H-Bridge configuration have been evaluated through simulation where module design is stable as switching device do not participate in resonance, further switching device voltage rating is substantially reduced. The rating of the modules is essentially driven by the maximum power handling capacity of the MOSFETs and ferrites in the combiner circuit. The output passive network including resonance tuned network and impedance matching network caters for soft switching and matches the load impedance to 50ohm respectively. This paper describes the conceptual design of a 200 kW high frequency power supply and experimental results of the prototype 600 W, 1 MHz source.

670-GHz Schottky Diode-Based Subharmonic Mixer with CPW Circuits and 70-GHz IF

NASA Technical Reports Server (NTRS)

Chattopadhyay, Goutam; Schlecht, Erich T.; Lee, Choonsup; Lin, Robert H.; Gill, John J.; Mehdi, Imran; Sin, Seth; Deal, William; Loi, Kwok K.; Nam, Peta;

Heating uniformity and differential heating of insects in almonds associated with radio frequency energy

USDA-ARS?s Scientific Manuscript database

Radio frequency (RF) treatments have potential as alternatives to chemical fumigation for phytosanitary disinfestation treatments in the dried nut industry. To develop effective RF treatment protocols for almonds, it is desirable to determine heating uniformity and the occurrence of differential hea...

47 CFR 95.607 - CB transmitter modification.

Code of Federal Regulations, 2010 CFR

2010-10-01

... transmitting frequencies, increased modulation level, a different form of modulation, or increased TP (RF... modulating frequency, typically 0.1 seconds at maximum power) or peak envelope power (TP averaged during 1 RF cycle at the highest crest of the modulation envelope), as measured at the transmitter output antenna...

Low Power Near Field Communication Methods for RFID Applications of SIM Cards.

PubMed

Chen, Yicheng; Zheng, Zhaoxia; Gong, Mingyang; Yu, Fengqi

2017-04-14

Power consumption and communication distance have become crucial challenges for SIM card RFID (radio frequency identification) applications. The combination of long distance 2.45 GHz radio frequency (RF) technology and low power 2 kHz near distance communication is a workable scheme. In this paper, an ultra-low frequency 2 kHz near field communication (NFC) method suitable for SIM cards is proposed and verified in silicon. The low frequency transmission model based on electromagnetic induction is discussed. Different transmission modes are introduced and compared, which show that the baseband transmit mode has a better performance. The low-pass filter circuit and programmable gain amplifiers are applied for noise reduction and signal amplitude amplification. Digital-to-analog converters and comparators are used to judge the card approach and departure. A novel differential Manchester decoder is proposed to deal with the internal clock drift in range-controlled communication applications. The chip has been fully implemented in 0.18 µm complementary metal-oxide-semiconductor (CMOS) technology, with a 330 µA work current and a 45 µA idle current. The low frequency chip can be integrated into a radio frequency SIM card for near field RFID applications.

A novel dual-frequency imaging method for intravascular ultrasound applications.

PubMed

Qiu, Weibao; Chen, Yan; Wong, Chi-Man; Liu, Baoqiang; Dai, Jiyan; Zheng, Hairong

2015-03-01

Intravascular ultrasound (IVUS), which is able to delineate internal structures of vessel wall with fine spatial resolution, has greatly enriched the knowledge of coronary atherosclerosis. A novel dual-frequency imaging method is proposed in this paper for intravascular imaging applications. A probe combined two ultrasonic transducer elements with different center frequencies (36 MHz and 78 MHz) is designed and fabricated with PMN-PT single crystal material. It has the ability to balance both imaging depth and resolution, which are important imaging parameters for clinical test. A dual-channel imaging platform is also proposed for real-time imaging, and this platform has been proven to support programmable processing algorithms, flexible imaging control, and raw RF data acquisition for IVUS applications. Testing results show that the -6 dB axial and lateral imaging resolutions of low-frequency ultrasound are 78 and 132 μm, respectively. In terms of high-frequency ultrasound, axial and lateral resolutions are determined to be as high as 34 and 106 μm. In vitro intravascular imaging on healthy swine aorta is conducted to demonstrate the performance of the dual-frequency imaging method for IVUS applications. Copyright © 2014 Elsevier B.V. All rights reserved.

Nonsurgical tightening of skin laxity: a new radiofrequency approach.

PubMed

Rusciani, Antonio; Curinga, Giuseppe; Menichini, Giulio; Alfano, Carmine; Rusciani, Luigi

2007-04-01

Improvement in skin laxity can be difficult to achieve without invasive surgical procedures. Monopolar radiofrequency (RF) treatment is used by physicians to heat skin and promote tissue tightening and contouring. RF technology produces an electric current that generates heat through resistance in the dermis and subcutaneous tissue. The thermal effect depends on the conductivity features of the treated tissue. When heated, collagen fibrils will denature and contract, which is believed to lead to the observed tissue tightening. Ninety-three consecutive patients with mild to moderate laxity were included in the study. The Surgitron Dual Frequency RF (Radiowave technology, Ellman International) was used to treat skin laxity. The application of RF energy took place in an ambulatory setting with no need for skin sterilization or anesthesia. Patients immediately noticed a microlifting retraction in the treated tissues according to the vectors mapped in the area. There were no significant complications and the majority of patients were satisfied with the procedure and able to return to their daily routine after leaving the office, thereby substantiating the popularity of noninvasive rejuvenating procedures.

A low-frequency versatile wireless power transfer technology for biomedical implants.

PubMed

Jiang, Hao; Zhang, Junmin; Lan, Di; Chao; Liou, Shyshenq; Shahnasser, Hamid; Fechter, Richard; Hirose, Shinjiro; Harrison, Michael; Roy, Shuvo

2013-08-01

Implantable biomedical sensors and actuators are highly desired in modern medicine. In many cases, the implant's electrical power source profoundly determines its overall size and performance . The inductively coupled coil pair operating at the radio-frequency (RF) has been the primary method for wirelessly delivering electrical power to implants for the last three decades . Recent designs significantly improve the power delivery efficiency by optimizing the operating frequency, coil size and coil distance . However, RF radiation hazard and tissue absorption are the concerns in the RF wireless power transfer technology (RF-WPTT) , . Also, it requires an accurate impedance matching network that is sensitive to operating environments between the receiving coil and the load for efficient power delivery . In this paper, a novel low-frequency wireless power transfer technology (LF-WPTT) using rotating rare-earth permanent magnets is demonstrated. The LF-WPTT is able to deliver 2.967 W power at  ∼ 180 Hz to an 117.1 Ω resistor over 1 cm distance with 50% overall efficiency. Because of the low operating frequency, RF radiation hazard and tissue absorption are largely avoided, and the power delivery efficiency from the receiving coil to the load is independent of the operating environment. Also, there is little power loss observed in the LF-WPTT when the receiving coil is enclosed by non-magnetic implant-grade stainless steel.

Radio Frequency Microelectromechanical Systems [Book Chapter Manuscript

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nordquist, Christopher; Olsson, Roy H.

2014-12-15

Radio frequency microelectromechanical system (RF MEMS) devices are microscale devices that achieve superior performance relative to other technologies by taking advantage of the accuracy, precision, materials, and miniaturization available through microfabrication. To do this, these devices use their mechanical and electrical properties to perform a specific RF electrical function such as switching, transmission, or filtering. RF MEMS has been a popular area of research since the early 1990s, and within the last several years, the technology has matured sufficiently for commercialization and use in commercial market systems.

Equivalent circuit of radio frequency-plasma with the transformer model

NASA Astrophysics Data System (ADS)

Nishida, K.; Mochizuki, S.; Ohta, M.; Yasumoto, M.; Lettry, J.; Mattei, S.; Hatayama, A.

2014-02-01

LINAC4 H- source is radio frequency (RF) driven type source. In the RF system, it is required to match the load impedance, which includes H- source, to that of final amplifier. We model RF plasma inside the H- source as circuit elements using transformer model so that characteristics of the load impedance become calculable. It has been shown that the modeling based on the transformer model works well to predict the resistance and inductance of the plasma.

Nanoionics-Based Switches for Radio-Frequency Applications

NASA Technical Reports Server (NTRS)

Nessel, James; Lee, Richard

2010-01-01

Nanoionics-based devices have shown promise as alternatives to microelectromechanical systems (MEMS) and semiconductor diode devices for switching radio-frequency (RF) signals in diverse systems. Examples of systems that utilize RF switches include phase shifters for electronically steerable phased-array antennas, multiplexers, cellular telephones and other radio transceivers, and other portable electronic devices. Semiconductor diode switches can operate at low potentials (about 1 to 3 V) and high speeds (switching times of the order of nanoseconds) but are characterized by significant insertion loss, high DC power consumption, low isolation, and generation of third-order harmonics and intermodulation distortion (IMD). MEMS-based switches feature low insertion loss (of the order of 0.2 dB), low DC power consumption (picowatts), high isolation (>30 dB), and low IMD, but contain moving parts, are not highly reliable, and must be operated at high actuation potentials (20 to 60 V) generated and applied by use of complex circuitry. In addition, fabrication of MEMS is complex, involving many processing steps. Nanoionics-based switches offer the superior RF performance and low power consumption of MEMS switches, without need for the high potentials and complex circuitry necessary for operation of MEMS switches. At the same time, nanoionics-based switches offer the high switching speed of semiconductor devices. Also, like semiconductor devices, nanoionics-based switches can be fabricated relatively inexpensively by use of conventional integrated-circuit fabrication techniques. More over, nanoionics-based switches have simple planar structures that can easily be integrated into RF power-distribution circuits.

Technique for Predicting the Radio Frequency Field Strength Inside an Enclosure

NASA Technical Reports Server (NTRS)

Hallett, Michael P.; Reddell, Jerry P.

1997-01-01

This technical memo represents a simple analytical technique for predicting the Radio Frequency (RF) field inside an enclosed volume in which radio frequency occurs. The technique was developed to predict the RF field strength within a launch vehicle fairing in which some payloads desire to launch with their telemetry transmitter radiating. This technique considers both the launch vehicle and the payload aspects.

RF Performance of Membrane Aperture Shells

NASA Technical Reports Server (NTRS)

Flint, Eirc M.; Lindler, Jason E.; Thomas, David L.; Romanofsky, Robert

2007-01-01

This paper provides an overview of recent results establishing the suitability of Membrane Aperture Shell Technology (MAST) for Radio Frequency (RF) applications. These single surface shells are capable of maintaining their figure with no preload or pressurization and minimal boundary support, yet can be compactly roll stowed and passively self deploy. As such, they are a promising technology for enabling a future generation of RF apertures. In this paper, we review recent experimental and numerical results quantifying suitable RF performance. It is shown that candidate materials possess metallic coatings with sufficiently low surface roughness and that these materials can be efficiently fabricated into RF relevant doubly curved shapes. A numerical justification for using a reflectivity metric, as opposed to the more standard RF designer metric of skin depth, is presented and the resulting ability to use relatively thin coating thickness is experimentally validated with material sample tests. The validity of these independent film sample measurements are then confirmed through experimental results measuring RF performance for reasonable sized doubly curved apertures. Currently available best results are 22 dBi gain at 3 GHz (S-Band) for a 0.5m aperture tested in prime focus mode, 28dBi gain for the same antenna in the C-Band (4 to 6 GHz), and 36.8dBi for a smaller 0.25m antenna tested at 32 GHz in the Ka-Band. RF range test results for a segmented aperture (one possible scaling approach) are shown as well. Measured antenna system actual efficiencies (relative to the unachievable) ideal for these on axis tests are generally quite good, typically ranging from 50 to 90%.

Noise elimination method using a transmission line for the diagnostics of radio frequency plasma

NASA Astrophysics Data System (ADS)

Shimizu, K.; Hallil, A.; Amemiya, H.

1997-04-01

A filter using a transmission line formed by a cascade connection of inverted L-type networks has been developed to reject the distortion of the probe characteristics by rf (radio-frequency) noise. Each inverse L network consists of two coaxial cables with the same physical constant and length. The filter can remove discrete frequency components including the fundamental and harmonic components, the cut-off frequencies being determined by the distributed circuit constant and the length of the cables. By inserting different kinds of the network in cascade, many noise components associated with the rf frequency can be eliminated at the end section of the filter. Experiments have been performed in rf plasmas by inserting three kinds of inverted L networks with the frequency f (13.56 MHz), 2 f and 4f as the cut-off frequency. Distortion free probe characteristics have been obtained, from which accurate determination of plasma parameter such as the electron energy distribution is possible.

Stepped frequency ground penetrating radar

DOEpatents

Vadnais, Kenneth G.; Bashforth, Michael B.; Lewallen, Tricia S.; Nammath, Sharyn R.

1994-01-01

A stepped frequency ground penetrating radar system is described comprising an RF signal generating section capable of producing stepped frequency signals in spaced and equal increments of time and frequency over a preselected bandwidth which serves as a common RF signal source for both a transmit portion and a receive portion of the system. In the transmit portion of the system the signal is processed into in-phase and quadrature signals which are then amplified and then transmitted toward a target. The reflected signals from the target are then received by a receive antenna and mixed with a reference signal from the common RF signal source in a mixer whose output is then fed through a low pass filter. The DC output, after amplification and demodulation, is digitized and converted into a frequency domain signal by a Fast Fourier Transform. A plot of the frequency domain signals from all of the stepped frequencies broadcast toward and received from the target yields information concerning the range (distance) and cross section (size) of the target.

Responses to pure tones and linear FM components of the CF-FM biosonar signal by single units in the inferior colliculus of the mustached bat.

PubMed

O'Neill, W E

1985-12-01

The responses of 682 single-units in the inferior colliculus (IC) of 13 mustached bats (Pteronotus parnellii parnellii) were measured using pure tones (CF), frequency modulations (FM) and pairs of CF-FM signals mimicking the species' biosonar signal, which are stimuli known to be essential to the responses of CF/CF and FM-FM facilitation neurons in auditory cortex. Units were arbitrarily classified into 'reference frequency' (RF), 'FM2' and 'Non-echolocation' (NE) categories according to the relationship of their best frequencies (BF) to the biosonar signal frequencies. RF units have high Q10dB values and are tuned to the reference frequency of each bat, which ranged between 60.73 and 62.73 kHz. FM2 units had BF's between 50 and 60 kHz, while NE units had BF's outside the ranges of the RF and FM2 classes. PST histograms of the responses revealed discharge patterns such as 'onset', 'onset-bursting' (most common), 'on-off', 'tonic-on','pauser', and 'chopper'. Changes in discharge patterns usually resulted from changes in the frequency and/or intensity of the stimuli, most often involving a change from onset-bursting to on-off. Different patterns were also elicited by CF and FM stimuli. Frequency characteristics and thresholds to CF and FM stimuli were measured. RF neurons were very sharply tuned with Q10dB's ranging from 50-360. Most (92%) also responded to FM2 stimuli, but 78% were significantly more sensitive (greater than 5 dB) to CF stimuli, and only 3% had significantly lower thresholds to FM2. The best initial frequency for FM2 sweeps in RF units was 65.35 +/- 2.138 kHz (n = 118), well above the natural frequency of the 2nd harmonic. FM2 and NE units were indistinguishable from each other, but were quite different from RF units: 41% of these two classes had lower thresholds to CF, 49% were about equally sensitive, and 10% had lower thresholds to FM. For FM2 units, mean best initial frequency for FM was 60.94 kHz +/- 3.162 kHz (n = 114), which is closely matched to the 2nd harmonic in the biosonar signal. Very few units (5) responded only to FM signals, i.e., were FM-specialized. The characteristics of spike-count functions were determined in 587 units. The vast majority (79%) of RF units (n = 228) were nonmonotonic, and about 22% had upper-thresholds.(ABSTRACT TRUNCATED AT 400 WORDS)

BIOLOGICAL INFLUENCES OF LOW-FREQUENCY SINUSOIDAL ELECTROMAGNETIC SIGNALS ALONE AND SUPERIMPOSED ON RF CARRIER WAVES

EPA Science Inventory

The report describes in a historical context the experiments that have been performed to examine the biological responses caused by exposure to low frequency electromagnetic radiation directly or as modulation of RF carrier waves. A detailed review is provided of the independentl...

Optimal Performance Monitoring of Hybrid Mid-Infrared Wavelength MIMO Free Space Optical and RF Wireless Networks in Fading Channels

NASA Astrophysics Data System (ADS)

Schmidt, Barnet Michael

An optimal performance monitoring metric for a hybrid free space optical and radio-frequency (RF) wireless network, the Outage Capacity Objective Function, is analytically developed and studied. Current and traditional methods of performance monitoring of both optical and RF wireless networks are centered on measurement of physical layer parameters, the most common being signal-to-noise ratio, error rate, Q factor, and eye diagrams, occasionally combined with link-layer measurements such as data throughput, retransmission rate, and/or lost packet rate. Network management systems frequently attempt to predict or forestall network failures by observing degradations of these parameters and to attempt mitigation (such as offloading traffic, increasing transmitter power, reducing the data rate, or combinations thereof) prior to the failure. These methods are limited by the frequent low sensitivity of the physical layer parameters to the atmospheric optical conditions (measured by optical signal-to-noise ratio) and the radio frequency fading channel conditions (measured by signal-to-interference ratio). As a result of low sensitivity, measurements of this type frequently are unable to predict impending failures sufficiently in advance for the network management system to take corrective action prior to the failure. We derive and apply an optimal measure of hybrid network performance based on the outage capacity of the hybrid optical and RF channel, the outage capacity objective function. The objective function provides high sensitivity and reliable failure prediction, and considers both the effects of atmospheric optical impairments on the performance of the free space optical segment as well as the effect of RF channel impairments on the radio frequency segment. The radio frequency segment analysis considers the three most common RF channel fading statistics: Rayleigh, Ricean, and Nakagami-m. The novel application of information theory to the underlying physics of the gamma-gamma optical channel and radio fading channels in determining the joint hybrid channel outage capacity provides the best performance estimate under any given set of operating conditions. It is shown that, unlike traditional physical layer performance monitoring techniques, the objective function based upon the outage capacity of the hybrid channel at any combination of OSNR and SIR, is able to predict channel degradation and failure well in advance of the actual outage. An outage in the information-theoretic definition occurs when the offered load exceeds the outage capacity under the current conditions of OSNR and SIR. The optical channel is operated at the "long" mid-infrared wavelength of 10000 nm. which provides improved resistance to scattering compared to shorter wavelengths such as 1550 nm.

Optically controlled phased-array antenna technology for space communication systems

NASA Technical Reports Server (NTRS)

Kunath, Richard R.; Bhasin, Kul B.

1988-01-01

Using MMICs in phased-array applications above 20 GHz requires complex RF and control signal distribution systems. Conventional waveguide, coaxial cable, and microstrip methods are undesirable due to their high weight, high loss, limited mechanical flexibility and large volume. An attractive alternative to these transmission media, for RF and control signal distribution in MMIC phased-array antennas, is optical fiber. Presented are potential system architectures and their associated characteristics. The status of high frequency opto-electronic components needed to realize the potential system architectures is also discussed. It is concluded that an optical fiber network will reduce weight and complexity, and increase reliability and performance, but may require higher power.

Raman spectroscopic evidence of tissue restructuring in heat-induced tissue fusion.

PubMed

Su, Lei; Cloyd, Kristy L; Arya, Shobhit; Hedegaard, Martin A B; Steele, Joseph A M; Elson, Daniel S; Stevens, Molly M; Hanna, George B

2014-09-01

Heat-induced tissue fusion via radio-frequency (RF) energy has gained wide acceptance clinically and here we present the first optical-Raman-spectroscopy study on tissue fusion samples in vitro. This study provides direct insights into tissue constituent and structural changes on the molecular level, exposing spectroscopic evidence for the loss of distinct collagen fibre rich tissue layers as well as the denaturing and restructuring of collagen crosslinks post RF fusion. These findings open the door for more advanced optical feedback-control methods and characterization during heat-induced tissue fusion, which will lead to new clinical applications of this promising technology. Copyright © 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.

Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata

DOE Office of Scientific and Technical Information (OSTI.GOV)

Som, Sumit; Seth, Sudeshna; Mandal, Aditya

2013-02-15

Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and {+-}0.2{sup 0}, respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages ('Dee' voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTemore » X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result.« less

Stable fiber-optic time transfer by active radio frequency phase locking.

PubMed

Yin, Feifei; Wu, Zhongle; Dai, Yitang; Ren, Tianpeng; Xu, Kun; Lin, Jintong; Tang, Geshi

2014-05-15

In this Letter we demonstrate a fiber link capable of stable time signal transfer utilizing our active long-distance radio frequency (RF) stabilization technology. Taking advantage of the chromatic dispersion in optical fiber, our scheme compensates dynamically the link delay variation by tuning the optical carrier wavelength to phase lock a round-trip RF reference. Since the time signal and the RF reference are carried by the same optical carrier, a highly stable time transfer is achieved at the same time. Experimentally, we demonstrate a stability of the time signal transfer over 50-km fiber with a time deviation of 40 ps at 1-s average and 2.3 ps at 1000-s average. The performance of the RF reference delivery is also tested, with an Allan deviation of 2×10(-15) at 1000-s average. According to our proposal, a simultaneous stable time and frequency transfer is expected.

Narrow field electromagnetic sensor system and method

DOEpatents

McEwan, Thomas E.

1996-01-01

A narrow field electromagnetic sensor system and method of sensing a characteristic of an object provide the capability to realize a characteristic of an object such as density, thickness, or presence, for any desired coordinate position on the object. One application is imaging. The sensor can also be used as an obstruction detector or an electronic trip wire with a narrow field without the disadvantages of impaired performance when exposed to dirt, snow, rain, or sunlight. The sensor employs a transmitter for transmitting a sequence of electromagnetic signals in response to a transmit timing signal, a receiver for sampling only the initial direct RF path of the electromagnetic signal while excluding all other electromagnetic signals in response to a receive timing signal, and a signal processor for processing the sampled direct RF path electromagnetic signal and providing an indication of the characteristic of an object. Usually, the electromagnetic signal is a short RF burst and the obstruction must provide a substantially complete eclipse of the direct RF path. By employing time-of-flight techniques, a timing circuit controls the receiver to sample only the initial direct RF path of the electromagnetic signal while not sampling indirect path electromagnetic signals. The sensor system also incorporates circuitry for ultra-wideband spread spectrum operation that reduces interference to and from other RF services while allowing co-location of multiple electronic sensors without the need for frequency assignments.

Narrow field electromagnetic sensor system and method

DOEpatents

McEwan, T.E.

1996-11-19

A narrow field electromagnetic sensor system and method of sensing a characteristic of an object provide the capability to realize a characteristic of an object such as density, thickness, or presence, for any desired coordinate position on the object. One application is imaging. The sensor can also be used as an obstruction detector or an electronic trip wire with a narrow field without the disadvantages of impaired performance when exposed to dirt, snow, rain, or sunlight. The sensor employs a transmitter for transmitting a sequence of electromagnetic signals in response to a transmit timing signal, a receiver for sampling only the initial direct RF path of the electromagnetic signal while excluding all other electromagnetic signals in response to a receive timing signal, and a signal processor for processing the sampled direct RF path electromagnetic signal and providing an indication of the characteristic of an object. Usually, the electromagnetic signal is a short RF burst and the obstruction must provide a substantially complete eclipse of the direct RF path. By employing time-of-flight techniques, a timing circuit controls the receiver to sample only the initial direct RF path of the electromagnetic signal while not sampling indirect path electromagnetic signals. The sensor system also incorporates circuitry for ultra-wideband spread spectrum operation that reduces interference to and from other RF services while allowing co-location of multiple electronic sensors without the need for frequency assignments. 12 figs.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noda, Akira; Iwashita, Yoshihisa; Souda, Hikaru

A phase rotation scheme of laser-produced ions from a solid target by the application of a synchronized RF electric voltage with a pulsed laser has been experimentally investigated with the use of a 100 TW laser, J-KAREN at JAEA, KPSI. Up to now, energy peaks of up to around 2.0 MeV have been created with a FWHM of 2.6% with good reproducibility using a two-gap resonator of a quarter wave length with the same frequency as the source laser (approx80 MHz). It is also found that the position of the peak can be well controlled by adjusting the relative phasemore » between the RF electric field and the laser, which is very promising for real applications of such laser-produced protons. In order to also apply such a phase rotation system for higher energy protons (<200 MeV), a scheme to use a small linear accelerator (LINAC) with multi-gaps is proposed as a phase rotator. With multi-gap structure, alternating focusing between longitudinal and transverse degrees of freedoms can be realized. From the point of compactness and realizing a small focused spot, however, a scheme combining separate quadrupole magnets just before and after the RF cavity excited with the Wideroee mode, might be more effective. The scheme presented here will realize laser-produced ions (protons) with good reproducibility by combining with RF technology.« less

Study of temperature effect on junctionless Si nanotube FET concerning analog/RF performance

NASA Astrophysics Data System (ADS)

Tayal, Shubham; Nandi, Ashutosh

2018-06-01

This paper for the first time investigates the effect of temperature variation on analog/RF performance of SiO2 as well as high-K gate dielectric based junctionless silicon nanotube FET (JL-SiNTFET). It is observed that the change in temperature does not variate the analog/RF performance of junctionless silicon nanotube FET by substantial amount. By increasing the temperature from 77 K to 400 K, the deterioration in intrinsic dc gain (AV) is marginal that is only ∼3 dB. Furthermore, the variation in cut-off frequency (fT), maximum oscillation frequency (fMAX), and gain-frequency product (GFP) with temperature is also minimal in JLSiNT-FET. More so, the same trend is observed even at scaled gate length (Lg = 15 nm). Furthermore, we have observed that the use of high-K gate dielectric deteriorates the analog/RF performance of JLSiNT-FET. However, the use of high-K gate dielectric negligibly changes the effect of temperature variation on analog/RF performance of JLSINT-FET device.

Exposure system to study hypotheses of ELF and RF electromagnetic field interactions of mobile phones with the central nervous system.

PubMed

Murbach, Manuel; Christopoulou, Maria; Crespo-Valero, Pedro; Achermann, Peter; Kuster, Niels

2012-09-01

A novel exposure system for double-blind human electromagnetic provocation studies has been developed that satisfies the precision, control of fields and potential artifacts, and provides the flexibility to investigate the response of hypotheses-driven electromagnetic field exposure schemes on brain function, ranging from extremely low frequency (ELF) to radio frequency (RF) fields. The system can provide the same exposure of the lateral cerebral cortex at two different RF frequencies (900 and 2140 MHz) but with different exposure levels at subcortical structures, and also allows uniform ELF magnetic field exposure of the brain. The RF modulation and ELF signal are obtained by a freely programmable arbitrary signal generator allowing a wide range of worst-case exposure scenarios to be simulated, including those caused by wireless devices. The maximum achievable RF exposure is larger than 60 W/kg peak spatial specific absorption rate averaged over 10 g of tissue. The maximum ELF magnetic field exposure of the brain is 800 A/m at 50 Hz with a deviation from uniformity of 8% (SD). Copyright © 2012 Wiley Periodicals, Inc.

Land 125 - Power Technologies Review

DTIC Science & Technology

2012-11-01

Metal Hydride (Battery) PEMFC Proton Exchange Membrane Fuel Cell PNNL Pacific Northwest National Laboratory RF Radio Frequency SLA Sealed Lead...battery experiences physical or electrical abuse [ 11 ]. Despite their safety issues, Li/SO2 batteries have been used in military communications ...batteries designed for high rate operation are used in military applications (TRL 9 [1]), including powering radios [1, 11 ]. 3.2.1.5 Lithium Iron

A revisit to self-excited push pull vacuum tube radio frequency oscillator for ion sources and power measurements

NASA Astrophysics Data System (ADS)

Hlondo, L. R.; Lalremruata, B.; Punte, L. R. M.; Rebecca, L.; Lalnunthari, J.; Thanga, H. H.

2016-04-01

Self-excited push-pull vacuum tube oscillator is one of the most commonly used oscillators in radio frequency (RF)-ion plasma sources for generation of ions using radio frequency. However, in spite of its fundamental role in the process of plasma formation, the working and operational characteristics are the most frequently skip part in the descriptions of RF ion sources in literatures. A more detailed treatment is given in the present work on the RF oscillator alone using twin beam power tetrodes 829B and GI30. The circuit operates at 102 MHz, and the oscillation conditions, stability in frequency, and RF output power are studied and analyzed. A modified form of photometric method and RF peak voltage detection method are employed to study the variation of the oscillator output power with plate voltage. The power curves obtained from these measurements are quadratic in nature and increase with increase in plate voltage. However, the RF output power as measured by photometric methods is always less than the value calculated from peak voltage measurements. This difference is due to the fact that the filament coil of the ordinary light bulb used as load/detector in photometric method is not a perfect inductor. The effect of inductive reactance on power transfer to load was further investigated and a technique is developed to estimate the amount of power correction needed in the photometric measurement result.

A revisit to self-excited push pull vacuum tube radio frequency oscillator for ion sources and power measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hlondo, L. R.; Lalremruata, B.; Punte, L. R. M.

Self-excited push-pull vacuum tube oscillator is one of the most commonly used oscillators in radio frequency (RF)-ion plasma sources for generation of ions using radio frequency. However, in spite of its fundamental role in the process of plasma formation, the working and operational characteristics are the most frequently skip part in the descriptions of RF ion sources in literatures. A more detailed treatment is given in the present work on the RF oscillator alone using twin beam power tetrodes 829B and GI30. The circuit operates at 102 MHz, and the oscillation conditions, stability in frequency, and RF output power aremore » studied and analyzed. A modified form of photometric method and RF peak voltage detection method are employed to study the variation of the oscillator output power with plate voltage. The power curves obtained from these measurements are quadratic in nature and increase with increase in plate voltage. However, the RF output power as measured by photometric methods is always less than the value calculated from peak voltage measurements. This difference is due to the fact that the filament coil of the ordinary light bulb used as load/detector in photometric method is not a perfect inductor. The effect of inductive reactance on power transfer to load was further investigated and a technique is developed to estimate the amount of power correction needed in the photometric measurement result.« less

A revisit to self-excited push pull vacuum tube radio frequency oscillator for ion sources and power measurements.

PubMed

Hlondo, L R; Lalremruata, B; Punte, L R M; Rebecca, L; Lalnunthari, J; Thanga, H H

2016-04-01

Self-excited push-pull vacuum tube oscillator is one of the most commonly used oscillators in radio frequency (RF)-ion plasma sources for generation of ions using radio frequency. However, in spite of its fundamental role in the process of plasma formation, the working and operational characteristics are the most frequently skip part in the descriptions of RF ion sources in literatures. A more detailed treatment is given in the present work on the RF oscillator alone using twin beam power tetrodes 829B and GI30. The circuit operates at 102 MHz, and the oscillation conditions, stability in frequency, and RF output power are studied and analyzed. A modified form of photometric method and RF peak voltage detection method are employed to study the variation of the oscillator output power with plate voltage. The power curves obtained from these measurements are quadratic in nature and increase with increase in plate voltage. However, the RF output power as measured by photometric methods is always less than the value calculated from peak voltage measurements. This difference is due to the fact that the filament coil of the ordinary light bulb used as load/detector in photometric method is not a perfect inductor. The effect of inductive reactance on power transfer to load was further investigated and a technique is developed to estimate the amount of power correction needed in the photometric measurement result.

Flying radio frequency undulator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuzikov, S. V.; Vikharev, A. A.; Savilov, A. V.

2014-07-21

A concept for the room-temperature rf undulator, designed to produce coherent X-ray radiation by means of a relatively low-energy electron beam and pulsed mm-wavelength radiation, is proposed. The “flying” undulator is a high-power short rf pulse co-propagating together with a relativistic electron bunch in a helically corrugated waveguide. The electrons wiggle in the rf field of the −1st spatial harmonic with the phase velocity directed in the opposite direction in respect to the bunch velocity, so that particles can irradiate high-frequency Compton's photons. A high group velocity (close to the speed of light) ensures long cooperative motion of the particlesmore » and the co-propagating rf pulse.« less

Spin-Flipping Polarized Deuterons At COSY

NASA Astrophysics Data System (ADS)

Yonehara, K.; Krisch, A. D.; Morozov, V. S.; Raymond, R. S.; Wong, V. K.; Bechstedt, U.; Gebel, R.; Lehrach, A.; Lorenz, B.; Maier, R.; Prasuhn, D.; Schnase, A.; Stockhorst, H.; Eversheim, D.; Hinterberger, F.; Rohdjess, H.; Ulbrich, K.; Scobel, W.

2004-02-01

We recently stored a 1.85 GeV/c vertically polarized deuteron beam in the COSY Ring in Jülich; we then spin-flipped it by ramping a new air-core rf dipole's frequency through an rf-induced spin resonance to manipulate the polarization direction of the deuteron beam. We first experimentally determined the resonance's frequency and set the dipole's rf voltage to its maximum; then we varied its frequency ramp time and frequency range. We used the EDDA detector to measure the vector and tensor polarization asymmetries. We have not yet extracted the deuteron's tensor polarization spin-flip parameters from the measured data, since our short run did not provide adequate tensor analyzing-power data at 1.85 GeV/c. However, with a 100 Hz frequency ramp and our longest ramp time of 400 s, the deuterons' vector polarization spin-flip efficiency was 48±1%.

Relativistic theory of radiofrequency current drive

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balescu, R.; Metens, T.

1991-05-01

A fully relativistic kinetic theory of rf current drive in a tokamak is developed for both the lower hybrid and the electron cyclotron mechanisms. The problem is treated as a generalization of the classical transport equations, in which the thermodynamic forces are modified by the addition of a rf-source term. In the limit of weak rf amplitude and neglecting toroidal effects (such as particle trapping), explicit analytical expressions are obtained for the rf-generated current, the dissipated power, and the current drive efficiency. These expressions are fully relativistic and are valid over the whole admissible range of frequencies and for allmore » electron temperatures. The relation between efficiency and parallel relativistic transport coefficients is exhibited. The most important relativistic effect is a dramatic broadening of the frequency range over which the rf-generated current is significantly different from zero.« less

Ultrafast electrical spectrum analyzer based on all-optical Fourier transform and temporal magnification.

PubMed

Duan, Yuhua; Chen, Liao; Zhou, Haidong; Zhou, Xi; Zhang, Chi; Zhang, Xinliang

2017-04-03

Real-time electrical spectrum analysis is of great significance for applications involving radio astronomy and electronic warfare, e.g. the dynamic spectrum monitoring of outer space signal, and the instantaneous capture of frequency from other electronic systems. However, conventional electrical spectrum analyzer (ESA) has limited operation speed and observation bandwidth due to the electronic bottleneck. Therefore, a variety of photonics-assisted methods have been extensively explored due to the bandwidth advantage of the optical domain. Alternatively, we proposed and experimentally demonstrated an ultrafast ESA based on all-optical Fourier transform and temporal magnification in this paper. The radio-frequency (RF) signal under test is temporally multiplexed to the spectrum of an ultrashort pulse, thus the frequency information is converted to the time axis. Moreover, since the bandwidth of this ultrashort pulse is far beyond that of the state-of-the-art photo-detector, a temporal magnification system is applied to stretch the time axis, and capture the RF spectrum with 1-GHz resolution. The observation bandwidth of this ultrafast ESA is over 20 GHz, limited by that of the electro-optic modulator. Since all the signal processing is in the optical domain, the acquisition frame rate can be as high as 50 MHz. This ultrafast ESA scheme can be further improved with better dispersive engineering, and is promising for some ultrafast spectral information acquisition applications.

Biologically Inspired Network (BiONet) Authentication using Logical and Pathological RF DNA Credential Pairs

DTIC Science & Technology

2017-09-14

e.g. 000111) may be emitted along an ultra- high frequency (UHF) communications path as a possible waveform state generated by some circuit...Positive Rate TN True Negative TNR True Negative Rate TVR True Verification Rate Tx Transmitter UHF Ultra High Frequency 21 BIOLOGICALLY...otherwise healthy RF networks. More specifically, a representative miniaturized ultra- high frequency (UHF) CubeSat uplink access boundary, protected

Direct measurement of density oscillation induced by a radio-frequency wave.

PubMed

Yamada, T; Ejiri, A; Shimada, Y; Oosako, T; Tsujimura, J; Takase, Y; Kasahara, H

2007-08-01

An O-mode reflectometer at a frequency of 25.85 GHz was applied to plasmas heated by the high harmonic fast wave (21 MHz) in the TST-2 spherical tokamak. An oscillation in the phase of the reflected microwave in the rf range was observed directly for the first time. In TST-2, the rf (250 kW) induced density oscillation depends mainly on the poloidal rf electric field, which is estimated to be about 0.2 kV/m rms by the reflectometer measurement. Sideband peaks separated in frequency by ion cyclotron harmonics from 21 MHz, and peaks at ion cyclotron harmonics which are suggested to be quasimodes generated by parametric decay, were detected.

Generation of X-rays and neutrons with a RF-discharge

NASA Technical Reports Server (NTRS)

Schneider, R. T.

1982-01-01

An experimental study concerning disk shaped plasma structures was performed. Such disk-shaped structures can be obtained using an rf discharge in hydrogen. The applied frequency was 1-2 Mhz. In case of operation in deuterium it was found that the discharge emits neutrons and X-rays, although the applied voltage is only 2 kV. This phenomenon was explained by assuming formation of plasma cavitons which are surrounded by high electric fields. The condition for formation of these cavitons is that the applied rf frequency is equal to the plasma frequency. The ions trapped in these resonance structures acquire sufficient energy that they can undergo fusion reactions with the ions in the surrounding gas.

Flexible radio-frequency single-crystal germanium switch on plastic substrates

NASA Astrophysics Data System (ADS)

Qin, Guoxuan; Cai, Tianhao; Yuan, Hao-Chih; Seo, Jung-Hun; Ma, Jianguo; Ma, Zhenqiang

2014-04-01

This Letter presents the realization and characterizations of the flexible radio-frequency (RF)/microwave switches on plastic substrates employing single-crystal germanium (Ge) nanomembranes. The fabricated flexible Ge single-pole, single-throw (SPST) switches display high frequency responses (e.g., insertion loss of <1.3 dB at up to 30 GHz and isolation >10 dB at up to ˜13 GHz). RF performance tradeoff exists for the flexible Ge switches and the major affecting parameters are determined. The flexible Ge SPST switch shows better RF property to that of the flexible Si SPST switch. Underlying mechanism is investigated by theoretical analysis and modeling of switches with different structures.

Electromagnetic analysis of the slotted-tube resonator with a circular cross section for MRI applications.

PubMed

Benabdallah, Nadia; Benahmed, Nasreddine; Benyoucef, Boumediene; Bouhmidi, Rachid; Khelif, M'Hamed

2007-08-21

In this paper we present electromagnetic (EM) analysis of the unloaded slotted-tube resonator (STR) with a circular cross section, using the finite element method (FEM) and method of moments (MoM) in two dimensions. This analysis allows the determination of the primary parameters: [L] and [C] matrices, optimization of the field homogeneity, and simulates the frequency response of S(11) at the RF port of the designed STR. The optimum configuration is presented, taking into account the effect of the thickness of the STR and the effect of the RF shield. As an application, we present the design results of a MRI probe using the STR and operating at 500 MHz (proton imaging at 11.74 T). The resonator has -69.37 dB minimum reflection and an unloaded quality factor (Q(o)) > 500 at 500 MHz.

A Simplified Theory of Coupled Oscillator Array Phase Control

NASA Technical Reports Server (NTRS)

Pogorzelski, R. J.; York, R. A.

1997-01-01

Linear and planar arrays of coupled oscillators have been proposed as means of achieving high power rf sources through coherent spatial power combining. In such - applications, a uniform phase distribution over the aperture is desired. However, it has been shown that by detuning some of the oscillators away from the oscillation frequency of the ensemble of oscillators, one may achieve other useful aperture phase distributions. Notable among these are linear phase distributions resulting in steering of the output rf beam away from the broadside direction. The theory describing the operation of such arrays of coupled oscillators is quite complicated since the phenomena involved are inherently nonlinear. This has made it difficult to develop an intuitive understanding of the impact of oscillator tuning on phase control and has thus impeded practical application. In this work a simpl!fied theory is developed which facilitates intuitive understanding by establishing an analog of the phase control problem in terms of electrostatics.

Exploring channeling optimized radiofrequency energy: a review of radiofrequency history and applications in esthetic fields.

PubMed

Belenky, Inna; Margulis, Ariel; Elman, Monica; Bar-Yosef, Udi; Paun, Silviu D

2012-03-01

Because of its high efficiency and safety, radiofrequency (RF) energy is widely used in the dermatological field for heating biological tissue in various esthetic applications, including skin tightening, skin lifting, body contouring, and cellulite reduction. This paper reviews the literature on the use of nonablative RF energy in the esthetic field and its scientific background. The purpose of this article is to describe in detail the extensive use of medical devices based on RF technology, the development of these medical devices over the years, and recent developments and trends in RF technology. The authors conducted a systematic search of publications that address safety and efficacy issues, technical system specifications, and clinical techniques. Finally, the authors focused on their own clinical experiences with the use of patented Channeling Optimized RF Energy technique and mechanical massage. An in-vivo study was conducted in domestic pigs, with a thermal video camera. Twenty-seven female patients participated in a cellulite and body shaping study. The treatments were conducted according to a three-phase protocol. An additional 16 females participated in a skin tightening case study. All of the patients underwent three treatment sessions at 3-week intervals, each according to a protocol specific to the area being treated. The review of the literature on RF-based systems revealed that these systems are safe, with low risks for potential side effects, and effective for cellulite, body contouring, and skin tightening procedures. The in-vivo measurements confirmed the theory that the penetration depth of RF is an inverse function of its frequency, and using a vacuum mechanism makes an additional contribution to the RF energy penetration. The heating effect of RF was also found to increase blood circulation and to induce collagen remodeling. The results from the cellulite and body shaping treatments showed an overall average improvement of 55% in the appearance of cellulite, with an average circumferential reduction of 3.31 cm in the buttocks, 2.94 cm in the thighs, and 2.14 cm in the abdomen. The results from the skin tightening procedure showed moderate improvement of skin appearance in 50% and significant improvement in 31%. At the follow-up visits the results were found to be sustained without any significant side effects. Of all tissue heating techniques, RF-based technologies appear to be the most established and clinically proven. The design and specifications of the described vacuumassisted bipolar RF device fall within the range of the specifications currently prescribed for esthetic, nonablative RF systems.

Ion source with external RF antenna

DOEpatents

Leung, Ka-Ngo; Ji, Qing; Wilde, Stephen

2005-12-13

A radio frequency (RF) driven plasma ion source has an external RF antenna, i.e. the RF antenna is positioned outside the plasma generating chamber rather than inside. The RF antenna is typically formed of a small diameter metal tube coated with an insulator. An external RF antenna assembly is used to mount the external RF antenna to the ion source. The RF antenna tubing is wound around the external RF antenna assembly to form a coil. The external RF antenna assembly is formed of a material, e.g. quartz, which is essentially transparent to the RF waves. The external RF antenna assembly is attached to and forms a part of the plasma source chamber so that the RF waves emitted by the RF antenna enter into the inside of the plasma chamber and ionize a gas contained therein. The plasma ion source is typically a multi-cusp ion source.

Capture, acceleration and bunching rf systems for the MEIC booster and storage rings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Shaoheng; Guo, Jiquan; Lin, Fanglei

2015-09-01

The Medium-energy Electron Ion Collider (MEIC), proposed by Jefferson Lab, consists of a series of accelerators. The electron collider ring accepts electrons from CEBAF at energies from 3 to 12 GeV. Protons and ions are delivered to a booster and captured in a long bunch before being ramped and transferred to the ion collider ring. The ion collider ring accelerates a small number of long ion bunches to colliding energy before they are re-bunched into a high frequency train of very short bunches for colliding. Two sets of low frequency RF systems are needed for the long ion bunch energymore » ramping in the booster and ion collider ring. Another two sets of high frequency RF cavities are needed for re-bunching in the ion collider ring and compensating synchrotron radiation energy loss in the electron collider ring. The requirements from energy ramping, ion beam bunching, electron beam energy compensation, collective effects, beam loading and feedback capability, RF power capability, etc. are presented. The preliminary designs of these RF systems are presented. Concepts for the baseline cavity and RF station configurations are described, as well as some options that may allow more flexible injection and acceleration schemes.« less

High Frequency GaAs Bulk Acousto-Optic Devices For Modulators And Frequency Shifters At 1.3um And 1.5um In Fiber-Optics

NASA Astrophysics Data System (ADS)

Soos, J. I.; Rosemeier, R. G.

1989-02-01

The edge of a transmission window for a GaAs Bragg cell starts about lum, which allows this material to be used for infrared fiber-optic applications, especially at 1.3um and 1.5um. The single crystal of GaAs is acoustically anisotropic and has the highest figure of merit, M2, along <111> direction for a longitudinal mode sound wave. Recently, Brimrose has designed and fabricated an acousto-optic modulator from GaAs operating at a carrier frequency of 2.3 GHz with a diffraction efficiency of 4%/RF watt.

Demonstrating the Principle of an rf Paul Ion Trap

NASA Astrophysics Data System (ADS)

Johnson, Andrew; Rabchuk, James

2008-03-01

An rf ion trap uses a time-varying electric field to trap charged ions. This is useful in applications related to quantum computing and mass spectroscopy. There are several mechanical devices described in the literature which have attempted to provide illustrative demonstrations of the principle of rf ion traps, including a mechanically-rotating ``saddle trap'' and the vertically-driven, inverted pendulum^1,2. Neither demonstration, however, successfully demonstrates BOTH the sinusoidal variation in the electric potential of the rf trap AND the parametric stability of the ions in the trap described by Mathieu's equation. We have modified a design of a one-dimensional ponderomotive trap^3 so that it satisfies both criteria for demonstrating the principle of an rf Paul trap. Our studies indicate that trapping stability is highly sensitive to fluxuations in the driving frequency. Results from the demonstration apparatus constructed by the authors will be presented. ^1 Rueckner, W., et al., ``Rotating saddle Paul trap,'' Am. J. Phys., 63 (2), February 1995. ^2 Friedman, M.H., et al., ``The inverted pendulum: A mechanical analogue of a quadrupole mass filter,'' Am. J. Phys., 50 (10), October 1982. ^3 Johnson, A.K. and Rabchuk, J.A., ``A One-Dimensional Ponderomotive Trap,'' ISAAPT 2007 spring meeting, WIU, March 30, 2007.

Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum

NASA Technical Reports Server (NTRS)

Brady, David A.; White, Harold G.; March, Paul; Lawrence, James T.; Davies, Frank J.

2014-01-01

This paper describes the test campaigns designed to investigate and demonstrate viability of using classical magnetoplasmadynamics to obtain a propulsive momentum transfer via the quantum vacuum virtual plasma. This paper will not address the physics of the quantum vacuum plasma thruster (QVPT), but instead will describe the recent test campaign. In addition, it contains a brief description of the supporting radio frequency (RF) field analysis, lessons learned, and potential applications of the technology to space exploration missions. During the first (Cannae) portion of the campaign, approximately 40 micronewtons of thrust were observed in an RF resonant cavity test article excited at approximately 935 megahertz and 28 watts. During the subsequent (tapered cavity) portion of the campaign, approximately 91 micronewtons of thrust were observed in an RF resonant cavity test article excited at approximately 1933 megahertz and 17 watts. Testing was performed on a low-thrust torsion pendulum that is capable of detecting force at a single-digit micronewton level. Test campaign results indicate that the RF resonant cavity thruster design, which is unique as an electric propulsion device, is producing a force that is not attributable to any classical electromagnetic phenomenon and therefore is potentially demonstrating an interaction with the quantum vacuum virtual plasma.

Effect of radio-frequency electromagnetic radiations (RF-EMR) on passive avoidance behaviour and hippocampal morphology in Wistar rats.

PubMed

Narayanan, Sareesh Naduvil; Kumar, Raju Suresh; Potu, Bhagath Kumar; Nayak, Satheesha; Bhat, P Gopalakrishna; Mailankot, Maneesh

2010-05-01

The interaction of mobile phone radio-frequency electromagnetic radiation (RF-EMR) with the brain is a serious concern of our society. We evaluated the effect of RF-EMR from mobile phones on passive avoidance behaviour and hippocampal morphology in rats. Healthy male albino Wistar rats were exposed to RF-EMR by giving 50 missed calls (within 1 hour) per day for 4 weeks, keeping a GSM (0.9 GHz/1.8 GHz) mobile phone in vibratory mode (no ring tone) in the cage. After the experimental period, passive avoidance behaviour and hippocampal morphology were studied. Passive avoidance behaviour was significantly affected in mobile phone RF-EMR-exposed rats demonstrated as shorter entrance latency to the dark compartment when compared to the control rats. Marked morphological changes were also observed in the CA(3) region of the hippocampus of the mobile phone-exposed rats in comparison to the control rats. Mobile phone RF-EMR exposure significantly altered the passive avoidance behaviour and hippocampal morphology in rats.

Fast shut-down protection system for radio frequency breakdown and multipactor testing.

PubMed

Graves, T P; Hanson, P; Michaelson, J M; Farkas, A D; Hubble, A A

2014-02-01

Radio frequency (RF) breakdown such as multipactor or ionization breakdown is a device-limiting phenomenon for on-orbit spacecraft used for communication, navigation, or other RF payloads. Ground testing is therefore part of the qualification process for all high power components used in these space systems. This paper illustrates a shut-down protection system to be incorporated into multipactor/ionization breakdown ground testing for susceptible RF devices. This 8 channel system allows simultaneous use of different diagnostic classes and different noise floors. With initiation of a breakdown event, diagnostic signals increase above a user-specified level, which then opens an RF switch to eliminate RF power from the high power amplifier. Examples of this system in use are shown for a typical setup, illustrating the reproducibility of breakdown threshold voltages and the lack of multipactor conditioning. This system can also be utilized to prevent excessive damage to RF components in tests with sensitive or flight hardware.

Radio Frequency Sensing of Particulate Matter Accumulation on a Gasoline Particulate Filter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parks, James; Prikhodko, Vitaly Y.; Sappok, Alex

Filter Sensing Technology’s radio frequency (RF) sensor for particulate filter on-board diagnostics (OBD) was studied on a lean gasoline engine at the National Transportation Research Center (NTRC) at Oak Ridge National Laboratory (ORNL). The response of the RF sensor to particulate matter (PM) or “soot” accumulation on the gasoline particulate filter (GPF) installed in the engine exhaust was evaluated. In addition, end plugs of the GPF were purposely removed, and subsequent changes to the RF sensor measured soot loading on the GPF were characterized. Results from the study showed that the RF sensor can accurately measure soot accumulation on amore » GPF; furthermore, the predicted decreased soot accumulation due to plug removal was detected by the RF sensor. Overall, the studies were short and preliminary in nature; however, clearly, the RF sensor demonstrated the capability of measuring GPF soot loading at a level suitable for use in lean gasoline engine emission control OBD and control.« less

Electroluminescence of hot electrons in AlGaN/GaN high-electron-mobility transistors under radio frequency operation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brazzini, Tommaso, E-mail: tommaso.brazzini@bristol.ac.uk; Sun, Huarui; Uren, Michael J.

2015-05-25

Hot electrons in AlGaN/GaN high electron mobility transistors are studied during radio frequency (RF) and DC operation by means of electroluminescence (EL) microscopy and spectroscopy. The measured EL intensity is decreased under RF operation compared to DC at the same average current, indicating a lower hot electron density. This is explained by averaging the DC EL intensity over the measured load line used in RF measurements, giving reasonable agreement. In addition, the hot electron temperature is lower by up to 15% under RF compared to DC, again at least partially explainable by the weighted averaging along the specific load line.more » However, peak electron temperature under RF occurs at high V{sub DS} and low I{sub DS} where EL is insignificant suggesting that any wear-out differences between RF and DC stress of the devices will depend on the balance between hot-carrier and field driven degradation mechanisms.« less

A low feed-through 3D vacuum packaging technique with silicon vias for RF MEMS resonators

NASA Astrophysics Data System (ADS)

Zhao, Jicong; Yuan, Quan; Kan, Xiao; Yang, Jinling; Yang, Fuhua

2017-01-01

This paper presents a wafer-level three-dimensional (3D) vacuum packaging technique for radio frequency microelectromechanical systems (RF MEMS) resonators. A Sn-rich Au-Sn solder bonding is employed to provide a vacuum encapsulation as well as electrical conductions. Vertical silicon vias are micro-fabricated by glass reflow process. The optimized grounding, via pitch, and all-round shielding effectively reduce feed-through capacitance. Thus the signal-to-background ratios (SBRs) of the transmission signals increase from 17 dB to 20 dB, and the quality factor (Q) values of the packaged resonators go from around 8000 up to more than 9500. The measured average leak rate and shear strength are (2.55  ±  0.9)  ×  10-8 atm-cc s-1 and 42.53  ±  4.19 MPa, respectively. Furthermore, thermal cycling test between  -40 °C and 100 °C and high temperature storage test at 150 °C show that the resonant-frequency drifts are less than  ±7 ppm. In addition, the SBRs and the Q values have no obvious change after the tests. The experimental results demonstrated that the proposed encapsulation technique is well suited for the applications of RF MEMS devices.

AuNP-RF sensor: An innovative application of RF technology for sensing pathogens electrically in liquids (SPEL) within the food supply chain.

PubMed

Matta, Leann Lerie; Karuppuswami, Saranraj; Chahal, Premjeet; Alocilja, Evangelyn C

2018-07-15

Rapid detection techniques of pathogenic bacteria in the liquid food supply chain are of significant research interest due to their pivotal role in preventing foodborne outbreaks, and in maintaining high standards of public health and safety. Milk and dairy products are of particular interest due to their widespread consumption across the globe. In this paper, a biosensor for detecting pathogenic bacteria in milk using dextrin-capped gold nanoparticles (d-AuNP) as labels decoded at microwave frequencies is presented. The SPEL (sensing pathogens electrically in liquids) biosensor consists of a 3D printed vial and uses an RF reader and an RFID (radio-frequency identification) compatible Split Ring Resonator (SRR) based tag. The SPEL biosensor is capable of detecting bacteria at 5 log CFU/mL within 75 min, with the possibility of testing multiple concurrent samples. Detection is based on impedance loading of SRR by d-AuNP bound to pathogenic bacteria. Spectrophotometry, along with carbohydrate-functionalized magnetic nanoparticle (MNP) cell capture, is used to verify the sensitivity of the SPEL biosensor with respect to d-AuNP presence. The proof-of-concept device, along with challenges and opportunities for commercialization, are also outlined. Copyright © 2018. Published by Elsevier B.V.

Multi-service highly sensitive rectifier for enhanced RF energy scavenging.

PubMed

Shariati, Negin; Rowe, Wayne S T; Scott, James R; Ghorbani, Kamran

2015-05-07

Due to the growing implications of energy costs and carbon footprints, the need to adopt inexpensive, green energy harvesting strategies are of paramount importance for the long-term conservation of the environment and the global economy. To address this, the feasibility of harvesting low power density ambient RF energy simultaneously from multiple sources is examined. A high efficiency multi-resonant rectifier is proposed, which operates at two frequency bands (478-496 and 852-869 MHz) and exhibits favorable impedance matching over a broad input power range (-40 to -10 dBm). Simulation and experimental results of input reflection coefficient and rectified output power are in excellent agreement, demonstrating the usefulness of this innovative low-power rectification technique. Measurement results indicate an effective efficiency of 54.3%, and an output DC voltage of 772.8 mV is achieved for a multi-tone input power of -10 dBm. Furthermore, the measured output DC power from harvesting RF energy from multiple services concurrently exhibits a 3.14 and 7.24 fold increase over single frequency rectification at 490 and 860 MHz respectively. Therefore, the proposed multi-service highly sensitive rectifier is a promising technique for providing a sustainable energy source for low power applications in urban environments.

Multi-Service Highly Sensitive Rectifier for Enhanced RF Energy Scavenging

PubMed Central

Shariati, Negin; Rowe, Wayne S. T.; Scott, James R.; Ghorbani, Kamran

2015-01-01

Due to the growing implications of energy costs and carbon footprints, the need to adopt inexpensive, green energy harvesting strategies are of paramount importance for the long-term conservation of the environment and the global economy. To address this, the feasibility of harvesting low power density ambient RF energy simultaneously from multiple sources is examined. A high efficiency multi-resonant rectifier is proposed, which operates at two frequency bands (478–496 and 852–869 MHz) and exhibits favorable impedance matching over a broad input power range (−40 to −10 dBm). Simulation and experimental results of input reflection coefficient and rectified output power are in excellent agreement, demonstrating the usefulness of this innovative low-power rectification technique. Measurement results indicate an effective efficiency of 54.3%, and an output DC voltage of 772.8 mV is achieved for a multi-tone input power of −10 dBm. Furthermore, the measured output DC power from harvesting RF energy from multiple services concurrently exhibits a 3.14 and 7.24 fold increase over single frequency rectification at 490 and 860 MHz respectively. Therefore, the proposed multi-service highly sensitive rectifier is a promising technique for providing a sustainable energy source for low power applications in urban environments. PMID:25951137

Identifying possible non-thermal effects of radio frequency energy on inactivating food microorganisms.

PubMed

Kou, Xiaoxi; Li, Rui; Hou, Lixia; Zhang, Lihui; Wang, Shaojin

2018-03-23

Radio frequency (RF) heating has been successfully used for inactivating microorganisms in agricultural and food products. Athermal (non-thermal) effects of RF energy on microorganisms have been frequently proposed in the literature, resulting in difficulties for developing effective thermal treatment protocols. The purpose of this study was to identify if the athermal inactivation of microorganisms existed during RF treatments. Escherichia coli and Staphylococcus aureus in apple juice and mashed potato were exposed to both RF and conventional thermal energies to compare their inactivation populations. A thermal death time (TDT) heating block system was used as conventional thermal energy source to simulate the same heating treatment conditions, involving heating temperature, heating rate and uniformity, of a RF treatment at a frequency of 27.12 MHz. Results showed that a similar and uniform temperature distribution in tested samples was achieved in both heating systems, so that the central sample temperature could be used as representative one for evaluating thermal inactivation of microorganisms. The survival patterns of two target microorganisms in two food samples were similar both for RF and heating block treatments since their absolute difference of survival populations was <1 log CFU/ml. The statistical analysis indicated no significant difference (P > 0.05) in inactivating bacteria between the RF and the heating block treatments at each set of temperatures. The solid temperature and microbial inactivation data demonstrated that only thermal effect of RF energy at 27.12 MHz was observed on inactivating microorganisms in foods. Copyright © 2018 Elsevier B.V. All rights reserved.

POWER DENSITY, FIELD INTENSITY, AND CARRIER FREQUENCY DETERMINANTS OF RF-ENERGY-INDUCED CALCIUM-ION EFFLUX FROM BRAIN TISSUE

EPA Science Inventory

To explain a carrier frequency dependence reported for radiofrequency (RF)-induced calcium-ion efflux from brain tissue, a chick-brain hemisphere bathed in buffer solution is modeled as a sphere within the uniform field of the incident electromagnetic wave. Calculations on a sphe...

Low jitter RF distribution system

DOEpatents

Wilcox, Russell; Doolittle, Lawrence; Huang, Gang

2012-09-18

A timing signal distribution system includes an optical frequency stabilized laser signal amplitude modulated at an rf frequency. A transmitter box transmits a first portion of the laser signal and receive a modified optical signal, and outputs a second portion of the laser signal and a portion of the modified optical signal. A first optical fiber carries the first laser signal portion and the modified optical signal, and a second optical fiber carries the second portion of the laser signal and the returned modified optical signal. A receiver box receives the first laser signal portion, shifts the frequency of the first laser signal portion outputs the modified optical signal, and outputs an electrical signal on the basis of the laser signal. A detector at the end of the second optical fiber outputs a signal based on the modified optical signal. An optical delay sensing circuit outputs a data signal based on the detected modified optical signal. An rf phase detect and correct signal circuit outputs a signal corresponding to a phase stabilized rf signal based on the data signal and the frequency received from the receiver box.

A Novel Application of Machine Learning Methods to Model Microcontroller Upset Due to Intentional Electromagnetic Interference

NASA Astrophysics Data System (ADS)

Bilalic, Rusmir

A novel application of support vector machines (SVMs), artificial neural networks (ANNs), and Gaussian processes (GPs) for machine learning (GPML) to model microcontroller unit (MCU) upset due to intentional electromagnetic interference (IEMI) is presented. In this approach, an MCU performs a counting operation (0-7) while electromagnetic interference in the form of a radio frequency (RF) pulse is direct-injected into the MCU clock line. Injection times with respect to the clock signal are the clock low, clock rising edge, clock high, and the clock falling edge periods in the clock window during which the MCU is performing initialization and executing the counting procedure. The intent is to cause disruption in the counting operation and model the probability of effect (PoE) using machine learning tools. Five experiments were executed as part of this research, each of which contained a set of 38,300 training points and 38,300 test points, for a total of 383,000 total points with the following experiment variables: injection times with respect to the clock signal, injected RF power, injected RF pulse width, and injected RF frequency. For the 191,500 training points, the average training error was 12.47%, while for the 191,500 test points the average test error was 14.85%, meaning that on average, the machine was able to predict MCU upset with an 85.15% accuracy. Leaving out the results for the worst-performing model (SVM with a linear kernel), the test prediction accuracy for the remaining machines is almost 89%. All three machine learning methods (ANNs, SVMs, and GPML) showed excellent and consistent results in their ability to model and predict the PoE on an MCU due to IEMI. The GP approach performed best during training with a 7.43% average training error, while the ANN technique was most accurate during the test with a 10.80% error.

ICRH antenna S-matrix measurements and plasma coupling characterisation at JET

NASA Astrophysics Data System (ADS)

Monakhov, I.; Jacquet, P.; Blackman, T.; Bobkov, V.; Dumortier, P.; Helou, W.; Lerche, E.; Kirov, K.; Milanesio, D.; Maggiora, R.; Noble, C.; Contributors, JET

2018-04-01

The paper is dedicated to the characterisation of multi-strap ICRH antenna coupling to plasma. Relevance of traditional concept of coupling resistance to antennas with mutually coupled straps is revised and the importance of antenna port excitation consistency for application of the concept is highlighted. A method of antenna S-matrix measurement in presence of plasma is discussed allowing deeper insight into the problem of antenna-plasma coupling. The method is based entirely on the RF plant hardware and control facilities available at JET and it involves application of variable phasing between the antenna straps during the RF plant operations at  >100 kW. Unlike traditional techniques relying on low-power (~10 mW) network analysers, the applied antenna voltage amplitudes are relevant to practical conditions of ICRH operations; crucially, they are high enough to minimise possible effects of antenna loading non-linearity due to the RF sheath effects and other phenomena which could affect low-power measurements. The method has been successfully applied at JET to conventional 4-port ICRH antennas energised at frequencies of 33 MHz, 42 MHz and 51 MHz during L-mode plasma discharges while different gas injection modules (GIMs) were used to maintain comparable plasma densities during the pulses. The S-matrix assessment and its subsequent processing yielding ‘global’ antenna coupling resistances in conditions of equalised port maximum voltages allowed consistent description of antenna coupling to plasma at different strap phasing, operational frequencies and applied GIMs. Comprehensive experimental characterisation of mutually coupled antenna straps in presence of plasma also provided a unique opportunity for in-depth verification of TOPICA computer simulations.

Characterization of conductive Al-doped ZnO thin films for plasmonic applications

NASA Astrophysics Data System (ADS)

Masouleh, F. F.; Sinno, I.; Buckley, R. G.; Gouws, G.; Moore, C. P.

2018-02-01

Highly conductive and transparent Al-doped zinc oxide films were produced by RF magnetron sputtering for plasmonic applications in the infrared region of the spectrum. These films were characterized using Fourier transform infrared spectroscopy, the Hall effect, Rutherford backscattering spectroscopy and spectral data analysis. Analysis of the results shows a carrier concentration of up to 2.6 × 1020 cm-3, as well as transmission over 80% near the plasma frequency where plasmonic properties are expected. The plasma frequency was calculated from the spectroscopy measurements and subsequent data analysis, and was in agreement with the results from the Hall effect measurements and the free electron gas (Drude) model. Based on these results, the Al-doped zinc oxide thin films are well-suited for plasmonic applications in the infrared region.

Systematic cavity design approach for a multi-frequency gyrotron for DEMO and study of its RF behavior

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalaria, P. C., E-mail: parth.kalaria@partner.kit.edu; Avramidis, K. A.; Franck, J.

High frequency (>230 GHz) megawatt-class gyrotrons are planned as RF sources for electron cyclotron resonance heating and current drive in DEMOnstration fusion power plants (DEMOs). In this paper, for the first time, a feasibility study of a 236 GHz DEMO gyrotron is presented by considering all relevant design goals and the possible technical limitations. A mode-selection procedure is proposed in order to satisfy the multi-frequency and frequency-step tunability requirements. An effective systematic design approach for the optimal design of a gradually tapered cavity is presented. The RF-behavior of the proposed cavity is verified rigorously, supporting 920 kW of stable output power withmore » an interaction efficiency of 36% including the considerations of realistic beam parameters.« less

Design and implementation of a beam-waveguide mirror control system for vernier pointing of the DSS-13 antenna

NASA Technical Reports Server (NTRS)

Alvarez, L. S.; Moore, M.; Veruttipong, W.; Andres, E.

1994-01-01

The design and implementation of an antenna beam-waveguide (BWG) mirror position control system at the DSS-13 34-m antenna is presented. While it has several potential applications, a positioner on the last flat-plate BWG mirror (M6) at DSS 13 is installed to demonstrate the conical scan (conscan) angle-tracking technique at the Ka-band (32-GHz) operating frequency. Radio frequency (RF) beam-scanning predictions for the M6 mirror, computed from a diffraction analysis, are presented. From these predictions, position control system requirements are then derived. The final mechanical positioner and servo system designs, as implemented at DSS 13, are illustrated with detailed design descriptions given in the appendices. Preliminary measurements of antenna Ka-band beam scan versus M6 mirror tilt made at DSS 13 in December 1993 are presented. After reduction, the initial measurements are shown to be in agreement with the RF predicts. Plans for preliminary conscan experimentation at DSS 13 are summarized.

Study on the steady operating state of a micro-pulse electron gun

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kui, Zhou; Xing, Luo; Institute of Applied Electronics, Chinese Academy of Engineering Physics, Mianyang 621900

Micro-pulse electron gun (MPG) employs the basic concept of multipacting to produce high-current and short-pulse electron beams from a radio-frequency (RF) cavity. The concept of MPG has been proposed for more than two decades. However, the unstable operating state of MPG vastly obstructs its practical applications. This paper presents a study on the steady operating state of a micro-pulse electron gun with theory and experiments. The requirements for the steady operating state are proposed through the analysis of the interaction between the RF cavity and the beam load. Accordingly, a MPG cavity with the frequency of 2856 MHz has been designed,more » constructed, and tested. Some primary experiments have been finished. Both the unstable and stable operating states of the MPG have been observed. The stable output beam current has been detected at about 3.8 mA. Further experimental study is under way now.« less

Universal discrete Fourier optics RF photonic integrated circuit architecture.

PubMed

Hall, Trevor J; Hasan, Mehedi

2016-04-04

This paper describes a coherent electro-optic circuit architecture that generates a frequency comb consisting of N spatially separated orders using a generalised Mach-Zenhder interferometer (MZI) with its N × 1 combiner replaced by an optical N × N Discrete Fourier Transform (DFT). Advantage may be taken of the tight optical path-length control, component and circuit symmetries and emerging trimming algorithms offered by photonic integration in any platform that offers linear electro-optic phase modulation such as LiNbO_3, silicon, III-V or hybrid technology. The circuit architecture subsumes all MZI-based RF photonic circuit architectures in the prior art given an appropriate choice of output port(s) and dimension N although the principal application envisaged is phase correlated subcarrier generation for all optical orthogonal frequency division multiplexing. A transfer matrix approach is used to model the operation of the architecture. The predictions of the model are validated by simulations performed using an industry standard software tool. Implementation is found to be practical.

Micropower RF material proximity sensor

DOEpatents

McEwan, Thomas E.

1998-01-01

A level detector or proximity detector for materials capable of sensing through plastic container walls or encapsulating materials is of the sensor. Thus, it can be used in corrosive environments, as well as in a wide variety of applications. An antenna has a characteristic impedance which depends on the materials in proximity to the antenna. An RF oscillator, which includes the antenna and is based on a single transistor in a Colpitt's configuration, produces an oscillating signal. A detector is coupled to the oscillator which signals changes in the oscillating signal caused by changes in the materials in proximity to the antenna. The oscillator is turned on and off at a pulse repetition frequency with a low duty cycle to conserve power. The antenna consists of a straight monopole about one-quarter wavelength long at the nominal frequency of the oscillator. The antenna may be horizontally disposed on a container and very accurately detects the fill level within the container as the material inside the container reaches the level of the antenna.

Micropower RF material proximity sensor

DOEpatents

McEwan, T.E.

1998-11-10

A level detector or proximity detector for materials capable of sensing through plastic container walls or encapsulating materials is disclosed. Thus, it can be used in corrosive environments, as well as in a wide variety of applications. An antenna has a characteristic impedance which depends on the materials in proximity to the antenna. An RF oscillator, which includes the antenna and is based on a single transistor in a Colpitt`s configuration, produces an oscillating signal. A detector is coupled to the oscillator which signals changes in the oscillating signal caused by changes in the materials in proximity to the antenna. The oscillator is turned on and off at a pulse repetition frequency with a low duty cycle to conserve power. The antenna consists of a straight monopole about one-quarter wavelength long at the nominal frequency of the oscillator. The antenna may be horizontally disposed on a container and very accurately detects the fill level within the container as the material inside the container reaches the level of the antenna. 5 figs.

Coherent coupling between radio frequency, optical, and acoustic waves in piezo-optomechanical circuits

PubMed Central

Balram, Krishna C.; Davanço, Marcelo I.; Song, Jin Dong; Srinivasan, Kartik

2016-01-01

Optomechanical cavities have been studied for applications ranging from sensing to quantum information science. Here, we develop a platform for nanoscale cavity optomechanical circuits in which optomechanical cavities supporting co-localized 1550 nm photons and 2.4 GHz phonons are combined with photonic and phononic waveguides. Working in GaAs facilitates manipulation of the localized mechanical mode either with a radio frequency (RF) field through the piezo-electric effect, which produces acoustic waves that are routed and coupled to the optomechanical cavity by phononic crystal waveguides, or optically through the strong photoelastic effect. Along with mechanical state preparation and sensitive readout, we use this to demonstrate an acoustic wave interference effect, similar to atomic coherent population trapping, in which RF-driven coherent mechanical motion is cancelled by optically-driven motion. Manipulating cavity optomechanical systems with equal facility through both photonic and phononic channels enables new architectures for signal transduction between the optical, electrical, and mechanical domains. PMID:27446234

Plasma Parameters From Reentry Signal Attenuation

DOE PAGES

Statom, T. K.

2018-02-27

This study presents the application of a theoretically developed method that provides plasma parameter solution space information from measured RF attenuation that occurs during reentry. The purpose is to provide reentry plasma parameter information from the communication signal attenuation. The theoretical development centers around the attenuation and the complex index of refraction. The methodology uses an imaginary index of the refraction matching algorithm with a tolerance to find suitable solutions that satisfy the theory. The imaginary matching terms are then used to determine the real index of refraction resulting in the complex index of refraction. Then a filter is usedmore » to reject nonphysical solutions. Signal attenuation-based plasma parameter properties investigated include the complex index of refraction, plasma frequency, electron density, collision frequency, propagation constant, attenuation constant, phase constant, complex plasma conductivity, and electron mobility. RF plasma thickness attenuation is investigated and compared to the literature. Finally, similar plasma thickness for a specific signal attenuation can have different plasma properties.« less

Plasma Parameters From Reentry Signal Attenuation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Statom, T. K.

This study presents the application of a theoretically developed method that provides plasma parameter solution space information from measured RF attenuation that occurs during reentry. The purpose is to provide reentry plasma parameter information from the communication signal attenuation. The theoretical development centers around the attenuation and the complex index of refraction. The methodology uses an imaginary index of the refraction matching algorithm with a tolerance to find suitable solutions that satisfy the theory. The imaginary matching terms are then used to determine the real index of refraction resulting in the complex index of refraction. Then a filter is usedmore » to reject nonphysical solutions. Signal attenuation-based plasma parameter properties investigated include the complex index of refraction, plasma frequency, electron density, collision frequency, propagation constant, attenuation constant, phase constant, complex plasma conductivity, and electron mobility. RF plasma thickness attenuation is investigated and compared to the literature. Finally, similar plasma thickness for a specific signal attenuation can have different plasma properties.« less

Panofsky magnet for the beam extraction from the synchrotron using a fast Q-magnet and RF-knockout

NASA Astrophysics Data System (ADS)

Masubuchi, S.; Nakanishi, T.

2011-12-01

The fast control of the beam spill extracted from a synchrotron is a key function for the spot scanning irradiation in cancer therapy application. The authors propose an extraction method which uses the quadruple field of fast response, as well as the RF-knockout. A Panofsky magnet was developed as a quadruple magnet, with a frequency response of around 10 kHz. The Panofsky magnet has a rectangular beam aperture and plate coils attached to the pole face. A model magnet has been manufactured with ferrite, and static and dynamic magnetic fields were measured. From the measurement we observed that the effects of eddy current in the plate coils were large and the uniformity of the magnetic field gradient in the beam aperture was worse than ±5% with a plate thickness of 0.02 cm and a frequency of current of 10 kHz. For the future, in a detailed design the eddy current effects have to be taken into account.

Time delay generation at high frequency using SOA based slow and fast light.

PubMed

Berger, Perrine; Bourderionnet, Jérôme; Bretenaker, Fabien; Dolfi, Daniel; Alouini, Mehdi

2011-10-24

We show how Up-converted Coherent Population Oscillations (UpCPO) enable to get rid of the intrinsic limitation of the carrier lifetime, leading to the generation of time delays at any high frequencies in a single SOA device. The linear dependence of the RF phase shift with respect to the RF frequency is theoretically predicted and experimentally evidenced at 16 and 35 GHz. © 2011 Optical Society of America

Design and Analysis of Megawatt Class Free Electron Laser Weapons

DTIC Science & Technology

2015-12-01

accelerating structure. The SRF linear accelerator stores RF fields within its niobium cavities. Superconductors require less average RF power than...is needed to cool the superconductor for the SRF linear accelerator. A current outstanding research topic is the RF frequency to use for the SRF

Prototype Control System for Compensation of Superconducting Cavities Detuning Using Piezoelectric Actuators

NASA Astrophysics Data System (ADS)

Przygoda, K.; Piotrowski, A.; Jablonski, G.; Makowski, D.; Pozniak, T.; Napieralski, A.

2009-08-01

Pulsed operation of high gradient superconducting radio frequency (SCRF) cavities results in dynamic Lorentz force detuning (LFD) approaching or exceeding the bandwidth of the cavity of order of a few hundreds of Hz. The resulting modulation of the resonance frequency of the cavity is leading to a perturbation of the amplitude and phase of the accelerating field, which can be controlled only at the expense of RF power. Presently, at various labs, a piezoelectric fast tuner based on an active compensation scheme for the resonance frequency control of the cavity is under study. The tests already performed in the Free Electron Laser in Hamburg (FLASH), proved the possibility of Lorentz force detuning compensation by the means of the piezo element excited with the single period of sine wave prior to the RF pulse. The X-Ray Free Electron Laser (X-FEL) accelerator, which is now under development in Deutsche Elektronen-Synchrotron (DESY), will consists of around 800 cavities with a fast tuner fixture including the actuator/sensor configuration. Therefore, it is necessary to design a distributed control system which would be able to supervise around 25 RF stations, each one comprised of 32 cavities. The Advanced Telecomunications Computing Architecture (ATCA) was chosen to design, develop, and build a Low Level Radio Frequency (LLRF) controller for X-FEL. The prototype control system for Lorentz force detuning compensation was designed and developed. The control applications applied in the system were fitted to the main framework of interfaces and communication protocols proposed for the ATCA-based LLRF control system. The paper presents the general view of a designed control system and shows the first experimental results from the tests carried out in FLASH facility. Moreover, the possibilities for integration of the piezo control system to the ATCA standards are discussed.

Visualization of frequency-modulated electric field based on photonic frequency tracking in asynchronous electro-optic measurement system

NASA Astrophysics Data System (ADS)

Hisatake, Shintaro; Yamaguchi, Koki; Uchida, Hirohisa; Tojyo, Makoto; Oikawa, Yoichi; Miyaji, Kunio; Nagatsuma, Tadao

2018-04-01

We propose a new asynchronous measurement system to visualize the amplitude and phase distribution of a frequency-modulated electromagnetic wave. The system consists of three parts: a nonpolarimetric electro-optic frequency down-conversion part, a phase-noise-canceling part, and a frequency-tracking part. The photonic local oscillator signal generated by electro-optic phase modulation is controlled to track the frequency of the radio frequency (RF) signal to significantly enhance the measurable RF bandwidth. We demonstrate amplitude and phase measurement of a quasi-millimeter-wave frequency-modulated continuous-wave signal (24 GHz ± 80 MHz with a 2.5 ms period) as a proof-of-concept experiment.

Quasi-Optical Network Analyzers and High-Reliability RF MEMS Switched Capacitors

NASA Astrophysics Data System (ADS)

Grichener, Alexander

The thesis first presents a 2-port quasi-optical scalar network analyzer consisting of a transmitter and receiver both built in planar technology. The network analyzer is based on a Schottky-diode mixer integrated inside a planar antenna and fed differentially by a CPW transmission line. The antenna is placed on an extended hemispherical high-resistivity silicon substrate lens. The LO signal is swept from 3-5 GHz and high-order harmonic mixing in both up- and down- conversion mode is used to realize the 15-50 GHz RF bandwidth. The network analyzer resulted in a dynamic range of greater than 40 dB and was successfully used to measure a frequency selective surface with a second-order bandpass response. Furthermore, the system was built with circuits and components for easy scaling to millimeter-wave frequencies which is the primary motivation for this work. The application areas for a millimeter and submillimeter-wave network analyzer include material characterization and art diagnostics. The second project presents several RF MEMS switched capacitors designed for high-reliability operation and suitable for tunable filters and reconfigurable networks. The first switched-capacitor resulted in a digital capacitance ratio of 5 and an analog capacitance ratio of 5-9. The analog tuning of the down-state capacitance is enhanced by a positive vertical stress gradient in the the beam, making it ideal for applications that require precision tuning. A thick electroplated beam resulted in Q greater than 100 at C to X-band frequencies, and power handling of 0.6-1.1 W. The design also minimized charging in the dielectric, resulting in excellent reliability performance even under hot-switched and high power (1 W) conditions. The second switched-capacitor was designed without any dielectric to minimize charging. The device was hot-switched at 1 W of RF power for greater than 11 billion cycles with virtually no change in the C-V curve. The final project presents a 7-channel channelizer based on the mammalian cochlea. The cochlea is an amazing channelizing filter, covering three decades of bandwidth with over 3,000 channels in a very small physical space. Using a simplified mechanical cochlear model and its electrical analogue, a design method is demonstrated for RF and microwave channelizers that retains the desirable features of the cochlea including the ability to cascade a large number of channels (for multiple-octave frequency coverage), and a high-order stop-band rejection. A 6-pole response is synthesized in each channel using the top-C coupled topology. A constant absolute 3 dB bandwidth of around 4.3 MHz and an insertion loss of around 3.9 dB is measured in each channel. A high isolation (greater than 35 dB) is achieved between adjacent channels. A reflection loss of greater than 15 dB is measured at the input port over the entire channelizer bandwidth. Application areas for the demonstrated channelizer include wideband, contiguous-channel receivers for signal intelligence or spectral analysis.

RF priming of a long pulse relativistic magnetron

NASA Astrophysics Data System (ADS)

White, William Michael

Rapid startup, increased pulsewidth and mode locking of magnetrons have been demonstrated experimentally on a relativistic magnetron by radio frequency (RF) priming. Experiments utilize a -300 kV, 2-8 kA, 300-500 ns electron beam to drive a Titan 6-vane relativistic magnetron (˜100 MW output power). The RF priming source is a 100 kW pulsed magnetron operating at 1.27-1.32 GHz. Tuning stubs were utilized in the Titan structure to adjust the operating frequency of the relativistic magnetron pi-mode upward by 30%. The tuning was guided by simulation in the MAGIC 3D code and experimental cold tests including a mapping of the azimuthal electric field inside the relativistic magnetron structure. The most successful tuning geometry was that of a standard anode resonant structure, but RF priming experiments were performed on a rising-sun structure as well. The Time Frequency Analysis (TFA) program was used to directly observe the effects of RF priming on the relativistic magnetron. RF priming was successful in decreasing mode competition by suppressing the generation of the 2pi/3-mode power by 41%. RF priming experiments were also successful in increasing microwave pulsewidth by 12% and decreasing microwave output delay by 22%. These improvements were observed while operating in a priming regime not satisfying Adler's Relation. Overall, the improvements made to the performance of the relativistic magnetron were modest because of the low priming power available (50-250 kW).

Fabrication and radio frequency test of large-area MgB 2 films on niobium substrates

DOE PAGES

Ni, Zhimao; Guo, Xin; Welander, Paul B.; ...

2017-01-19

Magnesium diboride (MgB 2) is a promising candidate material for superconducting radio frequency (RF) cavities because of its higher transition temperature and critical field compared with niobium. To meet the demand of RF test devices, the fabrication of large-area MgB 2 films on metal substrates is needed. Here, in this work, high quality MgB 2 films with 50 mm diameter were fabricated on niobium by using an improved HPCVD system at Peking University, and RF tests were carried out at SLAC National Accelerator Laboratory. The transition temperature is approximately 39.6 K and the RF surface resistance is about 120 μΩmore » at 4 K and 11.4 GHz. Finally, the fabrication processes, surface morphology, DC superconducting properties and RF tests of these large-area MgB 2 films are presented.« less

Fabrication and radio frequency test of large-area MgB 2 films on niobium substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ni, Zhimao; Guo, Xin; Welander, Paul B.

Magnesium diboride (MgB 2) is a promising candidate material for superconducting radio frequency (RF) cavities because of its higher transition temperature and critical field compared with niobium. To meet the demand of RF test devices, the fabrication of large-area MgB 2 films on metal substrates is needed. Here, in this work, high quality MgB 2 films with 50 mm diameter were fabricated on niobium by using an improved HPCVD system at Peking University, and RF tests were carried out at SLAC National Accelerator Laboratory. The transition temperature is approximately 39.6 K and the RF surface resistance is about 120 μΩmore » at 4 K and 11.4 GHz. Finally, the fabrication processes, surface morphology, DC superconducting properties and RF tests of these large-area MgB 2 films are presented.« less

Spin transfer driven resonant expulsion of a magnetic vortex core for efficient rf detector

NASA Astrophysics Data System (ADS)

Menshawy, S.; Jenkins, A. S.; Merazzo, K. J.; Vila, L.; Ferreira, R.; Cyrille, M.-C.; Ebels, U.; Bortolotti, P.; Kermorvant, J.; Cros, V.

2017-05-01

Spin transfer magnetization dynamics have led to considerable advances in Spintronics, including opportunities for new nanoscale radiofrequency devices. Among the new functionalities is the radiofrequency (rf) detection using the spin diode rectification effect in spin torque nano-oscillators (STNOs). In this study, we focus on a new phenomenon, the resonant expulsion of a magnetic vortex in STNOs. This effect is observed when the excitation vortex radius, due to spin torques associated to rf currents, becomes larger than the actual radius of the STNO. This vortex expulsion is leading to a sharp variation of the voltage at the resonant frequency. Here we show that the detected frequency can be tuned by different parameters; furthermore, a simultaneous detection of different rf signals can be achieved by real time measurements with several STNOs having different diameters. This result constitutes a first proof-of-principle towards the development of a new kind of nanoscale rf threshold detector.

Repetitively Pulsed High Power RF Solid-State System

NASA Astrophysics Data System (ADS)

Bowman, Chris; Ziemba, Timothy; Miller, Kenneth E.; Prager, James; Quinley, Morgan

2017-10-01

Eagle Harbor Technologies, Inc. (EHT) is developing a low-cost, fully solid-state architecture for the generation of the RF frequencies and power levels necessary for plasma heating and diagnostic systems at validation platform experiments within the fusion science community. In Year 1 of this program, EHT has developed a solid-state RF system that combines an inductive adder, nonlinear transmission line (NLTL), and antenna into a single system that can be deployed at fusion science experiments. EHT has designed and optimized a lumped-element NLTL that will be suitable RF generation near the lower-hybrid frequency at the High Beta Tokamak (HBT) located at Columbia University. In Year 2, EHT will test this system at the Helicity Injected Torus at the University of Washington and HBT at Columbia. EHT will present results from Year 1 testing and optimization of the NLTL-based RF system. With support of DOE SBIR.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bogdanova, M. A.; Zyryanov, S. M.; Faculty of Physics, Moscow State University, MSU, Moscow

Energy distribution and the flux of the ions coming on a surface are considered as the key-parameters in anisotropic plasma etching. Since direct ion energy distribution (IED) measurements at the treated surface during plasma processing are often hardly possible, there is an opportunity for virtual ones. This work is devoted to the possibility of such indirect IED and ion flux measurements at an rf-biased electrode in low-pressure rf plasma by using a “virtual IED sensor” which represents “in-situ” IED calculations on the absolute scale in accordance with a plasma sheath model containing a set of measurable external parameters. The “virtualmore » IED sensor” should also involve some external calibration procedure. Applicability and accuracy of the “virtual IED sensor” are validated for a dual-frequency reactive ion etching (RIE) inductively coupled plasma (ICP) reactor with a capacitively coupled rf-biased electrode. The validation is carried out for heavy (Ar) and light (H{sub 2}) gases under different discharge conditions (different ICP powers, rf-bias frequencies, and voltages). An EQP mass-spectrometer and an rf-compensated Langmuir probe (LP) are used to characterize plasma, while an rf-compensated retarded field energy analyzer (RFEA) is applied to measure IED and ion flux at the rf-biased electrode. Besides, the pulsed selfbias method is used as an external calibration procedure for ion flux estimating at the rf-biased electrode. It is shown that pulsed selfbias method allows calibrating the IED absolute scale quite accurately. It is also shown that the “virtual IED sensor” based on the simplest collisionless sheath model allows reproducing well enough the experimental IEDs at the pressures when the sheath thickness s is less than the ion mean free path λ{sub i} (s < λ{sub i}). At higher pressure (when s > λ{sub i}), the difference between calculated and experimental IEDs due to ion collisions in the sheath is observed in the low energy range. The effect of electron impact ionization in the sheath on the origin and intensity of low-energy peaks in IED is discussed compared to ion charge-exchange collisions. Obviously, the extrapolation of the “virtual IED sensor” approach to higher pressures requires developing some other sheath models, taking into account both ion and electron collisions and probably including even a model of the whole plasma volume instead of plasma sheath one.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Na; Wu, Yu-Ping; Min, Hao

A radio-frequency (RF) source designed for cold atom experiments is presented. The source uses AD9858, a direct digital synthesizer, to generate the sine wave directly, up to 400 MHz, with sub-Hz resolution. An amplitude control circuit consisting of wideband variable gain amplifier and high speed digital to analog converter is integrated into the source, capable of 70 dB off isolation and 4 ns on-off keying. A field programmable gate array is used to implement a versatile frequency and amplitude co-sweep logic. Owing to modular design, the RF sources have been used on many cold atom experiments to generate various complicatedmore » RF sequences, enriching the operation schemes of cold atoms, which cannot be done by standard RF source instruments.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, R.; Lu, R.; Gong, S.

We demonstrate a room-temperature semiconductor-based photodetector where readout is achieved using a resonant radio-frequency (RF) circuit consisting of a microstrip split-ring resonator coupled to a microstrip busline, fabricated on a semiconductor substrate. The RF resonant circuits are characterized at RF frequencies as function of resonator geometry, as well as for their response to incident IR radiation. The detectors are modeled analytically and using commercial simulation software, with good agreement to our experimental results. Though the detector sensitivity is weak, the detector architecture offers the potential for multiplexing arrays of detectors on a single read-out line, in addition to high speedmore » response for either direct coupling of optical signals to RF circuitry, or alternatively, carrier dynamics characterization of semiconductor, or other, material systems.« less

SU-E-T-558: An Exploratory RF Pulse Sequence Technique Used to Induce Differential Heating in Tissues Containing Iron Oxide Nanoparticles for a Possible Hyperthermic Adjuvant Effect to Radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yee, S; Ionascu, D; Wilson, G

2014-06-01

Purpose: In pre-clinical trials of cancer thermotherapy, hyperthermia can be induced by exposing localized super-paramagnetic iron oxide nanoparticles (SPION) to external alternating magnetic fields generated by a solenoid electrical circuit (Zhao et al., Theranostics 2012). Alternatively, an RF pulse technique implemented in a regular MRI system is explored as a possible hyperthermia induction technique . Methods: A new thermal RF pulse sequence was developed using the Philips pulse programming tool for the 3T Ingenia MRI system to provide a sinusoidal magnetic field alternating at the frequency of 1.43 kHz (multiples of sine waves of 0.7 ms period) before each excitationmore » RF pulse for imaging. The duration of each thermal RF pulse routine was approximately 3 min, and the thermal pulse was applied multiple times to a phantom that contains different concentrations (high, medium and low) of SPION samples. After applying the thermal pulse each time, the temperature change was estimated by measuring the phase changes in the T1-weighted inversion-prepared multi-shot turbo field echo (TFE) sequence (TR=5.5 ms, TE=2.7 ms, inversion time=200 ms). Results: The phase values and relative differences among them changed as the number of applied thermal RF pulses increased. After the 5th application of the thermal RF pulse, the relative phase differences increased significantly, suggesting the thermal activation of the SPION. The increase of the phase difference was approximately linear with the SPION concentration. Conclusion: A sinusoidal RF pulse from the MRI system may be utilized to selectively thermally activate tissues containing super-paramagnetic iron oxide nanoparticles.« less

Telemetry Standards, RCC Standard 106-17. Chapter 21. Telemetry Network Standard Introduction

DTIC Science & Technology

2017-07-01

Critical RF radio frequency RFC Request for Comment SNMP Simple Network Management Protocol TA test article TCP Transmission Control Protocol...chapters might be of most interest for a particular reader. In order to guide the reader toward the chapters of further interest , the applicable... Simple Network Management Protocol (SNMP) to pass management information through the system. The SNMP management information bases (MIBs) provide

Detection of NMR signals with a radio-frequency atomic magnetometer.

PubMed

Savukov, I M; Seltzer, S J; Romalis, M V

2007-04-01

We demonstrate detection of proton NMR signals with a radio-frequency (rf) atomic magnetometer tuned to the NMR frequency of 62 kHz. High-frequency operation of the atomic magnetometer makes it relatively insensitive to ambient magnetic field noise. We obtain magnetic field sensitivity of 7 fT/Hz1/2 using only a thin aluminum shield. We also derive an expression for the fundamental sensitivity limit of a surface inductive pick-up coil as a function of frequency and find that an atomic rf magnetometer is intrinsically more sensitive than a coil of comparable size for frequencies below about 50 MHz.

The dielectric properties of human pineal gland tissue and RF absorption due to wireless communication devices in the frequency range 400-1850 MHz.

PubMed

Schmid, Gernot; Uberbacher, Richard; Samaras, Theodoros; Tschabitscher, Manfred; Mazal, Peter R

2007-09-07

In order to enable a detailed analysis of radio frequency (RF) absorption in the human pineal gland, the dielectric properties of a sample of 20 freshly removed pineal glands were measured less than 20 h after death. Furthermore, a corresponding high resolution numerical model of the brain region surrounding the pineal gland was developed, based on a real human tissue sample. After inserting this model into a commercially available numerical head model, FDTD-based computations for exposure scenarios with generic models of handheld devices operated close to the head in the frequency range 400-1850 MHz were carried out. For typical output power values of real handheld mobile communication devices, the obtained results showed only very small amounts of absorbed RF power in the pineal gland when compared to SAR limits according to international safety standards. The highest absorption was found for the 400 MHz irradiation. In this case the RF power absorbed inside the pineal gland (organ mass 96 mg) was as low as 11 microW, when considering a device of 500 mW output power operated close to the ear. For typical mobile phone frequencies (900 MHz and 1850 MHz) and output power values (250 mW and 125 mW) the corresponding values of absorbed RF power in the pineal gland were found to be lower by a factor of 4.2 and 36, respectively. These results indicate that temperature-related biologically relevant effects on the pineal gland induced by the RF emissions of typical handheld mobile communication devices are unlikely.

Hybrid simulations of solenoidal radio-frequency inductively coupled hydrogen discharges at low pressures

NASA Astrophysics Data System (ADS)

Yang, Wei; Li, Hong; Gao, Fei; Wang, You-Nian

2016-12-01

In this article, we have described a radio-frequency (RF) inductively coupled H2 plasma using a hybrid computational model, incorporating the Maxwell equations and the linear part of the electron Boltzmann equation into global model equations. This report focuses on the effects of RF frequency, gas pressure, and coil current on the spatial profiles of the induced electric field and plasma absorption power density. The plasma parameters, i.e., plasma density, electron temperature, density of negative ion, electronegativity, densities of neutral species, and dissociation degree of H2, as a function of absorption power, are evaluated at different gas pressures. The simulation results show that the utilization efficiency of the RF source characterized by the coupling efficiency of the RF electric field and power to the plasma can be significantly improved at the low RF frequency, gas pressure, and coil current, due to a low plasma density in these cases. The densities of vibrational states of H2 first rapidly increase with increasing absorption power and then tend to saturate. This is because the rapidly increased dissociation degree of H2 with increasing absorption power somewhat suppresses the increase of the vibrational states of H2, thus inhibiting the increase of the H-. The effects of absorption power on the utilization efficiency of the RF source and the production of the vibrational states of H2 should be considered when setting a value of the coil current. To validate the model simulations, the calculated electron density and temperature are compared with experimental measurements, and a reasonable agreement is achieved.

Phase stable RF transport system

DOEpatents

Curtin, Michael T.; Natter, Eckard F.; Denney, Peter M.

1992-01-01

An RF transport system delivers a phase-stable RF signal to a load, such as an RF cavity of a charged particle accelerator. A circuit generates a calibration signal at an odd multiple frequency of the RF signal where the calibration signal is superimposed with the RF signal on a common cable that connects the RF signal with the load. Signal isolating diplexers are located at both the RF signal source end and load end of the common cable to enable the calibration to be inserted and extracted from the cable signals without any affect on the RF signal. Any phase shift in the calibration signal during traverse of the common cable is then functionally related to the phase shift in the RF signal. The calibration phase shift is used to control a phase shifter for the RF signal to maintain a stable RF signal at the load.

Novel remote sensor systems: design, prototyping, and characterization

NASA Astrophysics Data System (ADS)

Kayastha, V.; Gibbons, S.; Lamb, J. E.; Giedd, R. E.

2014-06-01

We have designed and tested a prototype TRL4 radio-frequency (RF) sensing platform containing a transceiver that interrogates a passive carbon nanotube (CNT)-based sensor platform. The transceiver can be interfaced to a server technology such as a Bluetooth® or Wi-Fi device for further connectivity. The novelty of a very-low-frequency (VLF) implementation in the transceiver design will ultimately enable deep penetration into the ground or metal structures to communicate with buried sensing platforms. The sensor platform generally consists of printed electronic devices made of CNTs on flexible poly(ethylene terephthalate) (PET) and Kapton® substrates. This novel remote sensing system can be integrated with both passive and active sensing platforms. It offers unique characteristics suitable for a variety of sensing applications. The proposed sensing platforms can take on different form factors and the RF output of the sensing platforms could be modulated by humidity, temperature, pressure, strain, or vibration signals. Resonant structures were designed and constructed to operate in the very-high-frequency (VHF) and VLF ranges. In this presentation, we will report results of our continued effort to develop a commercially viable transceiver capable of interrogating the conformally mounted sensing platforms made from CNTs or silver-based nanomaterials on polyimide substrates over a broad range of frequencies. The overall performance of the sensing system with different sensing elements and at different frequency ranges will be discussed.

Injection locking of optomechanical oscillators via acoustic waves

NASA Astrophysics Data System (ADS)

Huang, Ke; Hossein-Zadeh, Mani

2018-04-01

Injection locking is a powerful technique for synchronization of oscillator networks and controlling the phase and frequency of individual oscillators using similar or other types of oscillators. Here, we present the first demonstration of injection locking of a radiation-pressure driven optomechanical oscillator (OMO) via acoustic waves. As opposed to previously reported techniques (based on pump modulation or direct application of a modulated electrostatic force), injection locking of OMO via acoustic waves does not require optical power modulation or physical contact with the OMO and it can easily be implemented on various platforms. Using this approach we have locked the phase and frequency of two distinct modes of a microtoroidal silica OMO to a piezoelectric transducer (PZT). We have characterized the behavior of the injection locked OMO with three acoustic excitation configurations and showed that even without proper acoustic impedance matching the OMO can be locked to the PZT and tuned over 17 kHz with only -30 dBm of RF power fed to the PZT. The high efficiency, simplicity and scalability of the proposed approach paves the road toward a new class of photonic systems that rely on synchronization of several OMOs to a single or multiple RF oscillators with applications in optical communication, metrology and sensing. Beyond its practical applications, injection locking via acoustic waves can be used in fundamental studies in quantum optomechanics where thermal and optical isolation of the OMO are critical.

8.0-Tesla human MR system: temperature changes associated with radiofrequency-induced heating of a head phantom.

PubMed

Kangarlu, Allahyar; Shellock, Frank G; Chakeres, Donald W

2003-02-01

To investigate if the heat induced in biological tissues by typical radio frequency (RF) energy associated with an 8.0-Tesla magnetic resonance (MR) system causes excessive temperature changes. Fluoroptic thermometry was used to measure temperatures in multiple positions in a head phantom made of ground turkey breast. A series of experiments were conducted with measurements obtained at RF power levels ranging from a specific absorption rate (SAR) of up to 4.0 W/kg for 10 minutes. The highest temperature increases were up to 0.7 degrees C. An inhomogeneous heating pattern was observed. In general, the deep regions within the phantom registered higher temperature increases compared to the peripheral sites. The expectation of an inhomogeneous RF distribution in ultra high field systems (> 4 T) was confirmed. At a frequency of 340 MHz and in-tissue RF wave length of about 10 cm, the RF inhomogeneity was measured to create higher temperatures in deeper regions of a human head phantom compared to peripheral tissues. Our results agree with the computational electromagnetic calculations for such frequencies. Importantly, these experiments indicated that there were no regions of heating that exceeded the current FDA guidelines. Copyright 2003 Wiley-Liss, Inc.

Static current-voltage characteristics for radio-frequency induction discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Budyansky, A.; Zykov, A.

1995-12-31

The aim of this work was to obtain experimentally such characteristic of Radio-Frequency Induction Discharge (RFID) that can play the role of its current-voltage characteristic (CVC) and to explain the nature of current and voltage jumps arising in RF coils at exciting of discharge. Experiments were made in quartz 5.5, 11, 20 cm diam tubes with outer RF coil at pressures 10--100 mTorr, at frequency 13.56 MHz and discharge power to 500 W. In case of outer coil as analogue of discharge voltage it`s convenient to use the value of the RF voltage U{sub R}, induced around outer perimeter ofmore » discharge tube. It is evident that current and voltage jumps arising at exciting of discharge are due to low output resistance of standard generators and negative slope of initial part of CVC. Three sets of such dependencies for different pressures were obtained for each diameter of tubes. The influence of different metal electrodes placed into discharge volume on CVC`s shape has been studied also. Experimental results can explain the behavior of HFI discharge as a load of RF generator and give data for calculation of RF circuit.« less

Signal Digitizer and Cross-Correlation Application Specific Integrated Circuit

NASA Technical Reports Server (NTRS)

Baranauskas, Gytis (Inventor); Lim, Boon H. (Inventor); Baranauskas, Dalius (Inventor); Zelenin, Denis (Inventor); Kangaslahti, Pekka (Inventor); Tanner, Alan B. (Inventor)

2017-01-01

According to one embodiment, a cross-correlator comprises a plurality of analog front ends (AFEs), a cross-correlation circuit and a data serializer. Each of the AFEs comprises a variable gain amplifier (VGA) and a corresponding analog-to-digital converter (ADC) in which the VGA receives and modifies a unique analog signal associates with a measured analog radio frequency (RF) signal and the ADC produces digital data associated with the modified analog signal. Communicatively coupled to the AFEs, the cross-correlation circuit performs a cross-correlation operation on the digital data produced from different measured analog RF signals. The data serializer is communicatively coupled to the summing and cross-correlating matrix and continuously outputs a prescribed amount of the correlated digital data.

A compact spin-exchange optical pumping system for 3He polarization based on a solenoid coil, a VBG laser diode, and a cosine theta RF coil

NASA Astrophysics Data System (ADS)

Lee, Sungman; Kim, Jongyul; Moon, Myung Kook; Lee, Kye Hong; Lee, Seung Wook; Ino, Takashi; Skoy, Vadim R.; Lee, Manwoo; Kim, Guinyun

2013-02-01

For use as a neutron spin polarizer or analyzer in the neutron beam lines of the HANARO (High-flux Advanced Neutron Application ReactOr) nuclear research reactor, a 3He polarizer was designed based on both a compact solenoid coil and a VBG (volume Bragg grating) diode laser with a narrow spectral linewidth of 25 GHz. The nuclear magnetic resonance (NMR) signal was measured and analyzed using both a built-in cosine radio-frequency (RF) coil and a pick-up coil. Using a neutron transmission measurement, we estimated the polarization ratio of the 3He cell as 18% for an optical pumping time of 8 hours.

Characterization of a Prototype Radio Frequency Space Environment Path Emulator for Evaluating Spacecraft Ranging Hardware

NASA Technical Reports Server (NTRS)

Mitchell, Jason W.; Baldwin, Philip J.; Kurichh, Rishi; Naasz, Bo J.; Luquette, Richard J.

2007-01-01

The Formation Flying Testbed (FFTB) at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) provides a hardware-in-the-loop test environment for formation navigation and control. The facility is evolving as a modular, hybrid, dynamic simulation facility for end-to-end guidance, navigation and control (GN&C) design and analysis of formation flying spacecraft. The core capabilities of the FFTB, as a platform for testing critical hardware and software algorithms in-the-loop, have expanded to include S-band Radio Frequency (RF) modems for interspacecraft communication and ranging. To enable realistic simulations that require RF ranging sensors for relative navigation, a mechanism is needed to buffer the RF signals exchanged between spacecraft that accurately emulates the dynamic environment through which the RF signals travel, including the effects of the medium, moving platforms, and radiated power. The Path Emulator for Radio Frequency Signals (PERFS), currently under development at NASA GSFC, provides this capability. The function and performance of a prototype device are presented.

Precision phase control for the radio frequency system of K500 superconducting cyclotron at Variable Energy Cyclotron Centre, Kolkata

DOE Office of Scientific and Technical Information (OSTI.GOV)

Som, Sumit; Ghosh, Surajit; Seth, Sudeshna

2013-11-15

Variable Energy Cyclotron Centre (VECC) has commissioned K500 Superconducting cyclotron (SCC) based on MSU and Texas A and M university cyclotrons. The radio frequency (RF) system of SCC has been commissioned with the stringent requirement of various RF parameters. The three-phase RF system of Superconducting cyclotron has been developed in the frequency range 9–27 MHz with amplitude and phase stability of 100 ppm and ±0.1°, respectively. The phase control system has the option to change the relative phase difference between any two RF cavities and maintain the phase stability within ±0.1° during round-the-clock cyclotron operation. The said precision phase loopmore » consists of both analogue In-phase/Quadrature modulator to achieve faster response and also Direct Digital Synthesis based phase shifter to achieve wide dynamic range as well. This paper discusses detail insights into the various issues of phase control for the K500 SCC at VECC, Kolkata.« less

Membrane Shell Reflector Segment Antenna

NASA Technical Reports Server (NTRS)

Fang, Houfei; Im, Eastwood; Lin, John; Moore, James

2012-01-01

The mesh reflector is the only type of large, in-space deployable antenna that has successfully flown in space. However, state-of-the-art large deployable mesh antenna systems are RF-frequency-limited by both global shape accuracy and local surface quality. The limitations of mesh reflectors stem from two factors. First, at higher frequencies, the porosity and surface roughness of the mesh results in loss and scattering of the signal. Second, the mesh material does not have any bending stiffness and thus cannot be formed into true parabolic (or other desired) shapes. To advance the deployable reflector technology at high RF frequencies from the current state-of-the-art, significant improvements need to be made in three major aspects: a high-stability and highprecision deployable truss; a continuously curved RF reflecting surface (the function of the surface as well as its first derivative are both continuous); and the RF reflecting surface should be made of a continuous material. To meet these three requirements, the Membrane Shell Reflector Segment (MSRS) antenna was developed.

BICMOS power detector for pulsed Rf power amplifiers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bridge, Clayton D.

2016-10-01

A BiCMOS power detector for pulsed radio-frequency power amplifiers is proposed. Given the pulse waveform and a fraction of the power amplifier's input or output signal, the detector utilizes a low-frequency feedback loop to perform a successive approximation of the amplitude of the input signal. Upon completion of the successive approximation, the detector returns 9-bits representing the amplitude of the RF input signal. Using the pulse waveform from the power amplifier, the detector can dynamically adjust the rate of the binary search operation in order to return the updated amplitude information of the RF input signal at least every 1ms.more » The detector can handle pulse waveform frequencies from 50kHz to 10MHz with duty cycles in the range of 5- 50% and peak power levels of -10 to 10dBm. The signal amplitude measurement can be converted to a peak power measurement accurate to within ±0.6dB of the input RF power.« less

Investigation of high sensitivity radio-frequency readout circuit based on AlGaN/GaN high electron mobility transistor

NASA Astrophysics Data System (ADS)

Zhang, Xiao-Yu; Tan, Ren-Bing; Sun, Jian-Dong; Li, Xin-Xing; Zhou, Yu; Lü, Li; Qin, Hua

2015-10-01

An AlGaN/GaN high electron mobility transistor (HEMT) device is prepared by using a semiconductor nanofabrication process. A reflective radio-frequency (RF) readout circuit is designed and the HEMT device is assembled in an RF circuit through a coplanar waveguide transmission line. A gate capacitor of the HEMT and a surface-mounted inductor on the transmission line are formed to generate LC resonance. By tuning the gate voltage Vg, the variations of gate capacitance and conductance of the HEMT are reflected sensitively from the resonance frequency and the magnitude of the RF reflection signal. The aim of the designed RF readout setup is to develop a highly sensitive HEMT-based detector. Project supported by the National Natural Science Foundation of China (Grant No. 61107093), the Suzhou Science and Technology Project, China (Grant No. ZXG2012024), and the Youth Innovation Promotion Association, Chinese Academy of Sciences (Grant No. 2012243).

RF Bearing Estimation in Wireless Sensor Networks

DTIC Science & Technology

2010-01-01

are the main design drivers. Techniques based on ultrasonic and infrared signal modalities have short range and require line-of-sight. Clearly, RF...generating a Doppler shifted RF signal . The small frequency change can be measured even on low cost resource constrained nodes using a radio...is already included in the power budget and RF range is superior to most other signals . Radio signal strength (RSS) based approaches are the most