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1

Radio-frequency energy in fusion power generation  

SciTech Connect

The history of radio-frequency (rf) energy in fusion experiments is reviewed, and the status of current efforts is described. Potential applications to tasks other than plasma heating are described, as are the research and development needs of rf energy technology.

Lawson, J.Q.; Becraft, W.R.; Hoffman, D.J.

1983-01-01

2

Digital avionics susceptibility to high energy radio frequency fields  

NASA Technical Reports Server (NTRS)

Generally, noncritical avionic systems for transport category aircraft have been designed to meet radio frequency (RF) susceptibility requirements set forth in RTCA DO 160B, environmental conditions and test procedures for airborne equipment. Section 20 of this document controls the electromagnetic interference (EMI) hardening for avionics equipment to levels of 1 and 2 V/m. Currently, US equipment manufacturers are designing flight-critical fly-by-wire avionics to a much higher level. The US Federal Aviation Administration (FAA) has requested that the RTCA SC-135 high-energy radio frequency (HERF) working group develop appropriate testing procedures for section 20 of RTCA DO 160B for radiated and conducted susceptibility at the box and systems level. The FAA has also requested the SAE AE4R committee to address installed systems testing, airframe shielding effects and RF environment monitoring. Emitters of interest include radar (ground, ship, and aircraft) commercial broadcast and TV station, mobile communication, and other transmitters that could possibly affect commercial aircraft.

Larsen, William E.

1988-01-01

3

Low energy booster radio frequency cavity structural analysis  

SciTech Connect

The structural design of the Superconducting Super Collider Low Energy Booster (LEB) Radio Frequency (RF) Cavity is very unique. The cavity is made of three different materials which all contribute to its structural strength while at the same time providing a good medium for magnetic properties. Its outer conductor is made of thin walled stainless steel which is later copper plated to reduce the electrical losses. Its tuner housing is made of a fiber reinforced composite laminate, similar to G10, glued to stainless steel plating. The stainless steel of the tuner is slotted to significantly diminish the magnetically-induced eddy currents. The composite laminate is bonded to the stainless steel to restore the structural strength that was lost in slotting. The composite laminate is also a barrier against leakage of the pressurized internal ferrite coolant fluid. The cavity's inner conductor, made of copper and stainless steel, is subjected to high heat loads and must be liquid cooled. The requirements of the Cavity are very stringent and driven primarily by deflection, natural frequency and temperature. Therefore, very intricate finite element analysis was used to complement conventional hand analysis in the design of the cavity. Structural testing of the assembled prototype cavity is planned to demonstrate the compliance of the cavity design to all of its requirements.

Jones, K.

1993-04-01

4

Low energy booster radio frequency cavity structural analysis  

SciTech Connect

The structural design of the Superconducting Super Collider Low Energy Booster (LEB) Radio Frequency (RF) Cavity is very unique. The cavity is made of three different materials which all contribute to its structural strength while at the same time providing a good medium for magnetic properties. Its outer conductor is made of thin walled stainless steel which is later copper plated to reduce the electrical losses. Its tuner housing is made of a fiber reinforced composite laminate, similar to G10, glued to stainless steel plating. The stainless steel of the tuner is slotted to significantly diminish the magnetically-induced eddy currents. The composite laminate is bonded to the stainless steel to restore the structural strength that was lost in slotting. The composite laminate is also a barrier against leakage of the pressurized internal ferrite coolant fluid. The cavity`s inner conductor, made of copper and stainless steel, is subjected to high heat loads and must be liquid cooled. The requirements of the Cavity are very stringent and driven primarily by deflection, natural frequency and temperature. Therefore, very intricate finite element analysis was used to complement conventional hand analysis in the design of the cavity. Structural testing of the assembled prototype cavity is planned to demonstrate the compliance of the cavity design to all of its requirements.

Jones, K.

1993-04-01

5

Radio-frequency and microwave energies, magnetic and electric fields  

NASA Technical Reports Server (NTRS)

The biological effects of radio frequency, including microwave, radiation are considered. Effects on body temperature, the eye, reproductive systems, internal organs, blood cells, the cardiovascular system, and the central nervous system are included. Generalized effects of electric and magnetic fields are also discussed. Experimentation with animals and clinical studies on humans are cited, and possible mechanisms of the effects observed are suggested.

Michaelson, S. M.

1975-01-01

6

Radio frequency detection assembly and method for detecting radio frequencies  

DOEpatents

A radio frequency detection assembly is described and which includes a radio frequency detector which detects a radio frequency emission produced by a radio frequency emitter from a given location which is remote relative to the radio frequency detector; a location assembly electrically coupled with the radio frequency detector and which is operable to estimate the location of the radio frequency emitter from the radio frequency emission which has been received; and a radio frequency transmitter electrically coupled with the radio frequency detector and the location assembly, and which transmits a radio frequency signal which reports the presence of the radio frequency emitter.

Cown, Steven H. (Rigby, ID); Derr, Kurt Warren (Idaho Falls, ID)

2010-03-16

7

The Frequency Spectrum Radio.  

ERIC Educational Resources Information Center

This journal issue focuses on the frequency spectrum used in radio communication and on the World Administrative Radio Conference, sponsored by the International Telecommunication Union, held in Geneva, Switzerland, in the fall of 1979. Articles describe the World Administrative Radio Conference as the most important radio communication conference…

Howkins, John, Ed.

1979-01-01

8

Radio Link Frequency Assignment  

Microsoft Academic Search

Abstract: The problem of radio frequency assignment is to provide communication channelsfrom limited spectral resources whilst keeping to a minimum the interference suered by thosewhishing to communicate in a given radio communication network. This problem is a combinatorial(NP-hard) optimization problem. In 1993, the CELAR (the French \\\\Centre d'Electronique del'Armement") built a suite of simplied versions of Radio Link Frequency Assignment

Bertrand Cabon; Simon De Givry; Lionel Lobjois; Thomas Schiex; Joost P. Warners

1999-01-01

9

Stabilized radio frequency quadrupole  

DOEpatents

A long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator.

Lancaster, Henry D. (Orinda, CA); Fugitt, Jock A. (Berkeley, CA); Howard, Donald R. (Danville, CA)

1984-01-01

10

Physiological interaction processes and radio-frequency energy absorption.  

PubMed

Because exposure to microwave fields at the resonant frequency may generate heat deep in the body, hyperthermia may result. This problem has been examined in an animal model to determine both the thresholds for response change and the steady-state thermoregulatory compensation for body heating during exposure at resonant (450 MHz) and supra-resonant (2,450 MHz) frequencies. Adult male squirrel monkeys, held in the far field of an antenna within an anechoic chamber, were exposed (10 min or 90 min) to either 450-MHz or 2,450-MHz CW fields (E polarization) in cool environments. Whole-body SARs ranged from 0-6 W/kg (450 MHz) and 0-9 W/kg (2,450 MHz). Colonic and several skin temperatures, metabolic heat production, and evaporative heat loss were monitored continuously. During brief RF exposures in the cold, the reduction of metabolic heat production was directly proportional to the SAR, but 2,450-MHz energy was a more efficient stimulus than was the resonant frequency. In the steady state, a regulated increase in deep body temperature accompanied exposure at resonance, not unlike that which occurs during exercise. Detailed analyses of the data indicate that temperature changes in the skin are the primary source of the neural signal for a change in physiological interaction processes during RF exposure in the cold. PMID:1482414

Adair, E R; Adams, B W; Hartman, S K

1992-01-01

11

Calibration of electromagnetic calorimeters in high energy experiments with a Radio Frequency Quadrupole accelerator  

Microsoft Academic Search

A fast, effective calibration technique has been developed for future Superconducting Supercollider (SSC) calorimeters based upon the radiative capture of protons from a pulsed Radio Frequency Quadrupole (RFQ) accelerator in a fluoride target. The intense flux of low energy photons acts as a clean ``pulse generator'' calibration signal equivalent to 20 GeV or more. This calibration technique has been demonstrated

H. Ma; H. Newman; R. Y. Zhu; R. Hamm

1989-01-01

12

Radio frequency picosecond phototube  

SciTech Connect

We propose a photon detector for recording low-level and ultra-fast optical signals, based on radio frequency (RF) analysis of low-energy photoelectrons (PEs). By using currently developed 500 MHz RF deflector, it is possible to scan circularly and detect single PEs, amplified in multi-channel plates (MCPs). The operation of the tube is investigated by means of thermionic electron source. It is demonstrated that the signals generated in the MCP can be processed event by event; by using available nanosecond electronics and that time resolution better than 20 ps can be achieved. Timing characteristics of the Cherenkov detector with RF phototube in a ''head-on'' geometry is investigated by means of Monte Carlo simulation.

A. Margaryan; R. Carlini; R. Ent; N. Grigoryan; K. Gyunashyan; O. Hashimoto; K. Hovater; M. Ispiryan; S. Knyazyan; B. Kross; S. Majewski; G. Marikyan; M. Mkrtchyan; L. Parlakyan; V. Popov; L. Tang; H. Vardanyan; C. Yan; S. Zhamkochyan; C. Zorn

2006-10-01

13

Energy Distribution of Ions Incident on Radio-Frequency Biased Electrodes in External Magnetic Field  

NASA Astrophysics Data System (ADS)

A radio-frequency (rf) plasma sheath model in an oblique magnetic field is established and the energy distribution of ions (IED) incident on the rf sheath biased electrodes is numerically investigated. The simulation results reveal that the external magnetic field can have a decisive impact on the ion flux and energy distribution of the sheath. The ion energy can be transferred between the perpendicular and parallel components under the action of a magnetic field.

Zou, Xiu; Feng, Xiaobing; Qiu, Minghui; Liu, Jinyuan; Gong, Ye

2010-02-01

14

Optimized trigger for ultra-high-energy cosmic-ray and neutrino observations with the low frequency radio array  

Microsoft Academic Search

When an ultra-high energy neutrino or cosmic-ray strikes the Lunar surface a radio-frequency pulse is emitted. We plan to use the LOFAR radio telescope to detect these pulses. In this work we propose an efficient trigger implementation for LOFAR optimized for the observation of short radio pulses.

K. Singh; M. Mevius; O. Scholten; J. M. Anderson; A. van Ardenne; M. Arts; M. Avruch; A. Asgekar; M. Bell; P. Bennema; M. Bentum; G. Bernadi; P. Best; A.-J. Boonstra; J. Bregman; R. van de Brink; C. Broekema; W. Brouw; M. Brueggen; S. Buitink; H. Butcher; W. van Cappellen; B. Ciardi; A. Coolen; S. Damstra; R. Dettmar; G. van Diepen; K. Dijkstra; P. Donker; A. Doorduin; M. Drost; A. van Duin; J. Eisloeffel; H. Falcke; M. Garrett; M. Gerbers; J. Griessmeier; T. Grit; P. Gruppen; A. Gunst; M. van Haarlem; M. Hoeft; H. Holties; J. H orandel; L. A. Horneffer; A. Huijgen; C. James; A. de Jong; D. Kant; E. Kooistra; Y. Koopman; L. Koopmans; G. Kuper; P. Lambropoulos; J. van Leeuwen; M. Loose; P. Maat; C. Mallary; R. McFadden; H. Meulman; J.-D. Mol; J. Morawietz; E. Mulder; H. Munk; L. Nieuwenhuis; R. Nijboer; M. J. Norden; J. Noordam; R. Overeem; H. Paas; V. N. Pandey; M. Pandey-Pommier; R. Pizzo; A. Polatidis; W. Reich; J. de Reijer; A. Renting; P. Riemers; H. Roettgering; J. Romein; J. Roosjen; M. Ruiter; A. Schoenmakers; G. Schoonderbeek; J. Sluman; O. Smirnov; B. Stappers; M. Steinmetz; H. Stiepel; K. Stuurwold; M. Tagger; Y. Tang; S. ter Veen; R. Vermeulen; M. de Vos; C. Vogt; E. van der Wal; H. Weggemans; S. Wijnholds; M. Wise; O. Wucknitz; S. Yattawatta; J. van Zwieten

2011-01-01

15

Energy harvesting of radio frequency and vibration energy to enable wireless sensor monitoring of civil infrastructure  

NASA Astrophysics Data System (ADS)

To power distributed wireless sensor networks on bridges, traditional power cables or battery replacement are excessively expensive or infeasible. This project develops two power harvesting technologies. First, a novel parametric frequency-increased generator (PFIG) is developed. The fabricated PFIG harvests the non-periodic and unprecedentedly low frequency (DC to 30 Hz) and low acceleration (0.55-9.8 m/s2) mechanical energy available on bridges with an average power > 2 ?W. Prototype power conversion and storage electronics were designed and the harvester system was used to charge a capacitor from arbitrary bridge-like vibrations. Second, an RF scavenger operating at medium and shortwave frequencies has been designed and tested. Power scavenging at MHz frequencies allows for lower antenna directivities, reducing sensitivity to antenna positioning. Furthermore, ambient RF signals at these frequencies have higher power levels away from cities and residential areas compared to the UHF and SHF bands utilized for cellular communication systems. An RF power scavenger operating at 1 MHz along with power management and storage circuitry has been demonstrated. It powers a LED at a distance of 10 km from AM radio stations.

Galchev, Tzeno; McCullagh, James; Peterson, Rebecca L.; Najafi, Khalil; Mortazawi, Amir

2011-03-01

16

Radio frequency identification (RFID)  

Microsoft Academic Search

First conceived in 1948, Radio Frequency Identification (RFID) has taken many years for the technology to mature to the point where it is sufficiently affordable and reliable for widespread use. From Electronic Article Surveillance (EAS) for article (mainly clothing) security to more sophisticated uses, RFID is seen by some as the inevitable replacement for bar codes. With increasing use comes

C. M. Roberts

2006-01-01

17

Thermal chondroplasty: effect of bipolar and monopolar radio frequency energy  

NASA Astrophysics Data System (ADS)

Cartilage fibrillation is commonly associated with injury and long-term degeneration. Contouring the articular surface with radiofrequency energy (RFE) may stabilize the surface, and improve clinical function, but subchondral bone injury has been reported in some patients. The purpose of this research was to document the effects of bipolar and monopolar RFE on articular cartilage. Bipolar RFE and monopolar RFE treatment of abraded bovine cartilage was investigated in an in vitro model. Bipolar RFE caused greater chondrocyte death than monopolar RFE, (bipolar RFE: 1700-mm; monopolar RFE: 800-mm) (p<0.05). Both bipolar RFE and monopolar RFE contoured the articular surface but the depth of chondrocyte death raised concerns regarding the clinical application of RFE. Further work investigated the arthroscopic application of bipolar RFE and monopolar RFE on human chondromalacic cartilage in vitro. Both devices smoothed the fibrillated surface, but bipolar RFE caused increased depth of chondrocyte death compared to monopolar RFE (bipolar RFE 2100-mm; monopolar RFE 620-mm (p<0.05). Fluoroptic thermometry has demonstrated cartilage matrix temperatures exceeding 70° C 2-mm below the articular surface during the application of bipolar RFE. The clinical use of the bipolar RFE systems available to date will likely result in unacceptable chondrocyte death and subchondral injury. While RFE demonstrates some promise for the management of cartilage injury, further work must be completed to define the parameters for its application.

Edwards, Ryland B.; Lu, Yan; Cole, Brian J.; Markel, Mark D.

2001-06-01

18

Radio frequency strain monitor  

NASA Technical Reports Server (NTRS)

A radio frequency strain monitor includes a voltage controlled oscillator for generating an oscillating signal that is input into a propagation path. The propagation path is preferably bonded to the surface of a structure to be monitored and produces a propagated signal. A phase difference between the oscillating and propagated signals is detected and maintained at a substantially constant value which is preferably a multiple of 90.degree. by changing the frequency of the oscillating signal. Any change in frequency of the oscillating signal provides an indication of strain in the structure to which the propagation path is bonded.

Heyman, Joseph S. (Inventor); Rogowski, Robert S. (Inventor); Holben, Jr., Milford S. (Inventor)

1989-01-01

19

Radio Frequency Interference Mitigation in Radio Astronomy.  

National Technical Information Service (NTIS)

The next generation of radio telescopes is expected to be one to two orders of magnitude more sensitive than the current generation. Examples of such new telescopes are the Low Frequency Array (LOFAR), currently under construction in the Netherlands, and ...

A. J. Boonstra

2005-01-01

20

Radio frequency pulse compression  

SciTech Connect

High gradients require peak powers. One possible way to generate high peak powers is to generate a relatively long pulse at a relatively low power and compress it into a shorter pulse with higher peak power. It is possible to compress before dc to rf conversion as is done for the relativistic klystron or after dc to rf conversion as is done with SLED. In this note only radio frequency pulse compression (RFPC) is considered. Three methods of RFPC will be discussed: SLED, BEC, and REC. 3 refs., 8 figs., 1 tab.

Farkas, Z.D.

1988-12-01

21

Beam Emittance Measurements for the Low-Energy Demonstration Accelerator Radio-Frequency Quadrupole  

Microsoft Academic Search

The Low-Energy Demonstration Accelerator (LEDA) radio-frequency quadrupole\\u000a(RFQ) is a 100% duty factor (CW) linac that delivers >100 mA of H+ beam at 6.7\\u000aMeV. The 8-m-long, 350-MHz RFQ structure accelerates a dc, 75-keV, 110-mA H+\\u000abeam from the LEDA injector with >90% transmission. LEDA [1,2] consists of a\\u000a75-keV proton injector, 6.7-MeV, 350-MHz CW RFQ with associated high-power and

J. D. Gilpatrick; W. P. Lysenko; L. J. Rybarcyk; J. D. Schneider; H. V. Smith; L. M. Young

2000-01-01

22

Radio frequency coaxial feedthrough  

DOEpatents

An improved radio frequency coaxial transmission line vacuum feed-through provided based on the use of a half-wavelength annular dielectric pressure barrier disk, or multiple disks comprising an effective half wavelength structure to eliminate reflections from the barrier surfaces. Gas-tight seals are formed about the outer and inner diameter surfaces of the barrier disk using a sealing technique which generates radial forces sufficient to form seals by forcing the conductor walls against the surfaces of the barrier disks in a manner which does not deform the radii of the inner and outer conductors, thereby preventing enhancement of the electric field at the barrier faces which limits voltage and power handling capabilities of a feedthrough.

Owens, Thomas L. (Kingston, TN)

1989-01-17

23

Laparoscopic Application Of Radio Frequency Energy Enables In Situ Renal Tumor Ablation And Partial Nephrectomy  

Microsoft Academic Search

PurposeTo our knowledge we present the initial series of renal mass in situ laparoscopic radio frequency ablation. We also discuss the indications for and results of subsequent laparoscopic partial nephrectomy.

LUCAS JACOMIDES; KENNETH OGAN; LORI WATUMULL; JEFFREY A. CADEDDU

2003-01-01

24

Investigation of effect of excitation frequency on electron energy distribution functions in low pressure radio frequency bounded plasmas  

SciTech Connect

Particle in cell (PIC) simulations are employed to investigate the effect of excitation frequency {omega} on electron energy distribution functions (EEDFs) in a low pressure radio frequency (rf) discharge. The discharge is maintained over a length of 0.10 m, bounded by two infinite parallel plates, with the coherent heating field localized at the center of the discharge over a distance of 0.05 m and applied perpendicularly along the y and z directions. On varying the excitation frequency f (={omega}/2{pi}) in the range 0.01-50 MHz, it is observed that for f {<=} 5 MHz the EEDF shows a trend toward a convex (Druyvesteyn-like) distribution. For f > 5 MHz, the distribution resembles more like a Maxwellian with the familiar break energy visible in most of the distributions. A prominent ''hot tail'' is observed at f{>=} 20 MHz and the temperature of the tail is seen to decrease with further increase in frequency (e.g., at 30 MHz and 50 MHz). The mechanism for the generation of the ''hot tail'' is considered to be due to preferential transit time heating of energetic electrons as a function of {omega}, in the antenna heating field. There exists an optimum frequency for which high energy electrons are maximally heated. The occurrence of the Druyvesteyn-like distributions at lower {omega} may be explained by a balance between the heating of the electrons in the effective electric field and elastic cooling due to electron neutral collision frequency {nu}{sub en}; the transition being dictated by {omega} {approx} 2{pi}{nu}{sub en}.

Bhattacharjee, Sudeep [Space plasma, Power and Propulsion, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia); Department of Physics, Indian Institute of Technology, Kanpur 208 016 (India); Lafleur, Trevor; Charles, Christine; Boswell, Rod [Space plasma, Power and Propulsion, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)

2011-07-15

25

Radio frequency interference mitigation in radio astronomy  

NASA Astrophysics Data System (ADS)

The next generation of radio telescopes is expected to be one to two orders of magnitude more sensitive than the current generation. Examples of such new telescopes are the Low Frequency Array (LOFAR), currently under construction in the Netherlands, and the Square Kilometer Array (SKA), currently in a concept study phase. Another trend is that technological advances in the fields of electronics and communications systems have led to a vast increase in radio communication applications and systems, and also to an increasing demand for radio spectrum. These two trends, more sensitive telescopes and a much denser spectrum use, imply that radio astronomy will become more vulnerable to interference from radio transmitters. Although protection criteria exist for radio astronomy, it becomes increasingly difficult to keep the radio astronomy frequency bands free from interference. In order to mitigate interference in radio astronomical data, filtering techniques can be used. In this thesis, modern array signal processing techniques have been applied to narrow-band multichannel interference detection and excision, and to narrow-band spatial interference filtering. By investigating the subspace structure of the telescope array output covariance matrices, new results were found, such as upper limits on interference residuals after excision and spatial filtering. The effect of bandwidth, extendedness of the interfering sources, and multipath effects on the detection and spatial filter effectiveness were studied as well. The advantage of a multichannel approach over a single telescope approach was demonstrated by using experimental data from the Westerbork Synthesis Radio Telescope (WSRT). As the performance of mitigation algorithms can be improved by calibration of the telescope gains and noise powers, calibration algorithms were developed. These algorithms were verified both for single and dual polarised arrays. Finally, a LOFAR interference mitigation strategy was developed.

Boonstra, Albert-Jan

2005-12-01

26

Modular System Concept For Soil Heating Using Radio-Frequency Energy  

NASA Astrophysics Data System (ADS)

Soil is one of the most important natural resources and its exploitation, preservation and regeneration are huge challenges for modern industrial society. For this reason it is essential to have innovative, efficient, cost-effective and reliable technologies for the decontamination and soil remediation. These technologies should be flexibly applicable for a wide spectrum of contaminants. Beside other biological, physical and chemical methods, research on thermally-supported soil remediation methods has increased over the last years. Due to a controlled heating of soil, the mobility of pollutants, their water solubility and their vapor pressures can be enhanced. To support biodegradation of pollutants, the maximum activity of most microorganisms can be realized by moderate heating independent of ambient temperature and seasonal conditions. A new technological approach for direct heating of large volumes of contaminated soil using radio-frequency (RF) energy is described. This method can be used to thermally enhance a variety of remediation techniques such as biodegradation and soil vapor extraction. The technical basis, a container-based modular and mobile radio-frequency platform is presented and the benefits of this platform working under harsh field conditions are demonstrated. Additionally, aspects of electromagnetic compatibility, system reliability and safety are discussed.

Holzer, Frank; Lippik, Dirk; Heimbold, Tilo; Roland, Ulf; Kopinke, Frank-Dieter; Schenk, Joachim

2010-06-01

27

Stabilized radio-frequency quadrupole  

DOEpatents

A long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator.

Lancaster, H.D.; Fugitt, J.A.; Howard, D.R.

1982-09-29

28

Improved fluid simulations of radio-frequency plasmas using energy dependent ion mobilities  

SciTech Connect

Symmetric and asymmetric capacitively coupled radio-frequency plasmas in oxygen at 40 Pa, 300 V voltage amplitude and a discharge gap of 40 mm are investigated by means of one-dimensional numerical semi-kinetic fluid modeling on the basis of a simplified reaction scheme including the dominant positive and negative ions, background gas, and electrons. An improved treatment, by accounting for the dependence of ion mobilities on E/N, is compared to the standard approach, based on using zero-field mobility values only. The charged particle dynamics as a result of direct electron impact ionization of oxygen, secondary electron release from the electrodes, the spatial distribution of all involved particles as well as impact of geometry and model modification on ion energies is analyzed and compared to independent simulations and experiments.

Greb, Arthur; Niemi, Kari; O'Connell, Deborah; Gans, Timo [York Plasma Institute, Department of Physics, University of York, York YO10 5DD (United Kingdom)] [York Plasma Institute, Department of Physics, University of York, York YO10 5DD (United Kingdom); Ennis, Gerard J.; MacGearailt, Niall [Intel Ireland Ltd., Leixlip (Ireland)] [Intel Ireland Ltd., Leixlip (Ireland)

2013-05-15

29

High power radio frequency attenuation device  

DOEpatents

A resistor device for attenuating radio frequency power includes a radio frequency conductor connected to a series of fins formed of high relative magnetic permeability material. The fins are dimensional to accommodate the skin depth of the current conduction therethrough, as well as an inner heat conducting portion where current does not travel. Thermal connections for air or water cooling are provided for the inner heat conducting portions of each fin. Also disclosed is a resistor device to selectively alternate unwanted radio frequency energy in a resonant cavity.

Kerns, Quentin A. (Bloomingdale, IL); Miller, Harold W. (Winfield, IL)

1984-01-01

30

Radio Frequency Identification  

NSDL National Science Digital Library

A wealth of information about RFID is available at this site (1), ranging from background material to case studies. A discussion highlighting the myriad of uses for RFID is included. Transponder News (2) offers several articles that explore the technology in greater detail. Two in particular look at current and future trends, while others are editorial essays and technical notes. Pacific Northwest National Laboratory (3) is involved in the development of advanced tags for RFID systems. The project's homepage outlines current research efforts for three different types of radio frequency tags, which are being designed for varying degrees of sophistication and functionality. While RFID technology can be very useful, the fact that information about items is collected remotely raises concerns about privacy and security. This issue is addressed in a research paper from the Massachusetts Institute of Technology (4). The authors review current RFID systems and their operation, and then propose a number of security mechanisms that could reduce the risk associated with their use. A paper presented at the 2002 European Wireless Conference (5) compares the performance of RFID systems that use ultra-high frequency (UHF) communications to those that use microwave communications. It is argued that although microwave-based devices, such as Bluetooth, are suitable for worldwide operation, systems that communicate in the UHF range have greater range and less interference. The introduction of RFID smart tags in goods is discussed in this article (6). Now that these tags are cheap enough to be attached to thousands of items, stores will be able to track goods as they are transferred from storehouses to retail shelves, thereby minimizing the possibility of loss or theft. RFID technology has found another use in the war with Iraq. An article from May 20, 2003 (7) describes wristbands embedded with an RFID chip. The status and position of a wounded soldier who is wearing such a wristband can be monitored while he or she is recovering at a medical facility. For additional updates on the development of RFID technology, RFID News (8) maintains current news about emerging standards, innovative applications, and general issues.

Leske, Cavin.

31

Frequency Allocation; The Radio Spectrum.  

ERIC Educational Resources Information Center

The Federal Communications Commission (FCC) assigns segments of the radio spectrum to categories of users, and specific frequencies within each segment to individual users. Since demand for channel space exceeds supply, the process is complex. The radio spectrum can be compared to a long ruler: the portion from 10-540 kiloHertz has been set aside…

Federal Communications Commission, Washington, DC.

32

Radio-Frequency Plasma Probes  

NASA Astrophysics Data System (ADS)

The utility of radio-frequency probes for diagnosing low-temperature plasmas has recently been extended through the use of a network analyzer to measure the small-signal, complex probe impedance Zac as a function of applied frequency and dc bias. To interpret the results, account must be taken of the gas pressure, the plasma density, the applied frequency, and the applied magnetic field if any. In this talk four different models are presented for use in different regimes. At high gas pressure, Re(Zac) is shown to give ne0/?, where ne0 is the ambient electron density and ? is the electron-neutral collision frequency. At low pressure Re(Zac) gives not only ne0 but also ne(r) within the sheath immediately outside the probe, the plasma potential, and the electron energy distribution and temperature. Magnetized plasmas can be treated by adding an external inductance in series with the probe and operating above the upper hybrid frequency; alternatively, rf voltage can be applied between two closely-spaced planar electrodes oriented either parallel or perpendicular to the field. As will be shown, rf probes not only provide more information than Langmuir probes, but the data is easier to analyze and generally less affected by noise. Additional advantages include the following: decreased sensitivity to secondary electron emission, ions, plasma flow, and high-energy beams; clear and unequivocal determination of ne0, even in magnetized plasmas; direct utility at high pressure; multiple checks on the results; and the ability to operate in reactive and depositing gases.

Fernsler, Richard

2011-11-01

33

Luminescent radio frequency radiation dosimetry.  

PubMed

Thermoluminescent dosimetry has been the industry standard for ionizing radiation dosimetry because it is inexpensive, sensitive, and accurate. No such system exists for radio frequency radiation. This paper describes the state of the art of efforts toward developing such a system. Thermochemiluminescent (TCL) dosimetry, first reported in 1991, is a first step toward achieving this goal. However, it has had problems in the production of TCL materials and in conversion of the luminescent signal into specific absorption rate (SAR). The former problem has been solved by the development of a genetically engineered Escherichia coli bacterium (JM 109/plC20RNR1.1), described herein, that produces the TCL material in a fermentation process. The latter problem stems from the difficulty in determining the structure of the currently best TCL material diazoluminomelanin. A theoretical approach for the solution of this problem has been achieved by combining equations for delayed fluorescence, temperature determination by TCL, and the free energy equation for equilibrium reactions. It has led to an explanation for the stable display of steady-state energy disposition, illustrated by TCL, in phantoms without the expected disruption by thermal conduction or convection, at frequencies ranging from 2.06 GHz to 35 GHz. PMID:10334714

Kiel, J L; Alls, J L; Mason, P A; Erwin, D N

1999-01-01

34

Radio Frequency Interference and the National Radio Astronomy Observatory  

NASA Astrophysics Data System (ADS)

Radio frequency interference (RFI) and radio astronomy have been closely linked since the emergence of radio astronomy as a scientific discipline in the 1930s. Even before the official establishment of the National Radio Astronomy Observatory, protection against contemporary and future radio noise levels was seen as crucial to ensure success of any new observatory. My talk will examine the various local, regional, national, and international efforts enacted to protect NRAO and other American radio astronomy sites from RFI.

Smith, Sierra

2014-01-01

35

Digital Channelizing Radio Frequency Receiver  

Microsoft Academic Search

HYPRES is developing a class of digital receivers featuring direct digitization at radio frequency (RF). Such a receiver consists of a wideband analog-to-digital converter (ADC) modulator and multiple digital channelizer units to extract different frequency bands-of-interest within the broad digitized spectrum. The single-bit oversampled data, from either a lowpass delta or bandpass delta-sigma modulator, are applied to one or more

Deepnarayan Gupta; Timur V. Filippov; Alexander F. Kirichenko; Dmitri E. Kirichenko; Igor V. Vernik; Anubhav Sahu; Saad Sarwana; Pavel Shevchenko; Andrei Talalaevskii; Oleg A. Mukhanov

2007-01-01

36

Radio frequency energy coupling to high-pressure optically pumped nonequilibrium plasmas  

NASA Astrophysics Data System (ADS)

This article presents an experimental demonstration of a high-pressure unconditionally stable nonequilibrium molecular plasma sustained by a combination of a continuous wave CO laser and a sub-breakdown radio frequency (rf) electric field. The plasma is sustained in a CO/N2 mixture containing trace amounts of NO or O2 at pressures of P=0.4-1.2 atm. The initial ionization of the gases is produced by an associative ionization mechanism in collisions of two CO molecules excited to high vibrational levels by resonance absorption of the CO laser radiation with subsequent vibration-vibration (V-V) pumping. Further vibrational excitation of both CO and N2 is produced by free electrons heated by the applied rf field, which in turn produces additional ionization of these species by the associative ionization mechanism. In the present experiments, the reduced electric field, E/N, is sufficiently low to preclude field-induced electron impact ionization. Unconditional stability of the resultant cold molecular plasma is enabled by the negative feedback between gas heating and the associative ionization rate. Trace amounts of nitric oxide or oxygen added to the baseline CO/N2 gas mixture considerably reduce the electron-ion dissociative recombination rate and thereby significantly increase the initial electron density. This allows triggering of the rf power coupling to the vibrational energy modes of the gas mixture. Vibrational level populations of CO and N2 are monitored by infrared emission spectroscopy and spontaneous Raman spectroscopy. The experiments demonstrate that the use of a sub-breakdown rf field in addition to the CO laser allows an increase of the plasma volume by about an order of magnitude. Also, CO infrared emission spectra show that with the rf voltage turned on the number of vibrationally excited CO molecules along the line of sight increase by a factor of 3-7. Finally, spontaneous Raman spectra of N2 show that with the rf voltage the vibrational temperature of nitrogen increases by up to 30%. This novel energy efficient approach allows sustaining large-volume high-pressure molecular plasmas without the use of a high-power CO laser. This opens a possibility of using the present technique for high-yield plasma chemical synthesis and plasma material processing.

Plönjes, Elke; Palm, Peter; Lee, Wonchul; Lempert, Walter R.; Adamovich, Igor V.

2001-06-01

37

Radio frequency coaxial feedthrough device  

DOEpatents

A radio frequency coaxial vacuum feedthrough is provided which utilizes a cylindrical ceramic vacuum break formed of an alumina ceramic. The cylinder is coaxially disposed and brazed between tapered coaxial conductors to form a vacuum sealed connection between a pressurized upstream coaxial transmission line and a utilization device located within a vacuum container. The feedthrough provides 50 ohm matched impedance RF feedthrough up to about 500 MHz at power levels in the multimegawatt range.

Owens, Thomas L. (Kingston, TN); Baity, Frederick W. (Oak Ridge, TN); Hoffman, Daniel J. (Oak Ridge, TN); Whealton, John H. (Oak Ridge, TN)

1987-01-01

38

Pulsed radio frequency energy therapy use for pain relief following surgery for tendinopathy-associated chronic pain: two case reports.  

PubMed

Chronic tendon pain from overuse is a common condition, with limited options for ongoing pain management. Two cases are presented in which pulsed radio frequency energy (PRFE) therapy was used for pain relief following surgical intervention for chronic tendinopathy-associated pain, unresponsive to conventional therapies. Both patients showed a dramatic reduction in pain following PRFE therapy after 2 to 3 weeks of treatment, and at the 7-month (case 1) and 6-month (case 2) follow-up visits, both patients reported that pain had not returned. Recent molecular evidence suggests a possible mechanism underlying PRFE-mediated pain relief. Further study into this promising technology is warranted. PMID:23764157

Cortes, Jane; Kubat, Nicole; Japour, Christopher

2013-01-01

39

Low Radio Frequency Picosatellite Missions  

NASA Astrophysics Data System (ADS)

The dramatic advances in cubesat and other picosatellite capabilities are opening the door for scientifically important observations at low radio frequencies. Because simple antennas are effective at low frequencies, and receiver technology allows low mass and low power instruments, these observations are an ideal match for very small spacecraft. A workshop on cubesat missions for low frequency radio astronomy was held at the Kiss Institute for Space Sciences, Caltech, to explore mission concepts involving one up to hundreds of picosatellites. One result from this workshop was that there are opportunities for viable missions throughout this large range. For example, the sky-integrated spectral signature of highly redshifted neutral hydrogen from the dark ages and cosmic dawn epochs can be measured by a single antenna on a single spacecraft. There are challenging issues of calibration, foreground removal, and RF interference that need to be solved, but the basic concept is appealingly simple. At the other extreme, imaging of angular structure in the high-redshift hydrogen signal will require an interferometer array with a very large number of antennas. In this case the primary requirement is a sufficiently low individual spacecraft mass that hundreds can be launched affordably. The technical challenges for large arrays are long-term relative station keeping and high downlink data rates. Missions using several to a few tens of picosatellites can image and track bright sources such as solar and planetary radio bursts, and will provide essential validation of technologies needed for much larger arrays.This work has been carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Jones, Dayton L.

2014-06-01

40

Radio-Frequency Strain Monitor  

NASA Technical Reports Server (NTRS)

Radio-frequency (RF) strain monitor developed to measure lengths of objects. RF waveguide or cable bonded to structure monitored. Propagation of RF signal along waveguide results in phase shift proportional to length of path traveled. Impedance mismatches placed in RF cable at nodes of structure. Records mismatches and detects overall length of line and lengths of intervals between nodes. Used to detect changes in elements of large structure with single cable. Monitor has potential for many applications, including monitoring stability of such large structures as aircraft, bridges, and buildings in Earthquake zones.

Heyman, Joseph S.; Rogowski, Robert S.; Holben, Milford S., Jr.

1988-01-01

41

Topic in Depth - Radio Frequency Identification  

NSDL National Science Digital Library

Radio frequency identification (RFID) technology allows nearly anything to be tracked without human intervention, using transceiver tags and an electronic reader with radio communication. It is often used in inventory management, theft prevention, and vehicle identification.

2010-09-14

42

Monochromatic radio frequency accelerating cavity  

DOEpatents

A radio frequency resonant cavity having a fundamental resonant frequency and characterized by being free of spurious modes. A plurality of spaced electrically conductive bars are arranged in a generally cylindrical array within the cavity to define a chamber between the bars and an outer solid cylindrically shaped wall of the cavity. A first and second plurality of mode perturbing rods are mounted in two groups at determined random locations to extend radially and axially into the cavity thereby to perturb spurious modes and cause their fields to extend through passageways between the bars and into the chamber. At least one body of lossy material is disposed within the chamber to damp all spurious modes that do extend into the chamber thereby enabling the cavity to operate free of undesired spurious modes.

Giordano, S.

1984-02-09

43

Monochromatic radio frequency accelerating cavity  

DOEpatents

A radio frequency resonant cavity having a fundamental resonant frequency and characterized by being free of spurious modes. A plurality of spaced electrically conductive bars are arranged in a generally cylindrical array within the cavity to define a chamber between the bars and an outer solid cylindrically shaped wall of the cavity. A first and second plurality of mode perturbing rods are mounted in two groups at determined random locations to extend radially and axially into the cavity thereby to perturb spurious modes and cause their fields to extend through passageways between the bars and into the chamber. At least one body of lossy material is disposed within the chamber to damp all spurious modes that do extend into the chamber thereby enabling the cavity to operate free of undesired spurious modes.

Giordano, Salvatore (Port Jefferson, NY)

1985-01-01

44

Coping with Radio Frequency Interference  

NASA Astrophysics Data System (ADS)

The radio spectrum is a finite resource, on which humanity makes many demands. And pressure on it is ever increasing with the development of new technology and ideas for radio services. After all, we all benefit from wifi and cell phones. Radio astronomers have a small percentage of the spectrum allocated to them at octave intervals in the metre-centimetre bands, and at important frequencies, such as that of the 21cm line of HI. Signals from other services, as well as from our own poorly-engineered equipment, sometimes contaminate our bands: these signals constitute RFI. These may totally obliterate the astronomical signal, or, in the case of CLOUDSAT, may be capable of completely destroying a receiver, which introduces us to the new possibility of 'destructive interference'. A geo-stationary satellite can block access to a piece of sky from one site. Good equipment design eliminates self-inflicted interference, while physical separation often provides adequate practical mitigation at many frequencies. However, new observatories end up being located in the West Australian desert or Antarctica. In future they may be on the back side of the Moon. But there is no Earth-bound protection via physical separation against satellite signals. Some mitigation can be achieved by frequent data dumps and the excision of RFI, or by real-time detection and blanking of the receiver, or by more sophisticated algoriths. Astronomers of necessity aim to achieve mitigation via coordination, at the local level, and by participating in spectrum management at the national and international levels. This involves them spending a lot of time in Geneva at the International Telegraphic Union protecting their access to spectrum, and access to clean spectrum from the L3 point and the far side of the Moon.

Lewis, B. M.

2009-01-01

45

DEMONSTRATION BULLETIN: RADIO FREQUENCY HEATING - KAI TECHNOLOGIES, INC.  

EPA Science Inventory

Radio frequency heating (RFH) is a process that uses electromagnetic energy in the radio frequency (RF) band to heat soil in situ, thereby potentially enhancing the performance of standard soil vapor extraction (SVE) technologies. An RFH system developed by KAI Technologies, I...

46

SITE TECHNOLOGY CAPSULE: IITRI RADIO FREQUENCY HEATING TECHNOLOGY  

EPA Science Inventory

Radio frequency heating (RFH) technologies use electromagnetic energy in the radio frequency i(RF) band to heat soil in-situ, thereby potentially enhancing the performances of standard soil vapor extraction (SVE) technologies. ontaminants are removed from in situ soils and transf...

47

Precision phase control for the radio frequency system of K500 superconducting cyclotron at Variable Energy Cyclotron Centre, Kolkata.  

PubMed

Variable Energy Cyclotron Centre (VECC) has commissioned K500 Superconducting cyclotron (SCC) based on MSU and Texas A&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 loop 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. PMID:24289392

Som, Sumit; Ghosh, Surajit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Roy, Suprakash

2013-11-01

48

Precision phase control for the radio frequency system of K500 superconducting cyclotron at Variable Energy Cyclotron Centre, Kolkata  

NASA Astrophysics Data System (ADS)

Variable Energy Cyclotron Centre (VECC) has commissioned K500 Superconducting cyclotron (SCC) based on MSU and Texas A&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 loop 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.

Som, Sumit; Ghosh, Surajit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Roy, Suprakash

2013-11-01

49

Precision phase control for the radio frequency system of K500 superconducting cyclotron at Variable Energy Cyclotron Centre, Kolkata  

SciTech Connect

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 loop 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.

Som, Sumit; Ghosh, Surajit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Roy, Suprakash [Variable Energy Cyclotron Centre, Kolkata (India)] [Variable Energy Cyclotron Centre, Kolkata (India)

2013-11-15

50

Location of acoustic radiators and inversion for energy density using radio-frequency sources and thunder recordings  

NASA Astrophysics Data System (ADS)

We use radio frequency (VHF) pulse locations mapped with the New Mexico Tech Lightning Mapping Array (LMA) to study the distribution of thunder sources in lightning channels. A least squares inversion is used to fit channel acoustic energy radiation with broadband (0.01 to 500 Hz) acoustic recordings using microphones deployed local (< 10 km) to the lightning. We model the thunder (acoustic) source as a superposition of line segments connecting the LMA VHF pulses. An optimum branching algorithm is used to reconstruct conductive channels delineated by VHF sources, which we discretize as a superposition of finely-spaced (0.25 m) acoustic point sources. We consider total radiated thunder as a weighted superposition of acoustic waves from individual channels, each with a constant current along its length that is presumed to be proportional to acoustic energy density radiated per unit length. Merged channels are considered as a linear sum of current-carrying branches and radiate proportionally greater acoustic energy. Synthetic energy time series for a given microphone location are calculated for each independent channel. We then use a non-negative least squares inversion to solve for channel energy densities to match the energy time series determined from broadband acoustic recordings across a 4-station microphone network. Events analyzed by this method have so far included 300-1000 VHF sources, and correlations as high as 0.5 between synthetic and recorded thunder energy were obtained, despite the presence of wind noise and 10-30 m uncertainty in VHF source locations.

Anderson, J.; Johnson, J. B.; Arechiga, R. O.; Edens, H. E.; Thomas, R. J.

2011-12-01

51

Testing of vacuum pumps for the Accelerator Production of Tritium/Low Energy Demonstration Accelerator radio frequency quadrupole  

SciTech Connect

Two vacuum systems were designed and built for the RFQ (Radio Frequency Quadrupole) cavity in the APT/LEDA (Low Energy Demonstration Accelerator) linac. The gas load from the proton beam required very high hydrogen pump speed and capacity. The gas load from the high power RF windows also required very high hydrogen pump speed for the RF window vacuum system. Cryopumps were chosen for the RFQ vacuum system and ST185 sintered non-evaporable getter (NEG) cartridges were chosen for the RF window vacuum system. Hydrogen pump speed and capacity measurements were carried out for a commercial cryopump and a NEG pump. This paper will discuss the test procedures and the results of the measurements.

Kishiyama, K.; Shen, S.; Behne, D. [Lawrence Livermore National Lab., CA (United States); Wilson, N.G. [AMPARO Inc., Los Alamos, NM (United States); Schrage, D.; Valdiviez, R. [Los Alamos National Lab., NM (United States)

1998-12-31

52

Orbiting Low Frequency Array for radio astronomy  

Microsoft Academic Search

Recently new and interesting science drivers have emerged for very low frequency radio astronomy from 0.3 MHz to 30 MHz. However Earth bound radio observations at these wavelengths are severely hampered by ionospheric distortions, man made interference, solar flares and even complete reflection below 10 MHz. OL- FAR is Orbiting Low Frequency ARray, a project whose aim is to develop

Raj Thilak Rajan; Steven Engelen; Mark Bentum; Chris Verhoeven

2011-01-01

53

Final report: In situ radio frequency heating demonstration.  

National Technical Information Service (NTIS)

A field demonstration of in situ radio frequency heating was performed at the Savannah River Site (SRS) as part of the US Department of Energy-Office of Technology Development's Integrated Demonstration. The objective of the demonstration was to investiga...

T. R. Jarosch R. J. Beleski D. Faust

1994-01-01

54

Design and development of a radio frequency quadrupole linac postaccelerator for the Variable Energy Cyclotron Center rare ion beam project  

SciTech Connect

A four-rod type heavy-ion radio frequency quadrupole (RFQ) linac has been designed, constructed, and tested for the rare ion beam (RIB) facility project at VECC. Designed for cw operation, this RFQ is the first postaccelerator in the RIB beam line. It will accelerate A/q{<=}14 heavy ions coming from the ion source to the energy of around 100 keV/u for subsequent acceleration in a number of Interdigital H-Linac. Operating at a resonance frequency of 37.83 MHz, maximum intervane voltage of around 54 kV will be needed to achieve the final energy over a vane length of 3.12 m for a power loss of 35 kW. In the first beam tests, transmission efficiency of about 90% was measured at the QQ focus after the RFQ for O{sup 5+} beam. In this article the design of the RFQ including the effect of vane modulation on the rf characteristics and results of beam tests will be presented.

Dechoudhury, S.; Naik, V.; Mondal, M.; Pandey, H. K.; Mandi, T. K.; Bandyopadhyay, A.; Karmakar, P.; Chouhan, P. S.; Ali, S.; Srivastava, S. C. L. [Variable Energy Cyclotron Center (VECC), 1/AF, Bidhan Nagar, Kolkata 700064 (India); Chatterjee, A. [CMERI, M.G. Avenue, Durgapur 713209 (India); Bhattacharjee, S. [UGC-DAE CSR, LB-8, Sector-III, Bidhan Nagar, Kolkata 700064 (India); Chakrabarti, A.

2010-02-15

55

Integrally formed radio frequency quadrupole  

DOEpatents

An improved radio frequency quadrupole (10) is provided having an elongate housing (11) with an elongate central axis (12) and top, bottom and two side walls (13a-d) symmetrically disposed about the axis, and vanes (14a-d) formed integrally with the walls (13a-d), the vanes (14a-d) each having a cross-section at right angles to the central axis (12) which tapers inwardly toward the axis to form electrode tips (15a-d) spaced from each other by predetermined distances. Each of the four walls (13a-d), and the vanes (14a-d) integral therewith, is a separate structural element having a central lengthwise plane (16) passing through the tip of the vane, the walls (13a-d) having flat mounting surfaces (17, 18) at right angles to and parallel to the control plane (16), respectively, which are butted together to position the walls and vane tips relative to each other.

Abbott, Steven R. (Concord, CA)

1989-01-01

56

High-power radio-frequency attenuation device  

DOEpatents

A resistor device for attenuating radio frequency power includes a radio frequency conductor connected to a series of fins formed of high relative magnetic permeability material. The fins are dimensional to accommodate the skin depth of the current conduction therethrough, as well as an inner heat conducting portion where current does not travel. Thermal connections for air or water cooling are provided for the inner heat conducting portions of each fin. Also disclosed is a resistor device to selectively alternate unwanted radio frequency energy in a resonant cavity.

Kerns, Q.A.; Miller, H.W.

1981-12-30

57

47 CFR 2.815 - External radio frequency power amplifiers.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false External radio frequency power amplifiers. 2.815 Section...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...AND REGULATIONS Marketing of Radio-frequency Devices § 2.815 External...

2013-10-01

58

Multi-mode radio frequency device  

DOEpatents

A transponder device having multiple modes of operation, such as an active mode and a passive mode, wherein the modes of operation are selected in response to the strength of a received radio frequency signal. A communication system is also provided having a transceiver configured to transmit a radio frequency signal and to receive a responsive signal, and a transponder configured to operate in a plurality of modes and to activate modes of operation in response to the radio frequency signal. Ideally, each mode of operation is activated and deactivated independent of the other modes, although two or more modes may be concurrently operational.

Gilbert, Ronald W. (Morgan Hill, CA); Carrender, Curtis Lee (Morgan Hill, CA); Anderson, Gordon A. (Benton City, WA); Steele, Kerry D. (Kennewick, WA)

2007-02-13

59

Process protocols based on radio frequency energy to control field and storage pests in in-shell walnuts  

Microsoft Academic Search

A practical process protocol was developed to control insect pests in in-shell walnuts using a 27 MHz pilot scale radio frequency (RF) system. Fifth-instars, that had been determined to be the most heat resistant life stage for navel orangeworm (Amyelois transitella [Walker]) using a heating block system, were selected as the targeted insect in the protocol development. RF heating to

S. Wang; J. Tang; J. A. Johnson; E. Mitcham; J. D. Hansen; R. P. Cavalieri; J. Bower; B. Biasi

2002-01-01

60

Frequency coupling in dual frequency capacitively coupled radio-frequency plasmas  

NASA Astrophysics Data System (ADS)

An industrial, confined, dual frequency, capacitively coupled, radio-frequency plasma etch reactor (Exelan®, Lam Research) has been modified for spatially resolved optical measurements. Space and phase resolved optical emission spectroscopy yields insight into the dynamics of the discharge. A strong coupling of the two frequencies is observed in the emission profiles. Consequently, the ionization dynamics, probed through excitation, is determined by both frequencies. The control of plasma density by the high frequency is, therefore, also influenced by the low frequency. Hence, separate control of plasma density and ion energy is rather complex.

Gans, T.; Schulze, J.; O'Connell, D.; Czarnetzki, U.; Faulkner, R.; Ellingboe, A. R.; Turner, M. M.

2006-12-01

61

Block Copolymer Nanoarchitectures for Radio Frequency Applications.  

National Technical Information Service (NTIS)

The goal of this research is to develop flexible polymeric nanocomposites having high permitivities and permeabilities for use in radio frequency (RF) applications. The nanocomposites are based on the self-assembly of block copolymers. A variety of mixed ...

P. Kofinas

2006-01-01

62

Improved fire resistant radio frequency anechoic materials  

NASA Technical Reports Server (NTRS)

Protective, flameproof foam covering improves the resistance to fire and surface contamination of low-cost radio frequency absorbing and shielding anechoic materials. This promotes safety of operating personnel and equipment being tested in an otherwise combustible anechoic chamber.

Robinson, D. A.

1969-01-01

63

Radio Frequency Idenfication Static Discharge Protection.  

National Technical Information Service (NTIS)

Methods and apparatuses for the protection of radio frequency identification (RFID) devices are described. In one aspect, a static dissipative material is applied to a web of antenna structures. A coating of the static dissipative material is applied cont...

G. S. Wiggins J. B. Hattick M. A. Hadley S. J. Herrmann

2004-01-01

64

Ion energy and angular distributions in inductively driven radio frequency discharges in chlorine  

Microsoft Academic Search

In this article, we report values of ion energy and angular distributions measured at the grounded electrode of an inductively coupled discharge in chlorine gas. The inductive rf drive in our cell produced high plasma densities (1011\\/cm3 electron densities) and stable plasma potentials. As a result, ion energy distributions typically consisted of a single peak well separated from zero energy.

J. R. Woodworth; M. E. Riley; P. A. Miller; G. A. Hebner; T. W. Hamilton

1997-01-01

65

Ion source requirements for a radio frequency high-energy ion implanter  

Microsoft Academic Search

Over the last several years, high-energy (in MeV range) ion implantation has become an integral part of mainstream semiconductor device manufacturing. The rapid growth in use of high-energy implanters has been driven by process and performance requirements for sub 0.25 mum device nodes. At Eaton, we have developed an rf linac based high-energy implanter, NV-GSD\\/VHE, capable of delivering in excess

Kourosh Saadatmand

1998-01-01

66

Ion energy and angular distributions in inductively driven radio frequency discharges in chlorine  

Microsoft Academic Search

In this article, we report values of ion energy and angular distributions measured at the grounded electrode of an inductively coupled discharge in chlorine gas. The inductive rf drive in our cell produced high plasma densities (10¹¹\\/cm³ electron densities) and stable plasma potentials. As a result, ion energy distributions typically consisted of a single peak well separated from zero energy.

J. R. Woodworth; M. E. Riley; P. A. Miller; G. A. Hebner; T. W. Hamilton

1997-01-01

67

47 CFR 80.927 - Antenna radio frequency indicator.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Antenna radio frequency indicator. 80.927 Section...CONTINUED) SAFETY AND SPECIAL RADIO SERVICES STATIONS IN THE MARITIME...Passenger Boats § 80.927 Antenna radio frequency indicator. The...

2013-10-01

68

47 CFR 80.1019 - Antenna radio frequency indicator.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Antenna radio frequency indicator. 80.1019 Section...CONTINUED) SAFETY AND SPECIAL RADIO SERVICES STATIONS IN THE MARITIME...Bridge-to-Bridge Act § 80.1019 Antenna radio frequency indicator. Each...

2013-10-01

69

Energy Harvesting using Piezoelectric Igniter for Self-Powered Radio Frequency (RF) Wireless Sensors  

Microsoft Academic Search

The field of miniature low-powered and low cost wireless sensor nodes has been growing tremendously and the wireless sensor nodes have been widely used in applications like medical implants, embedded sensors in building, military applications, etc. However, little research works have been carried out on the energy sources of the wireless sensors such that the sensor nodes become self-powered. This

Yen Kheng Tan; K. Y. Hoe; Sanjib Kumar Panda

2006-01-01

70

Efficient Far-Field Radio Frequency Energy Harvesting for Passively Powered Sensor Networks  

Microsoft Academic Search

An RF-DC power conversion system is designed to efficiently convert far-field RF energy to DC voltages at very low received power and voltages. Passive rectifier circuits are designed in a 0.25 mum CMOS technology using floating gate transistors as rectifying diodes. The 36-stage rectifier can rectify input voltages as low as 50 mV with a voltage gain of 6.4 and

Triet Le; Karti Mayaram; Terri Fiez

2008-01-01

71

Radio Propagation at Frequencies above 30 Megacycles  

Microsoft Academic Search

Radio propagation is affected by many factors, including the frequency, distance, antenna heights, curvature of the earth, atmospheric conditions, and the presence of hills and buildings. The influence of each of these factors at frequencies above about 30 megacycles is discussed, with most of the quantitative data being presented in a series of nomograms. By means of three or four

K. Bullington

1947-01-01

72

Chipless Radio Frequency Identification (RFID) Device  

Microsoft Academic Search

A novel technique for radio frequency identification devices (RFID) based on remote measurement of complex impedance at microwave frequencies is presented. The low cost read-only tags do not need semiconductor elements and can be implemented by printing a conducting pattern on a low cost dielectric substrate. Multiple tags are simultaneously illuminated by a chirped microwave signal with a bandwidth of

Somnath Mukherjee

2007-01-01

73

HIGH-FREQUENCY RADIO SPECTRAL ENERGY DISTRIBUTIONS AND POLARIZATION FRACTIONS OF SOURCES IN AN ATACAMA COSMOLOGY TELESCOPE SURVEY FIELD  

SciTech Connect

We present flux densities and polarization percentages of 159 radio galaxies based on nearly simultaneous Very Large Array observations at four frequencies, 4.86, 8.46, 22.46, and 43.34 GHz. This sample is selected from the high-frequency Australia Telescope 20 GHz (AT20G) survey and consists of all sources with flux density S{sub 20GHz} > 40 mJy in an equatorial field of the Atacama Cosmology Telescope (ACT) survey. For a subset of 25 of these sources, we used the Green Bank Telescope (GBT) to obtain 90 GHz data. The goals of this program are: (1) a characterization of the spectra, polarization, and variability of high-frequency-selected radio sources, (2) extrapolating from the few GHz regime to the {approx}150 GHz regime of the ACT survey, allowing for more accurate removal of the radio source signal in our particular field, and (3) providing a data set that will allow more accurate modeling of the high-frequency radio source contamination in current and future Sunyaev-Zeldovich and cosmic microwave background experiments. We find that, as expected, this sample consists of flatter spectrum and more compact or point-like sources than low-frequency-selected samples. In the K band, variability is typically {approx}<20%, although there are exceptions. The higher frequency data are well suited to the detection of extreme gigahertz peak spectrum sources. The inclusion of the 43 GHz data causes the relative fraction of inverted spectrum sources to go down and of peaked spectrum sources to go up when compared with the AT20G survey results. The trend largely continues with the inclusion of the 90 GHz data, although {approx}10% of the sources with GBT data show a spectral upturn from 43 GHz to 90 GHz. The measured polarization fractions are typically <5%, although in some cases they are measured to be up to {approx}20%. For sources with detected polarized flux in all four bands, about 40% of the sample, the polarization fractions typically increase with frequency. This trend is stronger for steeper spectrum sources as well as for the lower flux density sources.

Sajina, Anna [Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); Partridge, Bruce; Evans, Tyler; Vechik, Nicholas [Department of Physics and Astronomy, Haverford College, Haverford, PA 19041 (United States); Stefl, Shannon [Kent State University, Kent, OH 44242 (United States); Myers, Steve [National Radio Astronomy Observatory, Socorro, NM 87801 (United States); Dicker, Simon; Korngut, Phillip [Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 (United States)

2011-05-01

74

An overview of the Low Energy Demonstration Accelerator (LEDA) project RF (radio frequency) systems  

SciTech Connect

Successful operation of the Accelerator Production of Tritium (APT) plant will require that accelerator downtime be kept to an absolute minimum. Over 230 separate 1 MW RF systems are expected to be used in the APT plant, making the efficiency and reliability of these systems two of the most critical factors in plant operation. The Low Energy Demonstration Accelerator (LEDA) being constructed at Los Alamos National Laboratory will serve as the prototype for APT. The design of the RF systems used in LEDA has been driven by the need for high efficiency and extremely high system reliability. The authors present details of the high voltage power supply and transmitter systems as well as detailed descriptions of the waveguide layout between the klystrons and the accelerating cavities. The first stage of LEDA operations will use four 1.2 MW klystrons to test the RFQ and supply power to one test stand. The RFQ will serve as a power combiner for multiple RF systems. They present some of the unique challenges expected in the use of this concept.

Bradley, J. III; Cummings, K.; Lynch, M.; Rees, D.; Roybal, W.; Tallerico, P. [Los Alamos National Lab., NM (United States); Toole, L. [Savannah River Site, SC (United States)

1997-05-12

75

Microelectromechanical resonators for radio frequency communication applications  

Microsoft Academic Search

Over the past few years, microelectromechanical system (MEMS) based on-chip resonators have shown significant potential for\\u000a sensing and high frequency signal processing applications. This is due to their excellent features like small size, large\\u000a frequency-quality factor product, low power consumption, low cost batch fabrication, and integrability with CMOS IC technology.\\u000a Radio frequency communication circuits like reference oscillators, filters, and mixers

Joydeep BasuTarun; Tarun Kanti Bhattacharyya

76

Evaluation of the combination of radio frequency, infrared energy and mechanical rollers with suction to improve skin surface irregularities (cellulite) in a limited treatment area  

Microsoft Academic Search

This IRB-approved (Institutional Review Board) study evaluated the efficacy of a device that combines radio frequency, infrared energy and mechanical rollers\\/suction (ELOS technology) to reduce skin surface irregularities in a limited treatment zone. Sixteen patients were enrolled and received two treatments per week for 4 consecutive weeks. Treatments were limited to a 20.53 cm633.02 cm area of the posterior or

Michael Kulick

2006-01-01

77

Low-frequency radio monitoring of microquasars  

NASA Astrophysics Data System (ADS)

Microquasars are radio-emitting X-ray binaries (REXBs) with a radio morphology like quasars and high X-ray luminosity. Sixteen known microquasar candidates were extensively monitored for the first time at low radio frequencies using the Giant Meter-wave Radio Telescope (GMRT) between 6-June 2003 and 22-Jan. 2005 at 0.235/0.61 (simultaneous) and 1.28 GHz. Nine out of sixteen sources were detected positively by the GMRT including all six high-mass X-ray binaries (HMXBs) and three low-mass X-ray binaries (LMXBs). Among the nine sources emitting at low frequencies, six are persistent in radio and three are transient at radio wavelengths. In the case of four persistent radio sources (Scorpius X-1, Cyg X-1, Cyg X-3, and LSI+61303) the contemporaneous data suggests a spectral turnover (S sb? = ??, ? > 0) and agrees with the synchrotron self absorption (SSA) effect expected at lower frequencies. The radio spectra of SS433 and LS5039 show a power law decay (S sb? = ??, ? < 0) with no signature of SSA even at the very low frequency of 0.235 GHz. This unique result suggests either that these sources are scatter-broadened at lower frequencies or that the low-frequency radio emission from these sources are superimposed by the emission from an extended region located near these sources. Five sources, GRO J1655-40, XTE J1118+480, 1E1740.7-2942, XTE J1748-288, and GRS 1758-258 were never detected during our observations, thus suggesting that they show the SSA effect at lower frequencies or that they are too faint to be detected at GMRT frequencies. Because interstellar scintillation becomes dominant at low frequencies and may lead to flux-density fluctuations, the scintillation time scale for each microquasar was calculated and compared to the variability time scale in the data. We confirm from these studies that Cyg X-1 and SS433 are most likely affected by scintillation and that LSI+61303, LS 5039, Sco X-1, and XTE J1118+480 may possibly be affected by scintillation. A comparative study of the radio luminosity from centimeter-(GHz) to meter-wavelength (MHz) suggests a decrease by a few orders of magnitude as one goes lower in frequency. We have also plotted the RXTE/ASM X-ray light curve for all the sixteen known microquasars. Based on the ASM data, the X-ray light curve can be classified as: (a) persistent, (b) quasi-persistent or (c) transient. From the analysis of these types and the information about their companion star, the persistent or transient nature of the radio jet can be confirmed. This paper provides a general review of the main observational results obtained up to now, as well as different models for the production of low-frequency radio emissions from these sources. Table 2 is only available in electronic form at http://www.aanda.org

Pandey, M.; Rao, A. P.; Ishwara-Chandra, C. H.; Durouchoux, P.; Manchanda, R. K.

2007-02-01

78

Monitoring Radio Frequency Interference in Southwest Virginia  

NASA Astrophysics Data System (ADS)

The radio signals received from astronomical objects are extremely weak. Because of this, radio sources are easily shrouded by interference from devices such as satellites and cell phone towers. Radio astronomy is very susceptible to this radio frequency interference (RFI). Possibly even worse than complete veiling, weaker interfering signals can contaminate the data collected by radio telescopes, possibly leading astronomers to mistaken interpretations. To help promote student awareness of the connection between radio astronomy and RFI, an inquiry-based science curriculum was developed to allow high school students to determine RFI levels in their communities. The Quiet Skies Project_the result of a collaboration between the National Aeronautics and Space Administration (NASA), the National Science Foundation (NSF), and the National Radio Astronomy Observatory (NRAO)_encourages students to collect and analyze RFI data and develop conclusions as a team. Because the project focuses on electromagnetic radiation, it is appropriate for physics, physical science, chemistry, or general science classes. My class-about 50 students from 15 southwest Virginia high schools-participated in the Quiet Skies Project and were pioneers in the use of the beta version of the Quiet Skies Detector (QSD), which is used to detect RFI. Students have been involved with the project since 2005 and have collected and shared data with NRAO. In analyzing the data they have noted some trends in RFI in Southwest Virginia.

Rapp, Steve

2010-01-01

79

Radio-frequency measurements of coherent transition and Cherenkov radiation: Implications for high-energy neutrino detection  

SciTech Connect

We report on measurements of (11--18)-cm wavelength radio emission from interactions of 15.2 MeV pulsed electron bunches at the Argonne Wakefield Accelerator. The electrons were observed both in a configuration where they produced primarily transition radiation from an aluminum foil, and in a configuration designed for the electrons to produce Cherenkov radiation in a silica sand target. Our aim was to emulate the large electron excess expected to develop during an electromagnetic cascade initiated by an ultrahigh-energy particle. Such charge asymmetries are predicted to produce strong coherent radio pulses, which are the basis for several experiments to detect high-energy neutrinos from the showers they induce in Antarctic ice and in the lunar regolith. We detected coherent emission which we attribute both to transition and possibly Cherenkov radiation at different levels depending on the experimental conditions. We discuss implications for experiments relying on radio emission for detection of electromagnetic cascades produced by ultrahigh-energy neutrinos.

Gorham, Peter W.; Saltzberg, David P.; Schoessow, Paul; Gai, Wei; Power, John G.; Konecny, Richard; Conde, M. E.

2000-12-01

80

Radio-frequency measurements of coherent transition and cherenkov radiation: implications for high-energy neutrino detection  

PubMed

We report on measurements of (11-18)-cm wavelength radio emission from interactions of 15.2 MeV pulsed electron bunches at the Argonne Wakefield Accelerator. The electrons were observed both in a configuration where they produced primarily transition radiation from an aluminum foil, and in a configuration designed for the electrons to produce Cherenkov radiation in a silica sand target. Our aim was to emulate the large electron excess expected to develop during an electromagnetic cascade initiated by an ultrahigh-energy particle. Such charge asymmetries are predicted to produce strong coherent radio pulses, which are the basis for several experiments to detect high-energy neutrinos from the showers they induce in Antarctic ice and in the lunar regolith. We detected coherent emission which we attribute both to transition and possibly Cherenkov radiation at different levels depending on the experimental conditions. We discuss implications for experiments relying on radio emission for detection of electromagnetic cascades produced by ultrahigh-energy neutrinos. PMID:11138159

Gorham; Saltzberg; Schoessow; Gai; Power; Konecny; Conde

2000-12-01

81

Low-frequency radio emissions at Neptune  

NASA Technical Reports Server (NTRS)

The Voyager 2 plasma wave receiver detected weak radio emissions from Neptune's magnetosphere in the frequency range of 3 - 60 kHz. The emissions occurred in bursts lasting for typically 1.5 hours, often occurring twice per planetary rotation. Most of these radio bursts were detected within several degrees of the magnetic equatorial plane. During the passage through the magnetosphere, electrostatic upper hybrid resonance bands were observed close to the magnetic equator in conjunction with intensifications of the radio emissions at frequencies close to and above the upper hybrid bands. Further, near closest approach, the radio emissions were observed to cross the right-hand cutoff frequency with no apparent attenuation. It is concluded that the Neptunian radio emissions below about 60 kHz are produced by mode conversion from the upper hybrid waves and propagate in the ordinary mode into beams within about 12 deg of the magnetic equator. There is also evidence of an extraordinary mode emission at about 60 kHz which is apparently generated by an entirely different source from the escaping continuum radiation.

Kurth, W. S.; Gurnett, D. A.; Cairns, I. H.; Barbosa, D. D.; Poynter, R. L.

1990-01-01

82

The characteristics of atmospheric radio frequency discharges with frequency increasing at a constant power density  

SciTech Connect

A computational model is used to investigate the characteristics of atmospheric radio frequency discharges by increasing frequency from 20 to 100 MHz at a constant power density. The simulation results show that increasing frequency can effectively enhance electron density before the transition frequency but after it the ignition is quenched then the electron density decreases. However this simulation also indicates the maximum time-averaged electron energy reduces monotonically with the excitation frequency increasing at a constant power density.

Zhang Yuantao; Li Qingquan; Lou Jie; Li Qingmin [School of Electrical Engineering, Shandong University, Jinan, Shandong Province 250061 (China)

2010-10-04

83

Radio Frequency Signals in Jupiter's Atmosphere  

PubMed

During the Galileo probe's descent through Jupiter's atmosphere, under the ionosphere, the lightning and radio emission detector measured radio frequency signals at levels significantly above the probe's electromagnetic noise. The signal strengths at 3 and 15 kilohertz were relatively large at the beginning of the descent, decreased with depth to a pressure level of about 5 bars, and then increased slowly until the end of the mission. The 15-kilohertz signals show arrival direction anisotropies. Measurements of radio frequency wave forms show that the probe passed through an atmospheric region that did not support lightning within at least 100 kilometers and more likely a few thousand kilometers of the descent trajectory. The apparent opacity of the jovian atmosphere increases sharply at pressures greater than about 4 bars. PMID:8662576

Lanzerotti; Rinnert; Dehmel; Gliem; Krider; Uman; Bach

1996-05-10

84

Trirotron: triode rotating beam radio frequency amplifier  

DOEpatents

High efficiency amplification of radio frequencies to very high power levels including: establishing a cylindrical cloud of electrons; establishing an electrical field surrounding and coaxial with the electron cloud to bias the electrons to remain in the cloud; establishing a rotating electrical field that surrounds and is coaxial with the steady field, the circular path of the rotating field being one wavelength long, whereby the peak of one phase of the rotating field is used to accelerate electrons in a beam through the bias field in synchronism with the peak of the rotating field so that there is a beam of electrons continuously extracted from the cloud and rotating with the peak; establishing a steady electrical field that surrounds and is coaxial with the rotating field for high-energy radial acceleration of the rotating beam of electrons; and resonating the rotating beam of electrons within a space surrounding the second field, the space being selected to have a phase velocity equal to that of the rotating field to thereby produce a high-power output at the frequency of the rotating field.

Lebacqz, Jean V. (Stanford, CA)

1980-01-01

85

Adversarial Model for Radio Frequency Identification  

Microsoft Academic Search

Abstract Radio Frequency Identification (RFID) systems aim to identify objects in open en - vironments with neither physical nor visual contact They consist of transponders inserted into objects, of readers, and usually of a database which contains information about the objects The key point is that authorised readers must be able to identify tags without an adversary being able to

G. Avoine

2006-01-01

86

Cost cutting using radio frequency inventory control.  

PubMed

Bar coding should be a staple in every hospital by now--but it's not. The author tells how bar coding and the use of radio frequency transmission of inventory data direct to their mainframe computer has saved them time and money. PMID:10117777

Weber, J

1992-05-01

87

Radio frequency interference at the geostationary orbit  

NASA Technical Reports Server (NTRS)

Growing demands on the frequency spectrum have increased the possibility of radio frequency interference (RFI). Various approaches to obtain in orbit RFI data are compared; this comparision indicates that the most practical way to obtain RFI data for a desired orbit (such as a geostationary orbit) is through the extrapolation of in orbit RFI measurements by a low orbit satellite. It is concluded that a coherent RFI program that uses both experimental data and analytical predictions provides accurate RFI data at minimal cost.

Sue, M. K.

1981-01-01

88

Commissioning of helium injector for coupled radio frequency quadrupole and separated function radio frequency quadrupole accelerator.  

PubMed

A project to study a new type of acceleration structure has been launched at Peking University, in which a traditional radio frequency quadrupole (RFQ) and a separated function radio frequency quadrupole are coupled in one cavity to accelerate the He+ beam. A helium injector for this project is developed. The injector consists of a 2.45 GHz permanent magnet electron cyclotron resonance ion source and a 1.16 m long low energy beam transport (LEBT). The commissioning of this injector was carried out and an onsite test was held in June 2013. A 14 mA He+ beam with the energy of 30 keV has been delivered to the end of the LEBT, where a diaphragm with the diameter of 7 mm is located. The position of the diaphragm corresponds to the entrance of the RFQ electrodes. The beam emittance and fraction were measured after the 7 mm diaphragm. Its rms emittance is about 0.14 ??mm?mrad and the fraction of He+ is about 99%. PMID:24593446

Peng, Shixiang; Chen, Jia; Ren, Haitao; Zhao, Jie; Xu, Yuan; Zhang, Tao; Zhang, Ailing; Xia, Wenlong; Gao, Shuli; Wang, Zhi; Luo, Yuting; Guo, Zhiyu; Chen, Jia'er

2014-02-01

89

Radio-frequency Ablation in the Treatment of Hepatic Malignancies  

Microsoft Academic Search

Tumour ablation using radio-frequency energy is attracting increasing attention as an effective minimally invasive ablative technique in the treatment of primary and secondary hepatic tumours. It has been shown to be safe and relatively well tolerated by patients, with few major complications and minimal patient discomfort, and is increasingly being used as an alternative to surgery in patients with unresectable

Richard HG; Lo FRCR

2004-01-01

90

Thermochemiluminescence as a technique for radio frequency radiation dosimetry  

Microsoft Academic Search

Radio frequency radiation (RFR) dosimetry is based on the rate of absorbed energy (specific absorption rate: SAR) per unit mass. It is most conveniently measured by acquiring changes in temperature per unit time and converting the results to joules per second (watts) per kilogram, based on the specific heat of the biological material interacting with the RFR. To date, SAR

Johnathan L. Kiel; John L. Alls; Eric A. Holwitt; Lucille J. V. Stribling; Jill E. Parker

1998-01-01

91

Low frequency radio observations of five rich clusters of galaxies  

SciTech Connect

Observations have been made at 43.0 and 73.8 MHz of five rich x-ray emitting clusters of galaxies: Abell 399/401, Abell 426 (the Perseus cluster), Abell 1367, Abell 1656 (the Coma cluster), and the Virgo cluster. A fan beam synthesis system has been used to search for extended radio emission, i.e., radio halos, in these clusters. Radio halos were detected in the Coma and Virgo clusters. No evidence was found for the existence of 3C84B, the halo source previously thought to exist in the Perseus cluster. If halo sources exist in Abell 399/401 or Abell 1367, they must be quite weak at frequencies less than 100 MHz. The observed sizes of the extended sources in Coma and Virgo imply that the rate of particle propagation away from strong radio galaxies greatly exceeds the Alfven velocity and is probably independent of particle energy.

Hanisch, R.J.; Erickson, W.C.

1980-03-01

92

78 FR 13893 - Certain Radio Frequency Identification (“RFID”) Products and Components Thereof; Notice of...  

Federal Register 2010, 2011, 2012, 2013

...Certain Radio Frequency Identification (``RFID'') Products and Components Thereof...Certain Radio Frequency Identification (``RFID'') Products and Components Thereof...certain radio frequency identification (``RFID'') products and components...

2013-03-01

93

Radio-frequency point-contact electrometer  

NASA Astrophysics Data System (ADS)

We fabricate and characterize a radio-frequency semiconductor point-contact (rf-PC) electrometer analogous to radio-frequency single-electron transistors (rf-SETs) [see Schoelkopf et al., Science 280, 1238 (1998)]. The point contact is formed by surface Schottky gates in a two-dimensional electron gas in an AlGaAs/GaAs heterostructure. In the present setup, the PC is operating as a simple voltage-controlled resistor rather than a quantum point contact and demonstrates a charge sensitivity of about 2×10-1e/Hz at a bandwidth of 30 kHz without the use of a cryogenic rf preamplifier. Since the impedance of a typical point-contact device is much lower than the impedance of the typical SET, a semiconductor-based rf-PC, equipped with practical cryogenic rf preamplifiers, could realize an ultrafast and ultrasensitive electrometer.

Qin, Hua; Williams, David A.

2006-05-01

94

Graphene radio frequency receiver integrated circuit.  

PubMed

Graphene has attracted much interest as a future channel material in radio frequency electronics because of its superior electrical properties. Fabrication of a graphene integrated circuit without significantly degrading transistor performance has proven to be challenging, posing one of the major bottlenecks to compete with existing technologies. Here we present a fabrication method fully preserving graphene transistor quality, demonstrated with the implementation of a high-performance three-stage graphene integrated circuit. The circuit operates as a radio frequency receiver performing signal amplification, filtering and downconversion mixing. All circuit components are integrated into 0.6?mm(2) area and fabricated on 200?mm silicon wafers, showing the unprecedented graphene circuit complexity and silicon complementary metal-oxide-semiconductor process compatibility. The demonstrated circuit performance allow us to use graphene integrated circuit to perform practical wireless communication functions, receiving and restoring digital text transmitted on a 4.3-GHz carrier signal. PMID:24477203

Han, Shu-Jen; Garcia, Alberto Valdes; Oida, Satoshi; Jenkins, Keith A; Haensch, Wilfried

2014-01-01

95

Graphene radio frequency receiver integrated circuit  

NASA Astrophysics Data System (ADS)

Graphene has attracted much interest as a future channel material in radio frequency electronics because of its superior electrical properties. Fabrication of a graphene integrated circuit without significantly degrading transistor performance has proven to be challenging, posing one of the major bottlenecks to compete with existing technologies. Here we present a fabrication method fully preserving graphene transistor quality, demonstrated with the implementation of a high-performance three-stage graphene integrated circuit. The circuit operates as a radio frequency receiver performing signal amplification, filtering and downconversion mixing. All circuit components are integrated into 0.6?mm2 area and fabricated on 200?mm silicon wafers, showing the unprecedented graphene circuit complexity and silicon complementary metal-oxide-semiconductor process compatibility. The demonstrated circuit performance allow us to use graphene integrated circuit to perform practical wireless communication functions, receiving and restoring digital text transmitted on a 4.3-GHz carrier signal.

Han, Shu-Jen; Garcia, Alberto Valdes; Oida, Satoshi; Jenkins, Keith A.; Haensch, Wilfried

2014-01-01

96

47 CFR 2.815 - External radio frequency power amplifiers.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 2009-10-01 false External radio frequency power amplifiers. 2.815 Section...GENERAL RULES AND REGULATIONS Marketing of Radio-frequency Devices § 2.815 External radio frequency power amplifiers. (a) As used...

2009-10-01

97

47 CFR 2.815 - External radio frequency power amplifiers.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false External radio frequency power amplifiers. 2.815 Section...GENERAL RULES AND REGULATIONS Marketing of Radio-frequency Devices § 2.815 External radio frequency power amplifiers. (a) As used...

2010-10-01

98

Review of radio frequency microelectromechanical systems technology  

Microsoft Academic Search

A review of radio frequency microelectromechanical systems (RF MEMS) technology, from the perspective of its enabling technologies (e.g. fabrication, RF micromachined components and actuation mechanisms) is presented.A unique roadmap is given that shows how enabling technologies, RF MEMS components, RF MEMS circuits and RF microsystems packaging are linked together; leading towards enhanced integrated subsystems.An overview of the associated fabrication technologies

S. Lucyszyn

2004-01-01

99

Radio frequency (RF) heated supersonic flow laboratory  

SciTech Connect

A unique supersonic flow apparatus which employs an inductively-coupled, radio frequency (RF) torch to supply high enthalpy source gas to the nozzle inlet is described. The main features of this system are the plasma tube, a cooled nozzle assembly, and a combustion/expansion chamber with a heat exchanger. A description of these components with current test data is presented. In addition, a discussion of anticipated experiments utilizing this system is included.

Wantuck, P.; Watanabe, H.

1990-01-01

100

Radio frequency assisted chemical vapor infiltration  

SciTech Connect

A process for the rapid densification of carbon/carbon composites has been developed. The method makes use of the direct radio frequency heating of three dimensional carbon preforms to establish inverted thermal gradients. Rapid densification from the inside-out, of 2.5 cm. diameter parts, in as little as 30 hours was demonstrated. A simple model is used to predict the initial thermal gradients and is compared to experimental measurements. The results are discussed in terms of frequency, part dimension and radiative heat loss.

Devlin, D.J.; Barbero, R.S.; Siebein, K.N. [Los Alamos National Lab., NM (United States). Materials Science and Technology Div.

1996-06-01

101

Radio frequency interference at QUASAR Network Observatories  

NASA Astrophysics Data System (ADS)

Different sources of radio frequency interference (RFI) at Quasar-network observatories and their affect on VLBIsessions are discussed. For example, the stronger of them registered last time are UMTS mobile phone base stations which were built not far from Quasar-network observatories location. These stations emit signals near 2100MHz and produce RFI of critical level. To control RFI level regular spectral measurements of the intermediate frequency signals at the outputs of the receivers are conducted. As a result, real spread of RFI sources, including DORIS, have to be taken into account in planning of VLBI observation sessions and especially it is concerned VLBI 2010 project realization.

Ilin, Gennadii

2011-07-01

102

Radio-frequency quadrupole vane-tip geometries  

Microsoft Academic Search

Radio-frequency quadrupole (RFQ) linacs are becoming widely accepted in the accelerator community. They have the remarkable capability of simultaneously bunching low-energy ion beams and accelerating them to energies at which conventional accelerators can be used, accomplishing this with high-transmission efficiencies and low-emittance growths. The electric fields, used for radial focusing, bunching, and accelerating, are determined by the geometry of the

K. R. Crandall; R. S. Mills; T. P. Wangler

1983-01-01

103

Part-body and multibody effects on absorption of radio-frequency electromagnetic energy by animals and by models of man  

NASA Technical Reports Server (NTRS)

Fine structure in the whole-body resonant curve for radio-frequency energy deposition in man can be attributed to part-body resonances. As for head resonance, which occurs near 350 MHz in man, the absorptive cross section is nearly three times the physical cross section of the head. The arm has a prominent resonance at 150 MHz. Numerical solutions, antenna theory, and experimental results on animals have shown that whole-body energy deposition may be increased by 50 percent or more because of multiple bodies that are strategically located in the field. Empirical equations for SARs are also presented along with test data for several species of laboratory animals. Barbiturate anesthesia is sufficiently disruptive of thermoregulation that delta Ts of colonic temperature yield energy dose values in several mammals that compare quite favorably with those based on whole-body calorimetry.

Gandhi, O. P.; Hagmann, M. J.; Dandrea, J. A.

1979-01-01

104

Cubesat Missions for Low Frequency Radio Astronomy  

NASA Astrophysics Data System (ADS)

There have been many concepts and several mission proposals for low frequency radio interferometers in space during the past two decades. Most of these idea are based on multiple small spacecraft, each acting as one antenna element in a three-dimensional array. The science goals for single cubesats or arrays operating at frequencies near and below Earth's ionosphere cutoff span a wide range research areas from solar and planetary observations to galactic and extragalactic astronomy to cosmological observations of large-scale structure evolution before the epoch of reionization. Recently several groups have realized that the rapid progress in the capabilities of cubesats make them a logical basis for such mission concepts. A workshop on cubesat-based low frequency radio astronomy missions was held at the Keck Institute for Space Studies (KISS) at Caltech during July 2012. This paper will summarize the discussions and conclusions from that workshop. These include a number of future mission ideas based on cubesat technologies, as well as recommendations for near-term technology demonstrations that would reduce risk for many of the potential missions. Portions of this work were carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Support from the JPL Center for Academic Partnerships and KISS is gratefully acknowledged.

Jones, Dayton L.

2013-01-01

105

Low Frequency Radio Observations of GRS1915+105 with GMRT  

NASA Astrophysics Data System (ADS)

We present the first detailed low frequency radio measurements of the galactic microquasar GRS1915+105 with GMRT. Simultaneous observations were carried out at 610 and 244 MHz. Our data does not show any signature of spectral turn over even at low radio frequency of 244 MHz. We propose that while the radio emission at high radio frequencies could predominantly come from compact jets, the emission at lower frequency originates in the lobes at the end of the jet which acts like a reservoir of low energy electrons.

Ishwara-Chandra, C. H.; Pramesh Rao, A.; Pandey, Mamta; Manchanda, R. K.; Durouchoux, Philippe

2005-06-01

106

The Mariner Mars 1971 radio frequency subsystem  

NASA Technical Reports Server (NTRS)

The radio frequency subsystem (RFS) for the Mariner Mars 1971 (MM'71) spacecraft is described. The MM'69 RFS was used as the baseline design for the MM'71 RFS, and the report describes the design changes made to the 1969 RFS for use on MM'71. It also cites various problems encountered during the fabrication and testing of the RFS, as well as the types of tests to which the RFS was subjected. In areas where significant problems were encountered, a detailed description of the problem and its solution is presented. In addition, some recommendations are given for modifications to the RFS and test techniques for future programs.

Hughes, R. S.

1972-01-01

107

Radio frequency identification applications in hospital environments.  

PubMed

Radio frequency identification (RFID) technology has recently begun to receive increased interest from practitioners and academicians. This interest is driven by mandates from major retailers such as Wal-Mart, Target and Metro Group, and the United States Department of Defense, in order to increase the efficiency and visibility of material and information flows in the supply chain. However, supply chain managers do not have a monopoly on the deployment of RFID. In this article, the authors discuss the potential benefits, the areas of applications, the implementation challenges, and the corresponding strategies of RFID in hospital environments. PMID:16913301

Wicks, Angela M; Visich, John K; Li, Suhong

2006-01-01

108

Optical generation of radio-frequency power  

SciTech Connect

An optical technique for high-power radio-frequency (RF) signal generation is described. The technique uses a unique photodetector based on a traveling-wave design driven by an appropriately modulated light source. The traveling-wave photodetector (TWPD) exhibits simultaneously a theoretical quantum efficiency approaching 100 % and a very large electrical bandwidth. Additionally, it is capable of dissipating the high-power levels required for the RF generation technique. The modulated light source is formed by either the beating together of two lasers or by the direct modulation of a light source. A system example is given which predicts RF power levels of 100`s of mW`s at millimeter wave frequencies with a theoretical ``wall-plug`` efficiency approaching 34%.

Hietala, V.M.; Vawter, G.A.; Brennan, T.M.; Hammons, B.E.; Meyer, W.J.

1994-11-01

109

Radio Frequency Heating of Foods: Principles, Applications and Related Properties—A Review  

Microsoft Academic Search

Radio frequency (RF) heating is a promising technology for food applications because of the associated rapid and uniform heat distribution, large penetration depth and lower energy consumption. Radio frequency heating has been successfully applied for drying, baking and thawing of frozen meat and in meat processing. However, its use in continuous pasteurization and sterilization of foods is rather limited. During

Punidadas Piyasena; Chantal Dussault; Tatiana Koutchma; H. S. Ramaswamy; G. B. Awuah

2003-01-01

110

Sensitive ultrasonic delineation of steroid treatment in living dystrophic mice with energy-based and entropy-based radio frequency signal processing.  

PubMed

Duchenne muscular dystrophy is a severe wasting disease, involving replacement of necrotic muscle tissue by fibrous material and fatty infiltrates. One primary animal model of this human disease is the X chromosome-linked mdx strain of mice. The goals of the present work were to validate and quantify the capability of both energy and entropy metrics of radio-frequency ultrasonic backscatter to differentiate among normal, dystrophic, and steroid-treated skeletal muscle in the mdx model. Thirteen 12-month-old mice were blocked into three groups: 4 treated mdx-dystrophic that received daily subcutaneous steroid (prednisolone) treatment for 14 days, 4 positive-control mdx-dystrophic that received saline injections for 14 days, and 5 negative-control animals. Biceps muscle of each animal was imaged in vivo using a 40-MHz center frequency transducer in conjunction with a Vevo-660 ultrasound system. Radio-frequency data were acquired (1 GHz, 8 bits) corresponding to a sequence of transverse images, advancing the transducer from "shoulder" to "elbow" in 100-micron steps. Data were processed to generate both "integrated backscatter" (log energy), and "entropy" (information theoretic receiver, H(f)) representations. Analyses of the integrated-backscatter values delineated both treated-and untreated-mdx biceps from normal controls (p < 0.01). Complementary analyses of the entropy images differentiated the steroid-treated and positive-control mdx groups (p < 0.01). To our knowledge, this study represents the first reported use of quantitative ultrasonic characterization of skeletal muscle in mdx mice. Successful differentiation among dystrophic, steroid-treated, and normal tissues suggests the potential for local noninvasive monitoring of disease severity and therapeutic effects. PMID:18051163

Wallace, Kirk D; Marsh, Jon N; Baldwin, Steven L; Connolly, Anne M; Keeling, Richard; Lanza, Gregory M; Wickline, Samuel A; Hughes, Michael S

2007-11-01

111

Introduction to special section on Mitigation of Radio Frequency Interference in Radio Astronomy  

NASA Astrophysics Data System (ADS)

The papers contained in this special section are extended versions of some of the papers presented at the Workshop on the Mitigation of Radio Frequency Interference in Radio Astronomy (RFI2004), held in Penticton, British Columbia, Canada, in July 2004.

Ellingson, Steven W.

2005-07-01

112

Comparison of radio frequency energy absorption in ear and eye region of children and adults at 900, 1800 and 2450 MHz  

NASA Astrophysics Data System (ADS)

The increasing use of mobile communication devices, especially mobile phones by children, has triggered discussions on whether there is a larger radio frequency (RF) energy absorption in the heads of children compared to that of adults. The objective of this study was to clarify possible differences in RF energy absorption in the head region of children and adults using computational techniques. Using the finite-difference time-domain (FDTD) computational method, a set of specific absorption rate (SAR) calculations were performed for anatomically correct adult and child head models. A half-wave dipole was used as an exposure source at 900, 1800 and 2450 MHz frequencies. The ear and eye regions were studied representing realistic exposure scenarios to current and upcoming mobile wireless communication devices. The differences in absorption were compared with the maximum energy absorption of the head model. Four magnetic resonance imaging (MRI) based head models, one female, one adult, two child head models, aged 3 and 7 years, were used. The head models greatly differ from each other in terms of size, external shape and the internal anatomy. The same tissue dielectric parameters were applied for all models. The analyses suggest that the SAR difference between adults and children is more likely caused by the general differences in the head anatomy and geometry of the individuals rather than age. It seems that the external shape of the head and the distribution of different tissues within the head play a significant role in the RF energy absorption.

Keshvari, J.; Lang, S.

2005-09-01

113

Comparison of radio frequency energy absorption in ear and eye region of children and adults at 900, 1800 and 2450 MHz.  

PubMed

The increasing use of mobile communication devices, especially mobile phones by children, has triggered discussions on whether there is a larger radio frequency (RF) energy absorption in the heads of children compared to that of adults. The objective of this study was to clarify possible differences in RF energy absorption in the head region of children and adults using computational techniques. Using the finite-difference time-domain (FDTD) computational method, a set of specific absorption rate (SAR) calculations were performed for anatomically correct adult and child head models. A half-wave dipole was used as an exposure source at 900, 1800 and 2450 MHz frequencies. The ear and eye regions were studied representing realistic exposure scenarios to current and upcoming mobile wireless communication devices. The differences in absorption were compared with the maximum energy absorption of the head model. Four magnetic resonance imaging (MRI) based head models, one female, one adult, two child head models, aged 3 and 7 years, were used. The head models greatly differ from each other in terms of size, external shape and the internal anatomy. The same tissue dielectric parameters were applied for all models. The analyses suggest that the SAR difference between adults and children is more likely caused by the general differences in the head anatomy and geometry of the individuals rather than age. It seems that the external shape of the head and the distribution of different tissues within the head play a significant role in the RF energy absorption. PMID:16148398

Keshvari, J; Lang, S

2005-09-21

114

Radio Frequency Mass Gauging of Propellants  

NASA Technical Reports Server (NTRS)

A combined experimental and computer simulation effort was conducted to measure radio frequency (RF) tank resonance modes in a dewar partially filled with liquid oxygen, and compare the measurements with numerical simulations. The goal of the effort was to demonstrate that computer simulations of a tank's electromagnetic eigenmodes can be used to accurately predict ground-based measurements, thereby providing a computational tool for predicting tank modes in a low-gravity environment. Matching the measured resonant frequencies of several tank modes with computer simulations can be used to gauge the amount of liquid in a tank, thus providing a possible method to gauge cryogenic propellant tanks in low-gravity. Using a handheld RF spectrum analyzer and a small antenna in a 46 liter capacity dewar for experimental measurements, we have verified that the four lowest transverse magnetic eigenmodes can be accurately predicted as a function of liquid oxygen fill level using computer simulations. The input to the computer simulations consisted of tank dimensions, and the dielectric constant of the fluid. Without using any adjustable parameters, the calculated and measured frequencies agree such that the liquid oxygen fill level was gauged to within 2 percent full scale uncertainty. These results demonstrate the utility of using electromagnetic simulations to form the basis of an RF mass gauging technology with the power to simulate tank resonance frequencies from arbitrary fluid configurations.

Zimmerli, Gregory A.; Vaden, Karl R.; Herlacher, Michael D.; Buchanan, David A.; VanDresar, Neil T.

2007-01-01

115

Imaging interplanetary CMEs at radio frequency from solar polar orbit  

NASA Astrophysics Data System (ADS)

Coronal mass ejections (CMEs) represent a great concentration of mass and energy input into the lower corona. They have come to be recognized as the major driver of physical conditions change in the Sun-Earth system. Consequently, observations of CMEs are important for understanding and ultimately predicting space weather conditions. This paper discusses a proposed mission, the Solar Polar Orbit Radio Telescope (SPORT) mission, which will observe the propagation of interplanetary CMEs to distances of near 0.35 AU from the Sun. The orbit of SPORT is an elliptical solar polar orbit. The inclination angle between the orbit and ecliptic plane should be about 90°. The main payload on board SPORT will be an imaging radiometer working at the meter wavelength band (radio telescope), which can follow the propagation of interplanetary CMEs. The images that are obtained by the radio telescope embody the brightness temperature of the objectives. Due to the very large size required for the antenna aperture of the radio telescope, we adopt interferometric imaging technology to reduce it. Interferometric imaging technology is based on indirect spatial frequency domain measurements plus Fourier transformation. The SPORT spacecraft will also be equipped with a set of optical and in situ measurement instruments such as a EUV solar telescope, a solar wind ion instrument, an energetic particle detector, a magnetometer, a wave detector and a solar radio burst spectrometer.

Wu, Ji; Sun, Weiying; Zheng, Jianhua; Zhang, Cheng; Liu, Hao; Yan, Jingye; Wang, Chi; Wang, Chuanbing; Wang, Shui

2011-09-01

116

Low Frequency Radio Emissions: Remote Sensing of the Energetic Heliosphere  

NASA Astrophysics Data System (ADS)

Low frequency radio emissions (below about 50 MHz) are tracers of energetic plasma instabilities. Their observation provides us with a unique proxy for instable energetic electron populations. In the solar wind, two types of emissions can be monitored: Type II and Type III radio bursts. The former are related to interplanetary shocks, while the latter are linked to energetic electron beams going out from the solar corona. The magnetized planets are also producing low frequency radio emissions linked to the auroral activity, and thus to the interaction between the planet and the solar wind. These radio emission are non-thermal emissions. They are very powerful (Jupiter is as intense as the Sun in this frequency range). Furthermore, the low frequency radio instrumentation in space has the advantage to be quasi-isotropic. The antenna systems have no intrinsic directivity. However, goniopolarimetric inversions have been developed to derive the observed radio waves parameters (assuming we see a single source at a given time). Hence, the low frequency radio systems can monitor the whole sky at once and provide direction of arrival for each event. We will present the various emission mechanisms involved for the low frequency radio emissions in the solar system, the various propagation effects along the wave path and the radio instrumentation necessary to derived all relevant wave parameters. We will discuss how these radio emissions can be used in a space weather perspective. We will finally overview the possible future steps in terms of instrumentation for this frequency range.

Cecconi, Baptiste

2014-05-01

117

An improved integrally formed radio frequency quadrupole  

DOEpatents

An improved radio frequency quadrupole is provided having an elongate housing with an elongate central axis and top, bottom and two side walls symmetrically disposed about the axis, and vanes formed integrally with the walls, the vanes each having a cross-section at right angles to the central axis which tapers inwardly toward the axis to form electrode tips spaced from each other by predetermined distances. Each of the four walls, and the vanes integral therewith, is a separate structural element having a central lengthwise plane passing through the tip of the vane, the walls having flat mounting surfaces at right angles to and parallel to the control plane, respectively, which are butted together to position the walls and vane tips relative to each other. 4 figs.

Abbott, S.R.

1987-10-05

118

Hybrid optical radio frequency airborne communications  

NASA Astrophysics Data System (ADS)

Optical RF Communications Adjunct Program flight test results provide validation of the theoretical models and hybrid optical radio frequency (RF) airborne system concepts developed by the Defense Advanced Research Projects Agency and the U.S. Air Force Research Laboratory. Theoretical models of the free-space optical communications (FSOC), RF, and network components accurately predict the flight test results under a wide range of day and night operating conditions. The FSOC system, including the adaptive optics and optical modem, can operate under high turbulence conditions. The RF and network mechanisms of Layer 2 retransmission and failover provide increased reliability, reducing end-to-end packet error rates. Overall the test results show that stable, long-range FSOC is possible and practical for near-term operations.

Bagley, Zachary C.; Hughes, David H.; Juarez, Juan C.; Kolodzy, Paul; Martin, Todd; Northcott, Malcolm; Pike, H. Alan; Plasson, Ned D.; Stadler, Brian; Stotts, Larry B.; Young, David W.

2012-05-01

119

Nb3Sn for Radio Frequency Cavities  

SciTech Connect

In this article, the suitability of Nb3Sn to improve theperformance of superconducting Radio-Frequency (RF)cavities is discussed.The use of Nb3Sn in RF cavitiesis recognized as an enabling technology toretain a veryhigh cavity quality factor (Q0) at 4.2 K and tosignificantly improve the cavity accelerating efficiency per unitlength(Eacc). This potential arises through the fundamental properties ofNb3Sn. The properties that are extensively characterized in theliterature are, however, mainly related to improvements in currentcarrying capacity (Jc) in the vortex state. Much less is available forthe Meissner state, which is of key importance to cavities. Relevantdata, available for the Meissner state is summarized, and it is shown howthis already validates the use of Nb3Sn. In addition, missing knowledgeis highlighted and suggestions are given for further Meissner statespecific research.

Godeke, A.

2006-12-18

120

Radio-frequency low-coherence interferometry.  

PubMed

A method for retrieving low-coherence interferograms, based on the use of a microwave photonics filter, is proposed and demonstrated. The method is equivalent to the double-interferometer technique, with the scanning interferometer replaced by an analog fiber-optics link and the visibility recorded as the amplitude of its radio-frequency (RF) response. As a low-coherence interferometry system, it shows a decrease of resolution induced by the fiber's third-order dispersion (?3). As a displacement sensor, it provides highly linear and slope-scalable readouts of the interferometer's optical path difference in terms of RF, even in the presence of third-order dispersion. In a proof-of-concept experiment, we demonstrate 20-?m displacement readouts using C-band EDFA sources and standard single-mode fiber. PMID:24978555

Fernández-Pousa, Carlos R; Mora, José; Maestre, Haroldo; Corral, Pablo

2014-06-15

121

Radio-frequency measurements of coherent transition and Cherenkov radiation: Implications for high-energy neutrino detection  

Microsoft Academic Search

We report on measurements of (11-18)-cm wavelength radio emission from interactions of 15.2 MeV pulsed electron bunches at the Argonne Wakefield Accelerator. The electrons were observed both in a configuration where they produced primarily transition radiation from an aluminum foil, and in a configuration designed for the electrons to produce Cherenkov radiation in a silica sand target. Our aim was

Peter W. Gorham; David P. Saltzberg; Paul Schoessow; Wei Gai; John G. Power; Richard Konecny; M. E. Conde

2000-01-01

122

Cassini/RPWS: A low frequency radio imager at Saturn  

NASA Astrophysics Data System (ADS)

The High Frequency Receiver (HFR) of the Radio and Plasma Waves Science experiment (RPWS) onboard Cassini is a sensitive, and versatile radio instrument. Although the radio antenna connected to this instrument have no intrinsic directivity, the HFR measurements can provide instantaneous direction of arrival, flux density and polarization degree of the observed radio waves. Hence, the HFR can be described as an full-sky radio imager. As the instrument provides direction of arrival, radio sources can be located with some assumption on the propagation between the source and the observer. Hence, it is possible to produce radio source maps and correlate them with observations at other wavelengths, such as UV or IR observations of the auroral regions of Saturn. The flux and polarization measurements together with the time-frequency shape of the radio emissions can also be used to identify the radio emission processes. We present a review of the results of the Cassini/RPWS/HFR observations since its arrival at Saturn in 2004: interpretation of the radio arc shapes and equatorial shadow zones; in-situ observations in the radio source region; comparison with other wavelengths and particle measurements; confirmation of the Cyclotron Maser Instability (CMI) as the main emission mechanism for auroral radio emissions; monitoring of the radio emission variability in time and location, etc.

Cecconi, Baptiste; Lamy, Laurent; Zarka, Philippe

2014-05-01

123

Systems and Methods for Determining Radio Frequency Interference.  

National Technical Information Service (NTIS)

The presence, frequency and amplitude of radio frequency interference superimposed on communication links originating from a terrestrial region and including a relay in a geostationary spacecraft are determined by pointing a narrow beam antenna on the sat...

K. Johannsen S. Sabaroff V. F. Henry

1976-01-01

124

Radio Frequency Interference Mitigation at the Westerbork Synthesis Radio Telescope: Algorithms, Test Observations, and System Implementation  

NASA Astrophysics Data System (ADS)

The sensitivity of radio astronomical stations is often limited by man-made radio frequency interference (RFI) due to a variety of terrestrial activities. An RFI mitigation subsystem (RFIMS) based on real-time digital signal-processing is proposed here for the Westerbork Synthesis Radio Telescope based on a powerful field programmable gate array processor. In this system the radio astronomy signals polluted by RFI are ``cleaned'' with the RFIMS before routine back-end correlation processing takes place. The high temporal and frequency resolution of RFIMS allows the detection and excision of RFI better than do standard radio telescope back-end configurations.

Baan, W. A.; Fridman, P. A.; Millenaar, R. P.

2004-08-01

125

Experimental radio frequency link for Ka-band communications applications  

NASA Technical Reports Server (NTRS)

An experimental radio frequency link has been demonstrated to provide two-way communication between a remote user ground terminal and a ground-based Ka-band transponder. Bit-error-rate performance and radio frequency characteristics of the communication link were investigated.

Fujikawa, Gene; Conray, Martin J.; Saunders, Alan L.; Pope, Dale E.

1988-01-01

126

Study on dedicated radio frequency for railway use  

Microsoft Academic Search

In this paper, the study on the allocation of dedicated radio frequency for the radio communication based CBTC (Communication Based Train Control) system is performed. The dedicated bandwidth for the railway use is figured out and the allocable frequency bands, which should be investigated hereafter, are proposed. The result of this study provides the basis to present the requirement of

Zhong-Hua Quan; Myung-Seon Ryou; Seung-Hwan Song; Duk-Hee Lee; Duk-Kyu Park

2010-01-01

127

Algorithms for the Radio Link Frequency Assignment Problem.  

National Technical Information Service (NTIS)

The radio link frequency assignment problem occurs when a network of radio links has to be established. Each link must be assigned an operating frequency from a given domain. The assignment has to satisfy certain restrictions so as to limit the interferen...

K. Aardal J. K. Lenstra S. Tiourine

1999-01-01

128

Investigations of the output energy deviation and other parameters during commissioning of the four-rod radio frequency quadrupole at the Fermi National Accelerator Laboratory  

NASA Astrophysics Data System (ADS)

After 30 years of operation, the Cockcroft-Walton based injector at the Fermi National Accelerator Laboratory has been replaced by a new beam line including a dimpled magnetron 35 keV source in combination with a 750 keV four-rod radio frequency quadrupole (RFQ). The new injector is followed by the existing drift tube linac. Prior to installation, a test beam line was built which included the magnetron source and the four-rod RFQ with a number of beam measurement instrumentation. The first beam test with the RFQ showed an output energy deviation greater than 2.5%. Other problems also showed up which led to investigations of the output energy, power consumption and transmission properties using rf simulations which were complemented with additional beam measurements. The sources of this deviation and the mechanical modifications of the RFQ to solve this matter will be presented in this paper. Meanwhile, the nominal output energy of 750 keV has been confirmed and the new injector with the four-rod RFQ is in full operation.

Schmidt, J. S.; Koubek, B.; Schempp, A.; Tan, C. Y.; Bollinger, D. S.; Duel, K. L.; Karns, P. R.; Pellico, W. A.; Scarpine, V. E.; Schupbach, B. A.; Kurennoy, S. S.

2014-03-01

129

Comparison of two cyclostationary detectors for radio frequency interference mitigation in radio astronomy  

NASA Astrophysics Data System (ADS)

Radio frequency interference (RFI) mitigation has become a significant issue for current and future radio telescopes. This paper presents a new scheme for removing radio frequency interference from astronomical data. It exploits a priori knowledge of the transmitters, namely, their cyclostationary statistical properties. Two real-time cyclostationary detectors are proposed and compared. Results on both synthetic and real data demonstrate the efficiency of this concept.

Bretteil, S.; Weber, R.

2005-07-01

130

Planck Early Results. XV. Spectral Energy Distributions and Radio Continuum Spectra of Northern Extragalactic Radio Sources  

NASA Technical Reports Server (NTRS)

Spectral energy distributions (SEDs) and radio continuum spectra are presented for a northern sample of 104 extragalactic radio sources. based on the Planck Early Release Compact Source Catalogue (ERCSC) and simultaneous multi frequency data. The nine Planck frequencies, from 30 to 857 GHz, are complemented by a set of simultaneous observations ranging from radio to gamma-rays. This is the first extensive frequency coverage in the radio and millimetre domains for an essentially complete sample of extragalactic radio sources, and it shows how the individual shocks, each in their own phase of development, shape the radio spectra as they move in the relativistic jet. The SEDs presented in this paper were fitted with second and third degree polynomials to estimate the frequencies of the synchrotron and inverse Compton (IC) peaks, and the spectral indices of low and high frequency radio data, including the Planck ERCSC data, were calculated. SED modelling methods are discussed, with an emphasis on proper. physical modelling of the synchrotron bump using multiple components. Planck ERCSC data also suggest that the original accelerated electron energy spectrum could be much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The implications of this are discussed for the acceleration mechanisms effective in blazar shock. Furthermore in many cases the Planck data indicate that gamma-ray emission must originate in the same shocks that produce the radio emission.

Aatrokoski, J.; Ade, P. A. R.; Aghanim, N.; Aller, H. D.; Aller, M. F.; Angelakis, E.; Amaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Balbi, A.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Battaner, E.; Benabed, K.; Benoit, A.; Berdyugin, A.; Bernard, J. P.; Bersanelli, M.; Bhatia, R.; Bonaldi, A.; Bonavera, L.; Gehrels, N.

2011-01-01

131

Wideband micromachined microphones with radio frequency detection  

NASA Astrophysics Data System (ADS)

There are many commercial, scientific, and military applications for miniature wideband acoustic sensors, including monitoring the condition or wear of equipment, collecting scientific data, and identifying and localizing military targets. The application of semiconductor micromachining techniques to sensor fabrication has the potential to transform acoustic sensing with small, reproducible, and inexpensive silicon-based microphones. However, such sensors usually suffer from limited bandwidth and from non-uniformities in their frequency response due to squeeze-film damping effects and narrow air gaps. Furthermore, they may be too fragile to be left unattended in a humid or dusty outdoor environment. Silicon microphones that incorporate capacitive micromachined ultrasonic transducer membranes overcome some of the drawbacks of conventional microphones. These micromachined membranes are small and robust enough to be vacuum-sealed, and can withstand atmospheric pressure and submersion in water. In addition, the membrane mechanical response is flat from dc up to ultrasonic frequencies, resulting in a wideband sensor for accurate spectral analysis of acoustic signals. However, a sensitive detection scheme is necessary to detect the small changes in membrane displacement that result from using smaller, stiffer membranes than do conventional microphones. We propose a radio frequency detection technique, in which the capacitive membranes are incorporated into a transmission line. Variations in membrane capacitance due to impinging sound pressure are sensed through the phase variations of a carrier signal that propagates along the line. This dissertation examines the design, fabrication, modeling, and experimental measurements of wideband micromachined microphones using sealed ultrasonic membranes and RF detection. Measurements of fabricated microphones demonstrate less than 0.5 dB variation in their output responses between 0.1 Hz to 100 kHz under electrostatic actuation of the membranes. The measured equivalent noise level of a fabricated 3 mm by 3 mm sensor is 53.8 dB(A) SPL in the audio band using a simple phase detection circuit operating at 2.8 GHz. Because the vacuum-sealed membrane structure has a low mechanical noise floor, sensitivity may be improved with higher carrier frequencies and more sophisticated detection circuitry.

Hansen, Sean Thomas

132

Directional Radio-Frequency Identification Tag Reader  

NASA Technical Reports Server (NTRS)

A directional radio-frequency identification (RFID) tag reader has been designed to facilitate finding a specific object among many objects in a crowded room. The device could be an adjunct to an electronic inventory system that tracks RFID-tagged objects as they move through reader-equipped doorways. Whereas commercial RFID-tag readers do not measure directions to tagged objects, the device is equipped with a phased-array antenna and a received signal-strength indicator (RSSI) circuit for measuring direction. At the beginning of operation, it is set to address only the RFID tag of interest. It then continuously transmits a signal to interrogate that tag while varying the radiation pattern of the antenna. It identifies the direction to the tag as the radiation pattern direction of peak strength of the signal returned by the tag. An approximate distance to the tag is calculated from the peak signal strength. The direction and distance can be displayed on a screen. A prototype containing a Yagi antenna was found to be capable of detecting a 915.5-MHz tag at a distance of approximately equal to 15 ft (approximately equal to 4.6 m).

Medelius, Pedro J.; Taylor, John D.; Henderson, John J.

2004-01-01

133

Soviet high-power radio frequency research  

NASA Astrophysics Data System (ADS)

A panel of U.S. scientists and engineers assessed Soviet research in high powered microwaves in the early 1980s, as reflected in information released publicly. In the centimeter band, the USSR is far ahead of the U.S. in developing backward wave oscillators (BWOs) at extremely high peak power levels and high efficiency. Soviet scientists are also far ahead in developing repetitively pulsed BWOs and magnetrons, and in compact packaging of these repetitively pulsed generators. In high power millimeter wave devices, Soviet capability is at the forefront in gyrotron development, but lags in free electron laser experiments. Soviet research on gyrotron amplifiers aimed at providing radio frequency power for linear supercolliders has produced a 60 dB amplifier at 7 GHz capable of producing 60 MW output pulses of 0.7 microsec duration. An almost complete absence in recent USSR literature on vircators or on phase locking of high power microwave sources is noted. Only one publication on high power microwave component development or high power microwave propagation was found in recent USSR literature. No mention of testing electronic components for damage by high microwaves was found, although references were made to effects of nuclear electromagnetic pulses.

Granatstein, V. L.; Benford, J. N.; Bombardt, J. N.; Gold, A.; Levush, B.; Thiele, G. A.; Vanlint, V. A. J.; McKenney, Barbara L.; McGrain, Moira; Taub, Renee G.

1988-07-01

134

Extending the ICRF to Higher Radio Frequencies  

NASA Technical Reports Server (NTRS)

The ICRF forms the basis for all astrometry including use as the inertial coordinate system for navigating deep space missions. This frame was defined using S/X-band observations over the past 20+ years. In January 2002, the VLBA approved our proposal for observing time to extend the ICRF to K-band (24 GHz) and Q-band (43 GHz). The first step will be observations at K- and Q-bands on a subset of ICRF sources. Eventually, K- and Q-band multi-epoch observations will be used to estimate positions, flux density and source structure for a large fraction of the current S/X-band ICRF source list. This work will benefit the radio astronomy community by extending the VLBA calibrator list at these bands. In the longer term, we would also like to extend the ICRF to Ka-band (32 GHz). A celestial reference frame will be needed at this frequency to support deep space navigation. A navigation demonstration is being considered for NASA's Mars 2005 mission. The initial K- and Q-band work will serve to identify candidate sources at Ka-band for use with that mission.

Jacobs, C. S.; Jones, D. L.; Lanyi, G. E.; Lowe, S. T.; Naudet, C. J.; Resch, G. M.; Steppe, J. A.; Zhang, L. D.; Ulvestad, J. S.; Taylor, G. B.

2002-01-01

135

Development and test results of the low-energy demonstration accelerator (LEDA) proton injector on a 1.25 MeV cw radio frequency quadrupole  

SciTech Connect

The low-energy demonstration accelerator (LEDA) 75-keV proton injector is being developed for tests of high-current (100-mA) cw linacs. The injector comprises a microwave proton source and a space-charge neutralized magnetic low-energy beam-transport system (LEBT). The LEDA injector has been configured to provide flexible 50-keV beam matching into a cw 1.25-MeV radio-frequency quadrupole (RFQ) brought from Chalk River Laboratories (CRL). The LEBT has two solenoid focus magnets separated by 117 cm. Between the solenoids are two steering magnets and diagnostic stations for measuring the beam current, profile, and position. The ion-source extraction system was modified to a 50-keV triode to test the injector/RFQ system. Beam-matching tests showed that injector-RFQ transmission is 90% for 50-mA RFQ current. At the RFQ design current of 75 mA the beam transmission decreased to 80--85%. Optimized injector tuning led to 100-mA beam accelerated through the RFQ.

Sherman, J.; Bolme, G.; Hansborough, L. [and others

1998-12-31

136

Tabu Search for Frequency Assignment in Mobile Radio Networks  

Microsoft Academic Search

The main goal of the Frequency Assignment Problem in mobile radio networksconsists of assigning a limited number of frequencies to each radio cell in a cellularnetwork while minimizing electro-magnetic interference due to the re-use of frequencies.This problem, known to be NP-hard, is of great importance in practice since bettersolutions will allow a telecommunications operator to manage larger cellular networks.This paper

Jin-kao Hao; Raphaël Dorne; Philippe Galinier

1998-01-01

137

Dynamics Of Ions In A Radio-Frequency Quadrupole Trap  

NASA Technical Reports Server (NTRS)

Report describes computer-simulation study of motions of various numbers of ions in Paul trap. Study part of continuing effort to understand motions of trapped charged particles (atoms, ions, molecules, or dust particles). Motions characterized in terms of heating by radio-frequency fields, formation of crystallike structures in cold clouds of trapped particles, and other phenomena important in operation of radio-frequency traps in frequency standards.

Prestage, John D.; Williams, Angelyn P.; Maleki, Lutfollah

1994-01-01

138

Fundamental investigations of capacitive radio frequency plasmas: simulations and experiments  

NASA Astrophysics Data System (ADS)

Capacitive radio frequency (RF) discharge plasmas have been serving hi-tech industry (e.g. chip and solar cell manufacturing, realization of biocompatible surfaces) for several years. Nonetheless, their complex modes of operation are not fully understood and represent topics of high interest. The understanding of these phenomena is aided by modern diagnostic techniques and computer simulations. From the industrial point of view the control of ion properties is of particular interest; possibilities of independent control of the ion flux and the ion energy have been utilized via excitation of the discharges with multiple frequencies. ‘Classical’ dual-frequency (DF) discharges (where two significantly different driving frequencies are used), as well as discharges driven by a base frequency and its higher harmonic(s) have been analyzed thoroughly. It has been recognized that the second solution results in an electrically induced asymmetry (electrical asymmetry effect), which provides the basis for the control of the mean ion energy. This paper reviews recent advances on studies of the different electron heating mechanisms, on the possibilities of the separate control of ion energy and ion flux in DF discharges, on the effects of secondary electrons, as well as on the non-linear behavior (self-generated resonant current oscillations) of capacitive RF plasmas. The work is based on a synergistic approach of theoretical modeling, experiments and kinetic simulations based on the particle-in-cell approach.

Donkó, Z.; Schulze, J.; Czarnetzki, U.; Derzsi, A.; Hartmann, P.; Korolov, I.; Schüngel, E.

2012-12-01

139

48 CFR 552.211-92 - Radio Frequency Identification (RFID) using passive tags.  

Code of Federal Regulations, 2010 CFR

...false Radio Frequency Identification (RFID) using passive tags. 552.211-92...211-92 Radio Frequency Identification (RFID) using passive tags. As prescribed...clause: Radio Frequency Identification (RFID) Using Passive Tags (JAN...

2010-10-01

140

78 FR 19311 - Certain Radio Frequency Identification (“RFID”) Products And Components Thereof; Institution of...  

Federal Register 2010, 2011, 2012, 2013

...Certain Radio Frequency Identification (``RFID'') Products And Components Thereof...certain radio frequency identification (``RFID'') products and components thereof by...certain radio frequency identification (``RFID'') products and components thereof...

2013-03-29

141

47 CFR 2.803 - Marketing of radio frequency devices prior to equipment authorization.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 false Marketing of radio frequency devices prior to equipment authorization...RULES AND REGULATIONS Marketing of Radio-frequency Devices § 2.803 Marketing of radio frequency devices prior to equipment...

2009-10-01

142

77 FR 35426 - Certain Radio Frequency Integrated Circuits and Devices Containing Same; Institution of...  

Federal Register 2010, 2011, 2012, 2013

...No. 337-TA-848] Certain Radio Frequency Integrated Circuits and Devices...after importation of certain radio frequency integrated circuits and devices...after importation of certain radio frequency integrated circuits and...

2012-06-13

143

47 CFR 2.803 - Marketing of radio frequency devices prior to equipment authorization.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Marketing of radio frequency devices prior to equipment authorization...RULES AND REGULATIONS Marketing of Radio-frequency Devices § 2.803 Marketing of radio frequency devices prior to equipment...

2010-10-01

144

75 FR 6818 - Revision to the Manual of Regulations and Procedures for Federal Radio Frequency Management  

Federal Register 2010, 2011, 2012, 2013

...Regulations and Procedures for Federal Radio Frequency Management AGENCY: National...Regulations and Procedures for Federal Radio Frequency Management (NTIA Manual...Regulations and Procedures for Federal Radio Frequency Management with which...

2010-02-11

145

77 FR 75567 - Revision to the Manual of Regulations and Procedures for Federal Radio Frequency Management  

Federal Register 2010, 2011, 2012, 2013

...Regulations and Procedures for Federal Radio Frequency Management AGENCY: National...Regulations and Procedures for Federal Radio Frequency Management (NTIA Manual...Regulations and Procedures for Federal Radio Frequency Management with which...

2012-12-21

146

76 FR 56984 - Revision to the Manual of Regulations and Procedures for Federal Radio Frequency Management  

Federal Register 2010, 2011, 2012, 2013

...Regulations and Procedures for Federal Radio Frequency Management AGENCY: National...Regulations and Procedures for Federal Radio Frequency Management (NTIA Manual...Regulations and Procedures for Federal Radio Frequency Management with which...

2011-09-15

147

76 FR 18652 - Revision to the Manual of Regulations and Procedures for Federal Radio Frequency Management  

Federal Register 2010, 2011, 2012, 2013

...Regulations and Procedures for Federal Radio Frequency Management AGENCY: National...Regulations and Procedures for Federal Radio Frequency Management (NTIA Manual...Regulations and Procedures for Federal Radio Frequency Management with which...

2011-04-05

148

47 CFR 15.204 - External radio frequency power amplifiers and antenna modifications.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 false External radio frequency power amplifiers and antenna...COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators § 15.204 External radio frequency power amplifiers and...

2009-10-01

149

78 FR 52097 - Revision to the Manual of Regulations and Procedures for Federal Radio Frequency Management  

Federal Register 2010, 2011, 2012, 2013

...Regulations and Procedures for Federal Radio Frequency Management AGENCY: National...Regulations and Procedures for Federal Radio Frequency Management (NTIA Manual...comply with when requesting use of radio frequency spectrum. DATES: This...

2013-08-22

150

75 FR 54790 - Revision to the Manual of Regulations and Procedures for Federal Radio Frequency Management  

Federal Register 2010, 2011, 2012, 2013

...Regulations and Procedures for Federal Radio Frequency Management AGENCY: National...Regulations and Procedures for Federal Radio Frequency Management (NTIA Manual...Regulations and Procedures for Federal Radio Frequency Management with which...

2010-09-09

151

47 CFR 15.204 - External radio frequency power amplifiers and antenna modifications.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false External radio frequency power amplifiers and antenna...COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators § 15.204 External radio frequency power amplifiers and...

2010-10-01

152

Radio frequency source power-induced ion energy impact on SiN films deposited by using a pulsed-PECVD in SiH 4–N 2 plasma at room temperature  

Microsoft Academic Search

Using a radio frequency (rf) pulsed-plasma enhanced chemical vapor deposition system, silicon nitride (SiN) films were deposited in a SiH4–N2 inductively coupled plasma. Effect of duty ratio and rf source powers on deposition rate at room temperature were investigated in the ranges 50–90% and 600–900W, respectively. Plasma diagnostics on ion energy was conducted and rf source power-induced ion energy impact

Hwajune Lee; Byungwhan Kim; Sanghee Kwon

2010-01-01

153

An overview of backscattered radio frequency identification system (RFID)  

Microsoft Academic Search

A radio frequency identification (RFID) system is a wireless communication system in which the radio link between the base station and the transponders are furnished by the modulated backscattered waves. The present paper is intended to provide a brief description of various subsystems of the RFID. The various applications of RFID are discussed. Sample results on read\\/write range for a

K. V. S. Rao

1999-01-01

154

Radio frequency identification in the UK: opportunities and challenges  

Microsoft Academic Search

Radio frequency identification (RFID) is the generic name for technologies that use radio waves to automatically identify individual items that carry such identification tags. Unlike barcodes, which need line of sight sensors, RFID tags do not. As the cost of this new technology falls, the take-up rate by the retail industry will be significant, revolutionizing retailers’ control of the product

Peter Jones; Colin Clarke-Hill; Peter Shears; Daphne Comfort; David Hillier

2004-01-01

155

Solar observations with a low frequency radio telescope  

NASA Astrophysics Data System (ADS)

We have set up a low frequency radio monitoring station for solar bursts at the Observatory of the Aristotle University in Thessaloniki. The station consists of a dual dipole phased array, a radio receiver and a dedicated computer with the necessary software installed. The constructed radio receiver is based on NASA's Radio Jove project. It operates continuously, since July 2010, at 20.1 MHz (close to the long-wavelength ionospheric cut-off of the radio window) with a narrow bandwidth (~5 kHz). The system is properly calibrated, so that the recorded data are expressed in antenna temperature. Despite the high interference level of an urban region like Thessaloniki (strong broadcasting shortwave radio stations, periodic experimental signals, CBs, etc), we have detected several low frequency solar radio bursts and correlated them with solar flares, X-ray events and other low frequency solar observations. The received signal is monitored in ordinary ASCII format and as audio signal, in order to investigate and exclude man-made radio interference. In order to exclude narrow band interference and calculate the spectral indices of the observed events, a second monitoring station, working at 36 MHz, is under construction at the village of Nikiforos near the town of Drama, about 130 km away of Thessaloniki. Finally, we plan to construct a third monitoring station at 58 MHz, in Thessaloniki. This frequency was revealed to be relatively free of interference, after a thorough investigation of the region.

Myserlis, I.; Seiradakis, J.; Dogramatzidis, M.

2012-01-01

156

Energy fluxes in a radio-frequency magnetron discharge for the deposition of superhard cubic boron nitride coatings  

NASA Astrophysics Data System (ADS)

Energy flux measurements by a calorimetric probe in a rf-magnetron plasma used for the deposition of super-hard c-BN coatings are presented and discussed. Argon as working gas is used for sputtering a h-BN target. Adding a certain amount of N2 is essential for the formation of stoichiometric BN films, since a lack of nitrogen will lead to boron rich films. Subsequently, the contributions of different plasma species, surface reactions, and film growth to the resulting variation of the substrate temperature in dependence on nitrogen admixture are estimated and discussed. In addition, SRIM simulations are performed to estimate the energy influx by sputtered neutral atoms. The influence of magnetron target power and oxygen admixture (for comparison with nitrogen) to the process gas on the total energy flux is determined and discussed qualitatively, too. The results indicate that variation of the energy influx due to additional nitrogen flow, which causes a decrease of electron and ion densities, electron temperature and plasma potential, is negligible, while the admixture of oxygen leads to a drastic increase of the energy influx. The typical hysteresis effect which can be observed during magnetron sputtering in oxygen containing gas mixtures has also been confirmed in the energy influx measurements for the investigated system. However, the underlying mechanism is not understood yet, and will be addressed in further investigations.

Bornholdt, S.; Ye, J.; Ulrich, S.; Kersten, H.

2012-12-01

157

A Two-Dimensional Model of Chemical Vapor Infiltration With Radio Frequency Heating  

Microsoft Academic Search

A comprehensive, two-dimensional, self-consistent model was developed and used to simulate chemical vapor infil- tration of fiber-reinforced composite materials with radio frequency heating. The model included equations for energy transport, multicomponent mass transport, and pore structure evolution, coupled to Maxwell's equations to determine self-consistently the power absorbed by the preform from a radio frequency induction coil. The model equations were

Vikas Midha; Demetre J. Economou

1997-01-01

158

Radio Frequency (RF) Trap for Confinement of Antimatter Plasmas Using Rotating Wall Electric Fields  

NASA Technical Reports Server (NTRS)

Perturbations associated with a rotating wall electric field enable the confinement of ions for periods approaching weeks. This steady state confinement is a result of a radio frequency manipulation of the ions. Using state-of-the-art techniques it is shown that radio frequency energy can produce useable manipulation of the ion cloud (matter or antimatter) for use in containment experiments. The current research focuses on the improvement of confinement systems capable of containing and transporting antimatter.

Sims, William Herbert, III; Pearson, J. Boise

2004-01-01

159

Continuous transmission line modeling for low and medium-energy linacs: DTL and RFQ. [DTL (Drift Tube Linac); RFQ (Radio Frequency Quadrupole)  

SciTech Connect

A continuous transmission line model is developed for the low and medium energy linacs. Drift Tube Linac is simulated as a waveguide that is operated at the TM[sub 010] mode. Radio Frequency Quadrupole has been treated as a waveguide that is operated at the TE[sub 210] mode. These waveguide are filled with a medium that is uniform, homogeneous, but not isotropic. The DTL can be seen as a cylindrical resonator filled with an electrically uniaxial medium with the optic axis along the accelerating axis. The RFQ can be treated as a cylindrical resonator filled with a magnetically uniaxial medium with its optic axis along the accelerating axis. The RFQ and the DTL have no explicit boundaries between cells and all cells are strongly coupled together. Unlike the coupled resonator model, this model considers the whole long linac tank as a uniform cylindrical resonator. Instead of separated resonators, all individual cells having the same resonant frequency are combined in a transmission line. To simulate a DTL, stems supporting the drift-tubes in the outer tank are treated as shunt inductances that have no effect on the constant current structure and little effect on the current ramp structure. An L-C circuit simulating the straight post coupler shows that the sensitivity to the perturbations can be reduced and accelerating fields can be stabilized in a constant field DTL. To stabilize fields in a ramped gradient DTL (RGDTL), bent posts are needed. These bent posts can be modeled by as their equivalent circuits. Ignoring the wall loss, there is a good agreement between the results obtained and the experimental results of J.H. Billen carrying in Los Alamos National Laboratory. Beam loading in DTL and RFQ can be dealt with by the use of resistive elements in transmission line representations. Feeding has been simulated by current sources with a shunt conductances.

Ke, M.K.

1993-01-01

160

Radio frequency self-interference from a data processing centre at a radio telescope site  

Microsoft Academic Search

Apart from externally generated Radio Frequency Interference (RFI), the occurrence of self-interference is a major concern\\u000a at any modern radio telescope site. Antenna servo motor controllers, data acquisition processors, and fast computing capabilities\\u000a operate very close to extremely sensitive and wideband radio astronomical receivers. In this paper, we present a set of measurements\\u000a of the RFI level generated by a

Roberto Ambrosini; Pietro Bolli; Claudio Bortolotti; Francesco Gaudiomonte; Filippo Messina; Mauro Roma

2010-01-01

161

Security and Privacy in Radio-Frequency Identification Devices  

Microsoft Academic Search

Radio Frequency Identification (RFID) systems are a common and useful tool in manufacturing, supply chain management and retail inventory control. Optical barcodes, another common automatic identification system, have been a familiar packaging feature on consumer items for years.

Stephen August Weis

2003-01-01

162

Radio Frequency Identification (RFID) for Naval Medical Treatment Facilities (MTF).  

National Technical Information Service (NTIS)

The application of Radio Frequency Identification (RFID) technology in hospitals is modest primarily due to cost and policy issues. Similar to the evolution of other electronic technologies, unit costs for components have been dramatically reduced in the ...

E. C. Macalanda

2006-01-01

163

Principles and Applications of Radio Frequency Impedance Probes.  

National Technical Information Service (NTIS)

The underlying principle of the radio frequency plasma probe is presented. The resonance properties of the probe's equivalent circuit with and without external magnetic field are analyzed. The admittance of the equivalent circuit is shown to posses a pole...

S. T. Lai

1981-01-01

164

Propagation Effects at Radio Frequencies on Satellite Navigation Systems.  

National Technical Information Service (NTIS)

The report discusses the effects of the neutral and ionized atmosphere on radio frequency signals used in satellite navigation systems. Knowledge of the signal velocity along the transmission path is necessary to properly interpret the navigation measurem...

V. L. Pisacane M. M. Feen

1974-01-01

165

An Investigation of Radio Frequency Auditory Training Units  

ERIC Educational Resources Information Center

Evaluated were the performances of eight radio frequency systems by means of a measurement procedure said to be applicable to the evaluation of auditory training systems in classrooms for the aurally handicapped. (DB)

Matkin, Noel D.; Olsen, Wayne

1973-01-01

166

Low frequency radio synthesis imaging of the galactic center region  

Microsoft Academic Search

The Very Large Array radio interferometer has been equipped with new receivers to allow observations at 330 and 74 MHz, frequencies much lower than were previously possible with this instrument. Though the VLA dishes are not optimal for working at these frequencies, the system is successful and regular observations are now taken at these frequencies. However, new data analysis techniques

Michael Evans Nord

2005-01-01

167

Radio frequency electromagnetic fields: mild hyperthermia and safety standards  

Microsoft Academic Search

This chapter is a short review of literature that serves as the basis for current safe exposure recommendations by ICNIRP (International Commission on Non-Ionizing Radiation Protection, 1998). and the IEEE C95.1 (IEEE Standard for Safety Levels with Respect to Human Exposure to Radio Frequency Electromagnetic Fields, 3kHz to 300GHz, 2005) for exposure to radio frequency electromagnetic radiation (RF-EMF). Covered here

John A. D’Andrea; John M. Ziriax; Eleanor R. Adair

2007-01-01

168

Radio frequency interference issues in impulse radio multiple access communication systems  

Microsoft Academic Search

Impulse radio systems use very short pulses. Consequently, the spectrum of the transmitted signal spreads over several gigahertz and overlaps with RF bands occupied by other communication systems. As a result, radio frequency interference (RFI) affects the received signal. We present an analysis of the effects of RFI to a victim UWB receiver. Conditions for RFI cancellation for a large

Maria StelIa Icrcobircci; Maria Gabriella Di Benedetto; L. De Nardis

2002-01-01

169

Planetary and exoplanetary low frequency radio observations from the Moon  

NASA Astrophysics Data System (ADS)

We analyze the planetary and exoplanetary science that can be carried out with precursor as well as future low frequency radio instruments on the Moon, assessing the limiting noise sources, comparing them to the average and peak spectra of all planetary radio components as they will be seen from the Lunar surface or orbit. We identify which objectives will be accessible with each class of instrument, and discuss the interest of these observations compared to observations by planetary probes and to ground-based observations by large low-frequency radio arrays. The interest of goniopolarimetry is emphasized for pathfinder missions.

Zarka, P.; Bougeret, J.-L.; Briand, C.; Cecconi, B.; Falcke, H.; Girard, J.; Grießmeier, J.-M.; Hess, S.; Klein-Wolt, M.; Konovalenko, A.; Lamy, L.; Mimoun, D.; Aminaei, A.

2012-12-01

170

Fiducialization of Superconducting Radio Frequency Cryomodules at Jefferson Lab  

SciTech Connect

During the early 1990's the Continuous Electron Beam Accelerator Facility (CEBAF), was under construction in Newport News, Virginia. The facility was to be the first of its kind in that it was to provide a continuous beam of electrons for experimental physics at energies of several GeV. One of the key elements of this unique machine was the 338 superconducting radio frequency (SRF) cavities built into 42 cryomodules and arranged in two linacs. These were linked by arcs of conventional magnets which allowed recirculation through the linacs up to five times, in order to achieve the design energy of 4GeV. Within each cryomodule the cavities were aligned and referenced to external fiducials allowing alignment on the design beampath. This paper describes the process developed to achieve this, how it evolved with improving instrumentation, and the results obtained. Suggestions for alternative methods which may prove useful for future projects are also discussed.

C. J. Curtis; J. Dahlberg; W. Oren; J. Preble; K. Tremblay

2006-09-26

171

In situ observations of medium frequency auroral radio emissions  

NASA Astrophysics Data System (ADS)

The auroral ionosphere is a region rich with plasma waves that can be studied both in space and on the ground. These waves may mediate energy exchange between particle populations and provide information about the local plasma properties and boundaries. Auroral medium frequency (MF) burst is an impulsive radio emission observed at ground-level from 1.3-4.5 MHz that is associated with local substorm onset. There have been two recent reports of impulsive, broadband, MF waves at high latitudes. Burchill and Pfaff [2005] reported observations from the FAST satellite of impulsive, broadband, MF and low frequency (LF) radio waves. Using data from the DEMETER satellite, Parrot et al. [2009] surveyed MF waves caused by lightning. This study did show a high-latitude population of MF waves. We investigate whether the waves observed by these two satellites are related to auroral MF burst. Using FAST satellite burst mode electric field data from high-latitude (> 60 degrees magnetic), low-altitude (< 1000 km) intervals of moderate to large geomagnetic activity (Kp > 3) from 1996-2002, we have found forty-four examples of impulsive MF waves, all of which are associated with impulsive LF waves. Although MF burst and the waves observed by FAST have similar spectral signatures, they have different magnetic local time dependencies, which suggests that they may be unrelated. A study of MF waves observed at high latitude by DEMETER is ongoing. In situ observations of MF burst could provide crucial information about this heretofore unexplained natural radio emission.

Broughton, M.; Labelle, J. W.; Pfaff, R. F.; Parrot, M.; Yan, X.; Burchill, J. K.

2013-12-01

172

Radio-frequency heating plans for CTX  

SciTech Connect

Even with present efforts to reduce impurity levels in the CTX experiment, electron thermal conduction and residual impurity radiation may still cause substantial cooling of the plasma toroid by the time it has formed inside the flux conserver. Auxiliary heating of the stable structure is needed. If an energy of several hundred joules is to be supplied over a hundred-microsecond time scale, several megawatts of power are required. Such levels can be achieved from pulsed rf sources at frequencies in the ion-cyclotron range and below (0.1 to 10 MHz). Encouraged by the successes reported from other experiments in this regime, we are undertaking the development of an rf heating system for CTX.

Knox, S.O.; Wright, B.L.

1981-01-01

173

Optical serial coherent analyzer of radio-frequency (OSCAR).  

PubMed

Optical serial coherent analyzer of radio-frequency is a novel scheme that enables fast-scanning microwave signal measurements in a large bandwidth. The measurements are performed based on serial channelization realized by using a fast scanning laser source as the local oscillator to down-convert the to-be-measured radio-frequency (RF) signals. Optical coherent detection effectively removes interferences induced by RF's self-beating and guarantees the accuracy of measurements. In the experimental demonstration, instantaneous multi-frequency measurements and vector information acquisition of RF signals can be achieved by this scheme within 2.8 ?s over 14 GHz bandwidth. PMID:24921552

Li, Ruiyue; Chen, Hongwei; Lei, Cheng; Yu, Ying; Chen, Minghua; Yang, Sigang; Xie, Shizhong

2014-06-01

174

Radio frequency hollow cathodes for the plasma processing technology  

Microsoft Academic Search

The present paper summarizes the main features of the hollow cathode discharges generated by a radio frequency (r.f.) instead of a d.c. field. The pressure of gas inside the hollow cathode is almost independent on the reactor pressure, which allows to generate discharge at high collision frequency and transport it into the low pressure reactor. The discharge forced out from

L. Bárdoš

1996-01-01

175

Radio Frequency Impedance Interrogation monitoring of hemodynamic parameters  

Microsoft Academic Search

Non-contact, non-invasive monitoring of hemodynamic parameters has long been deemed to be important to medical monitoring in a variety of environments. Radio Frequency Impedance Interrogation (RFII) measures hemodynamic function via resonance frequency coupling to a hydrophilic protein molecule. We examined the use of RFII for hemodynamic monitoring of human subjects during Lower Body Negative Pressure (LBNP) and physiological hemodynamic maneuvers

Marc O Griofa; Rebecca Blue; Robert Friedman; Kenneth Cohen; Philip Hamski; Andrew Pal; Robert Rinehart; Tom Merrick

2011-01-01

176

Chipless radio frequency identification by remote measurement of complex impedance  

Microsoft Academic Search

A novel technique for radio frequency identification devices (RFID) based on remote measurement of complex impedance at microwave frequencies is presented. The low cost read-only tags do not need semiconductor elements and can be implemented by printing a conducting pattern on a low cost dielectric substrate. Multiple tags are simultaneously illuminated by a chirped microwave signal with a bandwidth of

S. Mukherjee

2007-01-01

177

Chipless Radio Frequency Identification by Remote Measurement of Complex Impedance  

Microsoft Academic Search

A novel technique for radio frequency identification devices (RFID) based on remote measurement of complex impedance at microwave frequencies is presented. The low cost read-only tags do not need semiconductor elements and can be implemented by printing a conducting pattern on a low cost dielectric substrate. Multiple tags are simultaneously illuminated by a chirped microwave signal with a bandwidth of

S. Mukherjee

2007-01-01

178

Tesla’s multi-frequency wireless radio controlled vessel  

Microsoft Academic Search

A review of the Teslapsilas contribution to dual-band wireless radio controlled vessel is presented. The intention of this paper is to describe multi-frequency remote controlled vessel using two transmitters and which operate a distant receiver which comprises two or more circuits, each of which is tuned to respond exclusively to the signals of one frequency and so arranged that the

Aleksandar Marincic; Djuradj Budimir

2008-01-01

179

Radio astronomical determination of ground state transition frequencies of CH  

NASA Technical Reports Server (NTRS)

From a comparison of the spectra of CH and other molecules toward the continuum source Cas A and four dark clouds, the ground state transition frequencies of CH have been determined and are reported. The relative errors in these frequencies are about twice as small as those obtained earlier by radio astronomical methods for the two main lines of ground state OH.

Rydbeck, O. E. H.; Ellder, J.; Sume, A.; Hjalmarson, A.; Irvine, W. M.

1974-01-01

180

Recent observations of the very low frequency interplanetary radio emission  

NASA Technical Reports Server (NTRS)

Observations of radio emissions in the frequency range of 2 to 3 kHz have been made in the distant heliosphere by the Voyager 1 and 2 plasma wave instruments. Based primarily on wideband observations made periodically throughout the cruise phases of the missions the radio emission, first observed in 1982, appears to have been present almost continuously since 1983. The spectrum is complex, usually showing two peaks, one near 2 and another near 3 kHz. Occasionally, only one of the peaks is observed. A possible source for the radio emissions is the terminal shock in the outer heliosphere.

Kurth, W. S.; Gurnett, D. A.; Scarf, F. L.

1986-01-01

181

Verification of frequency scaling laws for capacitive radio-frequency discharges using two-dimensional simulations  

SciTech Connect

Weakly ionized processing plasmas are studied in two dimensions using a bounded particle-in-cell (PIC) simulation code with a Monte Carlo collision (MCC) package. The MCC package models the collisions between charged and neutral particles, which are needed to obtain a self-sustained plasma and the proper electron and ion energy loss mechanisms. A two-dimensional capacitive radio-frequency (rf) discharge is investigated in detail. Simple frequency scaling laws for predicting the behavior of some plasma parameters are derived and then compared with simulation results, finding good agreements. It is found that as the drive frequency increases, the sheath width decreases, and the bulk plasma becomes more uniform, leading to a reduction of the ion angular spread at the target and an improvement of ion dose uniformity at the driven electrode.

Vahedi, V.; Birdsall, C.K.; Lieberman, M.A. (Department of Electrical Engineering and Computer Science and the Electronics Research Laboratory, University of California, Berkeley, Berkeley, California 94720 (United States)); DiPeso, G.; Rognlien, T.D. (Lawrence Livermore National Laboratory, Livermore, California 94550 (United States))

1993-07-01

182

Radio frequency identification enabled wireless sensing for intelligent food logistics.  

PubMed

Future technologies and applications for the Internet of Things (IoT) will evolve the process of the food supply chain and create added value of business. Radio frequency identifications (RFIDs) and wireless sensor networks (WSNs) have been considered as the key technological enablers. Intelligent tags, powered by autonomous energy, are attached on objects, networked by short-range wireless links, allowing the physical parameters such as temperatures and humidities as well as the location information to seamlessly integrate with the enterprise information system over the Internet. In this paper, challenges, considerations and design examples are reviewed from system, implementation and application perspectives, particularly with focus on intelligent packaging and logistics for the fresh food tracking and monitoring service. An IoT platform with a two-layer network architecture is introduced consisting of an asymmetric tag-reader link (RFID layer) and an ad-hoc link between readers (WSN layer), which are further connected to the Internet via cellular or Wi-Fi. Then, we provide insights into the enabling technology of RFID with sensing capabilities. Passive, semi-passive and active RFID solutions are discussed. In particular, we describe ultra-wideband radio RFID which has been considered as one of the most promising techniques for ultra-low-power and low-cost wireless sensing. Finally, an example is provided in the form of an application in fresh food tracking services and corresponding field testing results. PMID:24797140

Zou, Zhuo; Chen, Qing; Uysal, Ismail; Zheng, Lirong

2014-01-01

183

Characteristics of Radio-Frequency Circuits Utilizing Ferroelectric Capacitors  

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

184

Radio Frequency Interference Suppression Techniques in FMCW Modulated HF Radars  

Microsoft Academic Search

High-frequency (HF) radars are operated in the 3-30 MHz frequency range and need to share the frequency bands with other radio services. Due to their over-the-horizon (OTH) capabilities, HF radars play an important role in remote sensing and surveillance. The propagation conditions of the electromagnetic wave depend on the earth's ionosphere and mailnly follow a daily cycle. Communication paths between

Klaus-Werner Gurgel; Y. Barbin; T. Schlick

2007-01-01

185

Radio frequency self-interference from a data processing centre at a radio telescope site  

NASA Astrophysics Data System (ADS)

Apart from externally generated Radio Frequency Interference (RFI), the occurrence of self-interference is a major concern at any modern radio telescope site. Antenna servo motor controllers, data acquisition processors, and fast computing capabilities operate very close to extremely sensitive and wideband radio astronomical receivers. In this paper, we present a set of measurements of the RFI level generated by a cluster of computers that will be installed at the site of the Sardinia Radio Telescope (SRT). The measured levels are compared to Recommendation ITU-R RA.769-2, which gives the threshold levels for interference detrimental to radio astronomy observations. Our analysis shows that, with proper shielding of the noisiest devices, it will be possible to preserve the present excellent RFI conditions of the SRT site.

Ambrosini, Roberto; Bolli, Pietro; Bortolotti, Claudio; Gaudiomonte, Francesco; Messina, Filippo; Roma, Mauro

2010-03-01

186

Radio-Controlled Cyborg Beetles: A Radio-Frequency System for Insect Neural Flight Control  

Microsoft Academic Search

We present the first report of radio control of a cyborg beetle in free-flight. The microsystem (Figs. 1,2) consisted of a radio-frequency receiver assembly, a micro battery and a live giant flower beetle platform (Mecynorhina polyphemus or Mecynorhina torquata). The assembly had six electrode stimulators implanted into the left and right optic lobes, brain, posterior pronotum (counter electrode), right and

H. SatoI; Y. Peeri; E. Baghoomian; C. W. Berry; M. M. Maharbiz

2009-01-01

187

Exposure of radio officers to radio frequency radiation on Danish merchant ships.  

PubMed

Exposure of radio officers to radio frequency radiation from telegraphy and telephony equipment on ships was investigated. Eighty-five measurements were made of 12 radio transmitters operating in the 400 kHz to 25 MHz range (power up to 1200 W) and three VHF telephony transmitters in the 150 MHz band. Field measurements were made at positions normally occupied by radio officers approximately 1 m, 0.5 m and 0.25 m from the antenna feed lines. The distance between the radio operator and the measurement location was at least 0.5 m. The ratio of the electric and magnetic field strength squared (MF and HF transmitters) to ANSI C95.1-1982 radio frequency protection guides ranged from 0.001 to 0.26 (geometric mean 0.02) at the location of the seated radio officer's head. A minimum distance of 0.5 m between antenna feed lines and personnel is recommended. This would normally ensure an exposure below the ANSI safety levels. PMID:6517023

Skotte, J

1984-12-01

188

Dual radio frequency plasma source: Understanding via electrical asymmetry effect  

NASA Astrophysics Data System (ADS)

On the basis of the global model, the influences of driving voltage and frequency on electron heating in geometrically symmetrical dual capacitively coupled radio frequency plasma have been investigated. Consistent with the experimental and simulation results, non-monotonic behavior of dc self bias and plasma heating with increasing high frequency is observed. In addition to the local maxima of plasma parameters for the integer values of the ratio between the frequencies (?), ourstudies also predict local maxima for odd integer values of 2? as a consequence of the electrical asymmetry effect produced by dual frequency voltage sources.

Bora, B.; Bhuyan, H.; Favre, M.; Wyndham, E.; Wong, C. S.

2013-04-01

189

Effective Collision Frequency and Radio Frequency Conductivity in the Magnetosphere.  

National Technical Information Service (NTIS)

The electron density and electron temperature profiles have been chosen, and with help of these data the effective electron collision frequency along various geomagnetic lines of force have been calculated. The effective electron collision frequency in th...

K. D. Misra P. K. Shukla R. N. Singh

1970-01-01

190

Low Frequency Radio Observations of GRS1915+105 with GMRT  

Microsoft Academic Search

We present the first detailed low frequency radio measurements of the galactic microquasar GRS1915+105 with GMRT. Simultaneous observations were carried out at 610 and 244 MHz. Our data does not show any signature of spectral turn over even at low radio frequency of 244 MHz. We propose that while the radio emission at high radio frequencies could predominantly come from

C. H. Ishwara-Chandra; A. Pramesh Rao; Mamta Pandey; R. K. Manchanda; Philippe Durouchoux

2005-01-01

191

Architecture for Coexistence with Multiple Users in Frequency Hopping Cognitive Radio Networks.  

National Technical Information Service (NTIS)

The radio frequency (RF) spectrum is a limited resource. Spectrum allotment disputes stem from this scarcity as many radio devices are con confined to a fixed frequency or frequency sequence. One alternative is to incorporate cognition within a configurab...

R. K. Mclean

2013-01-01

192

Low frequency radio synthesis imaging of the galactic center region  

NASA Astrophysics Data System (ADS)

The Very Large Array radio interferometer has been equipped with new receivers to allow observations at 330 and 74 MHz, frequencies much lower than were previously possible with this instrument. Though the VLA dishes are not optimal for working at these frequencies, the system is successful and regular observations are now taken at these frequencies. However, new data analysis techniques are required to work at these frequencies. The technique of self- calibration, used to remove small atmospheric effects at higher frequencies, has been adapted to compensate for ionospheric turbulence in much the same way that adaptive optics is used in the optical regime. Faceted imaging techniques are required to compensate for the noncoplanar image distortion that affects the system due to the wide fields of view at these frequencies (~2.3° at 330 MHz and ~11° at 74 MHz). Furthermore, radio frequency interference is a much larger problem at these frequencies than in higher frequencies and novel approaches to its mitigation are required. These new techniques and new system are allowing for imaging of the radio sky at sensitivities and resolutions orders of magnitude higher than were possible with the low frequency systems of decades past. In this work I discuss the advancements in low frequency data techniques required to make high resolution, high sensitivity, large field of view measurements with the new Very Large Array low frequency system and then detail the results of turning this new system and techniques on the center of our Milky Way Galaxy. At 330 MHz I image the Galactic center region with roughly 10 inches resolution and 1.6 mJy beam -1 sensitivity. New Galactic center nonthermal filaments, new pulsar candidates, and the lowest frequency detection to date of the radio source associated with our Galaxy's central massive black hole result. At 74 MHz I image a region of the sky roughly 40° x 6° with, ~10 feet resolution. I use the high opacity of H II regions at 74 MHz to extract three-dimensional data on the distribution of Galactic cosmic ray emissivity, a measurement possible only at low radio frequencies.

Nord, Michael Evans

2005-11-01

193

A radio-frequency sheath model for complex waveforms  

NASA Astrophysics Data System (ADS)

Plasma sheaths driven by radio-frequency voltages occur in contexts ranging from plasma processing to magnetically confined fusion experiments. An analytical understanding of such sheaths is therefore important, both intrinsically and as an element in more elaborate theoretical structures. Radio-frequency sheaths are commonly excited by highly anharmonic waveforms, but no analytical model exists for this general case. We present a mathematically simple sheath model that is in good agreement with earlier models for single frequency excitation, yet can be solved for arbitrary excitation waveforms. As examples, we discuss dual-frequency and pulse-like waveforms. The model employs the ansatz that the time-averaged electron density is a constant fraction of the ion density. In the cases we discuss, the error introduced by this approximation is small, and in general it can be quantified through an internal consistency condition of the model. This simple and accurate model is likely to have wide application.

Turner, M. M.; Chabert, P.

2014-04-01

194

Systems and methods for determining radio frequency interference  

NASA Technical Reports Server (NTRS)

The presence, frequency and amplitude of radio frequency interference superimposed on communication links originating from a terrestrial region and including a relay in a geostationary spacecraft are determined by pointing a narrow beam antenna on the satellite at the terrestrial region. The level of noise radiated from the region to the antenna is measured at a terrestrial station that is usually remote from the region. Calibrating radio signals having a plurality of predetermined EIRP's (Effective Isotropic Radiated Power) and frequencies in the spectrum are transmitted from the region through the spacecraft narrow beam antenna back to the station. At the station, the levels of the received calibrating signals are separately measured for each of the frequency bands and EIRP's.

Johannsen, K. G.; Sabaroff, S.; Henry, V. F. (inventors)

1978-01-01

195

Survey of radio-frequency quadrupole accelerators  

SciTech Connect

Over the last several years the RFQ has proved to be a very flexible low-energy accelerator for bunching and accelerating both low- and high-current beams. It uses low-voltage dc injectors, has excellent bunching properties and high transmission efficiency. Applications include injectors for higher energy machines, such as drift-tube linacs, cyclotrons, or synchrotrons. The RFQ can also be used alone for applications that require a fixed-energy beam. 41 references, 4 figures, 2 tables.

Billen, J.H.

1984-01-01

196

Simulation study on radio frequency safety of electric explosive device  

NASA Astrophysics Data System (ADS)

Radio frequency (RF) is a great danger to the electric explosive device (EED) of typical ordnance. This paper introduced the RF firing mechanism of the EED and the measuring method of its RF impedance. Through the professional antenna simulation software CST, a dipole antenna model of the EED was set up, the gain coefficient of the antenna model was obtained, and the RF power penetrating into the EED was calculated. The multi-frequency analysis of the emulation indicates that in the certain frequency range of 0.5-2 GHz, the gain coefficient of the antenna model increases as the frequency does.

Yang, Peijie; Tan, Zhiliang; Liu, Chaoyang; Du, Zhide

2013-03-01

197

Radio frequency interference of electric motors and associated controls  

Microsoft Academic Search

Problems of radio-frequency interference (RFI) caused by electric motors used in appliances are discussed in general terms, and some possible solutions are given. Elimination of such noise or suppression to permissible levels is difficult and expensive. Various aspects of motor design, like electric\\/magnetic loading ratio, commutation and sparkling, and brushes and brush gears, which all affect RFI, are discussed. Suppression

M. A. Jabbar; M. A. Rahman

1991-01-01

198

29. View of typical radio frequency monitor group electronic tubetype ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

29. View of typical radio frequency monitor group electronic tube-type cabinet. System is water-cooled with antenna assist. - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

199

A Portable Miniature Transistorized Radio-Frequency Coupled Cardiac Pacemaker  

Microsoft Academic Search

A miniature, transistorized radio-frequency-coupled cardiac pacemaker was developed to eliminate wires penetrating the skin when electrodes are placed on the heart to drive it. The design also eliminates the need for totally implanting a pacemaker with its batteries. The stimulating impulse is transmitted via amplitude modulation to a tuned circuit and detector assembly implanted below the skin. The output of

D. M. Hickman; L. A. Geddes; H. E. Hoff; M. Hinds; A. G. Moore; C. K. Francis; T. Engen

1961-01-01

200

75. Transmitter building no. 102, view of typical radio frequency ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

75. Transmitter building no. 102, view of typical radio frequency switching group for lower antenna A & B and upper antenna A & B and MIP/MWOC automated interface cabinet. - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

201

Fabrication of the APS Storage Ring radio frequency accelerating cavities  

SciTech Connect

Specification, heat treatment, strength, and fatigue life of the Advanced Photon Source (APS) Storage Ring 352-MHz radio frequency (RF) accelerating cavity copper is discussed. Heat transfer studies, including finite element analysis, and configuration of water cooling is described. Requirements for and techniques of machining are considered. Braze and electron beam joint designs are compared. Vacuum considerations during fabrication are discussed.

Primdahl, K.; Bridges, J.; DePaola, F.; Kustom, R. [Argonne National Lab., IL (US); Snee, D. [Fermi National Accelerator Lab., Batavia, IL (US)

1993-07-01

202

Authentication of Radio Frequency Identification Devices Using Electronic Characteristics  

ERIC Educational Resources Information Center

Radio frequency identification (RFID) tags are low-cost devices that are used to uniquely identify the objects to which they are attached. Due to the low cost and size that is driving the technology, a tag has limited computational capabilities and resources. This limitation makes the implementation of conventional security protocols to prevent…

Chinnappa Gounder Periaswamy, Senthilkumar

2010-01-01

203

Modification of the DSN radio frequency angular tropospheric refraction model  

NASA Technical Reports Server (NTRS)

The previously derived DSN Radio Frequency Angular Tropospheric Refraction Model contained an assumption which was subsequently seen to be at a variance with the theoretical basis of angular refraction. The modification necessary to correct the model is minor in that the value of a constant is changed.

Berman, A. L.

1977-01-01

204

Radio frequency analog electronics based on carbon nanotube transistors  

Microsoft Academic Search

The potential to exploit single-walled carbon nanotubes (SWNTs) in advanced electronics represents a continuing, major source of interest in these materials. However, scalable integration of SWNTs into circuits is challenging because of difficulties in controlling the geometries, spatial positions, and electronic properties of individual tubes. We have implemented solutions to some of these challenges to yield radio frequency (RF) SWNT

Coskun Kocabas; Hoon-Sik Kim; Tony Banks; John A. Rogers; Aaron A. Pesetski; James E. Baumgardner; S. V. Krishnaswamy; Hong Zhang

2008-01-01

205

Self-consistent simulations of multipacting in superconducting radio frequencies  

Microsoft Academic Search

Multipacting continues to be an important issue in Superconducting Radio Frequency (SRF) cavities, particularly near waveguide couplers. Most modern simulations of multipacting are not self-consistent, using the fields from a purely electromagnetic simulation to drive the motion of multipacting electrons. This approach works well for the onset on multipacting but as the electron density increases in the cavity it can

C. Nieter; S. Ovtchinnikov; D. N. Smithe; P. H. Stoltz; P. J. Mullowney

2007-01-01

206

Method of making radio frequency ion source antenna  

Microsoft Academic Search

In the method, the radio frequency (RF) antenna is made by providing a clean coil made of copper tubing or other metal conductor, which is coated with a tacky organic binder, and then with a powdered glass frit, as by sprinkling the frit uniformly over the binder. The coil is then heated internally in an inert gas atmosphere, preferably by

Kenneth W. Ehlers; Ka-Ngo Leung

1988-01-01

207

Radio-frequency controllable quantum interference in Mössbauer spectroscopy  

Microsoft Academic Search

The role of quantum interference (QI) in spectra of the resonant Mssbauer scattering is investigated. As a mechanism ensuring\\u000a the QI conditions, the radio-frequency (RF) mixing of the spin sublevels of the excited nuclear state is considered. It is\\u000a shown that QI leads to a significant intensity redistribution of the elastic and Raman scattering.

E. K. Sadykov; V. V. Arinin; G. I. Petrov; A. V. Pyataev; F. G. Vagizov; O. A. Kocharovskaya

2006-01-01

208

Radio-frequency controllable quantum interference in Mössbauer spectroscopy  

Microsoft Academic Search

The role of quantum interference (QI) in spectra of the resonant Mossbauer scattering is investigated. As a mechanism ensuring the QI conditions, the radio-frequency (RF) mixing of the spin sublevels of the excited nuclear state is considered. It is shown that QI leads to a significant intensity redistribution of the elastic and Raman scattering.

E. K. Sadykov; V. V. Arinin; G. I. Petrov; A. V. Pyataev; F. G. Vagizov; O. A. Kocharovskaya

2007-01-01

209

Nanotechnology of transparent metals for radio frequency electromagnetic shielding  

Microsoft Academic Search

The aim of this paper is to present an innovative one-dimensional photonic bandgap structure on plastic substrate, for electromagnetic field shielding applications in the radio frequency range. A complete study is performed, from material characterization and design, to fabrication and experimental test of a prototype sample consisting of seven alternating zinc oxide and silver (Ag) layers, on Lexan polycarbonate. The

Maria Sabrina Sarto; Francesca Sarto; Maria Cristina Larciprete; Michael Scalora; M. D'Amore; C. Sibilia; M. Bertolotti

2003-01-01

210

Delay Tolerant, Radio Frequency Identification (RFID)-enabled Sensing  

NASA Technical Reports Server (NTRS)

In this paper, we describe a method of providing guaranteed delivery of sensor data gathered at arbitrary times using an only intermittently available radio frequency identification (RFID) transport scheme. This technique provides a passive (e.g., non-powered) interface for a powerconstrained embedded device to transport sensor data while overcoming the limitation of infrequent access to an RFID interrogator.

Wagner, Raymond S.; Barton, Richard J.

2014-01-01

211

Tracked 3D ultrasound in radio-frequency liver ablation  

Microsoft Academic Search

Recent studies have shown that radio frequency (RF) ablation is a simple, safe and potentially effective treatment for selected patients with liver metastases. Despite all recent therapeutic advancements, however, intra-procedural target localization and precise and consistent placement of the tissue ablator device are still unsolved problems. Various imaging modalities, including ultrasound (US) and computed tomography (CT) have been tried as

Emad M. Boctor; Gabor Fichtinger; Russell H. Taylor; Michael A. Choti

2003-01-01

212

Tracked 3D Ultrasound in Radio-Frequency Liver Ablation  

Microsoft Academic Search

Recent studies have shown that radio frequency (RF) ablation is a simple, safe and potentially effective treatment for selected patients with liver metastases. Despite all recent therapeutic advancements, however, intra-procedural target localization and precise and consistent placement of the tissue ablator device are still unsolved problems. Various imaging modalities, including ultrasound (US) and computed tomography (CT) have been tried as

Emad M. Boctora; Gabor Fichtinger; Russell H. Taylor; Michael A. Choti

2003-01-01

213

Experimental development and theoretical studies of radio-frequency absorbers  

Microsoft Academic Search

A mathematical model based on the equivalence with a sequence of lossy transmission lines has been developed and applied, by numerical calculus, to the study of radio-frequency absorbers of piramidal shape, made of polyurethane foam impregnated with finely powered carbon black. The model has been used to find the expected performance of absorbers with different electrical conductivities in the microwave

J. L. L. M. Massa

1991-01-01

214

Operating a radio-frequency plasma source on water vapor  

Microsoft Academic Search

A magnetically enhanced radio-frequency (rf) plasma source operating on water vapor has an extensive list of potential applications. In this work, the use of a rf plasma source to dissociate water vapor for hydrogen production is investigated. This paper describes a rf plasma source operated on water vapor and characterizes its plasma properties using a Langmuir probe, a residual gas

Sonca V. T. Nguyen; John E. Foster; Alec D. Gallimore

2009-01-01

215

Global Measurements of Low-Frequency Radio Noise.  

National Technical Information Service (NTIS)

We report illustrative results obtained by Stanford University's global survey of ELF/VLF radio noise (frequencies in the range 10 Hz - 32 kHz). Particular comparison is made between the noise measurements made at high (polar) latitudes with those at lowe...

A. Bernardi A. C. Fraser-Smith M. E. Ladd P. R. McGill R. A. Helliwell

1992-01-01

216

Global Measurements of Low-Frequency Radio Noise.  

National Technical Information Service (NTIS)

This final technical report reviews progress in Stanford University's ONR-sponsored global survey of ELF'/VLF radio noise (frequencies in the range 10 Hz - 32 kliz) during the period 1 November 1989 through 31 October 1991, i.e., the period covered by ONR...

A. C. Fraser-Smith R. A. Helliwell

1995-01-01

217

Localized radio frequency communication using asynchronous transfer mode protocol  

DOEpatents

A localized wireless communication system for communication between a plurality of circuit boards, and between electronic components on the circuit boards. Transceivers are located on each circuit board and electronic component. The transceivers communicate with one another over spread spectrum radio frequencies. An asynchronous transfer mode protocol controls communication flow with asynchronous transfer mode switches located on the circuit boards.

Witzke, Edward L. (Edgewood, NM); Robertson, Perry J. (Albuquerque, NM); Pierson, Lyndon G. (Albuquerque, NM)

2007-08-14

218

INNOVATIVE TECHNOLOGY EVALUATION REPORT: RADIO FREQUENCY HEATING, KAI TECHNOLOGIES, INC.  

EPA Science Inventory

A demonstration of KAI Technologies in-situ radio frequency heating system for soil treatment was conducted from January 1994 to July 1994 at Kelly Air Force Base in San Antonio, Texas. his demonstration was conducted as a joint effort between the USEPA and the USAF. he technolog...

219

INNOVATIVE TECHNOLOGY EVALUATION REPORT: RADIO FREQUENCY HEATING, KAI TECHNOLOGIES, INC.  

EPA Science Inventory

A demonstration of KAI Technologies in-situ radio frequency heating system for soil treatment was conducted from January 1994 to July 1994 at Kelly Air Force Base in San Antonio, Texas. This demonstration was conducted as a joint effort between the USEPA and the USAF. The technol...

220

Computer simulations of ions in radio-frequency traps  

NASA Technical Reports Server (NTRS)

The motion of ions in a trapped-ion frequency standard affects the stability of the standard. In order to study the motion and structures of large ion clouds in a radio-frequency (RF) trap, a computer simulation of the system that incorporates the effect of thermal excitation of the ions was developed. Results are presented from the simulation for cloud sizes up to 512 ions, emphasizing cloud structures in the low-temperature regime.

Williams, A.; Prestage, J. D.; Maleki, L.; Djomehri, J.; Harabetian, E.

1990-01-01

221

A tunable EBG absorber for radio-frequency power imaging  

Microsoft Academic Search

Absorption characteristics of a tunable electromagnetic band-gap (EBG) absorber are analyzed, which is designed to capture 2d radio-frequency (RF) power distributions incident on the absorber surface. The EBG absorber has lumped resistors interconnecting the mushroom-type surface patches to absorb the incident RF power at the resonance frequency where the EBG structure exhibits a high-impedance feature. The absorbed RF power distribution

Satoshi Yagitani; Keigo Katsuda; Ryo Tanaka; Masayuki Nojima; Yoshiyuki Yoshimura; Hirokazu Sugiura

2011-01-01

222

Four-Sector Cylindrical Radio-Frequency Ion Trap  

NASA Technical Reports Server (NTRS)

Proposed linear radio-frequency ion trap consists of closed metal cylinder partitioned into four equal cylindrical-sector electrodes and two circular end electrodes. Features include relatively large ion-storage capacity and shielding against external fields. Used in frequency-standard laboratories to confine 199Hg+ ions electrodynamically in isolation from external environment. Similar to device described in "Linear Ion Trap for Atomic Clock" (NPO-17758).

Melbourne, Ruthann K.; Prestage, John D.; Maleki, Lutfollah

1992-01-01

223

Graphene radio frequency devices on flexible substrate  

NASA Astrophysics Data System (ADS)

Graphene is a very promising candidate for applications in flexible electronics due to its high carrier mobility and mechanical flexibility. In this paper, we present results on graphene RF devices fabricated on polyimide substrates with cutoff frequencies as high as 10 GHz. Excellent channel mobility and current saturation are observed in graphene long channel devices on polyimide. Graphene devices on polyimide also show very good temperature stability from 4.4 K to 400 K and excellent mechanical flexibility up to a bending radius of 1 mm. These demonstrated properties make graphene an excellent candidate for flexible wireless applications.

Zhu, Wenjuan; Farmer, Damon B.; Jenkins, Keith A.; Ek, Bruce; Oida, Satoshi; Li, Xuesong; Bucchignano, Jim; Dawes, Simon; Duch, Elizabeth A.; Avouris, Phaedon

2013-06-01

224

Radio frequency arraying method for receivers  

NASA Technical Reports Server (NTRS)

A method and apparatus for increasing the signal to noise ratio of a receiving facility for coherent frequency reception by arraying receiving systems using separate antennas for each, or one antenna for all systems are presented. One system is operated with a carrier tracking loop to provide a first local oscillator frequency for the first and all other systems arrayed, with individual tracking loops in all other systems operated at IF for tracking out any phase differences due to separate group delays using an adjustable phase shifter for a second reference to compensate for different group delays in the antenna and low noise amplifier of each of the other systems. The second IF output of all systems is summed into the first system. This technique may also be used when two systems are arrayed to an antenna designed for circular or linear polarization diversity reception to effectively provide the same signal to noise ratio for both polarized signal transmission channels that would result from matched polarization. An arrangement adapted to high rate telemetry reception is disclosed. With additional components, the same arrangement is adapted to provide low rate telemetry reception as well.

Brockman, M. H.; Easterling, M. F. (inventors)

1980-01-01

225

Monitoring Radio Frequency Interference: The Quiet Skies Project  

NASA Astrophysics Data System (ADS)

The Quiet Skies Project is a result of the Research Experience for Teacher (RET) program during the summer of 2004. Teachers were involved in discovering the relationship between radio frequency interference (RFI) and radio astronomy observations. S. Rapp participated in astronomy observations with the Green Bank Telescope in order to characterize RFI issues at radio observatories and worked closely with the Green Bank Interference Protection Group. This work included such tasks as mitigation of locally-generated RFI from power poles and running radiation propagation studies for transmitters within the National Radio Quiet Zone. A curriculum was created to allow high school students to participate in a research effort to determine RFI levels in their communities. The aim of the project is to promote student awareness of radio astronomy and radio frequency interference through an inquiry-based science curriculum. It is hoped that the project will go national by 2007. A prototype RFI detector was created and tested at four wavelengths; 850, 900, 1425, and 1675 MHz. High school students used a beta version of the RFI detector to explore the occurrence of RFI at their schools and in their communities. The student goals of the Quiet Skies Project are to: Measure interference levels at their schools and in their communities; Reduce and transmit their data to an NRAO data base; Use online spectrum allocation data, and local information to determine possible causes of interference in their area; Analyze the complex trade-offs between radio astronomy's need for quiet skies, and other commercial, and non-commercial uses of the spectrum and share their insights with others. This work was funded by the NSF-RET program and a grant from the NASA-IDEAS program

Rapp, S.; Gear, C.; Maddalena, R. J.; Heatherly, S. A.

2004-12-01

226

Report on a 2009 Mini-Demonstration of the ARG-US Radio Frequency Identification (RFID) System in Transportation.  

National Technical Information Service (NTIS)

The Packaging Certification Program (PCP) of the U.S. Department of Energy (DOE) Environmental Management (EM), Office of Packaging and Transportation (EM-14), has developed a radio frequency identification (RFID) tracking and monitoring system for the ma...

B. Craig H. Tsai K. Chen M. Jusko Y. Liu

2009-01-01

227

Radio-frequency quadrupole vane-tip geometries  

SciTech Connect

Radio-frequency quadrupole (RFQ) linacs are becoming widely accepted in the accelerator community. They have the remarkable capability of simultaneously bunching low-energy ion beams and accelerating them to energies at which conventional accelerators can be used, accomplishing this with high-transmission efficiencies and low-emittance growths. The electric fields, used for radial focusing, bunching, and accelerating, are determined by the geometry of the vane tips. The choice of the best vane-tip geometry depends on considerations such as the peak surface electric field, per cent of higher multipole components, and ease of machining. We review the vane-tip geometry based on the ideal two-term potential function and briefly describe a method for calculating the electric field components in an RFQ cell with arbitrary vane-tip geometry. We describe five basic geometries and use the prototype RFQ design for the Fusion Materials Irradiation Test (FMIT) accelerator as an example to compare the characteristics of the various geometries.

Crandall, K.R.; Mills, R.S.; Wangler, T.P.

1983-01-01

228

TORE SUPRA fast reciprocating radio frequency probe  

SciTech Connect

A fast reciprocating ion cyclotron range of frequencies (ICRF) probe was installed and operated on TORE SUPRA during 1992/1993. The body of the probe was originally used on the ATF experiment at Oak Ridge National Laboratory. The probe was adapted for use on TORE SUPRA, and mounted on one of the two fast reciprocating probe mounts. The probe consists of two orthogonal single-turn wire loops, mounted so that one loop senses toroidal rf magnetic fields and the other senses poloidal rf magnetic fields. The probe began operation in June, 1993. The probe active area is approximately 5 cm long by 2 cm, and the reciprocating mount has a slow stroke (5 cm/s) of 30 cm and a fast stroke (1.5 m/s) of about 10 cm. The probe was operated at distances from the plasma edge ranging from 30 to [minus]5 cm (i.e., inside the last closed flux surface). The probe design, electronics, calibration, data acquisition, and data processing are discussed. First data from the probe are presented as a function of ICRF power, distance from the plasma, loop orientation, and other plasma parameters. Initial data show parametric instabilities do not play an important role for ICRF in the TORE SUPRA edge and scrape-off-layer (SOL) plasmas. Additionally it is observed that the probe signal has little or no dependence on position in the SOL/plasma edge.

Thomas, C.E. Jr.; Harris, J.H.; Haste, G.R.; Kwon, M.; Goulding, R.H.; Hoffman, D.J. (Fusion Energy Division, Oak Ridge National Laboratory (ORNL), Oak Ridge, Tennessee 37831 (United States)); Saoutic, B.; Becoulet, A.; Fraboulet, D.; Beaumont, B.; Kuus, H.; Ladurelle, L.; Pascal, J.Y. (TORE SUPRA/DRFC, Centre d'Etudes de Cadarache, Association EURATOM-CEA, 13108 Saint-Paul-Lez-Durance, Cedex (France))

1995-02-01

229

A Low-Frequency Distributed Aperture Array for Radio Astronomy in Space  

Microsoft Academic Search

The frequency band below 30 MHz is one of the last unexplored bands in radio astronomy. This band is well suited for studying the early cosmos at high hydrogen redshifts, the so-called dark ages, extragalactic surveys, (extra) solar planetary bursts, and high energy particle physics. In addition, space research such as space weather tomography, are also areas of scientific interest.

Albert-Jan Boonstra; Noah Saks; Heino Falcke; Marc Klein-Wolt; Ark Bentum; Raj Thilak Rajan; Ir. Stefan J. Wijnholds; Michel Arts; Kees van-T Klooster; Frederik Belien

2010-01-01

230

Proton beam verification using RF power measurement data for a CW radio frequency quadrupole linac  

Microsoft Academic Search

A cw radio frequency quadrupole (RFQ) LINAC section and klystrode based rf system was obtained from the Chalk River Laboratories and was recommissioned at LANL to conduct demonstration proton beam experiments in support of a spallation neutron source driver for tritium production. A variation of the Low Energy Demonstration Accelerator (LEDA) proton injector, modified to operate at 50 keV, was

G. O. Bolme; L. D. Hansborough; D. J. Hodgkins; D. R. Keffeler; J. D. Sherman; H. V. Smith; R. R. Stevens; L. M. Young; T. J. Zaugg; A. H. Arvin; A. S. Bolt; M. C. Richards; P. P. Balleyguier; J. H. Kamperschroer

1999-01-01

231

Radio-Frequency Driven Dielectric Heaters for Non-Nuclear Testing in Nuclear Core Development  

NASA Technical Reports Server (NTRS)

Apparatus and methods are provided through which a radio-frequency dielectric heater has a cylindrical form factor, a variable thermal energy deposition through variations in geometry and composition of a dielectric, and/or has a thermally isolated power input.

Sims, William Herbert, III (Inventor); Godfroy, Thomas J. (Inventor); Bitteker, Leo (Inventor)

2004-01-01

232

Transurethral radio frequency ablation of the prostate  

NASA Astrophysics Data System (ADS)

Since 1993, radiofrequency ablation of the prostate has been studied as a potential treatment for symptomatic bladder outlet obstruction due to benign prostatic hyperplasia. Two transurethral radiofrequency delivery systems have been developed to the point of undergoing initial human clinical trials. The TUNATM system involves focal interstitial radiofrequency energy application, while the TURAPYTM system involves a circumferential application of radiofrequency energy to the prostatic urethra via a simple delivery catheter. Experimental studies in animal models and human prostate tissue have demonstrated the nature of radiofrequency induced tissue heating and thermal injury. Observed thermal effects are relatively focused, with steep temperature gradients occurring over a few millimeters from the radiofrequency emission source. This allows precise and focused tissue treatment with little or no danger of injury to surrounding structures. Early human clinical experience in the treatment of benign prostatic hyperplasia has demonstrated efficacy in the relief of voiding symptoms and safety and minimal morbidity associated with this technology. The existing operative approaches are relatively simple. Ongoing development of more versatile delivery systems for radiofrequency ablation of the prostate is expected. Results from larger clinical trials with longer term followup will eventually allow adequate assessment of the role of radiofrequency ablation in the surgical management of benign prostatic hyperplasia.

Kabalin, John N.

1996-05-01

233

Population density effect on radio frequencies interference (RFI) in radio astronomy  

NASA Astrophysics Data System (ADS)

Radio astronomical observation is infected by wide range of Radio Frequency Interference (RFI). We will also use information gathered from on-site RFI level measurements on selected 'good' areas generated by this study. After investigating a few suitable sites we will commence to the site and construct the RFI observation. Eventually, the best area we will be deciding from the observations soon. The result of this experiment will support our planning to build the first radio telescope in Malaysia. Radio observatories normally are located in remote area, in order to combat RFI from active spectrum users and radio noise produced in industrial or residential areas. The other solution for this problem is regulating the use of radio frequencies in the country (spectrum management). Measurement of RFI level on potential radio astronomical site can be done to measure the RFI levels at sites. Seven sites are chosen divide by three group, which is A, B and C. In this paper, we report the initial testing RFI survey for overall spectrum (0-2GHz) for those sites. The averaged RFI level above noise level at the three group sites are 19.0 (+/-1.79) dBm, 19.5 (+/-3.71) dBm and 17.0 (+/-3.71) dBm and the averaged RFI level above noise level for without main peaks are 20.1 (+/-1.77) dBm, 19.6 (+/-3.65) dBm and 17.2 (+/-1.43) dBm respectively.

Umar, Roslan; Abidin, Zamri Zainal; Ibrahim, Zainol Abidin; Hassan, Mohd Saiful Rizal; Rosli, Zulfazli; Hamidi, Zety Shahrizat

2012-06-01

234

76 FR 58142 - Defense Federal Acquisition Regulation Supplement; Passive Radio Frequency Identification (DFARS...  

Federal Register 2010, 2011, 2012, 2013

...passive radio frequency identification (RFID). DATES: Effective Date: September...passive radio frequency identification (RFID). II. Discussion and Analysis DoD received...rule. Comment: A respondent stated that RFID tags will play an expanded role in...

2011-09-20

235

Remote Sensing: Radio Frequency Detection for High School Physics Students  

NASA Astrophysics Data System (ADS)

In an effort to give high school students experience in real world science applications, we have partnered with Loranger High School in Loranger, LA to mentor 9 senior physics students in radio frequency electromagnetic detection. The effort consists of two projects: Mapping of 60 Hz noise around the Laser Interferometer Gravitational Wave Observatory (LIGO), and the construction of a 20 MHz radio telescope for observations of the Sun and Jupiter (Radio Jove, NASA). The results of the LIGO mapping will aid in strategies to reduce the 60 Hz line noise in the LIGO noise spectrum. The Radio Jove project will introduce students to the field of radio astronomy and give them better insight into the dynamic nature of large solar system objects. Both groups will work together in the early stages as they learn the basics of electromagnetic transmission and detection. The groups will document and report their progress regularly. The students will work under the supervision of three undergraduate mentors. Our program is designed to give them theoretical and practical knowledge in radiation and electronics. The students will learn how to design and test receiver in the lab and field settings.

Huggett, Daniel; Jeandron, Michael; Maddox, Larry; Yoshida, Sanichiro

2011-10-01

236

Ion Dynamics Model for Collisionless Radio Frequency Sheaths  

NASA Technical Reports Server (NTRS)

Full scale reactor model based on fluid equations is widely used to analyze high density plasma reactors. It is well known that the submillimeter scale sheath in front of a biased electrode supporting the wafer is difficult to resolve in numerical simulations, and the common practice is to use results for electric field from some form of analytical sheath model as boundary conditions for full scale reactor simulation. There are several sheath models in the literature ranging from Child's law to a recent unified sheath model [P. A. Miller and M. E. Riley, J. Appl. Phys. 82, 3689 (1997)l. In the present work, the cold ion fluid equations in the radio frequency sheath are solved numerically to show that the spatiotemporal variation of ion flux inside the sheath, commonly ignored in analytical models, is important in determining the electric field and ion energy at the electrode. Consequently, a semianalytical model that includes the spatiotemporal variation of ion flux is developed for use as boundary condition in reactor simulations. This semianalytical model is shown to yield results for sheath properties in close agreement with numerical solutions.

Bose, Deepak; Govindan, T.R.; Meyyappan, M.

2000-01-01

237

Analyzing Radio-Frequency Coverage for the ISS  

NASA Technical Reports Server (NTRS)

The Interactive Coverage Analysis Tool (iCAT) is an interactive desktop computer program serving to (1) support planning of coverage, and management of usage of frequencies, of current and proposed radio communication systems on and near the International Space Station (ISS) and (2) enable definition of requirements for development of future such systems. The iCAT can also be used in design trade studies for other (both outer-space and terrestrial) communication systems. A user can enter the parameters of a communication-system link budget in a table in a worksheet. The nominal (onaxis) link values for the bit-to-noise-energy ratio, received isotropic power (RIP), carrier-to-noise ratio (C/N), power flux density (PFD), and link margin of the system are calculated and displayed in the table. Plots of field gradients for the RIP, C/N, PFD, and link margin are constructed in an ISS coordinate system, at a specified link range, for both the forward and return link parameters, and are displayed in worksheets. The forward and reverse link antenna gain patterns are also constructed and displayed. Line-of-sight (LOS) obstructions can be both incorporated into the gradient plots and displayed on separate plots.

Bolen, Steven M.; Sham, Catherine C.

2007-01-01

238

Optimization framework for a radio frequency gun based injector  

NASA Astrophysics Data System (ADS)

Linear accelerator based light sources are used to produce coherent x-ray beams with unprecedented peak intensity. In these devices, the key parameters of the photon beam such as brilliance and coherence are directly dependent on the electron beam parameters. This leads to stringent beam quality requirements for the electron beam source. Radio frequency (RF) guns are used in such light sources since they accelerate electrons to relativistic energies over a very short distance, thus minimizing the beam quality degradation due to space charge effects within the particle bunch. Designing such sources including optimization of its beam parameters is a complex process where one needs to meet many requirements simultaneously. It is useful to have a tool to automate the design optimization in the context of the injector beam dynamics performance. Evolutionary and genetic algorithms are powerful tools to apply to nonlinear multi-objective optimization problems, and they have been successfully used in injector optimizations where the electric field profiles for the accelerating devices are fixed. Here the genetic algorithm based approach is extended to modify and optimize the electric field profile for an RF gun concurrently with the injector performance. Two field modification methods are used. This dissertation presents an overview of the optimization system and examples of its application to a state of the art RF gun. Results indicate improved injector performance is possible with unbalanced electric field profiles where the peak field in the cathode cell is larger than in subsequent cells.

Hofler, Alicia S.

239

Overview of technical approaches to radio frequency interference mitigation  

NASA Astrophysics Data System (ADS)

This overview provides an interface between lines of thought on radio frequency interference (RFI) mitigation in the fields of radio astronomy and signal processing. The goal is to explore the commonality of different approaches to help researchers in both fields interpret each other's concepts and jargon. The paper elaborates on the astronomers' concept of gain closure relations and how they may be used in a ``self-calibrating'' system of RFI cancellation. Further discussion of the eigen-decomposition method in terms of RFI power and antenna gains introduces adaptive nulling and RFI cancellation through matrix partitioning. While multipath scattering appears at first glance to be fatal to methods of RFI cancellation, its effect is easily incorporated in frequency-dependent gain coefficients under many circumstances.

Briggs, F. H.; Kocz, J.

2005-07-01

240

Adaptive filters revisited: Radio frequency interference mitigation in pulsar observations  

NASA Astrophysics Data System (ADS)

Pulsar detection and timing experiments are applications where adaptive filters seem eminently suitable tools for radio frequency interference (RFI) mitigation. We describe a novel variant which works well in field trials of pulsar observations centered on an observing frequency of 675 MHz and a bandwidth of 64 MHz and with 2-bit sampling. Adaptive filters have generally received bad press for RFI mitigation in radio astronomical observations with their most serious drawback being a spectral echo of the RFI embedded in the filtered signals. Pulsar observations are intrinsically less sensitive to this as they operate in the (pulsar period) time domain. The field trials have allowed us to identify those issues which limit the effectiveness of the adaptive filter. We conclude that adaptive filters can significantly improve pulsar observations in the presence of RFI.

Kesteven, M.; Hobbs, G.; Clement, R.; Dawson, B.; Manchester, R.; Uppal, T.

2005-05-01

241

Radio frequency wave reducing material and methods for manufacturing same  

US Patent & Trademark Office Database

An improved radio frequency wave attenuating wall (ceiling or floor) or door material comprises a laminated structure having as an integral part thereof one or more layers of a viscoelastic material which also functions as a glue and one or more electrically conducting layers. An electrically conducting material such as tape or a formed metal channel provides an electrical connection between the electrically conducting material and an exposed outer surface of the laminated structure. In one embodiment the electrically conducting material is paint. In one embodiment, standard wallboard, typically gypsum, comprises the external surfaces of the laminated structure and one or more conductive layers are constructed between the gypsum exterior. In one embodiment, the conducting layer material is selected to provide physical security in addition to radio frequency wave attenuation. The construction is such that acoustical attenuation is also achieved.

2011-10-04

242

X-ray imaging of superconducting radio frequency cavities  

NASA Astrophysics Data System (ADS)

The goal of this research was to develop an improved diagnostic technique to identify the location of defects that limit superconducting radio frequency (SRF) cavity performance during cavity testing or in existing accelerators. SRF cavities are primarily constructed of niobium. Electrons within the metal of a cavity under high electric field gradient have a probability of tunneling through the potential barrier. i e. leave the surface or are field emitted in regions where defects are encountered. Field emitted electrons are accelerated in the electric fields within the cavity. The electrons can have complicated trajectories and strike the cavity walls thus producing x-rays via Coulomb interactions and/or bremsstrahlung radiation. The endpoint energy of an x-ray spectrum predicts the electron maximum final kinetic energy within the cavity. Field emission simulations can then predict the source of the field-emitted electrons and the defect(s). In a multicell cavity the cells are coupled together and act as a set of coupled oscillators. There are multiple passbands of excitation for a multicell structure operating in a particular mode. For different passbands of operation the direction and amplitude of the fields within a cavity change from that of the normal accelerating mode. Field emitted electrons have different trajectories depending on the mode and thus produce x-rays in different locations. Using a collimated sodium iodide detector and subjecting a cavity to multiple passband modes at high electric field gradient the source of a cavity's x-rays can be determined. Knowing the location of the x-rays and the maximum electron kinetic energy; field emission simulations for different passband modes can be used to determine and verify the source of the field emitted electrons from mode to mode. Once identified, the defect(s) can be repaired or modifications made to the manufacturing process.

Musser, Susan Elizabeth

243

78 FR 49529 - Radio Frequency Wireless Technology in Medical Devices; Guidance for Industry and Food and Drug...  

Federal Register 2010, 2011, 2012, 2013

...formerly Docket No. 2006D-0504) Radio Frequency Wireless Technology in Medical...of the guidance entitled ``Radio Frequency Wireless Technology in Medical...incorporation and integration of radio frequency (RF) wireless technology...

2013-08-14

244

Radio-frequency spectroscopy of polarons in ultracold Bose gases  

NASA Astrophysics Data System (ADS)

Recent experimental advances enabled the realization of mobile impurities immersed in a Bose-Einstein condensate (BEC) of ultracold atoms. Here, we consider impurities with two or more internal hyperfine states, and study their radio-frequency (rf) absorption spectra, which correspond to transitions between two different hyperfine states. We calculate rf spectra for the case when one of the hyperfine states involved interacts with the BEC, while the other state is noninteracting, by performing a nonperturbative resummation of the probabilities of exciting different numbers of phonon modes. In the presence of interactions, the impurity gets dressed by Bogoliubov excitations of the BEC, and forms a polaron. The rf signal contains a ?-function peak centered at the energy of the polaron measured relative to the bare impurity transition frequency with a weight equal to the amount of bare impurity character in the polaron state. The rf spectrum also has a broad incoherent part arising from the background excitations of the BEC, with a characteristic power-law tail that appears as a consequence of the universal physics of contact interactions. We discuss both the direct rf measurement, in which the impurity is initially in an interacting state, and the inverse rf measurement, in which the impurity is initially in a noninteracting state. In the latter case, in order to calculate the rf spectrum, we solve the problem of polaron formation: a mobile impurity is suddenly introduced in a BEC, and dynamically gets dressed by Bogoliubov phonons. Our solution is based on a time-dependent variational ansatz of coherent states of Bogoliubov phonons, which becomes exact when the impurity is localized. Moreover, we show that such an ansatz compares well with a semiclassical estimate of the propagation amplitude of a mobile impurity in the BEC. Our technique can be extended to cases when both initial and final impurity states are interacting with the BEC.

Shashi, Aditya; Grusdt, Fabian; Abanin, Dmitry A.; Demler, Eugene

2014-05-01

245

Optical-radio-frequency resonances free from power broadening  

SciTech Connect

We have demonstrated a new mode of operation of an optical-radio-frequency double-resonance measurement, which allows high-resolution rf spectroscopy with negligible power broadening. The method is based on saturating, resonant excitation, and nonresonant detection of an atomic alignment of alkali-metal atoms by magneto-optical means. Its application to precision measurements, in particular to atomic magnetometry, is discussed.

Chalupczak, W.; Josephs-Franks, P.; Pustelny, S.; Gawlik, W. [National Physical Laboratory, Hampton Road, Teddington, TW11 0LW (United Kingdom); Centrum Badan Magnetooptycznych, M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, PL-30-059 Krakow (Poland)

2010-01-15

246

Radio-frequency ablation of renal cell carcinoma  

Microsoft Academic Search

Purpose: To report the authors' early experience with radio-frequency (RF) ablation of renal cell carcinoma.Materials and Methods: Twenty-four percutaneous RF ablation treatments for nine tumors were performed in eight patients with renal cell carcinoma. Indications included coexistent morbidity, previous surgery, or solitary kidney in patients with a life expectancy shorter than 10 years. Smaller (?3-cm) peripheral lesions (n = 3)

DA Gervais; FJ McGovern; BJ Wood; SN Goldberg; WS McDougal; PR Mueller

2002-01-01

247

Pancakes and Cigars - Low Frequency Variability of Extragalactic Radio Sources  

NASA Astrophysics Data System (ADS)

Results from monitoring low frequency variable radio sources suggest that there may be at least two types of sub-GHz variations: delayed bursts and nondelayed bursts. The expanding-cloud model accounts qualitatively for the spectral behavior of delayed bursts, but not for that of nondelayed (simultaneous or advanced) bursts. The author examines a possible modification of the expanding-cloud model which can in principle account qualitatively for the spectral behavior of nondelayed bursts.

Odell, S. L.

248

Development of radio frequency induction plasma generators for neutral beams  

Microsoft Academic Search

The techniques, operational aspects, and experimental results of a radio frequency induction plasma generator, with an internal rf power coupler, intended for intense neutral beam applications are described. One of the development sources suitable for 10×10-cm2 extraction optics was operated to a deuterium ion current density of 250 mA\\/cm2, uniform to 5%, over a circular extraction area 15 cm in

W. F. Divergilio; H. Goede; V. V. Fosnight

1986-01-01

249

South Polar in situ radio-frequency ice attenuation  

Microsoft Academic Search

We have determined the in situ electric field attenuation length Lalpha (defined as the length over which the signal amplitude diminishes by a factor 1\\/e) for radio-frequency signals broadcast vertically through South Polar ice and reflected off the underlying bed. Conservatively assuming a bedrock field reflectivity R = 1.0, we estimate Lalpha = 1450+300-150 m for f = 380 MHz,

S. Barwick; D. Besson; P. Gorham; D. Saltzberg

2005-01-01

250

Division X Working Group on Radio Frequency Interference Mitigation  

NASA Astrophysics Data System (ADS)

The IAU Working Group on Radio Frequency Interference (RFI) Mitigation was setup in the 2000 IAU GA in Manchester and its mandate was renewed at subsequent IAU GAs in 2003 and 2006. It was noted that that there are important issues related to RFI mitigation that extend beyond the regulatory function of IUCAF, and hence a more extended working group, which may include IUCAF members, was established.

Tzioumis, Tasso; Baan, Willem; Emerson, Darrel; Ohishi, Masatoshi; Gergely, Tomas; Fisher, Rick; Ponsoby, John; Boonstra, JAlbert-Jan; Ekers, Ron; van Driel, Wim; Zhang, Haiyan

2010-05-01

251

Tests of niobium cathode for the superconducting radio frequency gun  

Microsoft Academic Search

For the superconducting all-niobium photocathode radio frequency gun project, we have studied the surface preparation techniques of the niobium cathode material. The quantum efficiency (QE) of high purity niobium (RRR=250) has been intensively measured at room temperature on a dedicated DC system. After buffer chemical polishing or electrolytic polishing, the initial QE is in the order of 10-7 range tested

Qiang Zhao; Triveni Srinivasan-Rao; M. Cole

2003-01-01

252

Excitation frequency dependent mode manipulation in radio-frequency atmospheric argon glow discharges  

NASA Astrophysics Data System (ADS)

An experimental investigation is presented to characterize the dependence of discharge operation modes (? and ? modes) and their transition on excitation frequency in radio-frequency atmospheric argon glow discharges. The current-voltage characteristics are used to distinguish the ? and ? modes at an excitation frequency range of 5-24 MHz. The operation regime of ? mode with stable and uniform discharge in large volume is found to expand at higher excitation frequency. It is shown that, when excitation frequency is below 10 MHz, the discharge evolves directly into ? mode after gas breakdown and, when excitation frequency is above 10 MHz, the discharge operates in the coexistence mode of ? and ? after mode transition.

Zhang, Jie; Ding, Ke; Wei, Kaya; Zhang, Jing; Shi, Jianjun

2009-09-01

253

Delay Tolerant, Radio Frequency Identification (RFID )-enabled Sensing  

NASA Technical Reports Server (NTRS)

Radio Frequency Identification (RFID) technology offers a completely passive method to transmit fixed data sequences from an RFID tag, which typically doesn't have its own power supply, to an interrogator. Radio frequency (RF) energy harvested from the interrogator is rectified by the tag and used to charge an integrated circuit (IC). The IC then modulates the received signal with the data stored on the tag and reflects the energy back to the interrogator. RFID has seen great proliferation in terrestrial inventory management applications, and it has recently made the jump to spaceflight applications onboard the International Space Station, augmenting an existing optical bar-code infrastructure for tracking supplies. A number of advanced automated logistics management (ALM) concepts employing RFID are currently being developed and evaluated, including so-called "smart" shelves, cubbies, and trash receptacles using low-power, embeddable RFID interrogators. An infrastructure where both crew members and robotic assistants, such as autonomous free flyers, are similarly equipped with small RFID interrogators seems likely. It therefore behooves us to consider extending this infrastructure beyond ALM to applications such as low power, embedded sensing. Typically, data on an RFID tag can only be written by an RFID interrogator, using interrogator energy. In recent years, however, a few efforts have focused on using that energy to drive data acquisition from the tag IC, allowing the tag to modify its stored data sequence with sensor data before replying to an interrogator. In this way, the tag can act as a completely passive sensing device. One problem exists with this approach, however: the tag cannot gather data when an interrogator is not present. Thus, strictly passive RFID sensing tags cannot gather data at regular intervals, in the manner of a typical wireless sensor network, without careful, and impractical, planning of mobile interrogator movements. To address this shortcoming, we look to a recent advance in RFID technology which allows an external microprocessor to power the tag IC and write directly into its RFID memory using a wired serial interface. In this paradigm, data gathering is driven by a small, on-board power supply (using batteries or harvested energy), and data transfer is provided passively through the RFID interrogation service. Since communication typically consumes the lion's share of power in WSNs, such a technique has the potential to enable extremely long-lived, embedded wireless sensing when used with extremely low-current microcontrollers. Since the communication channel is only open when an interrogator is present and actively interrogating the RFID sensing tag, transport of periodically-sampled sensor data presents itself as a delay/disruption-tolerant networking (DTN) problem. In this paper, we present the design of a DTN-like overlay on the common EPC Global, Class 1, Generation 2 RFID standard. This overlay allows seamless, guaranteed data transfer using the EPC Global protocol, supporting extremely low-power, embedded sensing using an infrastructure likely to be already in place for ALM applications. We evaluate a prototype implementation of a complete end-to-end system using a robotic RFID interrogation agent, and we present future directions for the development of this sensing technique.

Wagner, Raymond S.; Barton, Richard; Fink, Patrick

2014-01-01

254

Imaging Interplanetary CMEs at Radio Frequency From Solar Polar Orbit  

NASA Astrophysics Data System (ADS)

Coronal mass ejections (CMEs) are violent discharges of plasma and magnetic fields from the Sun's corona. They have come to be recognized as the major driver of physical conditions in the Sun-Earth system. Consequently, the detection of CMEs is important for un-derstanding and ultimately predicting space weather conditions. The Solar Polar Orbit Radio Telescope (SPORT) is a proposed mission to observe the propagation of interplanetary CMEs from solar polar orbit. The main payload (radio telescope) on board SPORT will be an in-terferometric imaging radiometer working at the meter wavelength band, which will follow the propagation of interplanetary CMEs from a distance of a few solar radii to near 1 AU from solar polar orbit. The SPORT spacecraft will also be equipped with a set of optical and in situ measurement instruments such as a EUV solar telescope, a solar wind plasma experiment, a solar wind ion composition instrument, an energetic particle detector, a wave detector, a mag-netometer and an interplanetary radio burst tracker. In this paper, we first describe the current shortage of interplanetary CME observations. Next, the scientific motivation and objectives of SPORT are introduced. We discuss the basic specifications of the main radio telescope of SPORT with reference to the radio emission mechanisms and the radio frequency band to be observed. Finally, we discuss the key technologies of the SPORT mission, including the con-ceptual design of the main telescope, the image retrieval algorithm and the solar polar orbit injection. Other payloads and their respective observation objectives are also briefly discussed. Key words: Interplanetary CMEs; Interferometric imaging; Solar polar orbit; Radiometer.

Wu, Ji; Sun, Weiying; Zheng, Jianhua; Zhang, Cheng; Wang, Chi; Wang, C. B.; Wang, S.

255

Experimental development and theoretical studies of radio-frequency absorbers  

NASA Astrophysics Data System (ADS)

A mathematical model based on the equivalence with a sequence of lossy transmission lines has been developed and applied, by numerical calculus, to the study of radio-frequency absorbers of piramidal shape, made of polyurethane foam impregnated with finely powered carbon black. The model has been used to find the expected performance of absorbers with different electrical conductivities in the microwave range of frequencies. The results agree with the measurements of reflectivity which have been previously obtained, by the arch method, during the phase of experimental development of the absorbers, when the carbon black concentration was progressively changed.

Massa, J. L. L. M.

1991-04-01

256

Multiplexing of Radio-Frequency Single Electron Transistors  

NASA Technical Reports Server (NTRS)

We present results on wavelength division multiplexing of radio-frequency single electron transistors. We use a network of resonant impedance matching circuits to direct applied rf carrier waves to different transistors depending on carrier frequency. A two-channel demonstration of this concept using discrete components successfully reconstructed input signals with small levels of cross coupling. A lithographic version of the rf circuits had measured parameters in agreement with electromagnetic modeling, with reduced cross capacitance and inductance, and should allow 20 to 50 channels to be multiplexed.

Stevenson, Thomas R.; Pellerano, F. A.; Stahle, C. M.; Aidala, K.; Schoelkopf, R. J.; Krebs, Carolyn (Technical Monitor)

2001-01-01

257

The highest frequency detection of a radio relic: 16 GHz AMI observations of the `Sausage' cluster  

NASA Astrophysics Data System (ADS)

We observed the cluster CIZA J2242.8+5301 with the Arcminute Microkelvin Imager at 16 GHz and present the first high radio-frequency detection of diffuse, non-thermal cluster emission. This cluster hosts a variety of bright, extended, steep-spectrum synchrotron-emitting radio sources, associated with the intracluster medium, called radio relics. Most notably, the northern, Mpc-wide, narrow relic provides strong evidence for diffusive shock acceleration in clusters. We detect a puzzling, flat-spectrum, diffuse extension of the southern relic, which is not visible in the lower radio-frequency maps. The northern radio relic is unequivocally detected and measures an integrated flux of 1.2 ± 0.3 mJy. While the low-frequency (<2 GHz) spectrum of the northern relic is well represented by a power law, it clearly steepens towards 16 GHz. This result is inconsistent with diffusive shock acceleration predictions of ageing plasma behind a uniform shock front. The steepening could be caused by an inhomogeneous medium with temperature/density gradients or by lower acceleration efficiencies of high energy electrons. Further modelling is necessary to explain the observed spectrum.

Stroe, Andra; Rumsey, Clare; Harwood, Jeremy J.; van Weeren, Reinout J.; Röttgering, Huub J. A.; Saunders, Richard D. E.; Sobral, David; Perrott, Yvette C.; Schammel, Michel P.

2014-06-01

258

RFID Transponders' Radio Frequency Emissions in Aircraft Communication and Navigation Radio Bands  

NASA Technical Reports Server (NTRS)

Radiated emissions in aircraft communication and navigation bands are measured from several active radio frequency identification (RFID) tags. The individual tags are different in design and operations. They may also operate in different frequency bands. The process for measuring the emissions is discussed, and includes tag interrogation, reverberation chamber testing, and instrument settings selection. The measurement results are described and compared against aircraft emission limits. In addition, interference path loss for the cargo bays of passenger aircraft is measured. Cargo bay path loss is more appropriate for RFID tags than passenger cabin path loss. The path loss data are reported for several aircraft radio systems on a Boeing 747 and an Airbus A320.

Nguyen, Truong X.; Ely, Jay J.; Williams, Reuben A.; Koppen, Sandra V.; Salud, Maria Theresa P.

2006-01-01

259

Low Frequency Radio Observations of GRS1915+105 with GMRT  

Microsoft Academic Search

We present the first detailed low frequency radio measurements of the\\u000agalactic microquasar GRS1915+105 with GMRT. Simultaneous observations were\\u000acarried out at 610 and 244 MHz. Our data does not show any signature of\\u000aspectral turn over even at low radio frequency of 244 MHz. We propose that\\u000awhile the radio emission at high radio frequencies could predominantly come\\u000afrom

C. H. Ishwara-Chandra; A. Pramesh Rao; Mamta Pandey; R. K. Manchanda; Philippe Durouchoux

2005-01-01

260

New observations of the low frequency interplanetary radio emissions  

NASA Technical Reports Server (NTRS)

Recent Voyager 1 observations reveal reoccurrences of the low frequency interplanetary radio emissions. Three of the new events are weak transient events which rise in frequency from the range of 2-2.5 kHz to about 3 kHz with drift rates of approximately 1.5 kHz/year. The first of the transient events begins in mid-1989 and the more recent pair of events both were first detected in late 1991. In addition, there is an apparent onset of a 2-kHz component of the emission beginning near day 70 of 1991. The new transient emissions are barely detectable on Voyager 1 and are below the threshold of detectability on Voyager 2, which is less sensitive than Voyager 1. The new activity provides new opportunities to test various theories of the triggering, generation, and propagation of the outer heliospheric radio emissions and may signal a response of the source of the radio emissions to the increased solar activity associated with the recent peak in the solar cycle.

Kurth, W. S.; Gurnett, D. A.

1991-01-01

261

H- radio frequency source development at the Spallation Neutron Source.  

PubMed

The Spallation Neutron Source (SNS) now routinely operates nearly 1 MW of beam power on target with a highly persistent ?38 mA peak current in the linac and an availability of ?90%. H(-) beam pulses (?1 ms, 60 Hz) are produced by a Cs-enhanced, multicusp ion source closely coupled with an electrostatic low energy beam transport (LEBT), which focuses the 65 kV beam into a radio frequency quadrupole accelerator. The source plasma is generated by RF excitation (2 MHz, ?60 kW) of a copper antenna that has been encased with a thickness of ?0.7 mm of porcelain enamel and immersed into the plasma chamber. The ion source and LEBT normally have a combined availability of ?99%. Recent increases in duty-factor and RF power have made antenna failures a leading cause of downtime. This report first identifies the physical mechanism of antenna failure from a statistical inspection of ?75 antennas which ran at the SNS, scanning electron microscopy studies of antenna surface, and cross sectional cuts and analysis of calorimetric heating measurements. Failure mitigation efforts are then described which include modifying the antenna geometry and our acceptance?installation criteria. Progress and status of the development of the SNS external antenna source, a long-term solution to the internal antenna problem, are then discussed. Currently, this source is capable of delivering comparable beam currents to the baseline source to the SNS and, an earlier version, has briefly demonstrated unanalyzed currents up to ?100 mA (1 ms, 60 Hz) on the test stand. In particular, this paper discusses plasma ignition (dc and RF plasma guns), antenna reliability, magnet overheating, and insufficient beam persistence. PMID:22380234

Welton, R F; Dudnikov, V G; Gawne, K R; Han, B X; Murray, S N; Pennisi, T R; Roseberry, R T; Santana, M; Stockli, M P; Turvey, M W

2012-02-01

262

H- radio frequency source development at the Spallation Neutron Source  

SciTech Connect

The Spallation Neutron Source (SNS) now routinely operates nearly 1 MW of beam power on target with a highly persistent {approx}38 mA peak current in the linac and an availability of {approx}90%. H{sup -} beam pulses ({approx}1 ms, 60 Hz) are produced by a Cs-enhanced, multicusp ion source closely coupled with an electrostatic low energy beam transport (LEBT), which focuses the 65 kV beam into a radio frequency quadrupole accelerator. The source plasma is generated by RF excitation (2 MHz, {approx}60 kW) of a copper antenna that has been encased with a thickness of {approx}0.7 mm of porcelain enamel and immersed into the plasma chamber. The ion source and LEBT normally have a combined availability of {approx}99%. Recent increases in duty-factor and RF power have made antenna failures a leading cause of downtime. This report first identifies the physical mechanism of antenna failure from a statistical inspection of {approx}75 antennas which ran at the SNS, scanning electron microscopy studies of antenna surface, and cross sectional cuts and analysis of calorimetric heating measurements. Failure mitigation efforts are then described which include modifying the antenna geometry and our acceptance/installation criteria. Progress and status of the development of the SNS external antenna source, a long-term solution to the internal antenna problem, are then discussed. Currently, this source is capable of delivering comparable beam currents to the baseline source to the SNS and, an earlier version, has briefly demonstrated unanalyzed currents up to {approx}100 mA (1 ms, 60 Hz) on the test stand. In particular, this paper discusses plasma ignition (dc and RF plasma guns), antenna reliability, magnet overheating, and insufficient beam persistence.

Welton, Robert F [ORNL; Pennisi, Terry R [ORNL; Roseberry, Ron T [ORNL; Stockli, Martin P [ORNL

2012-01-01

263

Physical properties of young radio sources: VLBA observations of high-frequency peaking radio sources  

NASA Astrophysics Data System (ADS)

Multifrequency Very Long Baseline Array (VLBA) observations were performed to study the radio morphology and synchrotron spectra of four high-frequency peaking radio sources. They are resolved into several compact components and the radio emission is dominated by hotspots/lobes. The core region is detected unambiguously in J1335+5844 and J1735+5049. The spectra of the main source components peak above 3 GHz. Assuming that the spectral peak is produced by synchrotron self-absorption, we estimate the magnetic field directly from observable quantities: in half of the components it agrees with the equipartition field, while in the others the difference exceeds an order of magnitude. By comparing the physical properties of the targets with those of larger objects, we found that the luminosity increases with linear size for sources smaller than a few kpc, while it decreases for larger objects. The asymmetric sources J1335+5844 and J1735+5049 suggest that the ambient medium is inhomogeneous and is able to influence the evolution of the radio emission even during its first stages. The core luminosity increases with linear size for sources up to a few kpc, while it seems constant for larger sources, suggesting an evolution independent of source total luminosity.

Orienti, M.; Dallacasa, D.

2014-02-01

264

Physical properties of conventional explosives deduced from radio frequency emissions  

SciTech Connect

Los Alamos National Laboratory collected broadband radio frequency (RF) electric field change measurements from multiple detonations of high explosives (HE). Three types of HE were used: small cylinders of flake TNT, solid TNT, and PBX-9501. Low frequency signals (<80 MHz) were shot-to-shot repeatable and occurred within the first 100 {mu} s at measured amplitudes of about 2 V m{sup -1} at 35 m distance. High frequency signals (>290 MHz) occurred later, were an order of magnitude lower in signal strength, and were not repeatable. There is a positive correlation between the maximum electric field change and the shock velocity of the HE. The amount of free charge produced in the explosion estimated from the first RF pulse is between 10 and 150 {mu} C. This implies a weakly ionized plasma with temperatures between 2600 and 2900 K.

Harlin, Jeremiah D [Los Alamos National Laboratory; Nemzek, Robert [Los Alamos National Laboratory

2008-01-01

265

Power absorption in electrically asymmetric dual frequency capacitive radio frequency discharges  

SciTech Connect

The symmetry of capacitive radio frequency discharges can be controlled via the electrical asymmetry effect by driving one electrode with a fundamental frequency and its second harmonic. In such electrically asymmetric discharges, the mean ion energies at both electrodes are controlled separately from the ion flux by tuning the phase angle {theta} between the harmonics at fixed voltage amplitudes. Here, the question why the ion flux is nearly independent of {theta} is answered by investigating the power absorbed by the electrons P{sub e} as a function of {theta} and time experimentally, by a particle in cell simulation, and an analytical model. The dynamics of P{sub e} is understood by the model and is found to be strongly affected by the choice of {theta}. However, on time average, P{sub e} is nearly constant, independently of {theta}. Thus, the ion flux remains approximately constant. In addition, it is shown that the absolute value of the individual voltages across the powered and grounded electrode sheath vary linearly with the dc self-bias. However, their sum remains constant. This yields, in combination with the constancy of the ion flux, a constant power absorbed by the ions and, in conclusion, a total power absorption that is independent of {theta}.

Schuengel, E.; Czarnetzki, U. [Institute for Plasma and Atomic Physics, Ruhr-University Bochum, 44780 Bochum (Germany); Schulze, J. [Institute for Plasma and Atomic Physics, Ruhr-University Bochum, 44780 Bochum (Germany); Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, 1525 Budapest (Hungary); Donko, Z. [Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, 1525 Budapest (Hungary)

2011-01-15

266

Radio Frequency Identification (RFID) in healthcare: a literature review.  

PubMed

Creating and maintaining a safe and high-quality health care environment is of great importance for global community. New technologies and their applications can help us achieve this goal. Radio-Frequency Identification (RIFD) technology is considered one of those technologies and even today there are some interesting deployments in the health industry. As a result, this work aims to present the basic idea behind RFID solutions, problems that can be addressed with the adoption of RFID and the benefits of relative applications. PMID:23823408

Kolokathi, Aikaterini; Rallis, Panagiotis

2013-01-01

267

Hollow metal target magnetron sputter type radio frequency ion source.  

PubMed

A 70 mm diameter 70 mm long compact ion source equipped with a hollow sputtering target has been designed and tested. The hollow sputtering target serves as the radio frequency (RF) plasma excitation electrode at 13.56 MHz. A stable beam of Cu(+) has been extracted when Ar was used as the discharge support gas. In the extracted beam, Cu(+) had occupied more than 85% of the total ion current. Further increase in Cu(+) ions in the beam is anticipated by increasing the RF power and Ar pressure. PMID:24593636

Yamada, N; Kasuya, T; Tsubouchi, N; Wada, M

2014-02-01

268

Protein adsorption enhanced radio-frequency heating of silica nanoparticles  

NASA Astrophysics Data System (ADS)

Measurements of specific-absorption-rate (SAR) of silica 30, 50, and 100 nm nanoparticles (NP) suspended in water were carried out at 30 MHz in 7 kV/m radio-frequency (rf) electric field. Size dependent, NP-suspension interface related heating of silica NP was observed. To investigate a possible mechanism of heating, bovine serum albumin was adsorbed on the surface of silica NPs in suspension. It resulted in significant enhancement of SAR when compared to bare silica NPs. A calorimetric and rf loss model was used to calculate effective conductivity of silica NP with/without adsorbed albumin as a function of silica size and albumin concentration.

Wosik, Jarek; Pande, Rohit; Xie, Leiming; Ketharnath, Dhivya; Srinivasan, Srimeenakshi; Godin, Biana

2013-07-01

269

Plasma plume propagation characteristics of pulsed radio frequency plasma jet  

SciTech Connect

A 4 cm long helium cold atmospheric pressure plasma jet with pulsed radio frequency (rf) excitation was obtained by a copper electrode inside a quartz tube. The plasma bullet propagation characteristics common to the microseconds direct current pulse and kilohertz plasma jet is not observed in this case. The space-, time-, and wavelength-resolved optical emission profiles suggest the pulsed rf plasma channel out of the tube was strengthened by ions and metastables with longer life time than the rf period, and the plasma propagation was actually an illumination of the plasma channel caused by energetic electrons accelerated along the channel.

Liu, J. H.; Liu, X. Y.; Hu, K.; Liu, D. W.; Lu, X. P. [Advanced Electromagnetic Engineering and Technology Laboratory, Huazhong University of Science and Technology, WuHan, HuBei 430074 (China); Iza, F.; Kong, M. G. [Department of Electronic and Electrical Engineering, Loughborough University, Leicestershire LE11 3TU (United Kingdom)

2011-04-11

270

The radio-frequency impedance of individual intrinsic Josephson junctions  

SciTech Connect

We have measured the response of an array of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} intrinsic Josephson junctions to irradiation at 3 GHz. By measuring the dependence of the switching current upon the radio-frequency current for five of the junctions in the array we show quantitatively that the junctions have identical impedances at 3 GHz, this impedance being given by the inverse of the slope of the current-voltage characteristics.

Leiner, Johannes; Saleem, Sajid; Fenton, J. C.; Warburton, P. A. [London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH (United Kingdom); Yamamoto, Takashi; Kadowaki, Kazuo [Institute of Materials Science, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan)

2009-12-21

271

Implantable Radio Frequency Identification Sensors: Wireless Power and Communication  

PubMed Central

There are significant technical challenges in the development of a fully implantable wirelessly powered neural interface. Challenges include wireless transmission of sufficient power to the implanted device to ensure reliable operation for decades without replacement, minimizing tissue heating, and adequate reliable communications bandwidth. Overcoming these challenges is essential for the development of implantable closed loop system for the treatment of disorders ranging from epilepsy, incontinence, stroke and spinal cord injury. We discuss the development of the wireless power, communication and control for a Radio-Frequency Identification Sensor (RFIDS) system with targeted power range for a 700mV, 30 to 40uA load attained at ?2dBm.

Hutchens, Chriswell; Rennaker, Robert L.; Venkataraman, Srinivasan; Ahmed, Rehan; Liao, Ran; Ibrahim, Tamer

2013-01-01

272

[Radio frequency ablation therapy in the elderly breast cancer patient].  

PubMed

Breast cancer is an important health care problem, especially in the increasing elderly generation. Treatment of these fragile patients is a challenge for the clinician. Undertreatment has been linked to a higher percentage of recurrence and cancer related morbidity, while overtreatment leads to treatment related morbidity and mortality. Minimally invasive techniques do offer new opportunities for patients, who are no candidates for conventional surgery. The tumor lesion is treated locally and selective with minimal damage to surrounding tissue, yielding an adequate local tumor control. Radio frequency ablation technique seems an effective and safe method for treatment of the elderly patient with small (< 3 cm) breast cancer. PMID:18807458

Looij, B G; Kreb, D L; Bosscha, K; Ernst, M F; Jager, G J; Rutten, M J C M

2008-09-01

273

Nonclassical crystallization of amorphous iron nanoparticles by radio frequency methods  

NASA Astrophysics Data System (ADS)

Amorphous iron nanoparticles were synthesized using an aqueous reduction in iron(II) sulfate with sodium borohydride and sodium citrate. Various radio frequency (rf) exposure times were investigated in order to determine trends in nonclassical crystallization. RF times from 15 to 300 s revealed an increase in crystallite size from 5 to 60 nm, as determined by powder x-ray diffraction. Also, solvent optimization revealed that ethanol produced the largest trends for increasing crystallite size without total oxidation of the samples. Magnetic characterization by room temperature vibrating sample magnetometry and high resolution transmission microscopy was performed to verify magnetic properties and particle morphology.

Carroll, K. J.; Pitts, J. A.; Zhang, Kai; Pradhan, A. K.; Carpenter, E. E.

2010-05-01

274

Radio-frequency quadrupole: general properties and specific applications  

SciTech Connect

The radio-frequency quadrupole (RFQ) linac structure is being developed for the acceleration of low-velocity ions. Recent experimental tests have confirmed its expected performance and have led to an increased interest in a wide range of possible applications. The general properties of RFQ accelerators are reviewed and beam dynamics simulation results are presented for their use in a variety of accelerating systems. These include the low-beta sections of the Fusion Materials Irradiation Test Accelerator, a 200-MHz proton linear accelerator, and a xenon accelerator for heavy ion fusion.

Stokes, R.H.; Crandall, K.R.; Hamm, R.W.

1980-01-01

275

Performance Assessment of Internet E-Mail Over Degraded High-Frequency Radio Channels.  

National Technical Information Service (NTIS)

The transmission of E-mail over high-frequency (HF) radio channels is experiencing widespread use in the Government and military communities. This ability is made possible trough the convergence of Internet and radio communication protocols, primarily by ...

C. Redding R. McLean

1998-01-01

276

Source Localization in a Cognitive Radio Environment Consisting of Frequency and Spatial Mobility.  

National Technical Information Service (NTIS)

Cognitive radio presents a unique challenge to source localization in that the radio has the ability to adapt to the environment, thus rendering current localization techniques ineffective due to a shifting combination of spatial, frequency, and temporal ...

A. Adams

2011-01-01

277

47 CFR 76.616 - Operation near certain aeronautical and marine emergency radio frequencies.  

Code of Federal Regulations, 2013 CFR

...Telecommunication 4 2013-10-01 2013-10-01 false Operation near certain aeronautical and marine emergency radio frequencies...TELEVISION SERVICE Technical Standards § 76.616 Operation near certain aeronautical and marine emergency radio...

2013-10-01

278

Sounds energetic: the radio producer's energy minibook  

SciTech Connect

The Minibook will be expanded into the final Radio Producer's Energy Sourcebook. Radio producers and broadcasters are asked to contribute ideas for presenting energy knowledge to the public and to be included in the Sourcebook. Chapter One presents a case study suggesting programming and promotion ideas and sample scripts for a radio campaign that revolves around no-cost or low-cost steps listeners can take to increase their home energy efficiency and save money. A variety of other energy topics and suggestions on ways to approach them are addressed in Chapter Two. Chapter Three contains energy directories for Baltimore, Philadelphia, Pittsburg, and Washington, DC. The directories will be expanded in the Sourcebook and will consist of a selection of local public and private sector energy-related organizations and list local experts and organizations and the best Federal, state, and local government programs that can provide consumers and citizens groups with information, technical assistance, and financial support. (MCW)

Not Available

1980-12-01

279

Electromagnetic interference of cardiac rhythmic monitoring devices to radio frequency identification: analytical analysis and mitigation methodology.  

PubMed

Increasing density of wireless communication and development of radio frequency identification (RFID) technology in particular have increased the susceptibility of patients equipped with cardiac rhythmic monitoring devices (CRMD) to environmental electro magnetic interference (EMI). Several organizations reported observing CRMD EMI from different sources. This paper focuses on mathematically analyzing the energy as perceived by the implanted device, i.e., voltage. Radio frequency (RF) energy transmitted by RFID interrogators is considered as an example. A simplified front-end equivalent circuit of a CRMD sensing circuitry is proposed for the analysis following extensive black-box testing of several commercial pacemakers and implantable defibrillators. After careful understanding of the mechanics of the CRMD signal processing in identifying the QRS complex of the heart-beat, a mitigation technique is proposed. The mitigation methodology introduced in this paper is logical in approach, simple to implement and is therefore applicable to all wireless communication protocols. PMID:21926027

Ogirala, Ajay; Stachel, Joshua R; Mickle, Marlin H

2011-11-01

280

Radio Frequency Station - Beam Dynamics Interaction in Circular Accelerators  

SciTech Connect

The longitudinal beam dynamics in circular accelerators is mainly defined by the interaction of the beam current with the accelerating Radio Frequency (RF) stations. For stable operation, Low Level RF (LLRF) feedback systems are employed to reduce coherent instabilities and regulate the accelerating voltage. The LLRF system design has implications for the dynamics and stability of the closed-loop RF systems as well as for the particle beam, and is very sensitive to the operating range of accelerator currents and energies. Stability of the RF loop and the beam are necessary conditions for reliable machine operation. This dissertation describes theoretical formalisms and models that determine the longitudinal beam dynamics based on the LLRF implementation, time domain simulations that capture the dynamic behavior of the RF station-beam interaction, and measurements from the Positron-Electron Project (PEP-II) and the Large Hadron Collider (LHC) that validate the models and simulations. These models and simulations are structured to capture the technical characteristics of the system (noise contributions, non-linear elements, and more). As such, they provide useful results and insight for the development and design of future LLRF feedback systems. They also provide the opportunity to study diverse longitudinal beam dynamics effects such as coupled-bunch impedance driven instabilities and single bunch longitudinal emittance growth. Coupled-bunch instabilities and RF station power were the performance limiting effects for PEP-II. The sensitivity of the instabilities to individual LLRF parameters, the effectiveness of alternative operational algorithms, and the possible tradeoffs between RF loop and beam stability were studied. New algorithms were implemented, with significant performance improvement leading to a world record current during the last PEP-II run of 3212 mA for the Low Energy Ring. Longitudinal beam emittance growth due to RF noise is a major concern for LHC. Simulations studies and measurements were conducted that clearly show the correlation between RF noise and longitudinal bunch emittance, identify the major LLRF noise contributions, and determine the RF component dominating this effect. With these results, LHC upgrades and alternative algorithms are evaluated to reduce longitudinal emittance growth during operations. The applications of this work are described with regard to future machines and analysis of new technical implementations, as well as to possible future work which would continue the directions of this dissertation.

Mastoridis, Themistoklis; /Stanford U., Elect. Eng. Dept. /SLAC

2011-03-01

281

Radio frequency treatments to control codling moth in in-shell walnuts  

Microsoft Academic Search

‘Diamond’ Walnuts (Juglansregia L.) in the shell were treated with radio frequency (RF) energy in a 27 MHz pilot-scale system to determine the treatment effect on third- and fourth-instar codling moth, Cydiapomonella (L.) (Lepidoptera: Tortricidae), mortality and walnut quality. After 2 and 3 min of RF treatments, infested in-shell walnuts were heated to 43 and 53°C. The corresponding insect mortality

S. Wang; J. N. Ikediala; J. Tang; J. D. Hansen; E. Mitcham; R. Maoa; B. Swanson

2001-01-01

282

Dielectric Properties of Fruits and Insect Pests as related to Radio Frequency and Microwave Treatments  

Microsoft Academic Search

Information on dielectric properties of commodities and insect pests is needed in developing thermal treatments for postharvest insect control based on radio frequency (RF) and microwave energy. Dielectric properties of six commodities along with four associated insect pests were measured between 1 and 1800MHz using an open-ended coaxial-line probe technique and at temperatures between 20 and 60°C. The dielectric loss

S. Wang; J. Tang; J. A. Johnson; E. Mitcham; J. D. Hansen; G. Hallman; S. R. Drake; Y. Wang

2003-01-01

283

Thin-Film Deposition of Cu2O by Reactive Radio-Frequency Magnetron Sputtering  

Microsoft Academic Search

Deposition conditions of cuprous oxide (Cu2O) thin films on glass substrates by reactive radio-frequency (rf) magnetron sputtering method were studied. The substrate temperature was found to be important for obtaining high-quality films, and the optimum substrate temperature was about 500°C. The Cu2O deposited at 500°C shows a band-gap energy of about 2.0 eV and a typical hole concentration of the

Shogo Ishizuka; Takahiro Maruyama; Katsuhiro Akimoto

2000-01-01

284

Radio frequency induction plasma generator 80kV test stand operation  

Microsoft Academic Search

Beam extraction tests at energies up to 80 kV were performed using a radio frequency induction (RFI) plasma generator hydrogen ion source. A 7×10-cm2, long pulse accelerator was operated with a 10×10-cm2 axial magnetic cusp bucket and a magnetic-filter bucket. Atomic fractions (up to 85% H+), plasma production efficiencies (≊0.6 A of beam per kW rf power), and beam divergence

H. Goede; W. F. Divergilio; V. V. Fosnight; M. C. Vella; K. W. Ehlers; D. Kippenhan; P. A. Pincosy; R. V. Pyle

1986-01-01

285

Industrial-scale radio frequency treatments for insect control in walnuts  

Microsoft Academic Search

Conducting industrial-scale confirmatory treatments is the final step in developing commercially and environmentally sound insect control technologies for in-shell walnuts using radio frequency (RF) energy as an alternative to chemical fumigation. Improving heating uniformity of in-shell walnuts in the industrial process is essential to ensure insect control without quality degradation. An industrial-scale 27MHz, 25kW RF system was used to determine

S. Wang; M. Monzon; J. A. Johnson; E. J. Mitcham; J. Tanga

2007-01-01

286

Collisional, magnetic, and nonlinear skin effect in radio-frequency plasmas  

NASA Astrophysics Data System (ADS)

The penetration of radio-frequency energy into cylindrical devices is relevant to the production of uniform plasmas for etching and deposition processes in the production of semiconductor circuits. The so-called ``anomalous skin effect'' has been invoked to explain irregularities not predicted by classical electromagnetic theory. These expectations are summarized for the collisionality regimes of interest, and new results are given for nonkinetic effects caused by small direct current magnetic fields and the ponderomotive force.

Chen, Francis F.

2001-06-01

287

Measurements of the Suitability of Large Rock Salt Formations for Radio Detection of High Energy Neutrinos  

Microsoft Academic Search

We have investigated the possibility that large rock salt formations might be suitable as target masses for detection of neutrinos of energies about 10 PeV and above. In neutrino interactions at these energies, the secondary electromagnetic cascade produces a coherent radio pulse well above ambient thermal noise via the Askaryan effect. We describe measurements of radio-frequency attenuation lengths and ambient

Peter Gorham; David Saltzberg; Allen Odian; Dawn Williams; David Besson; George Frichter; Sami Tantawi

2001-01-01

288

Radio-frequency probe for bubble size and velocity measurements.  

PubMed

A radio frequency (rf) probe that can provide local void fraction and interface velocity measurements in a gas-liquid two-phase flow was developed. The probe response to bubble passage was investigated with single-bubble controlled experiments. For a fixed geometry, the probe response was dependent on the dielectric constant of the medium surrounding the probe tip (air or water) and on the frequency of the carrier signal supplied to the probe. Bubble lengths (< 1 cm) and average bubble approach velocities (< 160 cm/s) were independently measured by two light sources and detectors placed at a known distance from each other and sensing the passage of each bubble. By choosing a sensitive probe tip length of 2.75-3 mm, the rf probe output provided enough information to determine the bubble length and velocity. The results obtained by the two independent methods show reasonable agreement (+/-10%). PMID:18699371

Abuaf, N; Feierabend, T P; Zimmer, G A; Jones, O C

1979-10-01

289

Radio frequency shielding for a linac-MRI system  

NASA Astrophysics Data System (ADS)

The real-time operation of a linac-MRI system will require proper radio frequency (RF) shielding such that the MRI images can be acquired without extraneous RF noise from the linac. We report on the steps taken to successfully shield the linac from the MRI such that the two devices can operate independently of one another. RF power density levels are reported internally and externally to the RF cage which houses the linac and MRI. The shielding effectiveness of the RF cage has been measured in the frequency range 1-50 MHz and is presented. Lastly MRI images of two phantoms are presented during linac operation. This work illustrates that the accelerating structure of a linac and an MRI can be housed within the same RF cage. The 6 MV linac can be operated to produce radiation with no measurable degradation in image quality due to RF effects.

Lamey, M.; Burke, B.; Blosser, E.; Rathee, S.; De Zanche, N.; Fallone, B. G.

2010-02-01

290

Hermetic aluminum radio frequency interconnection and method for making  

DOEpatents

The present invention provides a light-weight, hermetic coaxial radio-frequency (RF) interconnection having an electrically conductive outer housing made of aluminum or an aluminum alloy, a central electrical conductor made of ferrous or non-ferrous material, and a cylinder of dielectric material comprising a low-melting-temperature, high-thermal-expansion aluminophosphate glass composition for hermetically sealing between the aluminum-alloy outer housing and the ferrous or non-ferrous center conductor. The entire RF interconnection assembly is made permanently hermetic by thermally fusing the center conductor, glass, and housing concurrently by bringing the glass to the melt point by way of exposure to an atmospheric temperature sufficient to melt the glass, less than 540.degree. C., but that does not melt the center conductor or the outer aluminum or aluminum alloy housing. The composition of the glass used is controlled to provide a suitable low dielectric constant so that an appropriate electrical characteristic impedance, for example 50 ohms, can be achieved for an electrical interconnection that performs well at high radio frequencies and also provides an interconnection maintaining a relatively small physical size.

Kilgo, Riley D. (Albuquerque, NM); Kovacic, Larry (Albuquerque, NM); Brow, Richard K. (Rolla, MO)

2000-01-01

291

Statistically Stable Estimates of Variance in Radio-Astronomy Observations as Tools for Radio-Frequency Interference Mitigation  

NASA Astrophysics Data System (ADS)

A selection of statistically stable (robust) algorithms for data variance calculating has been made. Their properties have been analyzed via computer simulation. These algorithms would be useful if adopted in radio-astronomy observations in the presence of strong sporadic radio-frequency interference (RFI). Several observational results have been presented here to demonstrate the effectiveness of these algorithms in RFI mitigation.

Fridman, P. A.

2008-05-01

292

Solar Corona and plasma effects on Radio Frequency waves  

NASA Astrophysics Data System (ADS)

Solar corona (plasma) effects on radio signal waves for three different frequency bands S (2.3 GHz), X (8.4 GHz), and Ka (32 GHz), currently used to track probes in the solar system, have been computed using different models of the total electron content (TEC) along the propagation path between the Earth and Mars. The Earth-Mars-Sun configuration has been obtained from the planetary ephemerides DE421 (using SPICE kernels) for the period from September 2004 to September 2006. This configuration is expressed as a function of the Sun-Earth-Probe (SEP) angles (the probe being in close orbit to Mars). We used the TEC values provided by the different models proposed in the literature in order to estimate the TEC along the propagation path (STEC, for Slant TEC). From these model-dependent STEC estimates, the time delay on the wave propagation as well as the associated frequency shift with a 10 seconds sampling time have been obtained for each of the three frequency bands. For the X-band mostly used in radio science, we have obtained estimates differing by up to several orders of magnitude due to the different STEC values derived from different models of TEC. For example, if the propagation path passes near the Sun such that SEP angle is 1.55° the STEC is ranging from 4.6x1020 electron/m2 to 6.07x1016 electron/m2, which corresponds to a time delay range between 0.87 ?s and 1.15x10-4 ?s, respectively. For SEP angles between 2° and 8°, the range of the different time delay values reduces to 2.8x10-1 ?s and becomes as small as 1.6x10-2 ?s for SEP angles larger than 8° (1x10-2 ?s is about the order of magnitude of the radioscience instrument precision). These results show that the correction of the solar corona effect on radio frequency waves can be reliably done on usual X-band tracking data of spacecraft for SEP angles >12°, but should be use with caution for lower SEP angles, especially lower than 2°.

Nkono, C.; Rosenblatt, P.; Dehant, V. M.

2009-12-01

293

A System for Measurements on Radio Frequency Discharges in the Frequency Range of 20 TO 80 Mhz.  

National Technical Information Service (NTIS)

A system for measuring the basic electrical properties of radio frequency gas discharges is described. The system provides the capability for investigating discharges in air at atmospheric pressure in the frequency range of 20 to 80 MHz. The discharges ar...

E. L. Price

1968-01-01

294

Realizacao Experimental E Estudos Teoricos de Absorvedores de Radio Frequencia (Experimental Development and Theoretical Studies of Radio-Frequency Absorbers).  

National Technical Information Service (NTIS)

A mathematical model based on the equivalence with a sequence of lossy transmission lines has been developed and applied, by numerical calculus, to the study of radio-frequency absorbers of piramidal shape, made of polyurethane foam impregnated with finel...

J. L. L. M. Massa

1991-01-01

295

Extending the ICRF to Higher Radio Frequencies -- Imaging Results  

NASA Astrophysics Data System (ADS)

We present source structure analysis of approximately 230 extragalactic sources observed using the Very Long Baseline Array (VLBA) at 24 GHz and 43 GHz as part of a joint NASA, USNO, NRAO and Bordeaux Observatory program to extend the International Celestial Reference Frame (ICRF) to higher radio frequencies. The long term goals of this program are a) to develop higher frequency reference frames for improved deep space navigation, b) to extend the VLBA calibrator catalog at 24 and 43 GHz, c) to provide the benefit of the ICRF catalog to new applications at these higher frequencies and d) to study source structure variation at 24 and 43 GHz in order to improve the astrometric accuracy. In this paper, we concentrate on the latter goal of evaluating the intrinsic structure of the observed sources. A large fraction of the 230 sources have been observed at multiple epochs allowing us to estimate structural variations over time. We classify the sources in terms of their suitability for use in the new high frequency reference frames based on their spatial compactness and temporal stability.

Fey, A. L.; Boboltz, D. A.; Charlot, P.; Fomalont, E. B.; Lanyi, G. E.; Zhang, L. D.; K-Q VLBI Survey Collaboration

2004-12-01

296

Packet error probabilities in frequency-hopped spread spectrum packet radio networks. Markov frequency hopping patterns considered  

Microsoft Academic Search

We compute the packet error probability induced in a frequency-hopped spread spectrum packet radio network, which utilizes first order Markov frequency hopping patterns. The frequency spectrum is divided into q frequency bins and the packets are divided into M bytes each. Every user in the network sends each of the M bytes of his packet at a frequency bin, which

M. Georgiopoulos; P. Kazakos

1987-01-01

297

Packet error probabilities in frequency hopped spread spectrum packet radio networks-Memoryless frequency hopping patterns considered  

Microsoft Academic Search

In this paper we compute the packet error probability induced in a frequency hopped spread spectrum packet radio network. The frequency spectrum is divided into q frequency bins and the packets are divided into M bytes each. Every user in the network sends each of the M bytes of his packet at a frequency chosen among the q frequencies with

M. Georgiopoulos

1987-01-01

298

Radio frequency electromagnetic field compliance assessment of multi-band and MIMO equipped radio base stations.  

PubMed

In this paper, different methods for practical numerical radio frequency exposure compliance assessments of radio base station products were investigated. Both multi-band base station antennas and antennas designed for multiple input multiple output (MIMO) transmission schemes were considered. For the multi-band case, various standardized assessment methods were evaluated in terms of resulting compliance distance with respect to the reference levels and basic restrictions of the International Commission on Non-Ionizing Radiation Protection. Both single frequency and multiple frequency (cumulative) compliance distances were determined using numerical simulations for a mobile communication base station antenna transmitting in four frequency bands between 800 and 2600?MHz. The assessments were conducted in terms of root-mean-squared electromagnetic fields, whole-body averaged specific absorption rate (SAR) and peak 10?g averaged SAR. In general, assessments based on peak field strengths were found to be less computationally intensive, but lead to larger compliance distances than spatial averaging of electromagnetic fields used in combination with localized SAR assessments. For adult exposure, the results indicated that even shorter compliance distances were obtained by using assessments based on localized and whole-body SAR. Numerical simulations, using base station products employing MIMO transmission schemes, were performed as well and were in agreement with reference measurements. The applicability of various field combination methods for correlated exposure was investigated, and best estimate methods were proposed. Our results showed that field combining methods generally considered as conservative could be used to efficiently assess compliance boundary dimensions of single- and dual-polarized multicolumn base station antennas with only minor increases in compliance distances. PMID:24523232

Thors, Björn; Thielens, Arno; Fridén, Jonas; Colombi, Davide; Törnevik, Christer; Vermeeren, Günter; Martens, Luc; Joseph, Wout

2014-05-01

299

Transverse radio-frequency-excited He-metal-vapor ion lasers  

NASA Astrophysics Data System (ADS)

The transverse radio-frequency discharge, the features of which resemble those of the hollow- cathode discharge plasma, is very efficient and suitable for excitation of the ionic transitions in the He-metal vapor mixtures. This is due to the relatively high number of the high-energy electrons capable of exciting the atoms and ions to the energetically high-lying states. The other advantages of the transverse radio-frequency discharge are: longitudinal homogeneity of the discharge, efficient transforming of the input power into the energy of fast electrons, simplicity of the discharge tube design, absence of the arc formation at higher input powers, and external electrodes enabling it to operate with the substances of high chemical activity. The He-metal vapor ion lasers excited by the transverse radio-frequency discharge also exhibit some negative features: discharge tube overheating due to the high input power and deterioration of the inner walls of the discharge tube by the ion bombardment.

Mizeraczyk, Jerzy

1995-03-01

300

78 FR 43916 - Certain Radio Frequency Identification (RFID) Products and Components Thereof; Commission...  

Federal Register 2010, 2011, 2012, 2013

...INTERNATIONAL TRADE COMMISSION [Investigation No. 337-TA-875] Certain Radio Frequency Identification (RFID) Products and Components Thereof; Commission Determination Not To Review an Initial Determination Terminating...

2013-07-22

301

77 FR 67833 - Certain Radio Frequency Integrated Circuits and Devices Containing Same; Notice of Commission...  

Federal Register 2010, 2011, 2012, 2013

...INTERNATIONAL TRADE COMMISSION [Investigation No. 337-TA-848] Certain Radio Frequency Integrated Circuits and Devices Containing Same; Notice of Commission Determination Not To Review an Initial...

2012-11-14

302

Point-to-point measurement of radio frequency attenuation in South Polar ice  

NASA Astrophysics Data System (ADS)

For ultra high energy (UHE) electromagnetic showers in a dense medium, radio frequency Cherenkov emission is enhanced due to the Askaryan effect. Present and future detectors such as RICE, ANITA, ARIANNA and the Askaryan Radio Array (ARA) exploit this effect to detect UHE neutrinos interacting with Antarctic ice. The radio frequency electromagnetic wave attenuation length (the distance over which signal amplitude diminishes by a factor of 1/e due to absorption or scattering) is of tantamount importance as it determines the size scale and effective volume of these detectors. Previous attenuation measurements rely on reflections off the bedrock of signals from a surface-mounted transmitter. Using RICE in-ice transmitters and IceCube Radio Extension in-ice receivers, we are conducting a point-to-point attenuation measurement in the upper 1500 meters of South Polar ice, the region of interest for planned near-surface detectors such as ARA. We will present the analysis method as well as preliminary results.

Richman, Michael; Hoffman, Kara

2011-04-01

303

Evaluation of a combined laser?radio frequency device (Polaris WR) for the nonablative treatment of facial wrinkles  

Microsoft Academic Search

Nonablative wrinkle reduction or skin tightening is desired by individuals who, ideally, hope to have the skin improvement associated with chemical or laser ablative techniques but without the undesirable recovery process. Electro-optical synergy (ELOS) technology that combines radio frequency (RF) and diode laser energy (900 nm) was used to treat 15 patients in this IRB sanctioned study. Energy settings were

Michael Kulick

2005-01-01

304

Interplanetary type 3 radio bursts that approach the plasma frequency: Ulysses observations  

NASA Technical Reports Server (NTRS)

We study a set of solar type 3 radio bursts where the emission is visible from the high-frequency limit of the radio astronomy receiver of the Ulysses Unified Radio and Plasma wave (URAP) experiment down to low frequencies, sometimes near the plasma frequency, and where Langmuir wave spikes are recorded by the radio and/or plasma receivers. Our results pose questions regarding radio emission by Langmuir waves. When Langmuir waves are observed, why is it only sometimes that radio radiation is emitted at the fundamental? Put another way, why is there often a gap or a cutoff in the radiation at a frequency well above the plasma frequency? In the few cases where the radiation at times of Langmuir wave spikes is at the harmonic, why is there no fundamental?

Hoang, S.; Dulk, G. A.; Leblanc, Y.

1994-01-01

305

Security risks associated with radio frequency identification in medical environments.  

PubMed

Radio frequency identification (RFID) is a form of wireless communication that is used to identify assets and people. RFID has significant benefits to the medical environment. However, serious security threats are present in RFID systems that must be addressed in a medical environment. Of particular interest are threats to patient privacy and safety based on interception of messages, interruption of communication, modification of data, and fabrication of messages and devices. This paper presents an overview of these security threats present in RFID systems in a medical environment and provides guidance on potential solutions to these threats. This paper provides a roadmap for researchers and implementers to address the security issues facing RFID in the medical space. PMID:22048780

Hawrylak, Peter J; Schimke, Nakeisha; Hale, John; Papa, Mauricio

2012-12-01

306

Low-frequency radio emissions in the outer heliosphere  

NASA Technical Reports Server (NTRS)

Progress is reported toward a model for the 2 and 3 kHz radio waves observed by Voyagers 1 and 2 during the 1983-1987 interval at radial distances from the sun of 17 and 13 AU, respectively. The brightness temperature and range of the volume emissivity for the radiation are calculated, and the results are compared with the characteristics of known radiation at multiples of the plasma frequency. The derived brightness temperatures are used to constrain the source of the Langmuir waves required to generate the observed emission and to rule out certain emission mechanisms. Minimum values of 3-30 micro-V/m are derived for the Langmuir wave electric field intensity and are found to be in reasonable agreement with observed values at planetary bow shocks. Path lengths required for the radiation to reach the observed levels are derived and discussed. The relevance of these ideas to possible direct observations of heliospheric boundaries is addressed.

Macek, W. M.; Cairns, I. H.; Kurth, W. S.; Gurnett, D. A.

1991-01-01

307

Radio frequency interference effect on PN code sequence lock detector  

NASA Technical Reports Server (NTRS)

The authors find the probabilities of detection and false alarm of the pseudonoise (PN) sequence code lock detector when strong radio frequency interference (RFI) hits the communications link. Both a linear model and a soft-limiter nonlinear model for a transponder receiver are considered. In addition, both continuous wave (CW) RFI and pulse RFI are analyzed, and a discussion is included of how strong CW RFI can knock out the PN code lock detector in a linear or a soft-limiter transponder. As an example, the Space Station Freedom forward S-band PN system is evaluated. It is shown that a soft-limiter transponder can protect the PN code lock detector against a typical pulse RFI, but it can degrade the PN code lock detector performance more than a linear transponder if CW RFI hits the link.

Kwon, Hyuck M.; Tu, Kwei; Loh, Y. C.

1991-01-01

308

SUPERCONDUCTING RADIO-FREQUENCY MODULES TEST FACILITY OPERATING EXPERIENCE  

SciTech Connect

Fermilab is heavily engaged and making strong technical contributions to the superconducting radio-frequency research and development program (SRF R and D). Four major SRF test areas are being constructed to enable vertical and horizontal cavity testing, as well as cryomodule testing. The existing Fermilab cryogenic infrastructure has been modified to service the SRF R and D needs. The project's first stage has been successfully completed, which allows for distribution of cryogens for a single-cavity cryomodule using the existing Cryogenic Test Facility (CTF) that houses three Tevatron satellite refrigerators. The cooling capacity available for cryomodule testing at Meson Detector Building (MDB) results from the liquefaction capacity of the CTF cryogenic system. The cryogenic system for a single 9-cell cryomodule is currently operational. The paper describes the status, challenges and operational experience of the initial phase of the project.

Soyars, W.; Bossert, R.; Darve, C.; Degraff, B.; Klebaner, A.; Martinez, A.; Pei, L.; Theilacker, J. [Fermi National Accelerator Laboratory Batavia, IL, 60510 (United States)

2008-03-16

309

Radio frequency heating of ceramic windows in fusion applications  

SciTech Connect

Ceramic windows will be used as material barriers for radio frequency plasma heating in fusion reactors. This report examines the theory behind rf heating phenomena. Heating calculations are presented for various window materials, thicknesses, wavelengths, and power densities. The most pertinent material properties are loss tangent, thermal conductivity, dielectric constant, strength, and radiation resistance. Calculations indicate that among candidate materials, beryllium oxide offers the most promise because of its large thermal conductivity and relatively low loss tangent and dielectric constant. On the other hand, beryllia is susceptible to neutron damage, and this may adversely affect its electrical properties. Another promising candidate is sapphire, particularly at lower temperatures where the thermal conductivity is high. Fused silica suffers from low thermal conductivity and large positive temperature coefficient for loss tangent, but it may be useful under some conditions. In summary, calculations of heating can lead to elimination of some candidate materials and selection of others for further study.

Fowler, J.D. Jr.

1981-11-01

310

Understanding Pound-Drever-Hall locking using voltage controlled radio-frequency oscillators: An undergraduate experiment  

NASA Astrophysics Data System (ADS)

We have developed a senior undergraduate experiment that illustrates frequency stabilization techniques using radio-frequency electronics. The primary objective is to frequency stabilize a voltage controlled oscillator to a cavity resonance at 800 MHz using the Pound-Drever-Hall method. This technique is commonly applied to stabilize lasers at optical frequencies. By using only radio-frequency equipment, it is possible to systematically study aspects of the technique more thoroughly, inexpensively, and free from eye hazards. Students also learn about modular radio-frequency electronics and basic feedback control loops. By varying the temperature of the resonator, students can determine the thermal expansion coefficients of copper, aluminum, and super invar.

Liekhus-Schmaltz, C. E.; Martin, J. D. D.

2012-03-01

311

The Radio Frequency Health Node Wireless Sensor System  

NASA Technical Reports Server (NTRS)

The Radio Frequency Health Node (RFHN) wireless sensor system differs from other wireless sensor systems in ways originally intended to enhance utility as an instrumentation system for a spacecraft. The RFHN can also be adapted to use in terrestrial applications in which there are requirements for operational flexibility and integrability into higher-level instrumentation and data acquisition systems. As shown in the figure, the heart of the system is the RFHN, which is a unit that passes commands and data between (1) one or more commercially available wireless sensor units (optionally, also including wired sensor units) and (2) command and data interfaces with a local control computer that may be part of the spacecraft or other engineering system in which the wireless sensor system is installed. In turn, the local control computer can be in radio or wire communication with a remote control computer that may be part of a higher-level system. The remote control computer, acting via the local control computer and the RFHN, cannot only monitor readout data from the sensor units but can also remotely configure (program or reprogram) the RFHN and the sensor units during operation. In a spacecraft application, the RFHN and the sensor units can also be configured more nearly directly, prior to launch, via a serial interface that includes an umbilical cable between the spacecraft and ground support equipment. In either case, the RFHN wireless sensor system has the flexibility to be configured, as required, with different numbers and types of sensors for different applications. The RFHN can be used to effect realtime transfer of data from, and commands to, the wireless sensor units. It can also store data for later retrieval by an external computer. The RFHN communicates with the wireless sensor units via a radio transceiver module. The modular design of the RFHN makes it possible to add radio transceiver modules as needed to accommodate additional sets of wireless sensor units. The RFHN includes a core module that performs generic computer functions, including management of power and input, output, processing, and storage of data. In a typical application, the processing capabilities in the RFHN are utilized to perform preprocessing, trending, and fusion of sensor data. The core module also serves as the unit through which the remote control computer configures the sensor units and the rest of the RFHN.

Valencia, J. Emilio; Stanley, Priscilla C.; Mackey, Paul J.

2009-01-01

312

Design, development, and acceleration trials of radio-frequency quadrupole.  

PubMed

A deuteron radio frequency quadrupole (RFQ) accelerator has been designed, fabricated, and tested at BARC, which will be used for neutron generation. The RFQ operates at a frequency of 350 MHz and needs an inter-vane voltage of 44 kV to accelerate the deuteron beam to 400 keV within a length of 1.03 m. The error analysis shows that the offset of two opposite vanes in the same direction by 100 ?m leads to a change in resonant frequency by 1.3 MHz and a significant change of fields in the quadrants (?±40% with respect to average field). From the 3D analysis, we have observed that the unwanted dipole mode frequencies are very near to the quadrupole mode frequency which will make structure sensitive to the perturbations. In order to move the dipole modes away from the quadrupole modes, we have used the dipole stabilizer rods. The 5 wire transmission line theory was used to study the perturbative analysis of the RFQ and based on this a computer program has been written to tune the cavity to get required field distribution. Based on these studies, a 1.03 m long RFQ made of OFE copper has been fabricated and tested. Even though the RFQ was designed for deuteron (D(+)) beam, we tested it by accelerating both the proton (H(+)) and D(+) beams. The RFQ was operated in pulsed mode and accelerated both H(+) and D(+) beams to designed values of 200 and 400 keV, respectively. The measured parameters are in good agreement with the designed values validating our simulations and fabrication processes. In this paper, simulations, RF measurements, and beam commissioning results are presented. PMID:24784599

Rao, S V L S; Jain, Piyush; Pande, Rajni; Roy, Shweta; Mathew, Jose V; Kumar, Rajesh; Pande, Manjiri; Krishnagopal, S; Gupta, S K; Singh, P

2014-04-01

313

Frequency allocations for passive use of the radio spectrum to make scientific studies  

NASA Technical Reports Server (NTRS)

The paper examines the legal implications of frequency allocations for passive use of the radio spectrum, which refer to receive-only radio services. Such receive-only services refer to the reception of radio signals generated by nonhuman agencies as in radio astronomy or in the search for extraterrestrial intelligence. Juridical interpretations of the public interest and of necessity are applied to these passive services.

Stull, M. A.; Alexander, G.

1976-01-01

314

A new Main Injector radio frequency system for 2.3 MW Project X operations  

SciTech Connect

For Project X Fermilab Main Injector will be required to provide up to 2.3 MW to a neutrino production target at energies between 60 and 120 GeV. To accomplish the above power levels 3 times the current beam intensity will need to be accelerated. In addition the injection energy of Main Injector will need to be as low as 6 GeV. The current 30 year old Main Injector radio frequency system will not be able to provide the required power and a new system will be required. The specifications of the new system will be described.

Dey, J.; Kourbanis, I.; /Fermilab

2011-03-01

315

Improvement of isentropic efficiency of a magnetohydrodynamic power generator by radio-frequency preionization  

SciTech Connect

We describe the effect of a radio-frequency (rf) power application on the performance of a magnetohydrodynamic (MHD) electrical power generator, as determined through shock-tunnel-based experiments and quasi-three-dimensional numerical simulations. The temporal plasma-fluid behavior, the one-dimensional plasma-fluid structure, the enthalpy-entropy diagram, the quality of the energy conversion efficiency, and the energy flow in the power-generating system are investigated. Preionization assistance by a small amount of rf power drastically changes the entire MHD power-generating system; the MHD extraction length is considerably extended and the isentropic efficiency is significantly improved.

Murakami, Tomoyuki; Okuno, Yoshihiro [Department of Energy Sciences, Tokyo Institute of Technology, 4259-G3-38 Nagatsuta, Midori-ku, Yokohama 226-8502 (Japan)

2009-01-15

316

A Semianalytical Ion Current Model for Radio Frequency Driven Collisionless Sheaths  

NASA Technical Reports Server (NTRS)

We propose a semianalytical ion dynamics model for a collisionless radio frequency biased sheath. The model uses bulk plasma conditions and electrode boundary condition to predict ion impact energy distribution and electrical properties of the sheath. The proposed model accounts for ion inertia and ion current modulation at bias frequencies that are of the same order of magnitude as the ion plasma frequency. A relaxation equation for ion current oscillations is derived which is coupled with a damped potential equation in order to model ion inertia effects. We find that inclusion of ion current modulation in the sheath model shows marked improvements in the predictions of sheath electrical properties and ion energy distribution function.

Bose, Deepak; Govindan, T. R.; Meyyappan, M.; Arnold, Jim (Technical Monitor)

2001-01-01

317

Radio-Frequency Tank Eigenmode Sensor for Propellant Quantity Gauging  

NASA Technical Reports Server (NTRS)

Although there are several methods for determining liquid level in a tank, there are no proven methods to quickly gauge the amount of propellant in a tank while it is in low gravity or under low-settling thrust conditions where propellant sloshing is an issue. Having the ability to quickly and accurately gauge propellant tanks in low-gravity is an enabling technology that would allow a spacecraft crew or mission control to always know the amount of propellant onboard, thus increasing the chances for a successful mission. The Radio Frequency Mass Gauge (RFMG) technique measures the electromagnetic eigenmodes, or natural resonant frequencies, of a tank containing a dielectric fluid. The essential hardware components consist of an RF network analyzer that measures the reflected power from an antenna probe mounted internal to the tank. At a resonant frequency, there is a drop in the reflected power, and these inverted peaks in the reflected power spectrum are identified as the tank eigenmode frequencies using a peak-detection software algorithm. This information is passed to a pattern-matching algorithm, which compares the measured eigenmode frequencies with a database of simulated eigenmode frequencies at various fill levels. A best match between the simulated and measured frequency values occurs at some fill level, which is then reported as the gauged fill level. The database of simulated eigenmode frequencies is created by using RF simulation software to calculate the tank eigenmodes at various fill levels. The input to the simulations consists of a fairly high-fidelity tank model with proper dimensions and including internal tank hardware, the dielectric properties of the fluid, and a defined liquid/vapor interface. Because of small discrepancies between the model and actual hardware, the measured empty tank spectra and simulations are used to create a set of correction factors for each mode (typically in the range of 0.999 1.001), which effectively accounts for the small discrepancies. These correction factors are multiplied to the modes at all fill levels. By comparing several measured modes with the simulations, it is possible to accurately gauge the amount of propellant in the tank. An advantage of the RFMG approach of applying computer simulations and a pattern-matching algorithm is that the Although there are several methods for determining liquid level in a tank, there are no proven methods to quickly gauge the amount of propellant in a tank while it is in low gravity or under low-settling thrust conditions where propellant sloshing is an issue. Having the ability to quickly and accurately gauge propellant tanks in low-gravity is an enabling technology that would allow a spacecraft crew or mission control to always know the amount of propellant onboard, thus increasing the chances for a successful mission. The Radio Frequency Mass Gauge (RFMG) technique measures the electromagnetic eigenmodes, or natural resonant frequencies, of a tank containing a dielectric fluid. The essential hardware components consist of an RF network analyzer that measures the reflected power from an antenna probe mounted internal to the tank. At a resonant frequency, there is a drop in the reflected power, and these inverted peaks in the reflected power spectrum are identified as the tank eigenmode frequencies using a peak-detection software algorithm. This information is passed to a pattern-matching algorithm, which compares the measured eigenmode frequencies with a database of simulated eigenmode frequencies at various fill levels. A best match between the simulated and measured frequency values occurs at some fill level, which is then reported as the gauged fill level. The database of simulated eigenmode frequencies is created by using RF simulation software to calculate the tank eigenmodes at various fill levels. The input to the simulations consists of a fairly high-fidelity tank model with proper dimensions and including internal tank harare, the dielectric properties of the fluid, and a defined liquid/vapor interface. Because of sma

Zimmerli, Gregory A.; Buchanan, David A.; Follo, Jeffrey C.; Vaden, Karl R.; Wagner, James D.; Asipauskas, Marius; Herlacher, Michael D.

2010-01-01

318

Tracking electric field exposure levels through radio frequency dosimetry  

SciTech Connect

The radio-frequency (rf) dosimeter developed by the Oak Ridge National Laboratory is a portable, pocket-sized cumulative-dose recording device designed to detect and record the strengths and durations of electric fields present in the work areas of naval vessels. The device measures an integrated dose and records the electric fields that exceed the permissible levels set by the American National Standards Institute. Features of the rf dosimeter include a frequency range of 30 MHz to 10 GHz and a three-dimensional sensor. Data obtained with the rf dosimeter will be used to determine the ambient field-strength profile for shipboard personnel over an extended time. Readings are acquired and averaged over a 6-min period corresponding to the rise time of the core body temperature. These values are stored for up to 6 months, after which the data are transferred to a computer via the dosimeter's serial port. The rf dosimeter should increase knowledge of the levels of electric fields to which individuals are exposed. 5 refs., 4 figs.

Ewing, P.D.; Moore, M.R.; Rochelle, R.W.; Thomas, R.S.; Hess, R.A.; Hoffheins, B.S.

1991-01-01

319

Extremely Low Frequency (ELF) Ionospheric Radio Propagation Studies Using Natural Sources  

Microsoft Academic Search

The purpose of this paper is to describe methods of studying the propagation of radio waves over the earth's surface in the extremely low frequency (ELF) frequency band (3 Hz-3 kHz) using natural (as distinct from \\

D. LLANWYN JONES

1974-01-01

320

A multi-frequency study of the SZE in giant radio galaxies  

NASA Astrophysics Data System (ADS)

Context. Radio galaxy (RG) lobes contain relativistic electrons embedded in a tangled magnetic field that produce, in addition to low-frequency synchrotron radio emission, inverse-Compton scattering (ICS) of the cosmic microwave background (CMB) photons. This produces a relativistic, non-thermal Sunyaev-Zel'dovich effect (SZE). Aims: We study the spectral and spatial properties of the non-thermal SZE in a sample of radio galaxies and make predictions for their detectability in both the negative and the positive part of the SZE, with space experiments like Planck, OLIMPO, and Herschel-SPIRE. These cover a wide range of frequencies, from radio to sub-mm. Methods: We model the SZE in a general formalism that is equivalent to the relativistic covariant one and describe the electron population contained in the lobes of the radio galaxies with parameters derived from their radio observations, namely, flux, spectral index, and spatial extension. We further constrain the electron spectrum and the magnetic field of the RG lobes using X-ray, gamma-ray, and microwave archival observations. Results: We determine the main spectral features of the SZE in RG lobes, namely, the minimum, the crossover, and the maximum of the SZE. We show that these typical spectral features fall in the frequency ranges probed by the available space experiments. We provide the most reliable predictions for the amplitude and spectral shape of the SZE in a sample of selected RGs with extended lobes. In three of these objects, we also derive an estimate of the magnetic field in the lobe at the ~?G level by combining radio (synchrotron) observations and X-ray (ICS) observations. These data, together with the WMAP upper limits, set constraints on the minimum momentum of the electrons residing in the RG lobes and allow realistic predictions for the visibility of their SZE to be derived with Planck, OLIMPO, and Herschel-SPIRE. Conclusions: We show that the SZE from several RG lobes can be observed with mm and sub-mm experiments like Planck, OLIMPO, and Herschel-SPIRE, as well as with ground-based telescopes that have ? mJy sensitivity and sub-arcmin spatial resolution. These measurements will be crucial to disentangle the relativistic electron distribution from that of the magnetic field in RG lobes and to constrain the properties of their ICS emission, which is also visible at very high X-ray and gamma-ray energies.

Colafrancesco, S.; Marchegiani, P.; de Bernardis, P.; Masi, S.

2013-02-01

321

High-energy neutrinos from radio galaxies  

NASA Astrophysics Data System (ADS)

The IceCube experiment has recently reported the first observation of high-energy cosmic neutrinos. Their origin is still unknown. In this paper, we investigate the possibility that they originate in active galaxies. We show that hadronic interactions (pp) in the generally less powerful, more frequent, FR-I radio galaxies are one of the candidate source classes being able to accommodate the observation while the more powerful, less frequent, class of FR-II radio galaxies has too low of a column depths to explain the signal.

Becker Tjus, J.; Eichmann, B.; Halzen, F.; Kheirandish, A.; Saba, S. M.

2014-06-01

322

1.8 GHz Radio Frequency signal radiation effects on human health  

Microsoft Academic Search

Radio Frequency (RF) radiation effects are strictly relying on few critical factors, ie frequency, period of exposure and distance. Certain frequency ranges are absorbed in body tissue more than the other frequency range. The second factor is the duration of exposure. Where, over the period of time, the body will absorb more RF frequencies which hence will worsened the human

Azizah Ahmad; Rusnani Ariffin; Norhayati Mohd Noor; Meor Adzmey Sagiruddin

2011-01-01

323

Exploring radio frequency identification technology and its impact on business systems  

Microsoft Academic Search

Purpose – To provide practitioners of management a sense of the importance of strategically leveraging the current and historic development of radio frequency identification (RFID) in order to find inexpensive applications of radio frequency-based (RF) technologies in many areas. Design\\/methodology\\/approach – A review of the applied literature on RFID, as well as from practical experience, resulted in a basic model

Alan D. Smith

2005-01-01

324

Technique for Predicting the Radio Frequency Field Strength Inside an Enclosure  

NASA Technical Reports Server (NTRS)

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.

Hallett, Michael P.; Reddell, Jerry P.

1997-01-01

325

Nanoionics-Based Switches for Radio-Frequency Applications  

NASA Technical Reports Server (NTRS)

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.

Nessel, James; Lee, Richard

2010-01-01

326

Frequency variations of solar radio zebras and their power-law spectra  

NASA Astrophysics Data System (ADS)

Context. During solar flares several types of radio bursts are observed. The fine striped structures of the type IV solar radio bursts are called zebras. Analyzing them provides important information about the plasma parameters of their radio sources. We present a new analysis of zebras. Aims: Power spectra of the frequency variations of zebras are computed to estimate the spectra of the plasma density variations in radio zebra sources. Methods: Frequency variations of zebra lines and the high-frequency boundary of the whole radio burst were determined with and without the frequency fitting. The computed time dependencies of these variations were analyzed with the Fourier method. Results: First, we computed the variation spectrum of the high-frequency boundary of the whole radio burst, which is composed of several zebra patterns. This power spectrum has a power-law form with a power-law index -1.65. Then, we selected three well-defined zebra-lines in three different zebra patterns and computed the spectra of their frequency variations. The power-law indices in these cases are found to be in the interval between -1.61 and -1.75. Finally, assuming that the zebra-line frequency is generated on the upper-hybrid frequency and that the plasma frequency ?pe is much higher than the electron-cyclotron frequency ?ce, the Fourier power spectra are interpreted to be those of the electron plasma density in zebra radio sources.

Karlický, M.

2014-01-01

327

The Low-frequency Radio Catalog of Flat-spectrum Sources  

NASA Astrophysics Data System (ADS)

A well known property of the ?-ray sources detected by Cos-B in the 1970s, by the Compton Gamma-Ray Observatory in the 1990s, and recently by the Fermi observations is the presence of radio counterparts, particularly for those associated with extragalactic objects. This observational evidence is the basis of the radio-?-ray connection established for the class of active galactic nuclei known as blazars. In particular, the main spectral property of the radio counterparts associated with ?-ray blazars is that they show a flat spectrum in the GHz frequency range. Our recent analysis dedicated to search blazar-like candidates as potential counterparts for the unidentified ?-ray sources allowed us to extend the radio-?-ray connection in the MHz regime. We also showed that blazars below 1 GHz maintain flat radio spectra. Thus, on the basis of these new results, we assembled a low-frequency radio catalog of flat-spectrum sources built by combining the radio observations of the Westerbork Northern Sky Survey and of the Westerbork in the southern hemisphere catalog with those of the NRAO Very Large Array Sky survey (NVSS). This could be used in the future to search for new, unknown blazar-like counterparts of ?-ray sources. First, we found NVSS counterparts of Westerbork Synthesis Radio Telescope radio sources, and then we selected flat-spectrum radio sources according to a new spectral criterion, specifically defined for radio observations performed below 1 GHz. We also described the main properties of the catalog listing 28,358 radio sources and their logN-logS distributions. Finally, a comparison with the Green Bank 6 cm radio source catalog was performed to investigate the spectral shape of the low-frequency flat-spectrum radio sources at higher frequencies.

Massaro, F.; Giroletti, M.; D'Abrusco, R.; Masetti, N.; Paggi, A.; Cowperthwaite, Philip S.; Tosti, G.; Funk, S.

2014-07-01

328

Reduction of In-Band Intermodulation Distortion Products in Radio Frequency Power Amplifiers with Digital Predistortion Linearization  

Microsoft Academic Search

Digital predistortion linearization has been successfully utilized for the reduction of intermodulation distortion (IMD) products of radio frequency (RF) power amplifiers (PA). In a typical amplifier, the signal energy is located at the center of the amplifier passband, and the IMD products extend equally on either side. However, less attention has been paid to a completely different situation in which

M. Franco; A. Guida; J. Katz; P. Herczfeld

2006-01-01

329

Diffusion tensor in electron transport in gases in a radio-frequency field  

SciTech Connect

Electron transport theory in gases in a radio-frequency field is developed in the hydrodynamic regime from the density gradient expansion method of the Boltzmann equation. Swarm parameters for the radio-frequency (rf) field with periodic time modulation are derived as functions of both reduced effective field strength and reduced angular frequency from the time dependent velocity distribution function. The rf electron transport in phase space is analyzed from the series of governing equations by a direct numerical procedure (DNP). Electron velocity distribution function and corresponding swarm parameters obtained from DNP agree with those of the Monte Carlo simulation in the frequency range 10{endash}200 MHz at 10 Td for Reid`s inelastic ramp model gas. The temporal modulation of the ensemble average of energy and the diffusion tensor are discussed. The appearance of the anomalous time behavior of the longitudinal diffusion coefficient is discussed in particular detail, and we provide an explanation of the observed effect. {copyright} {ital 1997} {ital The American Physical Society}

Maeda, K.; Makabe, T.; Nakano, N. [Department of Electronics, Keio University, 3-14-1 Hiyoshi, Yokohama 223 (Japan)] [Department of Electronics, Keio University, 3-14-1 Hiyoshi, Yokohama 223 (Japan); Bzenic, S.; Petrovic, Z.L. [Institute of Physics, University of Belgrade, P.O. Box 57, 11001, Belgrade (Yugoslavia)] [Institute of Physics, University of Belgrade, P.O. Box 57, 11001, Belgrade (Yugoslavia)

1997-05-01

330

The Stabiliy of Radio-Frequency Plasma Treated Polydimethylsiloxane Surface  

PubMed Central

Polydimethylsiloxane (PDMS) is a widely used material for manufacturing lab-on-chip devices. However, the hydrophobic nature of PDMS is a disadvantage in micro-fluidic systems. To transform the hydrophobic PDMS surface to hydrophilic it has been treated with radio frequency (RF) air plasma at 150, 300 and 500 mtorr pressure for up to 30 minutes. Following the surface treatment, the PDMS specimens were stored in air, deionized water or 0.14 M NaCl solution at 4 °C, 20 °C, and 70 °C. The change in the hydrophilicity (wettability) of the PDMS surfaces has been followed by contact angle measurements and Fourier Transform Infrared Attenuated Total Reflectance (FTIR-ATR) Spectroscopy as a function of time. As an effect of the RF plasma treatment the contact angles measured on PDMS surfaces dropped from 113±4 degrees to 9±3 degrees. The chamber pressure and the treatment time had no or negligible effect on the results. However, the PDMS surface gradually lost its hydrophilic properties in time. The rate of this process is influenced by the difference in the dielectric constants of the PDMS and its ambient environment. It has been the smallest at low temperatures in deionized water and largest at high temperatures in air. Apparently, the OH groups generated on the PDMS surface during the plasma treatment tend towards a more hydrophilic/less hydrophobic environment during the relaxation processes. The correlation between FTIR–ATR spectral information and contact angle data supports this interpretation.

Chen, I-Jane

2008-01-01

331

Radio-Frequency Current Drive in DIII-D  

SciTech Connect

Two methods of radio-frequency (rf) current drive that are well suited to controlling and sustaining the current profile in burning plasma experiments have been studied in the DIII-D tokamak. Fast-wave current drive (FWCD) gave centrally peaked current densities that increased linearly with central electron temperature. While high harmonic absorption of the fast waves on energetic beam ions could reduce the available power for current drive, FWCD figures of merit as high as {gamma}{sub FW} = 0.5 x 10{sup 19} A/m{sup 2}.W were still achieved. Electron cyclotron current drive (ECCD) was shown to be localized to the region of power deposition, with a current drive efficiency that decreased as the magnetic well depth increased. The detrimental effect of the magnetic well could be mitigated by raising the electron beta. ECCD figures of merit as high as {gamma}{sub EC} = 0.5 x 10{sup 19} A/m{sup 2}.W were measured for central deposition. The experimental FWCD and ECCD were both extensively tested against theoretical models and were found to be in excellent agreement. Validation of these predictive models of rf current drive aids in scenario development for next-step tokamaks.

Petty, C.C. [General Atomics (United States)

2005-10-15

332

Three-dimensional effects for radio frequency antenna modeling  

SciTech Connect

Electromagnetic field calculations for radio frequency (rf) antennas in two dimensions (2-D) neglect finite antenna length effects as well as the feeders leading to the main current strap. The 2-D calculations predict that the return currents in the sidewalls of the antenna structure depend strongly on the plasma parameters, but this prediction is suspect because of experimental evidence. To study the validity of the 2-D approximation, the Multiple Antenna Implementation System (MAntIS) has been used to perform three-dimensional (3-D) modeling of the power spectrum, plasma loading, and inductance for a relevant loop antenna design. Effects on antenna performance caused by feeders to the main current strap and conducting sidewalls are considered. The modeling shows that the feeders affect the launched power spectrum in an indirect way by forcing the driven rf current to return in the antenna structure rather than the plasma, as in the 2-D model. It has also been found that poloidal dependencies in the plasma impedance matrix can reduce the loading predicted from that predicted in the 2-D model. For some plasma parameters, the combined 3-D effects can lead to a reduction in the predicted loading by as much as a factor of 2 from that given by the 2-D model, even with end-effect corrections for the 2-D model.

Carter, M.D.; Batchelor, D.B.; Stallings, D.C. (Oak Ridge National Laboratory, Oak Ridge, Tennessee 37821-8071 (United States))

1994-10-15

333

Manufacture of Radio Frequency Micromachined Switches with Annealing  

PubMed Central

The fabrication and characterization of a radio frequency (RF) micromachined switch with annealing were presented. The structure of the RF switch consists of a membrane, coplanar waveguide (CPW) lines, and eight springs. The RF switch is manufactured using the complementary metal oxide semiconductor (CMOS) process. The switch requires a post-process to release the membrane and springs. The post-process uses a wet etching to remove the sacrificial silicon dioxide layer, and to obtain the suspended structures of the switch. In order to improve the residual stress of the switch, an annealing process is applied to the switch, and the membrane obtains an excellent flatness. The finite element method (FEM) software CoventorWare is utilized to simulate the stress and displacement of the RF switch. Experimental results show that the RF switch has an insertion loss of 0.9 dB at 35 GHz and an isolation of 21 dB at 39 GHz. The actuation voltage of the switch is 14 V.

Lin, Cheng-Yang; Dai, Ching-Liang

2014-01-01

334

Method of making radio frequency ion source antenna  

DOEpatents

In the method, the radio frequency (RF) antenna is made by providing a clean coil made of copper tubing or other metal conductor, which is coated with a tacky organic binder, and then with a powdered glass frit, as by sprinkling the frit uniformly over the binder. The coil is then heated internally in an inert gas atmosphere, preferably by passing an electrical heating current along the coil. Initially, the coil is internally heated to about 200.degree. C. to boil off the water from the binder, and then to about 750.degree. C.-850.degree. C. to melt the glass frit, while also burning off the organic binder. The melted frit forms a molten glass coating on the metal coil, which is then cooled to solidify the glass, so that the metal coil is covered with a thin continuous homogeneous impervious glass coating of substantially uniform thickness. The glass coating affords complete electrical insulation and complete dielectric protection for the metal coil of the RF antenna, to withstand voltage breakdown and to prevent sputtering, while also doubling the plasma generating efficiency of the RF antenna, when energized with RF power in the vacuum chamber of an ion source for a particle accelerator or the like. The glass frit preferably contains apprxoimately 45% lead oxide.

Ehlers, Kenneth W. (Alamo, CA); Leung, Ka-Ngo (Hercules, CA)

1988-01-01

335

Radio frequency operation of a quantum point contact charge detector  

NASA Astrophysics Data System (ADS)

Quantum point contact (QPC) charge detectors are sensitive electrometers, and their ease of fabrication and integration into semiconductor-based qubit systems makes them an attractive candidate as a readout device for spin or charge based qubits in quantum dots. Nevertheless, QPC performance to date has been limited by relatively low operational speeds and 1/f noise. Here we report the operation of a QPC charge sensor realized in an GaAs/AlGaAs two dimensional electron gas at radio- frequencies (RF-QPC), in a mode analogous to rf operation of the single electron transistor [1]. For a typical QPC detector coupled to a quantum dot (QD), a charge oscillation of one electron in the QD corresponds to a change in the QPC conductance of 1-3 percent. We simulate these operating conditions by applying a small ac voltage to the QPC gate to cause a similar change in the zero bias QPC conductance. When operated this way the signal to noise ratio of the RF-QPC is about 30dB, which corresponds to a charge sensitivity of about 7x10-4e/?Hz referred to the dot charge. The operational characteristics of the RF-QPC at 4.2K also will be discussed. [1] R. J. Schoelkopf et al., Science 280, 1238 1242 (1998).

Thalakulam, Madhu; Rimberg, A. J.; Pfeiffer, L. N.; West, K. W.

2007-03-01

336

Radio Frequency Identification (RFID) technology and patient safety  

PubMed Central

Background: Radio frequency identification (RFID) systems have been successfully applied in areas of manufacturing, supply chain, agriculture, transportation, healthcare, and services to name a few. However, the different advantages and disadvantages expressed in various studies of the challenges facing the technology of the use of the RFID technology have been met with skepticism by managers of healthcare organizations. The aim of this study was to express and display the role of RFID technology in improving patient safety and increasing the impact of it in healthcare. Materials and Methods: This study was non-systematical review, which the literature search was conducted with the help of libraries, books, conference proceedings, PubMed databases and also search engines available at Google, Google scholar in which published between 2004 and 2013 during Febuary 2013. We employed the following keywords and their combinations; RFID, healthcare, patient safety, medical errors, and medication errors in the searching areas of title, keywords, abstract, and full text. Results: The preliminary search resulted in 68 articles. After a careful analysis of the content of each paper, a total of 33 papers was selected based on their relevancy. Conclusion: We should integrate RFID with hospital information systems (HIS) and electronic health records (EHRs) and support it by clinical decision support systems (CDSS), it facilitates processes and reduce medical, medication and diagnosis errors.

Ajami, Sima; Rajabzadeh, Ahmad

2013-01-01

337

Radio frequency heating of beef rolls from biceps femoris muscle.  

PubMed

Chemical, physical and sensory aspects of quality were compared on encased rolls (1kg) prepared from single muscle beef (biceps femoris) cooked in a steam oven (80°C) or by radio frequency (RF) heating (500W, 27.12MHz) under recirculating water at 80°C. The RF protocol reduced cooking times to 23 and 31% of steam cooking times, respectively, in non-injected meat (PG1) and in rolls prepared with curing brines possessing similar dielectric properties (PG2-4). Compared to steam heating, cooking yields were significantly higher (P<0.05) and instrumental texture measurements related to toughness significantly lower (P<0.05) for RF cooked PG1 rolls and for meat injected with brines containing water binding dielectrically inactive additives (PG4) but not for brined rolls lacking the latter ingredients (PG2 and PG3). Participants in a 50 member untrained sensory panel were unable to detect texture differences which had been indicated by instrumental analysis for PG1 and PG4. PMID:22061730

Tang, Xueyan; Lyng, James G; Cronin, Denis A; Durand, Caroline

2006-03-01

338

Operating a radio-frequency plasma source on water vapor  

SciTech Connect

A magnetically enhanced radio-frequency (rf) plasma source operating on water vapor has an extensive list of potential applications. In this work, the use of a rf plasma source to dissociate water vapor for hydrogen production is investigated. This paper describes a rf plasma source operated on water vapor and characterizes its plasma properties using a Langmuir probe, a residual gas analyzer, and a spectrometer. The plasma source operated first on argon and then on water vapor at operating pressures just over 300 mtorr. Argon and water vapor plasma number densities differ significantly. In the electropositive argon plasma, quasineutrality requires n{sub i}{approx_equal}n{sub e}, where n{sub i} is the positive ion density. But in the electronegative water plasma, quasineutrality requires n{sub i+}=n{sub i-}+n{sub e}. The positive ion density and electron density of the water vapor plasma are approximately one and two orders of magnitude lower, respectively, than those of argon plasma. These results suggest that attachment and dissociative attachment are present in electronegative water vapor plasma. The electron temperature for this water vapor plasma source is between 1.5 and 4 eV. Without an applied axial magnetic field, hydrogen production increases linearly with rf power. With an axial magnetic field, hydrogen production jumps to a maximum value at 500 W and then saturates with rf power. The presence of the applied axial magnetic field is therefore shown to enhance hydrogen production.

Nguyen, Sonca V. T.; Gallimore, Alec D. [Plasmadynamics and Electric Propulsion Laboratory, University of Michigan, Ann Arbor, Michigan 48108 (United States); Foster, John E. [Plasma Science and Technology Laboratory, University of Michigan, Ann Arbor, Michigan 48108 (United States)

2009-08-15

339

Radio frequency coil technology for small-animal MRI.  

PubMed

A review of the theory, technology, and use of radio frequency (RF) coils for small-animal MRI is presented. It includes a brief overview of MR signal-to-noise (S/N) analysis and discussions of the various coils commonly used in small-animal MR: surface coils, linear volume coils, birdcages, and their derivatives. The scope is limited to mid-range coils, i.e. coils where the product (fd) of the frequency f and the coil diameter d is in the range 2-30 MHz-m. Common applications include mouse brain and body coils from 125 to 750 MHz, rat body coils up to 500 MHz, and small surface coils at all fields. In this regime, all the sources of loss (coil, capacitor, sample, shield, and transmission lines) are important. All such losses may be accurately captured in some modern full-wave 3D electromagnetics software, and new simulation results are presented for a selection of surface coils using Microwave Studio 2006 by Computer Simulation Technology, showing the dramatic importance of the "lift-off effect". Standard linear circuit simulators have been shown to be useful in optimization of complex coil tuning and matching circuits. There appears to be considerable potential for trading S/N for speed using phased arrays, especially for a larger field of view. Circuit simulators are shown to be useful for optimal mismatching of ultra-low-noise preamps based on the enhancement-mode pseudomorphic high-electron-mobility transistor for optimal coil decoupling in phased arrays. Cryogenically cooled RF coils are shown to offer considerable opportunity for future gains in S/N in smaller samples. PMID:17451180

Doty, F David; Entzminger, George; Kulkarni, Jatin; Pamarthy, Kranti; Staab, John P

2007-05-01

340

Radio Frequency (RF) Attenuation Measurements of the Space Shuttle Vehicle  

NASA Technical Reports Server (NTRS)

Following the loss of Columbia, the Columbia Accident Investigation Board (CAIB) provided recommendations to be addressed prior to Return To Flight (RTF). As a part of CAIB Recommendation 3.4.1 - Ground Based Imagery, new C-band and X-band radars were added to the array of ground-based radars and cameras already in-situ at Kennedy Space Center. Because of higher power density considerations and new operating frequencies, the team of Subject Matter Experts (SMEs) assembled to investigate the technical details of introducing the new radars recommended a series of radio frequency (RF) attenuation tests be performed on the Space Shuttle vehicle to establish the attenuation of the vehicle outer mold line structure with respect to its external RF environment. Because of time and complex logistical constraints, it was decided to split the test into two separate efforts. The first of these would be accomplished with the assistance of the Air Force Research Laboratory (AFRL), performing RF attenuation measurements on the aft section of OV-103 (Discovery) while in-situ in Orbiter Processing Facility (OPF) 3, located at Kennedy Space Center. The second would be accomplished with the assistance of the National Institute of Standards and Technology (NIST) and the electromagnetic interference (EMI) laboratory out of the Naval Air Warfare Center, Patuxent River, Maryland (PAX River), performing RF attenuation measurements on OV-105 (Endeavour) in-situ inside the Space Shuttle Landing Facility (SLF) hangar, also located at Kennedy Space Center. This paper provides a summary description of these efforts and their results.

Scully, R. C.; Kent, B. M.; Kempf, D. R.; Johnk, R. T.

2006-01-01

341

The driving frequency effects on the atmospheric pressure corona jet plasmas from low frequency to radio frequency  

SciTech Connect

Lately, the atmospheric pressure jet type corona plasma, which has been typically driven by dc to low frequency (LF: several tens of kHz), is often generated by using radio frequency of 13.56 MHz. Yet, the relationship between the plasma and its driving frequency has seldom been investigated. Hence, in this study, dependence of the atmospheric pressure corona plasma characteristics on the driving frequency was explored experimentally from LF to rf (5 kHz-13.56 MHz). The plasmas generated by the driving frequency under 2 MHz were cylindrical shape of several tens of millimeters long while the 13.56 MHz plasma is spherical and a few millimeters long. As the driving frequency was increased, the plasma length became shortened. At the lower driving frequencies (below 2 MHz), the plasmas existed as positive streamer and negative glow for each half period of the applied voltage, but the discharge was more continuous in time for the 13.56 MHz plasma. It was inferred from the measured I-V curves that the higher driving frequency induced higher discharge currents, and the gas temperature was increased as the driving frequency was increased.

Kim, Dan Bee [Division of Physical Metrology, Korea Research Institute of Standards and Science, 209 Gajeongno, Yuseong-gu, Daejeon 305-340 (Korea, Republic of); Jung, H.; Gweon, B.; Rhee, J. K.; Choe, W. [Department of Physics, Korea Advanced Institute of Science and Technology, 335 Gwahangno, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Moon, S. Y. [LG Electronics Advanced Research Institute, 16 Woomyeon-Dong, Seocho-Gu, Seoul 137-724 (Korea, Republic of)

2011-04-15

342

The driving frequency effects on the atmospheric pressure corona jet plasmas from low frequency to radio frequency  

NASA Astrophysics Data System (ADS)

Lately, the atmospheric pressure jet type corona plasma, which has been typically driven by dc to low frequency (LF: several tens of kHz), is often generated by using radio frequency of 13.56 MHz. Yet, the relationship between the plasma and its driving frequency has seldom been investigated. Hence, in this study, dependence of the atmospheric pressure corona plasma characteristics on the driving frequency was explored experimentally from LF to rf (5 kHz-13.56 MHz). The plasmas generated by the driving frequency under 2 MHz were cylindrical shape of several tens of millimeters long while the 13.56 MHz plasma is spherical and a few millimeters long. As the driving frequency was increased, the plasma length became shortened. At the lower driving frequencies (below 2 MHz), the plasmas existed as positive streamer and negative glow for each half period of the applied voltage, but the discharge was more continuous in time for the 13.56 MHz plasma. It was inferred from the measured I-V curves that the higher driving frequency induced higher discharge currents, and the gas temperature was increased as the driving frequency was increased.

Kim, Dan Bee; Jung, H.; Gweon, B.; Moon, S. Y.; Rhee, J. K.; Choe, W.

2011-04-01

343

Tuning the work function of graphene by nitrogen plasma treatment with different radio-frequency powers  

NASA Astrophysics Data System (ADS)

Graphene prepared by the chemical vapor deposition method was treated with nitrogen plasma under different radio-frequency (rf) power conditions in order to experimentally study the change in the work function. Control of the rf power could change the work function of graphene from 4.91 eV to 4.37 eV. It is shown that the increased rf power may lead to the increased number of graphitic nitrogen, increasing the electron concentration, and shifting the Fermi level to higher energy. The ability to controllably tune the work function of graphene is essential for optimizing the efficiency of optoelectronic and electronic devices.

Zeng, Jian-Jhou; Lin, Yow-Jon

2014-06-01

344

Thin-Film Deposition of Cu2O by Reactive Radio-Frequency Magnetron Sputtering  

NASA Astrophysics Data System (ADS)

Deposition conditions of cuprous oxide (Cu2O) thin films on glass substrates by reactive radio-frequency (rf) magnetron sputtering method were studied. The substrate temperature was found to be important for obtaining high-quality films, and the optimum substrate temperature was about 500°C. The Cu2O deposited at 500°C shows a band-gap energy of about 2.0 eV and a typical hole concentration of the order of 1015 cm-3 with a Hall mobility of 60 cm2/V{\\cdot}s, which is the highest mobility reported thus far.

Ishizuka, Shogo; Maruyama, Takahiro; Akimoto, Katsuhiro

2000-08-01

345

Radio Frequency Generation of an Electron Plasma in a Malmberg-Penning Trap  

NASA Astrophysics Data System (ADS)

The generation of an electron plasma via low-power Radio Frequency (RF) excitation has been observed in the Malmberg-Penning trap ELTRAP under ultra-high vacuum conditions. The process is sensitive to the RF parameters as well as to the trapping length. The electron heating mechanism necessary to reach the ionization energy of the residual gas has been modeled with the use of a simple one-dimensional iterative map, whose properties show a behavior similar to that of the Fermi acceleration map.

Paroli, B.; de Luca, F.; Maero, G.; Pozzoli, R.; Romé, M.

2010-06-01

346

Diagnostics of the radio frequency magnetron discharge plasma used for TiO 2 thin film sputtering deposition  

Microsoft Academic Search

The density, temperature and energy distribution function of the electrons of the plasma nearby the deposition substrate of a radio frequency magnetron discharge used for sputtering deposition of TiO2 thin films were measured by a cylindrical Langmuir probe. In the low-energy domain (0–15 eV), the electron energy distributions resembled a Maxwell distribution with a temperature value that decreased from 5

Lucel Sirghi; Toru Aoki; Yoshinori Hatanaka

2004-01-01

347

Radio Observations of Explosive Energy Releases on the Sun  

NASA Technical Reports Server (NTRS)

This chapter is devoted to a discussion of the radio observations of explosive energy releases (normal flares and small-scale energy releases) on the Sun. Radio imaging observations of solar flares and coronal transients and the relationship of radio phenomena with those observed in hard and soft X-rays and underlying physics are discussed.

Kundu, Mukul R.; White, S. M.

2003-01-01

348

Impact of radio frequency source power-induced ion energy on a refractive index of SiN film deposited by a pulsed-PECVD at room temperature  

Microsoft Academic Search

Using a pulsed-plasma enhanced chemical vapor deposition system, silicon nitride films were deposited at room temperature. A refractive index was examined in the range of bias power and duty ratio, 200–800W and 40–90%, respectively. Ion energy diagnostics was related to the refractive index. The refractive index decreased with decreasing the duty ratio at all powers but 800W. For all the

Suyeon Kim; Byungwhan Kim

2010-01-01

349

Potential radio frequency interference with the GPS L5 band for radio occultation measurements  

NASA Astrophysics Data System (ADS)

New Radio Occultation (RO) receivers are planned to utilize the newly implemented Global Positioning System (GPS) L5 signal centered at 1176.45 MHz. Since there are currently no operational GPS L5 receivers used for space-based RO applications, the interference environment is unclear. Distance Measuring Equipment (DME) and Tactical Air Navigation (TACAN) stations share the same frequency band as the GPS L5 signal. DME/TACAN signals have been identified to be a means of interference for any GPS L5 receiver. This study focuses on implementing a Systems Tools Kit (STK) simulation to gain insight into the power received by a RO satellite in Low Earth Orbit (LEO) from a DME/TACAN transmission. In order to confirm the validity of utilizing STK for communication purposes, a theoretical scenario was recreated as a simulation and the results were confirmed. Once the method was validated, STK was used to output a received power level aboard a RO satellite from a DME/TACAN station as well as a tool to predict the number of interfering DME/TACAN stations at any point in time. Taking a conservative approach, the signal power received was much greater than the typical power level received by a RO satellite from a GPS satellite transmission. This relatively high received power along with a high number of interfering DME/TACAN stations as an RO satellite passes over North America or Western Europe indicate that DME/TACAN interference may conflict with RO receivers.

Wolff, A. M.; Akos, D. M.; Lo, S.

2014-05-01

350

Investigation on the Frequency Allocation for Radio Astronomy at the L Band  

NASA Astrophysics Data System (ADS)

In this paper, the frequency allocation reserved for radio astronomy in the L band set by the International Telecommunication Union (ITU), which is between 1400 and 1427 MHz, is reviewed. We argue that the nearby frequencies are still very important for radio astronomers on the ground by investigating radio objects (H i sources) around 1300-1500 MHz. The L-band window is separated into a group of four windows, namely 1400-1427 MHz (window A), 1380-1400 MHz (window B), 1350-1380 MHz (window C), and 1300-1350 MHz (window D). These windows are selected according to their redshifts from a rest frequency for hydrogen spectral line at 1420.4057 MHz. Radio objects up to z ? 0.1 or frequency down to 1300 MHz are examined. We argue that since window B has important radio objects within the four windows, this window should also be given to radio astronomy. They are galaxies, spiral galaxies, and galaxy clusters. This underlines the significance of window B for radio astronomers on the ground. By investigating the severeness of radio frequency interference (RFI) within these windows, we have determined that window B still has significant, consistent RFI. The main RFI sources in the four windows have also been identified. We also found that the Department of Civil Aviation of Malaysia is assigned a frequency range of 1215-1427 MHz, which is transmitted within the four windows and inside the protected frequency for radio astronomy. We also investigated the RFI in the four windows on proposed sites of future radio astronomy observatories in Malaysia and Thailand and found the two best sites as Universiti Pendidikan Sultan Idris (UPSI) and Ubon Ratchathani, respectively. It has also been determined that RFI in window B increases with population density.

Abidin, Z. Z.; Umar, R.; Ibrahim, Z. A.; Rosli, Z.; Asanok, K.; Gasiprong, N.

2013-09-01

351

[Microstrip antenna design and system research of radio frequency identification temperature sensor].  

PubMed

Radio frequency identification sensor network, which is a product of integrating radio frequency identification (RFID) with wireless sensor network (WSN), is introduced in this paper. The principle of radio frequency identification sensor is analyzed, and the importance of the antenna is emphasized. Then three kinds of common antennae, namely coil antenna, dipole antenna and microstrip antenna, are discussed. Subsequently, according to requirement, we have designed a microstrip antenna in a wireless temperature-monitoring and controlling system. The measurement of factual effect showed the requirement was fulfilled. PMID:19166222

Yang, Hao; Yang, Xiaohe; Chen, Yuquan; Pan, Min

2008-12-01

352

Surface Impedance of Superconducting Radio Frequency (SRF) Materials  

NASA Astrophysics Data System (ADS)

Superconducting radio frequency (SRF) technology is widely adopted in particle accelerators. There remain many open questions, however, in developing a systematic understanding of the fundamental behavior of SRF materials, including niobium treated in different ways and various other bulk/thin film materials that are fabricated with different methods under assorted conditions. A facility that can measure the SRF properties of small samples in a range of 2˜40 K temperature is needed in order to fully answer these questions. The Jefferson Lab surface impedance characterization (SIC) system has been designed to attempt to meet this requirement. It consists of a sapphire-loaded cylindrical Nb TE011 cavity at 7.4 GHz with a 50 mm diameter flat sample placed on a non-contacting end plate and uses a calorimetric technique to measure the radio frequency (RF) induced heat on the sample. Driving the resonance to a known field on this surface enables one to derive the surface resistance of a relatively small localized area. TE011 mode identification has been done at room temperature and 4 K, and has been compared with Microwave Studio® and SuperFish simulation results. RF loss mechanisms in the SIC system are under investigation. A VCO phase lock loop system has been used in both CW and pulsed mode. Two calorimeters, with stainless steel and Cu as the thermal path material for high precision and high power versions, respectively, have been designed and commissioned for the SIC system to provide low temperature control and measurement. A power compensation method has been developed to measure the RF induced power on the sample. Simulation and experimental results show that with these two calorimeters, the whole thermal range of interest for SRF materials has been covered, The power measurement error in the interested power range is within 1.2% and 2.7% for the high precision and high power versions, respectively. Temperature distributions on the sample surface for both versions have been simulated and the accuracy of sample temperature measurements have been analysed. Both versions have the ability to accept bulk superconductors and thin film superconducting samples with a variety of substrate materials such as Al, A12O3, Cu, MgO, Nb and Si. Tests with polycrystalline and large grain bulk Nb samples have been done at <15 mT magnetic field. Based on BCS surface impedance, least-squares fittings have been done using SuperFit2.0, a code developed by G. Ciovati and the author. Microstructure analyses and SRF measurements of large scale epitaxial MgB2 films have been reported. MgB2 films on 5 cm dia. sapphire disks were fabricated by a Hybrid Physical Chemical Vapor Deposition (HPCVD) technique. The electron-beam backscattering diffraction (EBSD) results suggest that the film is a single crystal complying with a MgB2(0001)//A1 2O3(0001) epitaxial relationship. The SRF properties of different film thicknesses (200 nm and 350 nm) were evaluated using SIC system under different temperatures and applied fields at 7.4 GHz. A surface resistance of 9±2 ?? has been observed at 2.2 K. Based on BCS theory with moving Cooper pairs, the electron states distribution at 0K and the probability of electron occupation with finite temperature have been derived and applied to anomalous skin effect theory to obtain the surface impedance of a superconductor with moving Cooper pairs. We present the numerical results for Nb.

Xiao, Binping

353

Utility of the Safe-Cross-guided radiofrequency total occlusion crossing system in chronic coronary total occlusions (results from the Guided Radio Frequency Energy Ablation of Total Occlusions Registry Study).  

PubMed

The Safe-Cross radiofrequency guidewire (IntraLuminal Therapeutics, Carlsbad, California) combines 3 capabilities: (1) steerability of a conventional 0.014-in intermediate-stiffness guidewire, (2) optical coherence reflectometry to warn the operator when the wire tip approaches within 1 mm of the vessel wall, and (3) delivery of radiofrequency energy pulses to the wire tip to facilitate passage through an occluded segment. The Guided Radio Frequency Energy Ablation of Total Occlusions Registry was a prospective, nonrandomized, multicenter registry that enrolled 116 patients who had long-term coronary total occlusions and in whom a >10-minute good-faith attempt to cross the occlusion using conventional guidewires had failed. The median known duration of occlusion was 22 months (32%; >1 year), and the median length of the occluded segment was 25 mm (25%; >30 mm). Device success was achieved in 63 of 116 of patients (54.3%), and major adverse events occurred in 6.9%, consisting predominantly of isolated increases in cardiac enzymes with no procedure-related deaths, Q-wave myocardial infarctions, or emergency bypass operations. Clinical perforation occurred in 2.6% of patients; of these, perforation in only 1 patient (0.9%) was adjudicated to be directly related to the Safe-Cross radiofrequency wire rather than to the stiff and/or hydrophilic wires used after an inability to advance with the Safe-Cross. Based on these data, the device has been approved in Europe and was recently (January 2004) granted 510K clearance by the Food and Drug Administration. PMID:15464664

Baim, Donald S; Braden, Greg; Heuser, Richard; Popma, Jeffrey J; Cutlip, Donald E; Massaro, Joseph M; Marulkar, Sachin; Arvay, Linda J; Kuntz, Richard E

2004-10-01

354

Scattering of radio frequency waves by blobs in tokamak plasmas  

SciTech Connect

The density fluctuations and blobs present in the edge region of magnetic fusion devices can scatter radio frequency (RF) waves through refraction, reflection, diffraction, and coupling to other plasma waves. This, in turn, affects the spectrum of the RF waves and the electromagnetic power that reaches the core of the plasma. The usual geometric optics analysis of RF scattering by density blobs accounts for only refractive effects. It is valid when the amplitude of the fluctuations is small, of the order of 10%, compared to the background density. In experiments, density fluctuations with much larger amplitudes are routinely observed, so that a more general treatment of the scattering process is needed. In this paper, a full-wave model for the scattering of RF waves by a blob is developed. The full-wave approach extends the range of validity well beyond that of geometric optics; however, it is theoretically and computationally much more challenging. The theoretical procedure, although similar to that followed for the Mie solution of Maxwell's equations, is generalized to plasmas in a magnetic field. Besides diffraction and reflection, the model includes coupling to a different plasma wave than the one imposed by the external antenna structure. In the model, it is assumed that the RF waves interact with a spherical blob. The plasma inside and around the blob is cold, homogeneous, and imbedded in a uniform magnetic field. After formulating the complete analytical theory, the effect of the blob on short wavelength electron cyclotron waves and longer wavelength lower hybrid waves is studied numerically.

Ram, Abhay K. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)] [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Hizanidis, Kyriakos; Kominis, Yannis [School of Electrical and Computer Engineering, National Technical University of Athens, Association EURATOM-Hellenic Republic, Athens, GR-15773 (Greece)] [School of Electrical and Computer Engineering, National Technical University of Athens, Association EURATOM-Hellenic Republic, Athens, GR-15773 (Greece)

2013-05-15

355

Three-dimensional effects for radio frequency antenna modeling  

SciTech Connect

Electromagnetic field calculations for radio frequency (rf) antennas in two dimensions (2-D) neglect finite antenna length effects as well as the feeders leading to the main current strap. Comparisons with experiments indicate that these 2-D calculations can overestimate the loading of the antenna and fail to give the correct reactive behavior. To study the validity of the 2-D approximation, the Multiple Antenna Implementation System (MAntIS) has been used to perform 3-D modeling of the power spectrum, plasma loading, and inductance for a relevant loop antenna design. Effects on antenna performance caused by feeders to the main current strap, conducting sidewalls, and finite phase velocity are considered. The plasma impedance matrix for the loading calculation is generated by use of the ORION-1D code. The 3-D model is benchmarked with the 2-D model in the 2-D limit. For finite-length antennas, inductance calculations are found to be in much more reasonable agreement with experiments for 3-D modeling than for the 2-D estimates. The modeling shows that the feeders affect the launched power spectrum in an indirect way by forcing the driven rf current to return in the antenna sidewalls rather than in the plasma as in the 2-D model. Thus, the feeders have much more influence than the plasma on the currents that return in the sidewall. It has also been found that poloidal dependencies in the plasma impedance matrix can reduce the loading from that predicted in the 2-D model. For some plasma parameters, the combined 3-D effects can lead to a reduction in the predicted loading by as much as a factor of 2 from that given by the 2-D model.

Carter, M.D.; Batchelor, D.B.; Stallings, D.C.

1993-09-01

356

A prediction model for personal radio frequency electromagnetic field exposure.  

PubMed

Radio frequency electromagnetic fields (RF-EMF) in our daily life are caused by numerous sources such as fixed site transmitters (e.g. mobile phone base stations) or indoor devices (e.g. cordless phones). The objective of this study was to develop a prediction model which can be used to predict mean RF-EMF exposure from different sources for a large study population in epidemiological research. We collected personal RF-EMF exposure measurements of 166 volunteers from Basel, Switzerland, by means of portable exposure meters, which were carried during one week. For a validation study we repeated exposure measurements of 31 study participants 21 weeks after the measurements of the first week on average. These second measurements were not used for the model development. We used two data sources as exposure predictors: 1) a questionnaire on potentially exposure relevant characteristics and behaviors and 2) modeled RF-EMF from fixed site transmitters (mobile phone base stations, broadcast transmitters) at the participants' place of residence using a geospatial propagation model. Relevant exposure predictors, which were identified by means of multiple regression analysis, were the modeled RF-EMF at the participants' home from the propagation model, housing characteristics, ownership of communication devices (wireless LAN, mobile and cordless phones) and behavioral aspects such as amount of time spent in public transports. The proportion of variance explained (R2) by the final model was 0.52. The analysis of the agreement between calculated and measured RF-EMF showed a sensitivity of 0.56 and a specificity of 0.95 (cut-off: 90th percentile). In the validation study, the sensitivity and specificity of the model were 0.67 and 0.96, respectively. We could demonstrate that it is feasible to model personal RF-EMF exposure. Most importantly, our validation study suggests that the model can be used to assess average exposure over several months. PMID:19819523

Frei, Patrizia; Mohler, Evelyn; Bürgi, Alfred; Fröhlich, Jürg; Neubauer, Georg; Braun-Fahrländer, Charlotte; Röösli, Martin

2009-12-15

357

Pulsed radio frequency therapy of experimentally induced arthritis in ponies.  

PubMed Central

The effect of pulsed radio frequency therapy (PRFT) was evaluated on seven ponies with no arthritis and in 28 ponies in which arthritis was created using intra-articular amphotericin B to induce synovitis in the right middle carpal joint. The ponies were divided into five treatment and two control groups. Two levels of arthritis were created and two dosage levels of PRFT were evaluated. The effect of PRFT on arthritic and nonarthritic joints was measured by comparing synovial fluid parameters, the degree and duration of lameness, the range of carpal motion, and carpus circumference, for treated and untreated groups. Lesions seen radiographically, at gross pathology, and by histopathology were also compared between the treated and control groups. In the ponies with a mild form of induced arthritis, PRFT significantly (p less than 0.05) reduced the severity and duration of lameness, swelling of the carpus, and the severity of gross pathological and radiographic changes. In these ponies the synovial acid phosphatase levels were lower, the mucin clot quality was superior, and the synovial protein levels were lower for the ponies receiving PRFT as compared to the arthritic ponies receiving no treatment. A dose response effect was evident. In ponies with a slightly more severe form of arthritis, PRFT was evaluated at one dosage level. The treated ponies were significantly improved over the untreated ponies with respect to carpal range of motion, degree of lameness, carpus swelling, and radiographic lesions. No deleterious effects were noted when normal, PRFT treated, middle carpal joints were compared to contralateral untreated, normal joints. It was concluded that significant beneficial effects resulted when affected ponies were treated with PRFT.

Crawford, W H; Houge, J C; Neirby, D T; Di Mino, A; Di Mino, A A

1991-01-01

358

Radiation effects on communication performance of radio frequency identification tags.  

PubMed

Radioactive materials (sources) are managed by bookkeeping and stocktaking. The radiation protection section staffs should check the sources manually. Annual effective dose concerning stocktaking of them are estimated at some mSv concerning fingers. A radio frequency identification (RFID) tag's absorbed dose is estimated at some dozen Gy. RFID for stocktaking automatically was devised. Radiation effects on the communication performance of RFID tags were investigated by using response times and read ranges as indices. The RFID system was composed of a computer, a detector, and transponders (tag) consisting of an integrated circuit chip and an antenna. The tag is joined to the source for identification. The tags were irradiated at doses between 5 and 5,000 Gy by an x-ray irradiator. The response times and the read ranges were tracked from 40 to 23,200 min after irradiation. Relative read ranges fluctuated between 0.9 and 1.1 in the dose region less than 2,000 Gy, but fluctuated greatly in the dose region beyond 2,000 Gy. Malfunctioning tags appeared from 3,000 Gy, and all tags malfunctioned in the dose region over 4,500 Gy. The threshold dose leading to malfunction was determined to be 2,100 Gy. Time variation of relative read ranges was classified into four patterns. The pattern shifted from pattern 1 to 4 when the dose was increased. The relative read ranges lengthened in pattern 1. The relative read rages were approximately 1.0 in pattern 2. The read ranges tentatively shortened, then recovered in pattern 3. The tags malfunctioned in pattern 4. Once the tags malfunctioned, they never recovered their performance. Radiation enhances or deteriorates communication performance depending on dosage. Tags can spontaneously recover from radiation deterioration. The time variation of the read ranges can be illustrated by enhancement, deterioration, and recovery. The mechanism of four patterns is explained based on the variation of the frequency harmonization strength and activation voltage by irradiation. The annual effective dose of radiation protection section staffs can be reduced considerably. PMID:20938239

Mori, Kazuyuki; Meng, Zhaowu; Kikuchi, Hirosumi; Kataoka, Yasuhide; Nakazato, Kazuhisa; Deji, Shizuhiko; Ito, Shigeki; Saze, Takuya; Hirota, Masahiro; Nishizawa, Kunihide

2010-11-01

359

Radio Frequency Field Calculations for Plasma Heating Simulations in VASIMR  

NASA Astrophysics Data System (ADS)

(VASIMR)1 is plasma heating by ion-cyclotron RF heating (ICRF). Mathematical simulation helps to design an ICRF antenna, i.e. make maximal absorption of RF power into the plasma in the resonance area. Another goal of a particle simulation is design of a magnetic nozzle and optimize the performance of VASIMR2. field in the plasma, 2) ion density and velocity, 3) ion-cyclotron radio-frequency electromagnetic field. The assumptions of quasineutral and collisionless plasma are based on the range of operating VASIMR parameters. Carlo simulations for systems of million of particles in a reasonable time and without the need for a powerful supercomputer. The particle to grid weighting method is used for calculating the ion density, which is used for recalculation of the electric potential and RF field. dimensional problem to a weighted sum over two-dimensional solutions. Absorption is introduced in the cold plasma model by adding an imaginary collision frequency to the RF driven frequency, which is equivalent to adding an imaginary particle mass in the dielectric tensor elements. static and RF fields using the VASIMR code2. The VASIMR and EMIR codes are then iterated to estimate the ICRF effects on the plasma density. The iteration is performed by calculating the RF fields with the EMIR code, and using these fields to follow nonlinear ion trajectories with the VASIMR code on the gyro-frequency time scale. The ion trajectories are used to generate RF power absorption values and a density input for the next EMIR calculation. The codes are iterated until the density profile becomes reasonably stable, then the collisional absorption parameter in the EMIR code is adjusted and the iteration is continued until the power deposited by the RF system matches the power absorbed by the ion trajectories in a global sense. electric field. The solved algebraic system of equations is represented by ill-conditioned 18-diagonal matrix with complex elements. Since early development of the EMIR code, the frontal method direct solver was used. That solver requires large CPU time and RAM, which both are proportional to Nr Nz2, for a grid of the size Nr x Nz. These requirements make almost impossible to use existent EMIR solver on PC to obtain RF fields with good accuracy. system. The suggested iterative method is Modified Incomplete Cholesky Preconditioned Conjugate Gradient Squared solver4. The solver involves a couple of the control parameters, which let a user tune the code to make iterations converge as fast as possible for a particular grid. Since the iterative solver does not require large RAM, and works much faster than the direct solver, the new algorithm lets us resolve RF fields on a PC with required accuracy. REFERENCES 1. Chang Díaz F.R., "Research Status of The Variable Specific Impulse Magnetoplasma Rocket", Proc. 39th Annual Meeting of the Division of Plasma Physics (Pittsburgh, PA, 1997), Bulletin of APS, 42 2057. 2. Ilin A.V., Chang Díaz F.R., Squire J.P. and Carter M.D. "Monte Carlo Particle Dynamics in a Variable Specific Impulse Magnetoplasma Rocket", (Proceedings of Open Systems' 98), Transactions of Fusion Technology, 35 330 - 334 (1999). 3. Jaeger E.F., Batchelor D.B., Weitzner H. and Whealton J.H. "ICRF Wave Propagation And Absorption in Tokamak And Mirror Magnetic Fields - A Full-wave Calculation", Computer Physics Com., 40 33 - 64 (1986). 4. Ilin, A. V., Bagheri, B., Scott, L. R., Briggs, J. M., and McCammon, J. A. "Parallelization of Poisson-Boltzmann and Brownian Dynamics calculation", Parallel Computing in Computational Chemistry, ACB Books, Washington D.C., (1995) 170-185.

Ilin, A. V.; Díaz, F. R. Chang; Squire, J. P.; Carter, M. D.

2002-01-01

360

A frequency hopping spread spectrum transmission scheme for uncoordinated cognitive radios  

Microsoft Academic Search

One of the major challenges to cognitive radios is the synchroniza- tion of distributed radios onto the same spectrum white spaces which vary in time and space. In this paper, we propose a frequency- hopping spread spectrum transmission scheme which works reliably without any a priori handshaking assumption. Each cognitive ra- dio independently detects white spaces, and then selects one

Xiaohua Li; Juite Hwu

2009-01-01

361

Simultaneous Multi-frequency Pulsar Observations: Investigation of the Radio Emission Mechanism  

Microsoft Academic Search

Despite the progress to date at the observational and theoretical fronts, understanding the physical processes that govern pulsar radio emission continues to be an outstanding problem in pulsar astronomy. In this paper, we report on recent, simultaneous, multi-frequency observations made between the Lovell, Effelsberg and GMRT (Giant Metre-wave Radio Telescope). The general goals of this project are: (i) investigating the

N. D. R. Bhat; A. Karastergiou; Y. Gupta; M. Kramer; A. G. Lyne

2001-01-01

362

URSI workshop report: Effects of the lower atmosphere on radio propagation at frequencies above 1 GHz  

NASA Astrophysics Data System (ADS)

This is a summary report of the workshops convened at the URSI Commission F Open Symposium, ‘Effects of the Lower Atmosphere on Radio Propagation at Frequencies above 1 GHz,’ Lennoxville, Quebec, Canada, May 26-30, 1980, prepared by URSI Commission F for CCIR Study Group 5. Document 5/120, Period 1978-1982, International Radio Consultative Committee (CCIR).

URSI Workshop Session Chairmen

363

Ion species mix and ion density measurements using radio frequency waves  

Microsoft Academic Search

Radio frequency wave applications have demonstrated great versatility in tokamak plasmas. Two applications, using the same diagnostic design, can make use of a fast Alfven wave to make ion species mix and ion density measurements. A discussion and derivation, using the cold plasma approximation, is given for a fast Alfven radio wave used for making an interferometry density measurement, a

George Wilder Watson III

2003-01-01

364

Calculus, Radio Dials and the Straight-Line Frequency Variable Capacitor  

ERIC Educational Resources Information Center

Most often radio dials of analogue radios are not uniformly graded; the frequencies are cramped on the left side or on the right side. This makes tuning more difficult. Why are dials made this way? We shall see here that simple calculus can help understand this problem and solve it. (Contains 7 figures.)

Boyadzhiev, Khristo N.

2010-01-01

365

Measurement of galactic radio emission at frequency 37 GHz from aboard spacecraft  

Microsoft Academic Search

It is postulated that the distribution of thermal galactic radio emission is dominated by extended low-density HII regions (ELD regions), with the remaining HII regions accounting for only 16. Until now it has been impossible to measure the parameters of extended sources of thermal radio emission with sufficient accuracy. This can be done by exoatmospheric scanning at relatively high frequencies.

I. A. Strukov; D. P. Skulachev

1988-01-01

366

Supplying the power requirements to a sensor network using radio frequency power transfer.  

PubMed

Wireless power transmission is a method of supplying power to small electronic devices when there is no wired connection. One way to increase the range of these systems is to use a directional transmitting antenna, the problem with this approach is that power can only be transmitted through a narrow beam and directly forward, requiring the transmitter to always be aligned with the sensor node position. The work outlined in this article describes the design and testing of an autonomous radio frequency power transfer system that is capable of rotating the base transmitter to track the position of sensor nodes and transferring power to that sensor node. The system's base station monitors the node's energy levels and forms a charge queue to plan charging order and maintain energy levels of the nodes. Results show a radio frequency harvesting circuit with a measured S11 value of -31.5 dB and a conversion efficiency of 39.1%. Simulation and experimentation verified the level of power transfer and efficiency. The results of this work show a small network of three nodes with different storage types powered by a central base node. PMID:23012506

Percy, Steven; Knight, Chris; Cooray, Francis; Smart, Ken

2012-01-01

367

Review of radio-frequency, nonlinear effects on the ionosphere  

SciTech Connect

Modification of the ionosphere by high power radio waves in the megahertz band has been intensively investigated over the past two decades. This research has yielded advances in aeronomy, geophysics, and plasma physics with applications to radio communication and has provided a fruitful interaction of radio theorists and experimentalists. There being almost no linear effects of powerful radio waves on the ionosphere, we concentrate on the nonlinear effects. To put the subject in perspective we trace its history beginning in the early 1930s and highlight the important events up to the late 1960s. We then shift to a phenomenological approach and deal in order with ohmic heating, parametric instabilities, self-focusing and kilometer-scale irregularities, meter-scale irregularities, and a collection of recently discovered effects. We conclude with the observation that stronger international cooperation would benefit this research, and describe a list of promising, difficult challenges.

Gordon, W.E.; Duncan, L.M.

1983-01-01

368

Coupling effects in inductive discharges with radio frequency substrate biasing  

SciTech Connect

Low pressure inductively coupled plasmas (ICP) operated in neon at 27.12 MHz with capacitive substrate biasing (CCP) at 13.56 MHz are investigated by phase resolved optical emission spectroscopy, voltage, and current measurements. Three coupling mechanisms are found potentially limiting the separate control of ion energy and flux: (i) Sheath heating due to the substrate biasing affects the electron dynamics even at high ratios of ICP to CCP power. At fixed CCP power, (ii) the substrate sheath voltage and (iii) the amplitude as well as frequency of plasma series resonance oscillations of the RF current are affected by the ICP power.

Schulze, J.; Schuengel, E.; Czarnetzki, U.

2012-01-09

369

Collisionless electron heating by radio frequency bias in low gas pressure inductive discharge  

NASA Astrophysics Data System (ADS)

We show experimental observations of collisionless electron heating by the combinations of the capacitive radio frequency (RF) bias power and the inductive power in low argon gas pressure RF biased inductively coupled plasma (ICP). With small RF bias powers in the ICP, the electron energy distribution (EED) evolved from bi-Maxwellian distribution to Maxwellian distribution by enhanced plasma bulk heating and the collisionless sheath heating was weak. In the capacitive RF bias dominant regime, however, high energy electrons by the RF bias were heated on the EEDs in the presence of the ICP. The collisionless heating mechanism of the high energy electrons transited from collisionless inductive heating to capacitive coupled collisionless heating by the electron bounce resonance in the RF biased ICP.

Lee, Hyo-Chang; Chung, Chin-Wook

2012-12-01

370

IS THE OBSERVED HIGH-FREQUENCY RADIO LUMINOSITY DISTRIBUTION OF QSOs BIMODAL?  

SciTech Connect

The distribution of QSO radio luminosities has long been debated in the literature. Some argue that it is a bimodal distribution, implying that there are two separate QSO populations (normally referred to as 'radio-loud' and 'radio-quiet'), while others claim it forms a more continuous distribution characteristic of a single population. We use deep observations at 20 GHz to investigate whether the distribution is bimodal at high radio frequencies. Carrying out this study at high radio frequencies has an advantage over previous studies as the radio emission comes predominantly from the core of the active galactic nucleus, and hence probes the most recent activity. Studies carried out at lower frequencies are dominated by the large-scale lobes where the emission is built up over longer timescales (10{sup 7}-10{sup 8} yr), thereby confusing the sample. Our sample comprises 874 X-ray-selected QSOs that were observed as part of the 6dF Galaxy Survey. Of these, 40% were detected down to a 3{sigma} detection limit of 0.2-0.5 mJy. No evidence of bimodality is seen in either the 20 GHz luminosity distribution or in the distribution of the R{sub 20} parameter: the ratio of the radio to optical luminosities traditionally used to classify objects as being either radio-loud or radio-quiet. Previous results have claimed that at low radio luminosities, star formation processes can dominate the radio emission observed in QSOs. We attempt to investigate these claims by stacking the undetected sources at 20 GHz and discuss the limitations in carrying out this analysis. However, if the radio emission was solely due to star formation processes, we calculate that this corresponds to star formation rates ranging from {approx}10 M{sub Sun} yr{sup -1} to {approx}2300 M{sub Sun} yr{sup -1}.

Mahony, Elizabeth K.; Sadler, Elaine M.; Croom, Scott M.; Murphy, Tara [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Ekers, Ronald D.; Feain, Ilana J., E-mail: emahony@physics.usyd.edu.au [Australia Telescope National Facility, CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia)

2012-07-20

371

Use of the radio-frequency quadrupole structure as a cyclotron axial-buncher system  

SciTech Connect

The radio-frequency quadrupole (RFQ) is a new linear accelerating structure being developed as a low-velocity linac. In this structure rf electric fields are used to simultaneously focus, bunch, and accelerate ions. The slow introduction of the accelerating field results in the adiabatic bunching of a dc ion beam with a large capture efficiency. Realistic computer simulations have shown that this new structure could also be used as a buncher in the axial injection system of a cyclotron. A description of the RFQ geometry and its general properties is given. A preliminary design is presented for a variable frequency RFQ to be used as buncher in the axial injection system of a variable energy cyclotron. The operating parameters for this RFQ are discussed.

Hamm, R.W.; Swenson, D.A.; Wangler, T.P.

1981-01-01

372

Radio Frequency Identification Devices: Effectiveness in Improving Safeguards at Gas-Centrifuge Uranium-Enrichment Plants.  

National Technical Information Service (NTIS)

Recent advances in radio frequency identification devices (RFIDs) have engendered a growing interest among international safeguards experts. Potentially, RFIDs could reduce inspection work, viz. the number of inspections, number of samples, and duration o...

J. Jo

2007-01-01

373

Random Access Algorithm for Frequency Hopped Spread Spectrum Packet Radio Networks.  

National Technical Information Service (NTIS)

The authors consider packet radio multi-user spread-spectrum environments, where frequency hopping spread spectrum techniques are deployed for protection against intelligent adversaries. When the users in such environments are mobile and bursty, random ac...

M. Georgiopoulos P. Papantoni-Kazakos

1986-01-01

374

Electronics and Electrical Engineering Laboratory Radio-Frequency Technology Division: Programs, Activities, and Accomplishments.  

National Technical Information Service (NTIS)

Contents: Welcome; Mission; Division Function; Our Technical Programs; Radio-Frequency Technology Division Organization; Fundamental Microwave Quantities (Power and Voltage, Scattering Parameters and Impedance, Noise); High-Speed Microelectronics; Wireles...

2001-01-01

375

Production of Seamless Superconducting Radio Frequency Cavities from Ultra-Fine Grained Niobium.  

National Technical Information Service (NTIS)

The positron and electron linacs of the International Linear Collider (ILC) will require over 14,000, nine-cell, one meter length, superconducting radio frequency (SRF) cavities (ILC Reference Design Report, 2007). Manufacturing on this scale will benefit...

R. Crooks W. Chang

2009-01-01

376

Studies on the Effect of Radio-Frequency Waves in Biological Macromolecules.  

National Technical Information Service (NTIS)

The effect of radio-frequency electric fields on various biologic materials was examined. Particularly, the effects on alcohol dehydrogenase and DNA were carefully investigated. To avoid the effects of heating, a pulsed electric field was used, and sample...

S. Takashima

1965-01-01

377

Defense Logistics: Better Strategic Planning Can Help Ensure DOD's Successful Implementation of Passive Radio Frequency Identification.  

National Technical Information Service (NTIS)

The Department of Defense (DOD) has had problems with tracking and identifying inventory for many years, most recently in Operation Iraqi Freedom. One of several tools DOD is using to address these inventory problems is radio frequency identification (RFI...

2005-01-01

378

76 FR 9714 - Defense Federal Acquisition Regulation Supplement; Passive Radio Frequency Identification (DFARS...  

Federal Register 2010, 2011, 2012, 2013

...of passive Radio Frequency Identification (RFID). DATES: Comments on the proposed rule should...identification, to-- --Clarify that the RFID requirement pertains solely to ``passive RFID''; --Supply a link to a web site in...

2011-02-22

379

The Astronomical Low Frequency Array: A Proposed Explorer Mission for Radio Astronomy  

NASA Technical Reports Server (NTRS)

A radio interferometer array in space providing high dynamic range images with unprecedented angular resolution over the broad frequency range from 0.030 - 30 MHz will open new vistas in solar, terrestial, galactic, and extragalactic astrophysics.

Jones, D.; Allen, R.; Basart, J.; Bastian, T.; Bougeret, J. L.; Dennison, B.; Desch, M.; Dwarakanath, K.; Erickson, W.; Finley, D.; Kaiser, M.; Kassim, N.; Kuiper, T.; MacDowall, R.; Mahoney, M.; Perley, R.; Preston, R.; Reiner, M.; Rodriguez, P.; Stone, R.; Unwin, S.; Weiler, K.; Woan, G.; Woo, R.

1999-01-01

380

Base-level management of radio-frequency radiation-protection program. Final report  

SciTech Connect

AFOEHL developed this report to assist the base-level aerospace medical team manage their radio-frequency radiation protection program. This report supersedes USAFOEHL Report 80-42, 'A practical R-F Guide for BEES.'

Rademacher, S.E.; Montgomery, N.D.

1989-04-01

381

Base-level management of radio-frequency radiation-protection program. Final report  

SciTech Connect

AFOEHL developed this report to assist the base-level aerospace medical team manage their radio-frequency radiation-protection program. This report supersedes USAFOEHL Report 80-42, 'A Practical R-F Guide for BEES.'

Rademacher, S.E.; Montgomery, N.D.

1989-04-01

382

Bipolar Cascade Emitters for Radio-Frequency and Electro-Optical Applications.  

National Technical Information Service (NTIS)

This final report details the development of two unique bipolar cascade emitter devices for radio frequency and electro-optical applications. The first device is a bipolar cascade vertical cavity surface emitting laser designed to demonstrate high slope e...

R. J. Turner W. J. Siskaninetz

2008-01-01

383

Extending the ICRF to Higher Radio Frequencies: Imaging and Source Structure  

NASA Technical Reports Server (NTRS)

We present imaging results and source structure analysis of extragalactic radio sources observed using the Very Long Baseline Array (VLBA) at 24 GHz and 43 GHz as part of an ongoing NASA, USNO, NRAO and Bordeaux Observatory collaboration to extend the International Celestial Reference Frame (ICRF) to higher radio frequencies. The K/Q-band image database now includes images of 108 sources at 43 GHz (Q-braid) and images of 230 sources at 24 GHz (K-band). Preliminary analysis of the observations taken to date shows that the sources are generally more compact as one goes from the ICRF frequency of 8.4 GHz to 24 GHz. This result is consistent with the standard theory of compact extragalactic radio sources and suggests that reference frames defined at these higher radio frequencies will be less susceptible to the effects of intrinsic source structure than those defined at lower frequencies.

Boboltz, David A.; Fey, Alan L.; Charlot, Patrick; Fomalont, Edward B.; Lanyi, Gabor E.; Zhang, Li-Wei

2004-01-01

384

Radio Frequency Hearing Aids: The Need for Complementary and Compatible Channel Allocation.  

ERIC Educational Resources Information Center

The article discusses the use of radio frequency hearing aids, which provide a practical means of improving the signal-to-noise ratio of conventional hearing aids used by the aurally handicapped. (Author/DLS)

Burgess, Vic; And Others

1979-01-01

385

POTENTIAL HUMAN STUDY POPULATIONS FOR NON-IONIZING (RADIO FREQUENCY) RADIATION HEALTH EFFECTS  

EPA Science Inventory

This research project was initiated to identify potential human populations for future epidemiological studies of the health effects of radio frequency radiation. Through a literature search and contacts with various groups and organizations, numerous occupations and applications...

386

FORTE observations of lightning radio-frequency signatures: Capabilities and basic results  

Microsoft Academic Search

The FORTE satellite, launched on August 29, 1997, carries both radio-frequency-receiver and optical (imaging and photometric) payloads for the study of lightning. The radio-frequency (RF) data for the first 7 months of operation are described, both to illustrate the satellite{close_quote}s capabilities and to explain the basic statistical findings so far. FORTE{close_quote}s multichannel RF trigger system represents a significant advance in

Abram R. Jacobson; Stephen O. Knox; Robert Franz; Donald C. Enemark

1999-01-01

387

Utilization of Software-Defined Radio in power line communication between motor and frequency converter  

Microsoft Academic Search

In this paper, a power line data transmission link based on Software-Defined Radio (GNU Radio) for motor cable communication between an electrical motor and a frequency converter is developed and tested. The test environment includes a frequency converter, an electrical motor (2.2 kW), and a 90-meter-long motor power cable. Two differential phase shift keying (DPSK) modulations, DBPSK and DQPSK, are

A. Pinomaa; H. Baumgartner; J. Ahola; A. Kosonen

2010-01-01

388

Coincidently Searching for Gravitational Waves and Low Frequency Radio Transients  

NASA Astrophysics Data System (ADS)

The transient sky has become an important area of astrophysical study, especially with the appearance of recent fast transients, but little is known about the sources of these transients. One possible approach which can shed light on this area is multi-messenger astronomy using gravitational waves and prompt emission meter-wavelength radio to observe fast transients. This is made possible with gravitational-wave detectors such as LIGO, VIRGO, and GEO (IndIGO and KAGRA proposed or under construction) and phased-array radio-telescopes such LWA, LOFAR, LoFASM, and MWA. This talk presents a method for coincidence of gravitational wave and meter-wavelength radio observations to enable multi-messenger astronomy and discusses the optimization of gravitational-wave and radio sensitivities to attain effective combined observational sensitivities. It is shown that coincidence provides a 52.9% increase to the sensitivity distance for LIGO and a 200% increase to the SNR of radio arrays for particular cases.

Kavic, Michael; Yancey, C.; Shawhan, P. S.; Cutchin, S.; Simonetti, J. H.; Bear, B.; Tsai, J.

2014-01-01

389

Indication of radio frequency interference (RFI) sources for solar burst monitoring in Malaysia  

NASA Astrophysics Data System (ADS)

Apart of monitoring the Sun project, the Radio Frequency Interference (RFI) surveying in the region of (1-1200) MHz has been conducted. The main objective of this surveying is to test and qualify the potential of monitoring a continuous radio emission of Solar in Malaysia. This work is also an initiative of International Space Weather Initiative (ISWI) project where Malaysia is one of the country that participate a e-Callisto Spectrometer network in order to study the behavior of Solar radio burst in frequency of (45-800) MHz region which will be install in this October. Detail results will indicate the potential of monitoring a solar in Malaysia.

Hamidi, Z. S.; Abidin, Z. Z.; Ibrahim, Z. A.; Shariff, N. N. M.

2012-06-01

390

Spontaneous Radio Frequency Emissions from Natural Aurora. Chapter 4  

NASA Technical Reports Server (NTRS)

At high latitudes, suitably sensitive radio experiments tuned below 5 MHz detect up to three types of spontaneous radio emissions from the Earth s ionosphere. In recent years, ground-based and rocket-borne experiments have provided strong evidence for theoretical explanations of the generation mechanism of some of these emissions, but others remain unexplained. Achieving a thorough understanding of these ionospheric emissions, accessible to ground-based experiments, will not only bring a deeper understanding of Earth s radio environment and the interactions between waves and particles in the ionosphere but also shed light on similar spontaneous emissions occurring elsewhere in Earth s environment as well as other planetary and stellar atmospheres.

LaBelle, J.

2009-01-01

391

Radio-frequency heating of sloshing ions in a straight field line mirror  

SciTech Connect

A scenario to sustain a sloshing ion population with radio-frequency heating in a newly proposed mirror device, the straight field line mirror, is examined. The possibilities of ion cyclotron heating in two-ion species plasma have been analyzed and a scheme with longitudinal wave conversion and fundamental harmonic heating of deuterium ions in tritium plasma has been investigated. This scheme provides efficient ion heating for high deuterium 'minority' concentration without substantial conversion to slow waves and heating of the electrons. Numerical calculations carried out for a reactor-scale device show that conversion of the fast magnetosonic wave to the fast Alfven wave occurs. For reasons of strong cyclotron absorption of the fast Alfven wave, only a small portion of the wave energy transits through the cyclotron layer and penetrates to the central part of the trap. The power deposition is peaked at the plasma core. The amount of deposited power does not depend sensitively on the parameters of the discharge. The study uses numerical three-dimensional calculations for the time-harmonic boundary problem for Maxwell's equations. For radio-frequency heating in this scheme, a simple efficient strap antenna is proposed. It has low Q antenna and operates in the regime of global resonance overlapping.

Moiseenko, V.E.; Aagren, O. [Division of Electricity and Lightning Research, Angstroem Laboratory, Uppsala University, Box 534, SE-751 21 Uppsala (Sweden)

2005-10-01

392

Spatial distribution of the plasma parameters in a radio-frequency driven negative ion source.  

PubMed

Results from initial stage of modeling of the SPIDER source of negative hydrogen/deuterium ions currently under development in Consorzio RFX (Padova) regarding ITER are presented. A 2D model developed within the fluid plasma theory for low-pressure discharges (free-fall regime maintenance) is applied to the gas-discharge conditions planned and required for the SPIDER source: gas pressure of 0.3 Pa and radio-frequency (rf) power of 100 kW absorbed in a single driver. The results are for the spatial distribution of the plasma characteristics (charged particle densities, electron temperature and electron energy flux, plasma potential, and dc electric field) with conclusions for the role of the electron energy flux in the formation of the discharge structure. PMID:24593544

Todorov, D; Tarnev, Kh; Paunska, Ts; Lishev, St; Shivarova, A

2014-02-01

393

Laboratory performance of the BEAR (Beam Experiment Aboard Rocket) RFQ (radio-frequency quadrupole)  

SciTech Connect

The BEAR (Beam Experiment Aboard Rocket) accelerator will be part of an experiment to demonstrate the operation of an ion accelerator in space and to characterize the exoatmospheric propagation of a neutral particle beam. The RFQ (radio-frequency quadrupole) has been designed to produce a 25-mA H/sup /minus// beam with an emittance of 0.01 cm-mrad (rms normalized) at an energy of 1 MeV. Because of the rigors of spaceflight, the accelerator design has been constrained by factors not normally applicable to conventional terrestrial accelerators. These factors and the mechanical features are described in a companion paper in these proceedings. The design techniques developed for BEAR would be applicable whenever, rugged, lightweight, or power-efficient systems are required. The BEAR RFQ has been operated under power with beam in the laboratory. This paper details of measured beam transport, emittance, and energy spectra. 6 refs., 4 figs.

O'Shea, P.G.; Schrage, D.L.; Young, L.M.; Zaugg, T.J.; Lynch, M.T.; McKenna, K.F.; Hansborough, L.D.

1988-01-01

394

An Electron Bunch Compression Scheme for a Superconducting Radio Frequency Linear Accelerator Driven Light Source  

SciTech Connect

We describe an electron bunch compression scheme suitable for use in a light source driven by a superconducting radio frequency (SRF) linac. The key feature is the use of a recirculating linac to perform the initial bunch compression. Phasing of the second pass beam through the linac is chosen to de-chirp the electron bunch prior to acceleration to the final energy in an SRF linac ('afterburner'). The final bunch compression is then done at maximum energy. This scheme has the potential to circumvent some of the most technically challenging aspects of current longitudinal matches; namely transporting a fully compressed, high peak current electron bunch through an extended SRF environment, the need for a RF harmonic linearizer and the need for a laser heater. Additional benefits include a substantial savings in capital and operational costs by efficiently using the available SRF gradient.

C. Tennant, S.V. Benson, D. Douglas, P. Evtushenko, R.A. Legg

2011-09-01

395

Packet error probabilities in frequency-hopped spread-spectrum packet radio networks-memoryless frequency-hopping patterns considered  

Microsoft Academic Search

The packet error probability induced in a frequency-hopped spread-spectrum packet radio network is computed. The frequency spectrum is divided into q frequency bins. Each packet is exactly one codeword from an (M, L) Reed-Solomon code [M=number of codeword symbols (bytes); L=number of information symbols (bytes)]. Every user in the network sends each of the M bytes of his packet at

M. Georgiopoulos

1988-01-01

396

Opportunistic use of radio-frequency spectrum: a network perspective  

Microsoft Academic Search

We address opportunistic use of RF spectrum for communication among frequency-agile nodes composing a network, under the assumptions that the network and its environment are time-varying and users external to the network may have precedence in access and use of certain frequencies under certain conditions. We consider three different frequency assignment problems: (1) finding a common broadcast frequency for a

M. E. Steenstrup

2005-01-01

397

Origin of pulsar radio emission. I. High frequency data  

Microsoft Academic Search

Using the pulse arrival times from pulsar observations made between 1.4 and 32 GHz, we constrain the location and size of the magnetospheric region which is responsible for the observed radio emission. We demonstrate that for long period pulsars the magnetic field maintains its dipolar form throughout the whole emission region. The emission region itself is located very close to

M. Kramer; K. M. Xilouris; A. Jessner; D. R. Lorimer; R. Wielebinski; A. G. Lyne

1997-01-01

398

Multi-frequency observations of X-shaped radio galaxies  

Microsoft Academic Search

X-shaped radio sources are some of the most peculiar things seen on the sky. They are distinguished by their secondary, presently non-active lobes, larger than and almost perpendicular to the presently active lobes. Such sources may be an indication of a recent merger event or tidal interaction of the host galaxy. The explanations usually invoked to explain the formation of

H. Rottmann; J. Dennet-Thorpe; U. Klein

1998-01-01

399

Frequency-domain equalization of mobile radio and terrestrial broadcast channels  

Microsoft Academic Search

For mobile radio and terrestrial broadcast applications, we compare orthogonal frequency-division multiplexing (OFDM) and single-carrier transmission with frequency-domain equalization. With respect to our earlier results, we include channel coding and frequency-domain interleaving which are necessary for OFDM systems on multipath fading channels characterized by deep notches in the signal spectrum. Our results indicate that a single-carrier system with a frequency-domain

H. Sari; G. Karam; I. Jeanclaudle

1994-01-01

400

Self-consistent modeling of radio-frequency plasma generation in stellarators  

SciTech Connect

A self-consistent model of radio-frequency (RF) plasma generation in stellarators in the ion cyclotron frequency range is described. The model includes equations for the particle and energy balance and boundary conditions for Maxwell’s equations. The equation of charged particle balance takes into account the influx of particles due to ionization and their loss via diffusion and convection. The equation of electron energy balance takes into account the RF heating power source, as well as energy losses due to the excitation and electron-impact ionization of gas atoms, energy exchange via Coulomb collisions, and plasma heat conduction. The deposited RF power is calculated by solving the boundary problem for Maxwell’s equations. When describing the dissipation of the energy of the RF field, collisional absorption and Landau damping are taken into account. At each time step, Maxwell’s equations are solved for the current profiles of the plasma density and plasma temperature. The calculations are performed for a cylindrical plasma. The plasma is assumed to be axisymmetric and homogeneous along the plasma column. The system of balance equations is solved using the Crank-Nicholson scheme. Maxwell’s equations are solved in a one-dimensional approximation by using the Fourier transformation along the azimuthal and longitudinal coordinates. Results of simulations of RF plasma generation in the Uragan-2M stellarator by using a frame antenna operating at frequencies lower than the ion cyclotron frequency are presented. The calculations show that the slow wave generated by the antenna is efficiently absorbed at the periphery of the plasma column, due to which only a small fraction of the input power reaches the confinement region. As a result, the temperature on the axis of the plasma column remains low, whereas at the periphery it is substantially higher. This leads to strong absorption of the RF field at the periphery via the Landau mechanism.

Moiseenko, V. E., E-mail: moiseenk@ipp.kharkov.ua; Stadnik, Yu. S., E-mail: stadnikys@kipt.kharkov.ua [National Academy of Sciences of Ukraine, National Science Center Kharkov Institute of Physics and Technology (Ukraine); Lysoivan, A. I., E-mail: a.lyssoivan@fz-juelich.de [Royal Military Academy, EURATOM-Belgian State Association, Laboratory for Plasma Physics (Belgium); Korovin, V. B. [National Academy of Sciences of Ukraine, National Science Center Kharkov Institute of Physics and Technology (Ukraine)] [National Academy of Sciences of Ukraine, National Science Center Kharkov Institute of Physics and Technology (Ukraine)

2013-11-15

401

Endotoxin removal by radio frequency gas plasma (glow discharge)  

NASA Astrophysics Data System (ADS)

Contaminants remaining on implantable medical devices, even following sterilization, include dangerous fever-causing residues of the outer lipopolysaccharide-rich membranes of Gram-negative bacteria such as the common gut microorganism E. coli. The conventional method for endotoxin removal is by Food & Drug Administration (FDA)-recommended dry-heat depyrogenation at 250°C for at least 45 minutes, an excessively time-consuming high-temperature technique not suitable for low-melting or heat-distortable biomaterials. This investigation evaluated the mechanism by which E. coli endotoxin contamination can be eliminated from surfaces during ambient temperature single 3-minute to cumulative 15-minute exposures to radio-frequency glow discharge (RFGD)-generated residual room air plasmas activated at 0.1-0.2 torr in a 35MHz electrodeless chamber. The main analytical technique for retained pyrogenic bio-activity was the Kinetic Chromogenic Limulus Amebocyte Lysate (LAL) Assay, sufficiently sensitive to document compliance with FDA-required Endotoxin Unit (EU) titers less than 20 EU per medical device by optical detection of enzymatic color development corresponding to < 0.5 EU/ml in sterile water extracts of each device. The main analytical technique for identification of chemical compositions, amounts, and changes during sequential reference Endotoxin additions and subsequent RFGD-treatment removals from infrared (IR)-transparent germanium (Ge) prisms was Multiple Attenuated Internal Reflection (MAIR) infrared spectroscopy sensitive to even monolayer amounts of retained bio-contaminant. KimaxRTM 60 mm x 15 mm and 50mm x 15mm laboratory glass dishes and germanium internal reflection prisms were inoculated with E. coli bacterial endotoxin water suspensions at increments of 0.005, 0.05, 0.5, and 5 EU, and characterized by MAIR-IR spectroscopy of the dried residues on the Ge prisms and LAL Assay of sterile water extracts from both glass and Ge specimens. The Ge prism MAIR-IR measurements were repeated after employing 3-minute RFGD treatments sequentially for more than 10 cycles to observe removal of deposited matter that correlated with diminished EU titers. The results showed that 5 cycles, for a total exposure time of 15 minutes to low-temperature gas plasma, was sufficient to reduce endotoxin titers to below 0.05 EU/ml, and correlated with concurrent reduction of major endotoxin reference standard absorption bands at 3391 cm-1, 2887 cm-1, 1646 cm -1 1342 cm-1, and 1103 cm-1 to less than 0.05 Absorbance Units. Band depletion varied from 15% to 40% per 3-minute cycle of RFGD exposure, based on peak-to-peak analyses. In some cases, 100% of all applied biomass was removed within 5 sequential 3-minute RFGD cycles. The lipid ester absorption band expected at 1725 cm-1 was not detectable until after the first RFGD cycle, suggesting an unmasking of the actual bacterial endotoxin membrane induced within the gas plasma environment. Future work must determine the applicability of this low-temperature, quick depyrogenation process to medical devices of more complicated geometry than the flat surfaces tested here.

Poon, Angela

402

Radio frequency seismic gathering system employing an airborne blimp  

Microsoft Academic Search

The central station of a radio-connected seismic surveying system uses a tethered blimp carrying an antenna and an electronics package including a dc voltage\\/rf decoupler, a variable dc controlled preamplifier, a p-i-n diode switch for changing the antenna from receive to transmit operation, a transmitter and modulator and a battery. An rf coaxial cable to ground provides means for controlling

R. A. Imm; W. T. McDavid; J. M. Mckeever

1980-01-01

403

Radio frequency source power effect on silicon nitride films deposited by a room-temperature pulsed-PECVD  

Microsoft Academic Search

Silicon nitride (SiN) films deposited by using a pulsed-plasma enhanced chemical vapor deposition system at room temperature were investigated as a function of radio frequency source power and duty ratio in the experimental ranges of 200–800 W and 40–90%, respectively. Diagnostic parameters, measured using a non-invasive ion energy analyzer, were related to SiN deposition rate. Decreasing the source power increased high

Byungwhan Kim; Suyeon Kim

2009-01-01

404

A model of capacitively coupled radio-frequency methane\\/hydrogen plasmas for III-V semiconductor etching applications  

Microsoft Academic Search

A model has been developed which follows electrons and ions through assumed time varying potentials in a radio-frequency methane\\/hydrogen plasma. The system modelled is relevant to a low-pressure (10-90 mTorr) plasma used in the etching of GaAs surfaces. To understand the etching process, a knowledge of the flux and energy distributions of all species at the surface is required and

R. L. Layberry; Z. Wronski; C. G. Pearce; J. L. Sullivan

1999-01-01

405

Radio-frequency probes of Antarctic ice at South Pole  

NASA Astrophysics Data System (ADS)

Using hardware developed for the ARA (Askaryan Radio Array) particle astrophysics experiment, we herein report on the amplitude and temporal characteristics of polarized surface radar echo data collected in South Polar ice using radio sounding equipment with 0.5-ns echo-time sampling. We observe strong echoes at 6, 9.6, 13.9, 17, and 19 ?s following vertical pulse emission from the surface, corresponding to reflectors in the upper half of the ice sheet. The synchronicity of those echoes for all broadcast azimuthal polarizations affirms the lack of observable birefringence over the upper half of the ice sheet. Of the five strongest echoes, three exhibit an evident amplitude correlation with the local surface ice flow direction, qualitatively consistent with measurements in East Antarctica. Combined with other radio echo sounding data, we conclude that observed birefringent asymmetries at South Pole are generated entirely in the lower half of the ice sheet. By contrast, birefringent asymmetries are observed at shallow depths in East Antarctica.

Besson, D.; Kravchenko, I.

2013-05-01

406

Analysis of a discrete spectrum analyzer for the detection of radio frequency interference  

NASA Technical Reports Server (NTRS)

As the radio frequency spectrum becomes increasingly overcrowded, interference with mission-critical DSN operations is rising at an alarming rate. To alleviate this problem the DSN is developing a wideband surveillance system for on-site detection and identification of potential sources of radio frequency interference (RFI), which will complement the existing frequency coordination activities. The RFI monitoring system is based on a wideband, multi-look discrete spectrum analyzer operating on fast Fourier transform principles. An extensive general statistical analysis is presented of such spectrum analyzers and derives threshold detection performance formulas for signals of interest. These results are then applied to the design of the RFI spectrum analyzer under development.

Levitt, B. K.

1977-01-01

407

A low-power CMOS integrated circuit for field-powered radio frequency identification tags  

Microsoft Academic Search

Cheap, compact radio frequency identification (RFID) tags will make a wide range of new applications cost-effective. Minimum cost can be achieved only in a passive tag (that acquires operating power from the interrogating RF field). A compact tag form factor demands a small tag antenna, that in turn demands either external components or a high-frequency RF carrier for effective tag

D. Friedman; H. Heinreich; D.-W. Duan

1997-01-01

408

Analysis of Single Pulses from Radio Pulsars at High Observing Frequencies  

NASA Astrophysics Data System (ADS)

Single pulses from eight strong pulsars were studied for the drifting subpulse behaviour. The pulsars were observed at 8.35 GHz at 100-m Effelsberg radio telescope. For almost all the pulsars we identified the features corressponding to the frequencies reported at low observing frequencies.

Honnappa, S.; Kijak, J.; Lewandowski, W.

2012-12-01

409

A random access algorithm for frequency hopped spread spectrum packet radio networks  

Microsoft Academic Search

The authors consider packet radio multi-user spread-spectrum environments, where frequency hopping spread spectrum techniques are deployed for protection against intelligent adversaries. When the users in such environments are mobile and bursty, random access frequency hopping transmission algorithms should be adopted, for efficiency in throughput and delay control. This paper proposes and analyzes such an algorithm, named Collision Resolution Algorithm for

M. Georgiopoulos; P. Papantoni-Kazakos

1986-01-01

410

Deposition of vertically oriented carbon nanofibers in atmospheric pressure radio frequency discharge  

Microsoft Academic Search

Deposition of vertically oriented carbon nanofibers (CNFs) has been studied in an atmospheric pressure radio frequency discharge without dielectric barrier covering the metallic electrodes. When the frequency is sufficiently high so that ions reside in the gap for more than one rf cycle (``trapped ions''), the operating voltage decreases remarkably and the transition from a uniform glow discharge to an

Tomohiro Nozaki; Tomoya Goto; Ken Okazaki; Kuma Ohnishi; Lorenzo Mangolini; Joachim Heberlein; Uwe Kortshagen

2006-01-01

411

Broadband operation of a radio frequency spectrum analyzer based on spectral hole burning  

Microsoft Academic Search

Summary form only given. We recently demonstrated the principle of radio frequency spectrum analysis based on the engraving of multiple monochromatic gratings in a Spectral Hole Burning (SHB) material. This device is considered for applications in radar and sub-millimeter wave astronomy. In the first experiment, the frequency scanning procedure limited the bandwidth to 35 MHz. With a new broadband setup

I. Lorgere; V. Lavielle

2002-01-01

412

Exposure to radio frequency radiation emitted by cell phone and mortality in chick embryos (Gallus domesticus)  

Microsoft Academic Search

The rapidly increasing use of cell phones since late 1990s has caused a general concern on the possible hazardous health effects of exposure to radio frequency electro-magnetic radiation (EMR) emitted by them. While considering the bio- logical effects of EMR on the human body, its intensity, frequency of radiation and duration of exposure are important determinants. Many researchers have reported

I. V. Ingole; S. K. Ghosh

2006-01-01

413

Upgrade of the Westerbork synthesis radio telescope: The multi frequency front end  

Microsoft Academic Search

The performance of a novel front end system, the Multi Frequency Front End (MEFE), for use in a synthesis radio telescope is discussed. This front end covers 9 frequency bands in the range from 250 MHz to 8600 MHz. All receivers are based on the double superheterodyne principle. Each receiver has two channels which are connected to dual polarized feed

G H Tan

1996-01-01

414

Electrical Properties of Radio Frequency Glow Discharges in Air at Atmospheric Pressure.  

National Technical Information Service (NTIS)

Gas discharges maintained by radio frequency power were examined in the frequency range 1-25 Mc/s. The discharges were maintained in air at atmospheric pressure between water cooled metal electrodes. The discharges were made symmetric by using two electro...

H. A. Schwab

1967-01-01

415

Gas Breakdown of Radio Frequency Glow Discharges in Helium at near Atmospheric Pressure  

NASA Astrophysics Data System (ADS)

A one-dimensional self-consistent fluid model was developed for radio frequency glow discharge in helium at near atmospheric pressure, and was employed to study the gas breakdown characteristics in terms of breakdown voltage. The effective secondary electron emission coefficient and the effective electric field for ions were demonstrated to be important for determining the breakdown voltage of radio frequency glow discharge at near atmospheric pressure. The constant of A was estimated to be 64±4 cm-1Torr-1, which was proportional to the first Townsend coefficient and could be employed to evaluate the gas breakdown voltage. The reduction in the breakdown voltage of radio frequency glow discharge with excitation frequency was studied and attributed to the electron trapping effect in the discharge gap.

Liu, Xinkun; Xu, Jinzhou; Cui, Tongfei; Guo, Ying; Zhang, Jing; Shi, Jianjun

2013-07-01

416

Radio frequency interference mitigation with phase-only adaptive beam forming  

NASA Astrophysics Data System (ADS)

Connected radio interferometers are sometimes used in the tied array mode: signals from antenna elements are coherently added and the sum signal applied to a very long baseline interferometry (VLBI) back-end or pulsar-processing machine. Usually, there is no computer-controlled amplitude weighting in the existing radio interferometer facilities. Radio frequency interference (RFI) mitigation with phase-only adaptive beam forming is proposed for this mode of observation. Small phase perturbations are introduced in each of the antenna's signals. The values of these perturbations are optimized in such a way that the signal from a radio source of interest is preserved and RFI signals are suppressed. An evolutionary programming algorithm is used for this task. Computer simulations, made for both one-dimensional and two-dimensional array setups, show considerable suppression of RFI and acceptable changes to the main array beam in the radio source direction.

Fridman, P. A.

2005-05-01

417

Stabilization of predissociating nitric oxide Rydberg molecules using microwave and radio-frequency fields  

NASA Astrophysics Data System (ADS)

We present three techniques for suppressing predissociation of the nitric oxide Rydberg states normally excited in pulsed-field ionization zero-kinetic-energy photoelectron spectroscopy. By applying a combination of appropriate dc and microwave fields it is possible to inhibit predissociation by resonantly mixing Stark states of adjacent principal quantum number n, with similar parabolic quantum number k. Lifetime enhancement is also obtained by using an appropriate radio-frequency field to resonantly mix Stark states of the same n. Finally, in the absence of dc fields, microwaves are used to stabilize optically excited nf Rydberg states, by inducing transitions to higher angular momentum states with longer lifetimes, specifically to the n+/-1, l>=4 states.

Murgu, Elena; Martin, J. D. D.; Gallagher, T. F.

2001-10-01

418

Large radio-frequency gas catchers and the production of radioactive nuclear beams  

NASA Astrophysics Data System (ADS)

Gas catchers provide a means to transform radioactive recoils from various production mechanisms into low-energy beams of good ion optical properties. Recent developments with large radio-frequency gas catchers have pushed back purity and space-charge limitations in this technology to the point that it can now be used reliably for producing radioactive beams intense enough for various secondary experiments to be possible. The basic technology available and the current demonstrated capabilities are presented in the following. A number of examples of such systems currently under commissioning/construction/design at ANL to produce beams from fusion-evaporation, fission, deep-inelastic and fragmentation reaction products will also be presented together with the specific challenges to each approach and the chosen solutions.

Savard, Guy

2011-09-01

419

A novel global model for radio-frequency driven plasmas at atmospheric pressure  

NASA Astrophysics Data System (ADS)

Over the last years microplasma research gained a lot of attention both from an experimental and theoretical perspective. One particular type of microplasma sources that shows a variety of interesting physics and applications are the so called plasma jets. Besides the more elaborated fluid or hybrid approaches the so called global models offer the ability to explore averaged species densities and energies while remaining computationally efficient. This contribution investigates a coplanar radio-frequency driven plasma jet by means of a novel global model. The model takes into account the strong modulation of the electric field in time and space both in the sheath and bulk region. By means of a consistent scale analysis we find an analytical expression for the electric field. We compare our obtained electric field to results from PIC simulations and present the general concept for this novel global model of the microplasma jet.

Hemke, Torben; Mussenbrock, Thomas; Brinkmann, Ralf Peter

2012-10-01

420

Effects of reactor pressure on two-dimensional radio-frequency methane plasma: a numerical study  

NASA Astrophysics Data System (ADS)

A self-consistent two-dimensional radio-frequency glow discharge model has been developed for methane gas using a fluid model. The objective of the study is to provide insights into charged-species dynamics and investigate their effects on deposition in a polyatomic gas discharge. Swarm data as a function of electron energy are provided as input to the model. The necessary dc bias for the discharge is also predicted consistently such that the cycle-averaged current to the powered electrode becomes zero. The predictions provide a comprehensive understanding of the various processes in methane discharges found in plasma-assisted chemical vapour deposition (PACVD) reactors for the deposition of carbon films. The effects of discharge pressure on discharge variables are identified and presented in the paper.

Bera, K.; Farouk, B.; Lee, Y. H.

1999-08-01

421

Heat Transfer During Radio Frequency Inductively Coupled Plasma Deposition of Tungsten  

NASA Astrophysics Data System (ADS)

Particle melting and substrate temperature are important in controlling deposited density and residual stress in thermal plasma deposition of refractory materials. In this paper, both the heating and cooling behaviours of tungsten particles inside a radio frequency inductively coupled plasma (ICP) and the plasma heat flux to the substrate were investigated. The distribution of the plasma-generated heat on device, powder injection probe, deposition chamber, and substrate was determined by measuring the water flow rate and the flow-in and flow-out water temperatures in the four parts. Substrate temperature was measured by a two-colour pyrometer during the ICP deposition of tungsten. Experimental results show that the heat flux to the substrate accounts for about 20% of the total plasma energy, the substrate temperature can reach as high as 2100 K, and the heat loss by radiation is significant in the plasma deposition of tungsten.

Jiang, Xianliang; M, I. Boulos

2007-08-01

422

Proton Beam Verification using RF Power Measurement Data for a cw Radio Frequency Quadrupole LINAC  

SciTech Connect

A cw radio frequency quadrupole (RFQ) LINAC section and klystrode based rf system was obtained from the Chalk River Laboratories and was recommissioned at LANL to conduct demonstration proton beam experiments in support of a spallation neutron source driver for tritium production. A variation of the Low Energy Demonstration Accelerator (LEDA) proton injector, modified to operate at 50 keV, was mated to the RFQ and was operated to support the high current (up to 100 mA), proton beam advance studies for the Accelerator Production of Tritium (APT) program. Detailed measurements and calibrations of the RFQ at both low and high power provided the corroborating data to other available beam measurements for verification of the accelerator design.

Bolme, G.O.; Hardek, T.W.; Hansborough, L.D.; Hodgkins, D.J.; Keffeler, D.R.; Sherman, J.D.; Smith, H.V.; Stevens, R.R.; Young, L.M.; Zaugg, T.J.; Arvin, A.H.; Bolt, A.S.; Richards, M.C.; Balleyguier, P.P.; Kamperschroer, J.H.

1999-03-29

423

Calculated characteristics of radio-frequency plasma display panel cells including the influence of xenon metastables  

NASA Astrophysics Data System (ADS)

Although alternating-current plasma display panels (ac PDPs) are now produced by several companies, improvements are still necessary. In particular, the overall efficiency of the discharge in the standard configuration is low, on the order of 1 lm/W i.e., about 0.5% of the power dissipated in the discharge is transformed into useful visible photons. One way to substantially improve the efficiency of PDPs is to use radio-frequency (rf) excitation because, when compared to ac PDPs, less of the electrical energy input is dissipated by ions in the sheath and relatively more power is deposited in excitation of the xenon, which produces the ultraviolet photons used to excite the phosphors. In this article, we show calculated discharge characteristics for typical rf PDP conditions and pay particular attention to the role of the xenon metastable atoms in the ionization balance. Our discussion is limited to the sustaining regime, the ``on-state,'' of a PDP cell.

Pitchford, L. C.; Kang, J.; Punset, C.; Boeuf, J. P.

2002-12-01

424

High power water load for microwave and millimeter-wave radio frequency sources  

DOEpatents

A high power water load for microwave and millimeter wave radio frequency sources has a front wall including an input port for the application of RF power, a cylindrical dissipation cavity lined with a dissipating material having a thickness which varies with depth, and a rear wall including a rotating reflector for the reflection of wave energy inside the cylindrical cavity. The dissipation cavity includes a water jacket for removal of heat generated by the absorptive material coating the dissipation cavity, and this absorptive material has a thickness which is greater near the front wall than near the rear wall. Waves entering the cavity reflect from the rotating reflector, impinging and reflecting multiple times on the absorptive coating of the dissipation cavity, dissipating equal amounts of power on each internal reflection.

Ives, R. Lawrence (Saratoga, CA); Mizuhara, Yosuke M. (Palo Alto, CA); Schumacher, Richard V. (Sunnyvale, CA); Pendleton, Rand P. (Saratoga, CA)

1999-01-01

425

Offset, tilted dipole models of Uranian smooth high-frequency radio emission  

NASA Technical Reports Server (NTRS)

The smooth high-frequency (SHF) component of the radio emission detected during the Voyager 2 encounter with Uranus (January 1986) is studied. An offset tilted dipole (OTD) investigation of the SHF emission at L shells is carried out within the range of the bursty source locations. A viable high L shell model is presented. It is suggested that Miranda, which reaches a minimum L shell at L = 5, may be related to the timing of several types of radio emissions.

Schweitzer, Andrea E.; Romig, Joseph H.; Evans, David R.; Sawyer, Constance B.; Warwick, James W.

1990-01-01

426

Offset, tilted dipole models of Uranian smooth high-frequency radio emission  

NASA Astrophysics Data System (ADS)

The smooth high-frequency (SHF) component of the radio emission detected during the Voyager 2 encounter with Uranus (January 1986) is studied. An offset tilted dipole (OTD) investigation of the SHF emission at L shells is carried out within the range of the bursty source locations. A viable high L shell model is presented. It is suggested that Miranda, which reaches a minimum L shell at L = 5, may be related to the timing of several types of radio emissions.

Schweitzer, Andrea E.; Romig, Joseph H.; Evans, David R.; Sawyer, Constance B.; Warwick, James W.

1990-09-01

427

Frequency effects on the electron density and {alpha}-{gamma} mode transition in atmospheric radio frequency discharges  

SciTech Connect

In this paper, a one-dimensional model is explored to investigate the frequency effects on the characteristics of atmospheric radio frequency discharges at a given power. The simulation data and analytical results show that the improvement of electron density can be observed with better discharge stability by increasing excitation frequency in an appropriate range. Using the analytical equations deduced from the model, the mean electron density could be inferred by means of the measured parameters. The {alpha}-{gamma} mode transition especially in high frequency discharges is also analytically discussed based on the theoretical equations.

Zhang Yuantao [Shandong Provincial Key Lab of UHV Technology and Gas Discharge Physics, School of Electrical Engineering, Shandong University, Jinan, Shandong Province 250061 (China); Cui Shaoyan [School of Mathematics and Information, Ludong University, Yantai, Shandong Province 264025 (China)

2011-08-15

428

Radio frequency science considerations. [technology utilization of telecommunications system  

NASA Technical Reports Server (NTRS)

Use of the 400 MHz telecommunications system to obtain scientific information, to provide backup information for the experiments flown, and to obtain measurements which aid in designing future probes is considered. Recommended objectives of such a program are summarized and include: measure 400 MHz amplitude to determine adsorption and perhaps scintillation (if data rate permits); measure noise strength near 400 MHz to reexamine 400 MHz choice and to observe thermal, cosmic, and local synchrotron noise trends; probe VSWR sensing to monitor integrity of system, icing, and possible plasma effects; after the probe is finished, have the bus radio occultation in the same region where the probe fell to evaluate the occultation.

Croft, T. A.

1974-01-01

429

Correction to `Packet error probabilities in frequency hopped spread-spectrum packet radio networks-memoryless frequency hopping patterns considered'  

Microsoft Academic Search

The author corrects the approach followed in the above-titled paper (see ibid., vol.36, no.6, p.720-3, 1988) to compute packet error probabilities in frequency-hopped spread-spectrum packet radio networks with memoryless frequency-hopping patterns. The nature of the error is that the sequence of symbol errors is not Markov, so that a formula which is instrumental for the computation of packet error probabilities,

M. Georgiopoulos

1991-01-01

430

Optical fiber sensor based on a radio frequency Mach-Zehnder interferometer.  

PubMed

This Letter proposes an optical fiber radio frequency (RF) Mach-Zehnder interferometer (MZI) for sensing applications. An RF modulated laser source is injected into an optical fiber RF-MZI and collected by a photodiode. The interference pattern is observed in the RF domain by sweeping the frequency using a network analyzer. The proposed sensor has a linear response to applied temperature change. In addition, the sensitivity, observation frequency range, and the length of the sensing arm are discussed. PMID:22344135

Wei, Tao; Huang, Jie; Lan, Xinwei; Han, Qun; Xiao, Hai

2012-02-15

431

Tunable Atomic Magnetometer for Detection of Radio-Frequency Magnetic Fields  

Microsoft Academic Search

We describe an alkali-metal magnetometer for detection of weak magnetic fields in the radio-frequency (rf) range. High sensitivity is achieved by tuning the Zeeman resonance of alkali atoms to the rf frequency and partially suppressing spin-exchange collisions in the alkali-metal vapor. We demonstrate magnetic field sensitivity of 2 fT\\/Hz¹² at a frequency of 99 kHz with a resonance width of

I. M. Savukov; S. J. Seltzer; M. V. Romalis; K. L. Sauer

2005-01-01

432

Tunable Atomic Magnetometer for Detection of Radio-Frequency Magnetic Fields  

Microsoft Academic Search

We describe an alkali-metal magnetometer for detection of weak magnetic fields in the radio-frequency (rf) range. High sensitivity is achieved by tuning the Zeeman resonance of alkali atoms to the rf frequency and partially suppressing spin-exchange collisions in the alkali-metal vapor. We demonstrate magnetic field sensitivity of 2 fT\\/Hz1\\/2 at a frequency of 99 kHz with a resonance width of

I. M. Savukov; S. J. Seltzer; M. V. Romalis; K. L. Sauer

2005-01-01

433

A review of organizations influencing radio frequency allocations to deep space research  

NASA Technical Reports Server (NTRS)

The charters and functions of various national and international scientific organizations were examined to identify those which have a direct or indirect influence on the allocation of radio frequencies for use in deep space research. Those organizations identified as having the ability to influence frequency allocations are described. A brief description of each organization is provided, and the members who are influential specifically in frequency allocations are listed. The interrelations between the organizations and how they influence allocations are explained.

1976-01-01

434

Non-detection at Venus of high-frequency radio signals characteristic of terrestrial lightning.  

PubMed

The detection of impulsive low-frequency (10 to 80 kHz) radio signals, and separate very-low-frequency (approximately 100 Hz) radio 'whistler' signals provided the first evidence for lightning in the atmosphere of Venus. Later, a small number of impulsive high-frequency (100 kHz to 5.6 MHz) radio signals, possibly due to lightning, were also detected. The existence of lightning at Venus has, however, remained controversial. Here we report the results of a search for high-frequency (0.125 to 16 MHz) radio signals during two close fly-bys of Venus by the Cassini spacecraft. Such signals are characteristic of terrestrial lightning, and are commonly heard on AM (amplitude-modulated) radios during thunderstorms. Although the instrument easily detected signals from terrestrial lightning during a later fly-by of Earth (at a global flash rate estimated to be 70 s(-1), which is consistent with the rate expected for terrestrial lightning), no similar signals were detected from Venus. If lightning exists in the venusian atmosphere, it is either extremely rare, or very different from terrestrial lightning. PMID:11201733

Gurnett, D A; Zarka, P; Manning, R; Kurth, W S; Hospodarsky, G B; Averkamp, T F; Kaiser, M L; Farrell, W M

2001-01-18

435

Measurements of time average series resonance effect in capacitively coupled radio frequency discharge plasma  

SciTech Connect

Self-excited plasma series resonance is observed in low pressure capacitvely coupled radio frequency discharges as high-frequency oscillations superimposed on the normal radio frequency current. This high-frequency contribution to the radio frequency current is generated by a series resonance between the capacitive sheath and the inductive and resistive bulk plasma. In this report, we present an experimental method to measure the plasma series resonance in a capacitively coupled radio frequency argon plasma by modifying the homogeneous discharge model. The homogeneous discharge model is modified by introducing a correction factor to the plasma resistance. Plasma parameters are also calculated by considering the plasma series resonances effect. Experimental measurements show that the self-excitation of the plasma series resonance, which arises in capacitive discharge due to the nonlinear interaction of plasma bulk and sheath, significantly enhances both the Ohmic and stochastic heating. The experimentally measured total dissipation, which is the sum of the Ohmic and stochastic heating, is found to increase significantly with decreasing pressure.

Bora, B.; Bhuyan, H.; Favre, M.; Wyndham, E.; Chuaqui, H. [Facultad de Fisica, Pontificia Universidad Catolica de Chile, Ave. Vicuna Mackenna 4860, Santiago 22 (Chile); Kakati, M. [Thermal Plasma Processed Materials Laboratory, Centre of Plasma Physics, Institute for Plasma Research, Sonapur 782 402, Assam (India)

2011-10-15

436

Radio frequency controlled synthetic wavelength sweep for absolute distance measurement by optical interferometry  

SciTech Connect

We present a new technique applied to the variable optical synthetic wavelength generation in optical interferometry. It consists of a chain of optical injection locking among three lasers: first a distributed-feedback laser is used as a master to injection lock an intensity-modulated laser that is directly modulated around 15 GHz by a radio frequency generator on a sideband. A second distributed-feedback laser is injection locked on another sideband of the intensity-modulated laser. The variable synthetic wavelength for absolute distance measurement is simply generated by sweeping the radio frequency over a range of several hundred megahertz, which corresponds to the locking range of the two slave lasers. In this condition, the uncertainty of the variable synthetic wavelength is equivalent to the radio frequency uncertainty. This latter has a relative accuracy of 10{sup -7} or better, resulting in a resolution of {+-}25 {mu}m for distances exceeding tens of meters. The radio frequency generator produces a linear frequency sweep of 1 ms duration (i.e., exactly equal to one absolute distance measurement acquisition time), with frequency steps of about 1 MHz. Finally, results of absolute distance measurements for ranges up to 10 m are presented.

Le Floch, Sebastien; Salvade, Yves; Mitouassiwou, Rostand; Favre, Patrick

2008-06-01

437

Propagation of Radio Frequency Waves in a Weakly Ionized Gas  

NASA Astrophysics Data System (ADS)

Long distance communication and diagnostics of the space environment rely on an understanding of the refraction, phase alteration and attenuation of electromagnetic waves in the ionosphere and plasmasphere. The nature of wave propagation in a spatially inhomogeneous plasma was explored using a numerical implementation of the eikonal approach(L. D. Landau and E. M. Lifshitz, Electrodynamics of Continuous Media), (Pergamon Press 1960), pp. 269-279. . The calculation was validated by comparing numerical results with analytic solutions( K. G. Budden, Radio Waves In the Ionosphere), (Cambridge University Press, 1966), pp. 179-182. for a horizontally stratified plasma with linear and exponential variations in the density. The treatment was extended to treat arbitrary plasma distributions. Ray trajectories and attentuation are presented for typical ionospheric profiles, exhibiting non-monotonic density variations, and profiles associated with a plasma generated by injection of a relativistic electron beam. USE ONLY)

Lockwood, Nathaniel P.; Bailey, Wm. F.

2000-10-01

438

Single shot time stamping of ultrabright radio frequency compressed electron pulses  

SciTech Connect

We demonstrate a method of time-stamping Radio Frequency compressed electron bunches for Ultrafast Electron Diffraction experiments in the sub-pC regime. We use an in-situ ultra-stable photo-triggered streak camera to directly track the time of arrival of each electron pulse and correct for the timing jitter in the radio frequency synchronization. We show that we can correct for timing jitter down to 30 fs root-mean-square with minimal distortion to the diffraction patterns, and performed a proof-of-principle experiment by measuring the ultrafast electron-phonon coupling dynamics of silicon.

Gao, M.; Dwayne Miller, R. J. [Department of Chemistry and Physics, University of Toronto, Toronto, ON. M5S 3H6 (Canada); Max Planck Research Department for Structural Dynamics, Department of Physics, Center for Free Electron Laser Science, University of Hamburg, DESY, D-22607 Hamburg (Germany); Jiang, Y.; Kassier, G. H. [Max Planck Research Department for Structural Dynamics, Department of Physics, Center for Free Electron Laser Science, University of Hamburg, DESY, D-22607 Hamburg (Germany)

2013-07-15

439

Radio frequency operation of clocked quantum-dot cellular automata latch  

NASA Astrophysics Data System (ADS)

The radio frequency operation of a single-electron latch based on Al-AlOx-Al tunnel junctions is presented. By capacitively coupling the latch to a radio frequency single electron transistor, charge switching on the microsecond timescale is demonstrated. The fast switching and high repeatability of the latch response indicates that high speed operation of pipelines, signal fan-outs, and more complex logic devices are possible with this technology. The experimental technique developed is also promising for enabling the investigation of the intrinsic switching speed in electronic quantum-dot cellular automata-based circuits.

Tang, Yong; Orlov, Alexei O.; Snider, Gregory L.; Fay, Patrick J.

2009-11-01

440

Routing in frequency-hop packet radio networks with partial-band jamming  

NASA Astrophysics Data System (ADS)

This paper describes research in adaptive, decentralized routing for frequency-hop packet radio networks with mobile partial-band jamming. A new routing technique, called least-resistance routing (LRR) is developed, and various versions of this routing method are examined. LRR uses a quantitative assessment of the interference environment experienced by a radio's receiver to determine a resistance value for that radio. Two components for the interference environment are considered: transmissions from other radios and partial-band jamming. The resistances for each of the radios in a particular path are combined to form the path resistance, and packets are forwarded on the path with the smallest resistance. Comparisons are made between different versions of LRR and between LRR and previously developed adaptive routing techniques. It is found that LRR is an effective way for dealing with mobile jamming in a frequency-hop packet radio network. Significant increases in throughput and end-to-end probability of success are obtained by use of LRR.

Pursley, Michael B.; Russell, Harlan B.

1993-07-01

441

A COMBINED LOW-RADIO FREQUENCY/X-RAY STUDY OF GALAXY GROUPS. I. GIANT METREWAVE RADIO TELESCOPE OBSERVATIONS AT 235 MHz AND 610 MHz  

SciTech Connect

We present new Giant Metrewave Radio Telescope observations at 235 MHz and 610 MHz of 18 X-ray bright galaxy groups. These observations are part of an extended project, presented here and in future papers, which combines low-frequency radio and X-ray data to investigate the interaction between central active galactic nuclei (AGNs) and the intra-group medium (IGM). The radio images show a very diverse population of group-central radio sources, varying widely in size, power, morphology, and spectral index. Comparison of the radio images with Chandra and XMM-Newton X-ray images shows that groups with significant substructure in the X-ray band and marginal radio emission at {approx}>1 GHz host low-frequency radio structures that correlate with substructures in IGM. Radio-filled X-ray cavities, the most evident form of AGN/IGM interaction in our sample, are found in half of the systems and are typically associated with small, low-, or mid-power double radio sources. Two systems, NGC5044 and NGC4636, possess multiple cavities, which are isotropically distributed around the group center, possibly due to group weather. In other systems the radio/X-ray correlations are less evident. However, the AGN/IGM interaction can manifest itself through the effects of the high-pressure medium on the morphology, spectral properties, and evolution of the radio-emitting plasma. In particular, the IGM can confine fading radio lobes in old/dying radio galaxies and prevent them from dissipating quickly. Evidence for radio emission produced by former outbursts that co-exist with current activity is found in six groups of the sample.

Giacintucci, Simona [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); O'Sullivan, Ewan; Vrtilek, Jan; David, Laurence P.; Mazzotta, Pasquale; Gitti, Myriam; Jones, Christine; Forman, William R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Raychaudhury, Somak; Ponman, Trevor [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Venturi, Tiziana [INAF-Istituto di Radioastronomia, via Gobetti 101, I-40129, Bologna (Italy); Athreya, Ramana M. [IISER, Pune, Maharashtra 411 008 (India); Clarke, Tracy E. [Naval Research Laboratory, 4555 Overlook Avenue SW, Code 7213, Washington, DC 20375 (United States); Murgia, Matteo [INAF-Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, I-09012 Capoterra (Italy); Ishwara-Chandra, C. H., E-mail: simona@astro.umd.edu [National Centre for Radio Astrophysics, TIFR, Post Bag No. 3, Ganeshkhind, Pune 411 007 (India)

2011-05-10

442

Radio frequency studies in the NASA Lewis Bumpy Torus  

NASA Technical Reports Server (NTRS)

The fluctuations in potential of the plasma in the NASA Lewis Bumpy Torus are observed using capacitive probes over frequencies from 1 kHz to 25 MHz and a wide range of operating conditions. The spectra are found to differ greatly above and below a background gas pressure of .000034 torr deuterium. Above this pressure, the spectrum is dominated by the ion spoke frequency and a spectral index may be defined. Below this pressure, the spectrum below 200 kHz is lower in amplitude by a factor of ten and no spectral index can be defined. At these lower pressures, fluctuations appearing to be ion spokes are observed, but have a dependence of frequency on operating conditions which is previously unreported.

Gerdin, G. A.

1974-01-01

443

Interpreting the low-frequency radio spectra of starburst galaxies: a pudding of Strömgren spheres  

NASA Astrophysics Data System (ADS)

The low-frequency radio emission of starburst galaxies is informative, but it can be absorbed in several ways. Most importantly, starburst galaxies are home to many H II regions, whose free-free absorption blocks low-frequency radio waves. These H II regions are discrete objects, but most multiwavelength models of starbursts assume a uniform medium of ionized gas, if they include the absorption at all. I calculate the effective absorption coefficient of H II regions in starbursts, which is ultimately a cross-section times the density of H II regions. The cross-sections are calculated by assuming that H II regions are Strömgren spheres. The coefficient asymptotes to a constant value at low frequencies, because H II regions partially cover the starburst and are buried part way into the starburst's synchrotron-emitting material. Considering Strömgren spheres around either OB stars or Super Star Clusters, I demonstrate the method by fitting to the low-frequency radio spectrum of M82. I discuss implications of the results for synchrotron spectrum shape, H II region pressure and free-free emission as a star formation rate indicator. However, these results are preliminary and could be affected by systematics. I argue that there is no volume-filling warm ionized medium in starbursts and that H II regions may be the most important absorption process down to ˜10 MHz. Future data at low and high radio frequency will improve our knowledge of the ionized gas.

Lacki, Brian C.

2013-06-01

444

Network protocols for frequency-hop packet radios with decoder side information  

NASA Astrophysics Data System (ADS)

Reliable data distribution within spread-spectrum packet radio networks requires high performance from the network protocols. This paper describes research in forwarding and routing protocols that are designed specifically for slow-frequency hop (SFH) packet radio networks in which some of the radios are subjected to excessive interference. It is shown that information extracted from the decoder can be used to aid the network protocols. New metrics are introduced that use this information to give a quantitative assessment of the interference environment experienced by the receiver in an SFH radio. Forwarding protocols are developed that can react quickly to local sources of interference, and the metrics that are introduced permit the routing algorithm to react to changes in the interference conditions in the network.

Pursley, Michael B.; Russell, Harlan B.

1994-05-01

445

Deriving Kinetic Luminosity Functions from the Low-Frequency Radio Luminosity Functions of FRII Sources  

NASA Astrophysics Data System (ADS)

FRII radio galaxies are relatively simple systems which can be used to determine the influence of jets on their environments. Even simple analytical models of FRII evolution can link the observed lobe luminosities and sizes to fundamental properties such as jet power and density of the ambient medium; these are crucial for understanding AGN feedback. However, due to strong flux selection effects interpreting FRII samples is not straightforward. To overcome this problem we construct Monte Carlo simulations to create artificial samples of radio galaxies. We explore jet power and external density distributions by using them as the simulation input parameters. Further, we compute radio luminosity functions (RLF) and fit them to the observed low-frequency radio data that cover redshifts up to z 2, which gives us the most plausible distributions of FRIIs' fundamental properties. Moreover, based on these RLFs, we obtain the kinetic luminosity functions of these powerful sources.

Kapinska, Anna D.; Uttley, P.; Kaiser, C. R.

2010-02-01

446

Enhanced pulsar and single pulse detection via automated radio frequency interference detection in multipixel feeds  

NASA Astrophysics Data System (ADS)

Single pixel feeds on large aperture radio telescopes have the ability to detect weak (˜10 mJy) impulsive bursts of radio emission and sub-mJy radio pulsars. Unfortunately, in large-scale blind surveys, radio frequency interference (RFI) mimics both radio bursts and radio pulsars, greatly reducing the sensitivity to new discoveries as real signals of astronomical origin get lost among the millions of false candidates. In this paper a technique that takes advantage of multipixel feeds to use eigenvector decomposition of common signals is used to greatly facilitate radio burst and pulsar discovery. Since the majority of RFI occurs with zero dispersion, the method was tested on the total power present in the 13 beams of the Parkes multibeam receiver using data from archival intermediate-latitude surveys. The implementation of this method greatly reduced the number of false candidates and led to the discovery of one new rotating radio transient or RRAT, six new pulsars and five new pulses that shared the swept-frequency characteristics similar in nature to the `Lorimer burst'. These five new signals occurred within minutes of 11 previous detections of a similar type. When viewed together, they display temporal characteristics related to integer seconds, with non-random distributions and characteristic 'gaps' between them, suggesting they are not from a naturally occurring source. Despite the success in removing RFI, false candidates present in the data that are only visible after integrating in time or at non-zero dispersion remained. It is demonstrated that with some computational penalty, the method can be applied iteratively at all trial dispersions and time resolutions to remove the vast majority of spurious candidates.

Kocz, J.; Bailes, M.; Barnes, D.; Burke-Spolaor, S.; Levin, L.

2012-02-01

447

An ASIC for transponder for radio frequency identification system  

Microsoft Academic Search

Presented is a novel and effective design of a batteryless, self-powered RFID transponder. It is compatible with the TIRIS, the popular RFID system by the Texas Instruments. Data transmission uses FSK modulation and the circuit is designed such that the output frequencies are implicitly determined, independent of the load of the antenna. The major part of the design uses digital

Sau-Mou Wu; Jeng-Rern Yang; Tzen-Yi Liu

1996-01-01

448

Radio frequency seismic gathering system employing an airborne blimp  

SciTech Connect

The central station of a radio-connected seismic surveying system uses a tethered blimp carrying an antenna and an electronics package including a dc voltage/rf decoupler, a variable dc controlled preamplifier, a p-i-n diode switch for changing the antenna from receive to transmit operation, a transmitter and modulator and a battery. An rf coaxial cable to ground provides means for controlling the preamplifier gain and for switching the central station to the transmit mode by using appropriate dc signals. In the receive mode, the cable carries detected field unit seismic signals, which are detected by the blimp-carried antenna and preamplified by the blimp preamplifier, to the ground for suitable recording and further processing in the ground portion of the central station. An audio channel can also be modulated onto the transmit carrier of approximately 70 mhz to provide voice communications via the blimp electronics, if desired. Both the ground portion and the blimp portion of the central station are packaged for helicopter transporting.

Imm, R.A.; McDavid, W.T.; Mckeever, J.M.

1980-11-25

449

High Frequency Radio Recombination Lines in Starburst Galaxies  

NASA Astrophysics Data System (ADS)

The observation of radio recombination lines (RRL) over a wide range of quantum levels gives valuable information on the physical state of the ionized gas. With the sensitivity of the existing radiotelescopes, at long as well as at short wavelengths, only less than 10 galaxies have been detected. The most distant galaxy detected so far is the starburst galaxy Arp 220. The remarkable feature in observing millimeter RRLs is that they allow to probe high density regions although this represent only a small fraction of the total mass of ionized gas. Starburst nuclei are heavily obscured in the visible but also in the near infrared, RRLs offer probably the unique tool to measure recent star formation rate (SFR). Centimeter lines can be used to determine the average SFR on a time scale of ~ 5 106 years while the millimeter lines offer the access to the very instantaneous SFR rate ( ~105 years). The total infrared luminosity is related to the average SFR on longer time scales, a few 107 years. Hence a multi-wavelength approach gives informations about the star formation history. Some recent results are presented. They illustrate the potentiality of ALMA which will have the sensitivity to detect a large number of galaxies and at much larger distances.

Viallefond, François; Anantharamiah, K. R.

1999-10-01

450

The Murchison Widefield Array: The Square Kilometre Array Precursor at Low Radio Frequencies  

NASA Astrophysics Data System (ADS)

The Murchison Widefield Array (MWA) is one of three Square Kilometre Array Precursor telescopes and is located at the Murchison Radio-astronomy Observatory in the Murchison Shire of the mid-west of Western Australia, a location chosen for its extremely low levels of radio frequency interference. The MWA operates at low radio frequencies, 80-300 MHz, with a processed bandwidth of 30.72 MHz for both linear polarisations, and consists of 128 aperture arrays (known as tiles) distributed over a ~3-km diameter area. Novel hybrid hardware/software correlation and a real-time imaging and calibration systems comprise the MWA signal processi