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1

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

2

Microminiature radio frequency transmitter for communication and tracking applications  

NASA Astrophysics Data System (ADS)

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

Crutcher, Richard I.; Emery, Mike S.; Falter, Kelly G.; Nowlin, C. H.; Rochelle, Jim M.; Clonts, Lloyd G.

1997-02-01

3

Impact of Mobile Transmitter Sources on Radio Frequency Wireless Energy Harvesting  

E-print Network

1 Impact of Mobile Transmitter Sources on Radio Frequency Wireless Energy Harvesting Antonio Organization, Tata Consultancy Services, India. Abstract--Wireless energy harvesting sensor networks consti battery resource, but are able to re-charge themselves through directed electromagnetic energy transfer

Sanyal, Sugata

4

Low Power Radio Transmitters for Broadcasting  

Microsoft Academic Search

This paper discusses the place of low powered installations in the existing radio broadcast system, and the importance of apparatus for such stations meeting the present-day requirements pertaining to frequency stability, modulation capability, fidelity, and radio-frequency harmonics. The characteristics and more interesting features of a new line of transmitters covering the range of output from 100 to 1000 watts are

A. W. Kishpaugh; R. E. Coram

1933-01-01

5

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

6

LOW POWER RADIO TRANSMITTER  

Microsoft Academic Search

A transmitter consisting of a volt- age controlled oscillator (VCO) and power ampli- fier (PA) for the 400 MHz Medical Implanted Com- munication System band (MICS) was built in a stan- dard 0.35-µm CMOS process. A push pull archi- tecture was used for both the VCO and the PA. Two off-chip inductors were needed. The design was optimized for 400

Johan Wernehag; Henrik Sjoland

7

TAIL-MOUNTED RADIO TRANSMITTERS FOR WATERFOWL  

Microsoft Academic Search

We successfully tested tail-mounted radio transmitters on Pink-footed Geese (Anser brachyrhynchus), Barnacle Geese (Branta leucopsis), Brant (Branta bernicla) and Eur- asian Wigeon (Anas penelope). The range of detection of the transmitters was approximately 1 km and some birds were tracked for up to 4 mo. Movements and activity of the birds were not affected by the packages. We conclude that

JEAN-FRANCOIS GIROUX; DAVID V. BELL; STEVE PERCIVAL; RON W. SUMMERS

8

Radio transmitter energy recovery system  

SciTech Connect

An am transmitter includes an rf signal generator and a switching-type rf signal amplifier. The rf amplifier output depends upon the energizing voltage applied thereacross, so it acts as a modulator. The energizing voltage is produced by a high -power audio amplifier which includes a pulse-width modulator driving a high-power audio switch. The switch terminals are coupled in series with an audio-frequency filter, energizing terminals of the rf amplifier and a source of direct energizing potential, for varying the voltage across the rf amplifier at an audio rate in response to the duty cycle of the width-modulated pulses for audio modulating the rf carrier. In order to reduce modulation distortion at low duty cycles resulting from the finite turn-on and turn-off time of the audio switch, an offset voltage generator is coupled to the filter by a diode. Energy stored in inductive components of the filter cause a voltage pulse during each turn-off of the audio switch. The voltage pulse is coupled to the offset voltage generator by the diode, and the voltage at the filter is maintained at the offset voltage while current flows in the offset voltage generator and the inductors lose energy. The offset generator includes a capacitor for storing energy resulting from the current flow in the inductor. A dc to ac inverter is coupled to the capacitor and generates alternating voltage. The ac is rectified and a pulsating direct current is coupled to the energizing source for recovering the energy in the inductive pulse.

Wolf, R.E.

1982-03-09

9

A radio transmitter attachment technique for soras  

USGS Publications Warehouse

We modified a figure-8 leg-loop harness designed for small passerines to attach successfully 1.8-g radio transmitters over the synsacrum of migrant Soras (Porzana carolina). Because of the short caudal region of Soras, addition of a waist loop was critical to securing the transmitter while leg loops were maintained to center the package. Thin gauge (0.6-mm diameter) elastic thread proved ideal for transmitter attachment and allowed for freedom of movement and girth expansion associated with fattening during a 6-10 week stopover. Of 110 Soras radio tagged during three field seasons, only a single mortality was observed and only a single bird lost its transmitter. Migration from the study area was confirmed for 76 (69%) and suspected for another 25 birds (total 92%).

Haramis, G.M.; Kearns, G.D.

2000-01-01

10

47 CFR 95.625 - CB transmitter channel frequencies.  

Code of Federal Regulations, 2010 CFR

... false CB transmitter channel frequencies. 95.625...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED...625 CB transmitter channel frequencies. (a) The CB transmitter channel frequencies are:...

2010-10-01

11

47 CFR 95.621 - GMRS transmitter channel frequencies.  

Code of Federal Regulations, 2010 CFR

...false GMRS transmitter channel frequencies. 95.621...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED...621 GMRS transmitter channel frequencies. (a) The GMRS transmitter channel frequencies...

2010-10-01

12

Exposure to radio-frequency electromagnetic fields from broadcast transmitters and risk of childhood cancer: a census-based cohort study.  

PubMed

We investigated the association between exposure to radio-frequency electromagnetic fields (RF-EMFs) from broadcast transmitters and childhood cancer. First, we conducted a time-to-event analysis including children under age 16 years living in Switzerland on December 5, 2000. Follow-up lasted until December 31, 2008. Second, all children living in Switzerland for some time between 1985 and 2008 were included in an incidence density cohort. RF-EMF exposure from broadcast transmitters was modeled. Based on 997 cancer cases, adjusted hazard ratios in the time-to-event analysis for the highest exposure category (>0.2 V/m) as compared with the reference category (<0.05 V/m) were 1.03 (95% confidence interval (CI): 0.74, 1.43) for all cancers, 0.55 (95% CI: 0.26, 1.19) for childhood leukemia, and 1.68 (95% CI: 0.98, 2.91) for childhood central nervous system (CNS) tumors. Results of the incidence density analysis, based on 4,246 cancer cases, were similar for all types of cancer and leukemia but did not indicate a CNS tumor risk (incidence rate ratio = 1.03, 95% CI: 0.73, 1.46). This large census-based cohort study did not suggest an association between predicted RF-EMF exposure from broadcasting and childhood leukemia. Results for CNS tumors were less consistent, but the most comprehensive analysis did not suggest an association. PMID:24651167

Hauri, Dimitri D; Spycher, Ben; Huss, Anke; Zimmermann, Frank; Grotzer, Michael; von der Weid, Nicolas; Spoerri, Adrian; Kuehni, Claudia E; Röösli, Martin

2014-04-01

13

Automatic frequency control for FM transmitter  

NASA Technical Reports Server (NTRS)

An automatic frequency control circuit for an FM television transmitter is described. The frequency of the transmitter is sampled during what is termed the back porch portion of the horizontal synchronizing pulse which occurs during the retrace interval, the frequency sample compared with the frequency of a reference oscillator, and a correction applied to the frequency of the transmitter during this portion of the retrace interval.

Honnell, M. A. (inventor)

1974-01-01

14

Radio frequency power load and associated method  

NASA Technical Reports Server (NTRS)

A radio frequency power load and associated method. A radio frequency power load apparatus includes a container and a fluid having an ion source therein, the fluid being contained in the container. Two conductors are immersed in the fluid. A radio frequency transmission system includes a radio frequency transmitter, a radio frequency amplifier connected to the transmitter and a radio frequency power load apparatus connected to the amplifier. The apparatus includes a fluid having an ion source therein, and two conductors immersed in the fluid. A method of dissipating power generated by a radio frequency transmission system includes the steps of: immersing two conductors of a radio frequency power load apparatus in a fluid having an ion source therein; and connecting the apparatus to an amplifier of the transmission system.

Sims, III, William Herbert (Inventor); Chavers, Donald Gregory (Inventor); Richeson, James J. (Inventor)

2010-01-01

15

47 CFR 95.629 - LPRS transmitter frequencies.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false LPRS transmitter frequencies. 95.629 Section 95.629 Telecommunication...Standards § 95.629 LPRS transmitter frequencies. (a) LPRS transmitters may operate on any frequency listed in paragraphs...

2013-10-01

16

47 CFR 95.629 - LPRS transmitter frequencies.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false LPRS transmitter frequencies. 95.629 Section 95.629 Telecommunication...Standards § 95.629 LPRS transmitter frequencies. (a) LPRS transmitters may operate on any frequency listed in paragraphs...

2012-10-01

17

47 CFR 95.629 - LPRS transmitter frequencies.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false LPRS transmitter frequencies. 95.629 Section 95.629 Telecommunication...Standards § 95.629 LPRS transmitter frequencies. (a) LPRS transmitters may operate on any frequency listed in paragraphs...

2010-10-01

18

47 CFR 95.629 - LPRS transmitter frequencies.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false LPRS transmitter frequencies. 95.629 Section 95.629 Telecommunication...Standards § 95.629 LPRS transmitter frequencies. (a) LPRS transmitters may operate on any frequency listed in paragraphs...

2011-10-01

19

47 CFR 80.209 - Transmitter frequency tolerances.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Transmitter frequency tolerances. 80.209 Section 80.209...Technical Standards § 80.209 Transmitter frequency tolerances. (a) The frequency tolerance requirements applicable to...

2013-10-01

20

Solar radio-transmitters on snail kites in Florida  

USGS Publications Warehouse

The effectiveness and safety of one- and two-stage solar radio-transmitters in tracking the movements and survival of adult and fledgling Snail Kites (Rostrhamus sociabilis) were evaluated between 1979 and 1983 in southern Florida. Transmitters were attached to birds with back-pack arrangements using teflon ribbon straps. Accessory plastic shields minimized feather coverage of the solar cells. Intact transmitters were seen on birds up to 47 mo after installation. Operating lives ranged from 8 to 21 mo for one-stage, and 10 to 14 mo for two-stage transmitters. Because survival of adult and nestling radio-marked kites was high, we conclude that our transmitter-attachment method had little effect on the birds.

Snyder, N.F.R.; Beissinger, S.R.; Fuller, M.R.

1989-01-01

21

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

22

Evaluation of 3 radio transmitters and collar designs for Amazona  

USGS Publications Warehouse

I evaluated 3 radio transmitter attachments and designs for adult parrots. Two of the transmitters and attachments were similar to those used previously in the study on fledgling and adult parrots. I designed, in collaboration with the manufacturer, a third transmitter and attachment that provided protection of key areas from chewing and eventual destruction of the attachment or transmitter. This design was used successfully to radio-track parrots an average of 43.4 weeks (range = 35.9-51.6 weeks). It was the only transmitter of the 3 tested to operate without failure (>36 weeks) caused by chewing damage to the transmitter, antenna, collar, or attachment mechanism (Fisher's exact test, 3 df, P = 0.0003). Its adjustable collar, made from 59 kg-test stainless steel wire covered with plastic heat-shrink tubing, was sturdy and easy to apply. Transmitters for parrots should be enclosed in a protective metal case (brass) and have metal crimped tubes (brass or copper) protecting key areas, such as the base of the antenna and mechanism for attachment of the collar.

Meyers, J.M.

1996-01-01

23

Frequency agile OPO-based transmitters for multiwavelength DIAL  

SciTech Connect

We describe a first generation mid-infrared transmitter with pulse-to- pulse frequency agility and both wide and narrow band capability. This transmitter was used to make multicomponent DIAL measurements in the field.

Velsko, S.P.; Ruggiero, A.; Herman, M.

1996-09-01

24

Long-term Retention of a Radio Transmitter by a Muskellunge  

Microsoft Academic Search

The use of surgically implanted radio transmitters in fish is widespread. There are, however, some questions concerning retention time of transmitters and effects on fish health. I serendipitously recovered a large adult muskellunge implanted with a radio transmitter for 13 years. Although a large fibrous mass was associated with the transmitter, this ripe female otherwise appeared to be disease-free.

Brian P. Mangan

1998-01-01

25

Oviduct Insertion of Radio Transmitters as a Means of Locating Northern Pike Spawning Habitat  

Microsoft Academic Search

I inserted radio transmitters into the oviducts of northern pike Esox lucius in an attempt to find their spawning grounds. Oviduct insertion of miniature radio transmitters was quick and easy. I hoped that transmitters would be expelled with the eggs to aid in identifying critical habitat used for egg deposition. Ten transmitters were implanted in the egg masses of female

Rodney B. Pierce

2004-01-01

26

Influence of radio transmitters on prairie falcons (Falco mexicanus)  

USGS Publications Warehouse

We examined the effects of backpack radio transmitters on Prairie Falcon (Falco mexicanus) reproduction (percentage of occupied territories producing young and number of nestlings produced) over four years. In addition, we observed falcon aeries during brood-rearing to determine attendance at the nest and in the territory, prey delivery rates, and prey composition. We found no effect of radio tagging on Prairie Falcon productivity (nesting success and brood size) among years, although productivity varied significantly among years. The sex of the falcon tagged did not affect productivity. Radio-tagged members of pairs did not differ significantly from un-tagged members of pairs in territory attendance, nest attendance, prey delivery rates, or caching rates. Nestlings raised by radio-tagged parents attained masses similar to those reared by control parents. During low prey years, radio-tagged males brought a greater proportion of small birds and reptiles, and fewer mammals to the nest area than control males.

Vekasy, M.S.; Marzluff, J.M.; Kochert, Michael N.; Lehman, Robert N.; Steenhof, Karen

1996-01-01

27

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

28

Hematological stress indices reveal no effect of radio-transmitters on wintering Hermit Thrushes  

Microsoft Academic Search

Radio-telemetry is often used to track birds, and several investigators have examined the possible effects of radio-transmitters on birds. One approach to this question is to determine if transmitters induce physiological stress. Using hematological indicators of stress (heterophil-lymphocyte (H\\/L) ratios), studies of captive birds have revealed no evidence that radio-transmitters cause stress. However, studies in captivity may not reflect conditions

Andrew K. Davis; Nora E. Diggs; Robert J. Cooper; Peter P. Marra

2008-01-01

29

47 CFR 95.623 - R/C transmitter channel frequencies.  

Code of Federal Regulations, 2010 CFR

...false R/C transmitter channel frequencies. 95.623...Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED...623 R/C transmitter channel frequencies. (a) The R/C transmitter channel frequencies are:...

2010-10-01

30

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

31

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.

32

Segmented acoustic transmitter for broad frequency investigation of a borehole  

Microsoft Academic Search

A broad bandwidth segmented acoustic transmitter is described formed of a plurality of differently sized, closely spaced acoustically active and separately energizable segments. Each segment is operated at a separate resonance to provide, with the acoustic energy from the other segments, a broad frequency spectrum composite acoustic pulse. In one embodiment the segments are aligned along a common axis with

Blizard

1983-01-01

33

Low-frequency radio navigation system  

NASA Technical Reports Server (NTRS)

A method of continuous wave navigation using four transmitters operating at sufficiently low frequencies to assure essentially pure groundwave operation is described. The transmitters are keyed to transmit constant bursts (1/4 sec) in a time-multiplexed pattern with phase modulation of at least one transmitter for identification of the transmitters and with the ability to identify the absolute phase of the modulated transmitter and the ability to modulate low rate data for transmission. The transmitters are optimally positioned to provide groundwave coverage over a service region of about 50 by 50 km for the frequencies selected in the range of 200 to 500 kHz, but their locations are not critical because of the beneficial effect of overdetermination of position of a receiver made possible by the fourth transmitter. Four frequencies are used, at least two of which are selected to provide optimal resolution. All transmitters are synchronized to an average phase as received by a monitor receiver.

Wallis, D. E. (inventor)

1983-01-01

34

Removal of nestling radio-transmitters by adult Sprague’s Pipit ( Anthus spragueii )  

Microsoft Academic Search

Fledgling birds are notoriously difficult to find and capture because of their cryptic behavior. As a result, researchers\\u000a usually affix transmitters to nestlings to study aspects of post-fledging ecology. However, parents may attempt to remove\\u000a nestling transmitters, which could negatively impact nestlings. We attached radio-transmitters to 95 Sprague’s Pipit (Anthus spragueii) nestlings using a modified Rappole and Tipton leg harness.

Ryan J. FisherKimberly; Kimberly M. Dohms; Stephen K. Davis

2010-01-01

35

Evaluation of three miniature radio transmitter attachment methods for small passerines  

USGS Publications Warehouse

Thirty-two immature common yellowthroats were used to evaluate three methods of attaching radio transmitters to the backs of small passerines: adhesive, velcro, and harness. There were no significant differences between the three methods; however, the adhesive method of transmitter attachment to small birds was found to be the preferred technique.

Sykes, P.W., Jr.; Carpenter, J.W.; Holzman, S.; Geissler, P.H.

1990-01-01

36

'Soft' harness for external attachment of large radio transmitters to northern pike (Esox lucius)  

USGS Publications Warehouse

We developed a 'soft' harness for dorsally attaching large, external radio transmitters to northern pike (Esox lucius). The key harness component was a soft, flexible, thick-walled tubing that prevented tissue abrasion by the attachment lines which passed through the tubing. Six field-tagged fish (1.5-7.5 kg) were monitored for 45-115 days before tracking was terminated. Tracking patterns of fish indicated no apparent effect of these large, external transmitters on movement behavior; further, the transmitters did not appear to entangle the fish in vegetation. One fish with its transmitter still secure was recaptured after 54 days, and there was minimal tissue erosion under the transmitter. With minor improvements for the attachment lines and the transmitter saddle, the method is suitable for externally attaching large telemetry transmitters to fish.

Herke, S.W.; Moring, J.R.

1999-01-01

37

Very low frequency radio astronomy  

NASA Astrophysics Data System (ADS)

Very low frequency (VLF) radio astronomy covers the frequency range below about 30 MHz (or the wavelength range above 10 m). This is the last window of the electromagnetic spectrum never to have been observed with spatial resolution. This is a range over which the Earth's ionosphere transmits either poorly or not at all. In this paper, we describe some means to observe this frequency range and we review what can be expected from exploring the astrophysics of the universe at very low radio frequencies. We present the scientific case for a large array to be set up on the far side of the Moon. This would open an entirely new field of remote probing of astrophysical plasmas in the Universe.

Bougeret, J.-L.

38

47 CFR 95.628 - MedRadio transmitters.  

Code of Federal Regulations, 2010 CFR

...i) For a transmitter intended to be implanted in a human body, radiated emissions and EIRP measurements for transmissions...may be made in accordance with a Commission-approved human body simulator and test technique. A formula for a...

2010-10-01

39

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

40

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

41

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

42

Superconducting Radio-Frequency Cavities  

NASA Astrophysics Data System (ADS)

Superconducting cavities have been operating routinely in a variety of accelerators with a range of demanding applications. With the success of completed projects, niobium cavities have become an enabling technology, offering upgrade paths for existing facilities and pushing frontier accelerators for nuclear physics, high-energy physics, materials science, and the life sciences. With continued progress in basic understanding of radio-frequency superconductivity, the performance of cavities has steadily improved to approach theoretical capabilities.

Padamsee, Hasan S.

2014-10-01

43

Low Frequency Radio Experiment (LORE)  

NASA Astrophysics Data System (ADS)

High temporal and frequency resolution observations of solar generated disturbances below 15 MHz in the near-Sun region and at Sun-Earth distances in conjunction with optical and high energy observations of Sun are essential to understand the structure and evolution of eruptions, such as, flares, coronal mass ejections (CMEs), and their associated solar wind disturbances at heights above the photosphere and their consequences in the interplanetary medium. This talk presents a case study of Low Frequency Radio Experiment (LORE) payload to probe the corona and the solar disturbances at solar offsets greater than 2 solar radii below 30 MHz. The LORE, although not part of Aditya-L1 mission, can be complimentary to planned Aditya-L1 coronagraph and its other on-board payloads as well as synergistic to ground based observations, which are routinely carried out by Ooty Radio Telescope. We discuss the baseline design and technical details of the proposed LORE and it is particularly suitable for providing data on the detailed time and frequency structure of fast drifting Type-III and slow drifting Type-II radio bursts with unprecedented time and frequency resolution as well as goniopolarimetry, made possible with better designed antennas and state-of-art electronics, employing FPGAs and an intelligent data management system. This would enable wide ranging studies such as studies of nonlinear plasma processes, CME in-situ radio emission, CME driven phenomena, interplanetary CME driven shocks, ICMEs driven by decelerating IP shocks and space weather effects of Solar Wind interaction regions. The talk will highlight the science objectives as well as the proposed technical design features.

Manoharan, Periasamy K.; Joshi, Bhal Chandra; Naidu, Arun Kumar

44

Magnetic-azimuth dependence of D-layer radio reflectivity, using lightning sferics as radio transmitters  

NASA Astrophysics Data System (ADS)

The Very Low Frequency (3-30 kHz) and Low-Frequency (30-300 kHz) radiation from lightning strokes provides a convenient intense source for studying radio propagation in the ionospheric D-region [Cheng and Cummer, 2005; Cheng et al., 2006; Cheng et al., 2007; Cummer et al., 1998; Jacobson et al., 2010; Shao and Jacobson, 2009]. In this poster we present a new study of the magnetic-azimuth dependence of D-layer radio reflectivity at relatively short ranges (r < 1000 km). This range regime is poorly adapted to a waveguide approach but is well treated by our discrete-reflection approach [Jacobson et al., 2009]. We use cloud-to-ground strokes, which are ~100X more numerous than the Narrow Bipolar Pulse sferics to which our method had previously been confined. Cheng, Z., and S. A. Cummer (2005), Broadband VLF measurements of lightning-induced ionospheric perturbations, Geophys. Res. Lett., 32, L08804, doi:08810.01029/02004GL022187. Cheng, Z., S. A. Cummer, D. N. Baker, and S. G. Kanekal (2006), Nighttime D region electron density profiles and variabilities inferred from broadband measurements using VLF radio emissions from lightning, J. Geophys. Res., 111, A05302, doi:05310.01029/02005JA011308. Cheng, Z., S. A. Cummer, H.-T. Su, and R.-R. Hsu (2007), Broadband very low frequency measurement of D region ionospheric perturbations caused by lightning electromagnetic pulses, J. Geophys. Res., 112, A06318. Cummer, S. A., U. S. Inan, and T. F. Bell (1998), Ionospheric D region remote sensing using VLF radio atmospherics, Radio Sci., 33, 1781-1792. Jacobson, A. R., X. Shao, and R. H. Holzworth (2009), Full-wave reflection of lightning long-wave radio pulses from the ionospheric D-region: Numerical model, J. Geophys. Res.- Space, 114, A03303, doi:03310.01029/02008JA013642. Jacobson, A. R., R. Holzworth, and X.-M. Shao (2010), Full-wave reflection of lightning long-wave radio pulses from the ionospheric D-region: Comparison with midday observations of broadband lightning signals, J. Geophys. Res. -Space, 115, A00E27, doi:10.1029/2009JA014540. Shao, X.-M., and A. R. Jacobson (2009), Model simulation of Very-Low-Frequency and Low-Frequency lightning signal propagation over intermediate ranges, IEEE Trans. Electromag. Compat., 51(3), 519-525.

Jacobson, A. R.; Shao, X.; Holzworth, R. H.; Lay, E. H.

2011-12-01

45

Updates on IceCube's Radio Frequency extension  

Microsoft Academic Search

A variety of radio frequency (RF) detectors were deployed in the Antarctic ice as an enhancement to the optically-based IceCube Neutrino Observatory, and as a step towards a large-scale high-energy neutrino detector. This RF addition includes a set of 5 deep-deployed (300m-1400m) digitizing detectors, a shallow array (˜35m) of transient detectors and a set of transmitters. All Are sensitive to

Hagar Landsman

2011-01-01

46

Legislated emergency locating transmitters and emergency position indicating radio beacons  

NASA Technical Reports Server (NTRS)

An emergency locating transmitting (ELT) system is disclosed which comprises a legislated ELT modified with an interface unit and connected by a multiwire cable to a remote control monitor (RCM), typically located at the pilot position. The RCM can remotely test the ELT by disabling the legislated swept tone and allowing transmission of a single tone, turn the ELT on for legislated ELT transmission, and reset the ELT to an armed condition. The RCM also provides visual and audio indications of transmitter operating condition as well as ELT battery condition. Removing the RCM or shorting or opening the interface input connections will not affect traditional ELT operation.

Wade, William R. (inventor)

1988-01-01

47

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

48

Intelligent Radio Frequency (RF) Monitoring  

E-print Network

? Intelligent Radio Frequency (RF) Monitoring ? 2009 Armstrong International, Inc. www.armstronginternational.com 2 ?Expect many enjoyable experiences!? David M. Armstrong Present Process Challenges ? Identifying a failure ? Procedure... day Weeks a Year 52 week Total Hours 8760 hr/hr *Max Flow Thru is Calculated Using a 7/64" Orifice @ 200 psig for Each Application Listed Above & Blow 1 Hour 1 Day 1 Week 1 Month 3 Months 1 Year Drip 97 2,328 16,296 69,840 209,520 849,720 Tracer...

Kimbrough, B.

49

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

50

Complication associated with abdominal surgical implantation of a radio transmitter in an American badger (Taxidea taxus).  

PubMed

Radio telemetry has greatly advanced the understanding of wild animal ecology. Telemetry studies must ensure that placement of transmitters does not influence the health and behavior of study animals. Here, 10 American badgers (Taxidea taxus) were implanted with beeswax-coated abdominal radio transmitters under general anesthesia and tracked for an average of 14 mo. Behavior and movements of all badgers indicated successful short-term recovery from implantation; however, three mortalities were observed between 5 mo and 15 mo after capture. Cause of death could not be determined for two badgers due to decomposition of the carcasses. A third badger that was recovered in good postmortem condition died from sepsis secondary to a transmitter-related omental torsion. This study indicates that there is some risk associated with abdominally implanted radio transmitters in badgers. Future studies involving implanted transmitters in mammals should focus on identifying safe and effective telemetry devices that do not affect the health of study animals. American badger, omental adhesion, peritoneal implant, telemetry, Taxidea taxus. PMID:20722276

Quinn, Jessica H; Gaffney, Patricia M; Gilardi, Kirsten; Murray, Michael; Jessup, David A; Johnson, Christine K

2010-03-01

51

Application of a modified harness design for attachment of radio transmitters to shorebirds  

USGS Publications Warehouse

Radio transmitter attachment methodology is important to the design of radio telemetry studies. In 1998, we attached 5 transmitters to a captive population of Western Sandpipers(Calidris mauri) and 7 transmitters to wild Killdeer (Charadriusv ociferus) using a modified version of the Rappolea nd Tipton (1991) figure-8 leg-loop harness. Captive birds fitted with harnesses did not exhibit quantifiable differences in behavior relative to control birds. Based on initial success in using the leg-loop harnesses, we used harnesses to attach transmitters in the wild to 30 Killdeer and 49 Dunlin (Calidris alpina) during the winters of 1998-1999 and 1999-2000. This was part of a study on movements of wintering shorebirds in the Willamette Valley of Oregon,USA. Wild birds showed no adverse effects of the harnesses.Thus, the described harness is a practical method for attachment of transmitters to shorebirds. Advantages of this harness method include a reduction in handling time at capture, elimination of the need to clip feathers for attachment, and increased transmitter retention time.

Sanzenbacher, Peter; Haig, Susan M.; Oring, L.W.

2000-01-01

52

Battery voltage variations and radio transmitter temperatures of the small spacecraft  

NASA Astrophysics Data System (ADS)

Diurnal variations of the storage battery voltages as well as temperatures of the radio transmitters on board the small satellite "Universitetsky" have been revealed. Double-humped dependences have been found, related to changes of the micro satellite position relative to the Earth and the Sun and to the on-board satellite systems' operation.

Shakhparonov, V. M.; Karagioz, O. V.

2014-05-01

53

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

54

Nonlethal gill biopsy does not affect juvenile chinook salmon implanted with radio transmitters  

USGS Publications Warehouse

Using gastric and surgical transmitter implantation, we compared radio-tagged juvenile chinook salmon Oncorhynchus tshawytscha (T(O)) with tagged fish also having a gill biopsy (T(B)) to determine biopsy effects on fish implanted with radio transmitters. We found no evidence during the 21-d period to suggest that a gill biopsy reduced survival, growth, or gross condition of the tagged-biopsy group, regardless of transmitter implantation technique. We recorded 100% survival of all treatment groups. Relative growth rates of T(O) and T(B) fish did not differ significantly. Leukocrit and lysozyme levels were not significantly different among groups, suggesting that no signs of infection were present. Our findings suggest that small chinook salmon can tolerate the combination of transmitter implantation and gill biopsy without compromising condition relative to fish receiving only the transmitter. We believe a gill biopsy can be used in field telemetry studies, especially when physiological data are needed in addition to behavioral data.

Martinelli-Liedtke, T. L.; Shively, R.S.; Holmberg, G.S.; Sheer, M.B.; Schrock, R.M.

1999-01-01

55

A radio frequency coaxial feedthrough  

DOEpatents

An improved radio frequency coaxial transmission line vacuum feedthrough is 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 reflection 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 the voltage and power handling capabilities of a feedthrough.

Owens, T.L.

1987-12-07

56

Worldwide OMEGA and Very Low Frequency (VLF) Transmitter Outages, January to December 1980.  

National Technical Information Service (NTIS)

An investigation of worldwide OMEGA and very low frequency (VLF) transmitter outages during 1980 was conducted with emphasis on simultaneous outages. Data includes frequency and duration of simultaneous outages and total yearly percentage shutdown for eac...

L. Rzonca

1981-01-01

57

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

E-print Network

Introduction to special section on Mitigation of Radio Frequency Interference in Radio Astronomy presented at the Workshop on the Mitigation of Radio Frequency Interference in Radio Astronomy (RFI2004), Introduction to special section on Mitigation of Radio Frequency Interference in Radio Astronomy, Radio Sci

Ellingson, Steven W.

58

Radio Frequency Identification iny integrated circuits equipped with radio an-  

E-print Network

checkout lines. Yet, despite the technology's current widespread use andsignificantfuturepotential their knowledge orconsent.TypicalofthiscoverageisaWiredNewsarticle that erroneously reported clothing giant Benetton's plans "to weave radio frequency ID chips into its garments to track its clothes worldwide."1

Han, Richard Y.

59

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

60

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

61

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

62

NASA Radio Frequency Spectrum Management Manual  

NASA Technical Reports Server (NTRS)

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

1989-01-01

63

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

64

47 CFR 2.815 - External radio frequency power amplifiers.  

Code of Federal Regulations, 2012 CFR

... External radio frequency power amplifiers. 2.815 Section 2.815 ...External radio frequency power amplifiers. (a) As used in this part, an external radio frequency power amplifier is any device which,...

2012-10-01

65

Security approaches for Radio Frequency Identification systems  

E-print Network

In this thesis, I explore the challenges related to the security of the Electronic Product Code (EPC) class of Radio Frequency Identification (RFID) tags and associated data. RFID systems can be used to improve supply chain ...

Foley, Joseph Timothy, 1976-

2007-01-01

66

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

67

A rapid transmittance algorithm for microwave sounding frequencies  

Microsoft Academic Search

A rapid transmittance algorithm for NOAA's Advanced Microwave Sounding Units A and B and possible future instruments has been devised. Window channels, water vapor channels, and oxygen-band channels are considered separately; each uses approximations to line-wing or near-line absorption from water vapor or oxygen as appropriate. Absorption by cloud liquid water is also included. For oxygen-band channels that sound the

Philip W. Rosenkranz

1994-01-01

68

Application of wave guide propagation to selection of transmitter power and frequency  

NASA Astrophysics Data System (ADS)

This paper is concerned with developing reasonable criteria for the selection of frequency and power for very low and low-frequency (VLF/LF) transmitting stations. The approach uses a wave guide model for low-frequency propagation and accounts for the variability of the ionosphere. A sample problem involving a hypothetical transmitter is described.

Ferguson, Jerry A.; Hansen, Peder M.

1992-04-01

69

An efficient space-frequency transmitter diversity scheme for DMB-T system  

Microsoft Academic Search

To improve the transmission performance of terrestrial digital multimedia\\/television broadcasting (DMB-T) system, the performance of an efficient space-frequency transmitter diversity scheme is introduced in this article. This scheme maintains the original transmitter branch and the network structure is simple to upgrade. DMB-T system is an important candidate for Chinese digital television terrestrial broadcasting (DTTB) standard. The system was simulated over

Jintao Wang; Zhixing Yang; Changyong Pan

2005-01-01

70

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

71

Radio Frequency (RF) strain monitor  

NASA Technical Reports Server (NTRS)

This invention relates to an apparatus for measuring strain in a structure. In particular, the invention detects strain in parts per million to over ten percent along an entire length (or other dimension) of a structure measuring a few millimeters to several kilometers. By using a propagation path bonded to the structure, the invention is not limited by the signal attenuation characteristics of the structure and thus frequencies in the megahertz to gigahertz range may be used to detect strain in part per million to over ten percent with high precision.

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

1988-01-01

72

Radio Frequency Identification: Beyond the myths  

Microsoft Academic Search

Abstract: Radio Frequency Identification (RFID) is one of the most promising,information system technologies for the health care industry today andin the future. Many experts and researchers consider that RFID should improve the tracking of patients, medical personnel, drugs, and equipment, decrease medical errors, provide positive identification of patients and

S. Bureau; B. S. Prabhu; R. Gadh

73

Privacy debate centers on radio frequency identification  

Microsoft Academic Search

The emergence of radio frequency identification (RFID) has brought with it a plethora of privacy concerns and experts are questioning whether the hoopla surrounding RFID is justified. Using RFID should trigger the same privacy concerns as other commonly used technology such as credit cards, cell phones, and the Internet. RFID's potential to revolutionize the retail industry by maximizing suppliers' ability

B. J. Alfonsi

2004-01-01

74

Single Frequency, Pulsed Laser Diode Transmitter for Dial Water Vapor Measurements at 935nm  

NASA Technical Reports Server (NTRS)

We report a tunable, single frequency, narrow linewidth, pulsed laser diode transmitter at 935.68nm for remote sensing of atmospheric water vapor. The transmitter consists of a CW, tunable, external cavity diode laser whose output is amplified 2OdB using a tapered diode amplifier. The output is pulsed for range resolved DIAL lidar by pulsing the drive current to the diode amplifier at 4kHz with a .5% duty cycle. The output from the transmitter is 36OnJ/pulse and is single spatial mode. It maintains a linewidth of less than 25MHz as its wavelength is tuned across the water vapor absorption line at 935.68nm. The transmitter design and its use in a water vapor measurement will be discussed.

Switzer, Gregg W.; Cornwell, Donald M., Jr.; Krainak, Michael A.; Abshire, James B.; Rall, Johnathan A. R.

1998-01-01

75

Extended heating of the nighttime D region by very low frequency transmitters: Subionospheric observations & modeling  

NASA Astrophysics Data System (ADS)

Very low frequency (VLF, 3-30 kHz) signals propagating in the Earth-ionosphere waveguide are used to probe the heated nighttime D region over three keyed U.S. Navy VLF transmitters. The keyed VLF transmitters are turned on-off in periodic formats for thirty to sixty minutes each day over the course of several months each, providing sensitive measurements of their heating effect on the surrounding ionosphere. On several occasions, the heating effect is observed on probe signal pathways at distances greater than 1500 km from the keyed transmitter. It is proposed that the heating effect of VLF transmitters extends over very large distances through the subionospheric propagation of its radiated signal. General statistics are presented on the observed extent of the heating region over the course of the experiments, and a combination of propagation, heating, and scattering models are used to analyze the results.

Graf, K. L.; Spasojevic, M.; Inan, U. S.; Marshall, R. A.; Foust, F.; Lehtinen, N. G.

2011-12-01

76

Characterization of an optical frequency-shift-keying transmitter based on carrier-suppressed phase modulation  

NASA Astrophysics Data System (ADS)

We experimentally characterize an optical frequency-shift-keying transmitter based on optical carrier-suppressed phase modulation. Only one laser source is needed to generate an optical FSK signal. The demonstration of 10-Gb/s FSK signal generation and 50-km transmission verified the improved performance of the proposed transmitter, compared with the previous two-laser schemes. To further reduce the complexity of the transmitter, the phase modulator is omitted and a single MZM modulator is used for both optical carrier-suppression (OCS) and phase modulation. This simplified structure is verified by simulation, implying the feasibility that a FSK transmitter can be constructed with only one laser source and one modulator.

Qiu, Yang; Chan, Chun-Kit

2013-06-01

77

Inflammatory reaction to fabric collars from percutaneous antennas attached to intracoelomic radio transmitters implanted in harlequin ducks (Histrionicus histrionicus)  

USGS Publications Warehouse

In wild birds implanted intracoelomically with radio transmitters, a synthetic fabric collar placed around the base of a percutaneous antenna is believed to function as a barrier to contamination of the coelom. We examined 13 fabric collars recovered from percutaneous antennas of radio transmitters implanted intracoelomically in harlequin ducks (Histrionicus histrionicus) 12 months earlier. Both the transmitters and antenna collars were encapsulated in fibrous connective tissue, with adhesions to internal organs. Histologically, bacteria were evident at the fabric-plastic interface in 8 of 10 collars examined in cross section and along the length of the collar in 3 collars examined longitudinally. Bacteria were confined within the fibrotic sheath surrounding the transmitter and the antenna collar in all birds. No evidence of chronic systemic effects secondary to implantation was present on hematologic or serum biochemical testing. These findings indicate that antenna collars do not prevent the entry of bacteria along the percutaneous antenna but may help stabilize the antenna and minimize coelomic contamination. We conclude that radio transmitters implanted into the coelom of harlequin ducks do not appear to cause significant health problems for at least 1 year after implantation. ?? 2007 by the Association of Avian Veterinarians.

Mulcahy, D.M.; Burek, K.A.; Esler, D.

2007-01-01

78

Extended lateral heating of the nighttime D region by very low frequency transmitters: Subionospheric observations & modeling  

NASA Astrophysics Data System (ADS)

Very low frequency (VLF, 3-30 kHz) signals propagating in the Earth-ionosphere waveguide are used to probe the heated nighttime D region over three keyed U.S. Navy VLF transmitters. The keyed VLF transmitters are turned on-off in periodic formats for thirty to sixty minutes each day over the course of several months each, providing sensitive measurements of their heating effect on the surrounding ionosphere. On several occasions, the heating effect is observed on probe signal pathways at distances greater than 1500 km from the keyed transmitter. It is proposed that the heating effect of VLF transmitters extends over very large distances through the subionospheric propagation of its radiated signal. General statistics are presented on the observed extent of the heating region over the course of the experiments, and a combination of propagation, heating, and scattering models are used to analyze the results. A series of two-dimensional finite difference frequency domain VLF propagation simulations estimates the keyed transmitter's radiated fields over a region extending 5000 km radially from the transmitter in all directions. The heated electron temperature is obtained as a secondary effect via the temperature balance equation which accounts for Ohmic heating and collisional cooling. Electron collision frequency changes exceeding 0.1% are estimated to occur at distances over 1000 km from the keyed transmitter. Further modeling suggests this amount of heating can produce observable perturbations on a second VLF signal used to probe the ionosphere at those distances, in agreement with our experimental observations.

Graf, K. L.; Spasojevic, M.; Marshall, R. A.; Lehtinen, N. G.; Inan, U. S.

2012-12-01

79

A power amplifier tube used to amplify weak microwave energy (provided by a radio-frequency exciter) to a high power level for  

E-print Network

Klystron · A power amplifier tube used to amplify weak microwave energy (provided by a radio are characterized by high peak power, small size, efficient operation, and low operating voltage.efficient operation- frequency exciter) to a high power level for a radar transmitter.a radar transmitter. · A klystron

Cruz-Pol, Sandra L.

80

SITE TECHNOLOGY CAPSULE: IITRI RADIO FREQUENCY HEATING TECHNOLOGY  

EPA Science Inventory

Radio frequency heating (RFH) technologies use 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. Contaminants are removed from in situ soils and transfe...

81

Frequency stability considerations in the design of battery-powered VHF transmitters  

E-print Network

BIT device characteristics caused by drifts in DC circuit biasing levels. Conventional circuit bias design techniques assume a constant supply voltage and target constant a constant bias point assuming variations in active device characteristics... . Cardiac Telemetry Wireless Voice Transmission for the Hearing Impaired . . . . . COMMERCIAL FM TRANSMITTER MODELS . . WAT-50. . Graymark CAUSES OF FREQUENCY DRIFT DESIGN METHODOLOGY THESIS CONTRIBUTIONS . . SUMMARY COMPUTER-AIDED CIRCUIT DESIGN...

Klughart, Kevin Mark

2012-06-07

82

Low Frequency Radio Signals from Sprite Streamers  

NASA Astrophysics Data System (ADS)

Sprites are mesospheric discharges that carry significant electrical currents and produce radio signals observed typically in the extremely low (ELF) to very low (VLF) frequency bands [Cummer et al., GRL, 25, 1281, 1998]. Recently, Low-Frequency (LF) radio observations of sprite-producing lightning discharges have shown the existence of consecutive broadband pulses exhibiting EM radiation that spans in the LF range, and it has been suggested that this LF radio signals may stem from non-luminous relativistic electron beams above thunderstorms [Fullekrug et al., JGR, 115, A00E09, 2010]. In this talk, we present the first theoretical estimates of the radio signals produced by individual sprite streamers using simulation results from a plasma fluid model. It is demonstrated that the spectral content of the radiation produced by sprite streamers is a function of the air density N and the lightning-induced quasi-static ambient electric field E in the regions of space where the sprite streamers are propagating. We demonstrate that the exponential growth of the current in sprite streamers at 75 km would be preferentially associated with electromagnetic radiation in the frequency range from 0 and up to ˜3 kHz, whereas the growth of the streamer current at 40 km could produce radiation with frequencies up to ˜300 kHz, consistently with the scaling of atmospheric air density [Kosar et al., JGR, 117, A08328, 2012]. We further conjecture that the periodic branching of streamers may lead to a radiation spectrum enhancement in the VLF to LF range. The present study shows that sprite streamers could be responsible for at least part of the LF radiation associated with sprite-producing lightning discharges that was detected recently by Fullekrug et al. [2010].

Qin, J.; Celestin, S. J.; Pasko, V. P.

2013-12-01

83

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

84

Joint Time-Frequency Spectrum Sensing for Cognitive Radio  

E-print Network

Joint Time-Frequency Spectrum Sensing for Cognitive Radio Wael Guib`ene and Aawatif Hayar EURECOM-frequency plane. Index Terms--Cognitive radio, sensing algorithm, Wigner Ville distribution , algebraic detector, joint time frequency detection. I. INTRODUCTION Cognitive Radio (CR) as introduced by Mitola [1

Paris-Sud XI, Université de

85

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

86

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

87

Radio-frequency scanning tunnelling microscopy.  

PubMed

The scanning tunnelling microscope (STM) relies on localized electron tunnelling between a sharp probe tip and a conducting sample to attain atomic-scale spatial resolution. In the 25-year period since its invention, the STM has helped uncover a wealth of phenomena in diverse physical systems--ranging from semiconductors to superconductors to atomic and molecular nanosystems. A severe limitation in scanning tunnelling microscopy is the low temporal resolution, originating from the diminished high-frequency response of the tunnel current readout circuitry. Here we overcome this limitation by measuring the reflection from a resonant inductor-capacitor circuit in which the tunnel junction is embedded, and demonstrate electronic bandwidths as high as 10 MHz. This approximately 100-fold bandwidth improvement on the state of the art translates into fast surface topography as well as delicate measurements in mesoscopic electronics and mechanics. Broadband noise measurements across the tunnel junction using this radio-frequency STM have allowed us to perform thermometry at the nanometre scale. Furthermore, we have detected high-frequency mechanical motion with a sensitivity approaching approximately 15 fm Hz(-1/2). This sensitivity is on par with the highest available from nanoscale optical and electrical displacement detection techniques, and the radio-frequency STM is expected to be capable of quantum-limited position measurements. PMID:17972882

Kemiktarak, U; Ndukum, T; Schwab, K C; Ekinci, K L

2007-11-01

88

Characterization of optical microring ultrasound detector by using a high frequency focused photoacoustic transmitter  

PubMed Central

We characterize a response of optical microring resonator to high frequency focused ultrasound. To properly evaluate the response over high frequency and broadband spectrum, we use a photoacoustic concave transmitter generating and subsequently focusing the ultrasound. A detected focused profile reveals two types of spatial peaks due to the special ring-shaped detector geometry interacting with the high frequency focused ultrasound. Spectral analysis shows that those peaks are contributed by the main and the side lobes of focused ultrasound, respectively. Experimental focal widths agree with theoretical values within ±2 ?m error, which can be attributed to the narrow width of waveguide. PMID:19902003

Won Baac, Hyoung; Ling, Tao; Huang, Sheng-Wen; Ashkenazi, Shai; Guo, L. Jay

2009-01-01

89

Wideband versatile radio-frequency spectrum analyzer.  

PubMed

Operation of a wideband, versatile optical spectrum analyzer for radio-frequency (RF) signals is demonstrated. The device is based on spectral hole burning (SHB). The demonstration features 2.3-GHz instantaneous bandwidth, 500-kHz resolution, and a 32-dB dynamic range. A true RF signal, transferred to the optical carrier with the help of a Mach-Zehnder modulator, is analyzed with optical carrier suppression and zooming capabilities. This is to the authors' knowledge the largest instantaneous bandwidth ever demonstrated for a SHB-based processor in rare-earth-doped crystals. PMID:12659254

Lavielle, V; Lorgeré, I; Le Gouët, J L; Tonda, S; Dolfi, D

2003-03-15

90

Radio-Frequency Spectroscopy of Ultracold Fermions  

E-print Network

Radio-frequency techniques were used to study ultracold fermions. We observed the absence of mean-field "clock" shifts, the dominant source of systematic error in current atomic clocks based on bosonic atoms. This is a direct consequence of fermionic antisymmetry. Resonance shifts proportional to interaction strengths were observed in a three-level system. However, in the strongly interacting regime, these shifts became very small, reflecting the quantum unitarity limit and many-body effects. This insight into an interacting Fermi gas is relevant for the quest to observe superfluidity in this system.

S. Gupta; Z. Hadzibabic; M. W. Zwierlein; C. A. Stan; K. Dieckmann; C. H. Schunck; E. G. M. van Kempen; B. J. Verhaar; W. Ketterle

2003-07-10

91

An overview of DREV's activities on pulsed CO2 laser transmitters: Frequency stability and lifetime aspects  

Microsoft Academic Search

After introducing the desired features in a transmitter for laser radar applications, the output characteristics of several configurations of frequency-stable TEA-CO2 lasers are reviewed. Based on work carried out at the Defence Research Establishment Valcartier (DREV), output pulses are examined from short cavity lasers, CW-TEA hybrid lasers, and amplifiers for low power pulses. It is concluded that the technique of

James Cruickshank; Paul Pace; Pierre Mathieu

1987-01-01

92

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

93

Tracing Ghost Cavities with Low Frequency Radio Observations  

E-print Network

We present X-ray and multi-frequency radio observations of the central radio sources in several X-ray cavity systems. We show that targeted radio observations are key to determining if the lobes are being actively fed by the central AGN. Low frequency observations provide a unique way to study both the lifecycle of the central radio source as well as its energy input into the ICM over several outburst episodes.

Tracy Clarke; Elizabeth Blanton; Craig Sarazin; Namir Kassim; Loren Anderson; Henrique Schmitt; Gopal-Krishna; Doris Neumann

2006-12-20

94

Heating of the nighttime D region by very low frequency transmitters  

NASA Astrophysics Data System (ADS)

VLF signals propagating in the Earth-ionosphere waveguide are used to probe the heated nighttime D region over three U.S. Navy very low frequency (VLF,3-30 kHz) transmitters. Ionospheric cooling and heating are observed when a transmitter turns off and on in the course of normal operations. Heating by the 24.0-kHz NAA transmitter in Cutler, Maine, (1000 kW radiated power) was observed by this method in 41 of 52 off/on episodes during December 1992, increasing the amplitude and retarding the phase of the 21.4-kHz NSS probe wave propagating from Annapolis, Maryland, to Gander, Newfoundland, by as much as 0.84 dB and 5.3 deg, respectively. In 6 of these 41 episodes, the amplitude of the 28.5-kHz NAU probe wave propagating from Puerto Rico to Gander was also perturbed by as much as 0.29 dB. The latter observations were unexpected due to the greater than 770 km distance between NAA and the NAU-Gander great circle path. Heating by the NSS (21.4 kHz, 265 kW) and NLK (24.8 kHz, 850 kW) transmitters was observed serendipitously in data from earlier measurements of the amplitudes of VLF signals propagating in the Earth-ionosphere waveguide. A three-dimensional model of wave absorption and electron heating in a magnetized, weakly ionized plasma is used to calculate the extent nad shape of the collision frequency (i.e., electron temperature) enhancement above a VLF transmitter. The enhancements are annular, with a geomagnetic north-south asymmetry and a radius at the outer half-maximum of the collision frequency enhancement of about 150 km. Heating by the NAA transmitter is predicted to increase the nighttime D region electron temperature by as much as a factor of 3. The calculated changes in the D region conductivity are used in a three-dimensional model of propagation in the Earth-ionosphere wavelength to predict the effect of the heated patch on a subionospheric VLF probe wave. The range of predicted scattered field amplitudes is in general consistent with the observed signal perturbations. Discrepanices in the predictions are attributed to lack of knowledge of the D region electron density profile along the probe wave great circle paths.

Rodriguez, Juan V.; Inan, Umran S.; Bell, Timothy F.

1994-12-01

95

Heating of the nighttime D region by very low frequency transmitters  

NASA Technical Reports Server (NTRS)

VLF signals propagating in the Earth-ionosphere waveguide are used to probe the heated nighttime D region over three U.S. Navy very low frequency (VLF,3-30 kHz) transmitters. Ionospheric cooling and heating are observed when a transmitter turns off and on in the course of normal operations. Heating by the 24.0-kHz NAA transmitter in Cutler, Maine, (1000 kW radiated power) was observed by this method in 41 of 52 off/on episodes during December 1992, increasing the amplitude and retarding the phase of the 21.4-kHz NSS probe wave propagating from Annapolis, Maryland, to Gander, Newfoundland, by as much as 0.84 dB and 5.3 deg, respectively. In 6 of these 41 episodes, the amplitude of the 28.5-kHz NAU probe wave propagating from Puerto Rico to Gander was also perturbed by as much as 0.29 dB. The latter observations were unexpected due to the greater than 770 km distance between NAA and the NAU-Gander great circle path. Heating by the NSS (21.4 kHz, 265 kW) and NLK (24.8 kHz, 850 kW) transmitters was observed serendipitously in data from earlier measurements of the amplitudes of VLF signals propagating in the Earth-ionosphere waveguide. A three-dimensional model of wave absorption and electron heating in a magnetized, weakly ionized plasma is used to calculate the extent nad shape of the collision frequency (i.e., electron temperature) enhancement above a VLF transmitter. The enhancements are annular, with a geomagnetic north-south asymmetry and a radius at the outer half-maximum of the collision frequency enhancement of about 150 km. Heating by the NAA transmitter is predicted to increase the nighttime D region electron temperature by as much as a factor of 3. The calculated changes in the D region conductivity are used in a three-dimensional model of propagation in the Earth-ionosphere wavelength to predict the effect of the heated patch on a subionospheric VLF probe wave. The range of predicted scattered field amplitudes is in general consistent with the observed signal perturbations. Discrepanices in the predictions are attributed to lack of knowledge of the D region electron density profile along the probe wave great circle paths.

Rodriguez, Juan V.; Inan, Umran S.; Bell, Timothy F.

1994-01-01

96

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

97

Modification of the Earth's Ionosphere by Very Low-Frequency Transmitters.  

NASA Astrophysics Data System (ADS)

This dissertation concerns the design and implementation of a controlled experiment aimed at determining the extent to which very-low-frequency (VLF, 3-30 kHz) transmitters operating worldwide modify the Earth's ionosphere. VLF signals propagating in the Earth-ionosphere waveguide are used to probe the heated nighttime D region of the ionosphere (50-90 km altitude) over three U. S. Navy VLF transmitters. Ionospheric cooling and heating are observed when a transmitter turns OFF and ON in the course of normal operations. Heating by the NAA transmitter (1000 kW radiated power) was observed by this method in 41 of 52 ON/OFF episodes during December 1992, increasing the amplitude and retarding the phase of the 21.4 kHz NSS subionospheric probe wave measured at Gander, Newfoundland, by as much as 0.84 dB and 5.3 ^circ, respectively. Heating by the NSS (21.4 kHz, 265 kW) and NLK (24.8 kHz, 850 kW) transmitters was observed serendipitously in data from earlier observations of VLF signals propagating in the Earth-ionosphere waveguide. A three-dimensional model of wave absorption and electron heating in a magnetized, weakly ionized plasma is used to calculate the extent and shape of the collision frequency (i.e., electron temperature) enhancement above a VLF transmitter. The heated patches are annular with a geomagnetic north-south asymmetry and a radius at the outer half-maximum of the collision frequency enhancement of about 150 km. Increases up to a factor of 3 in the electron temperature are predicted to occur in the nighttime D region due to heating by the NAA transmitter. The calculated changes in the D region conductivity are used in a three -dimensional model of propagation in the Earth-ionosphere waveguide to predict the effect of the heated patch on a subionospheric VLF probe wave. The range of predicted scattered field amplitudes is in general consistent with the perturbations of NSS-Gander observed during December 1992. One possible consequence of electron heating, the modification of the nighttime D region electron number density, is investigated theoretically using a four-species model of the ion chemistry. The effects of a 100 kW (NAU), a 265 kW (NSS), and a 1000 kW (NAA) VLF transmitter are calculated for different ambient electron density profiles. The dominant effect of the heating on electron number density is a reduction in the D region electron density due to an increase in the three-body attachment rate of electrons to O_2. Results indicate that the electron density is depleted by up to 26% at ~ 80 km altitude over a 1000 kW transmitter.

Rodriguez, Juan Valentin

98

The Current Status of Low Frequency Radio Astronomy from Space  

Microsoft Academic Search

Ground-based radio astronomy is severely limited by the Earth's ionosphere. Below 15 -- 20 MHz, space-based radio observations are superior or even mandatory. Three different areas of astronomical research manifest themselves at low radio frequencies: solar, planetary, and galactic-extragalactic. Space-based observations of solar phenomena at low frequencies are a natural extension of high-frequency ground-based observations that have been carried out

M. L. Kaiser; K. W. Weiler

2000-01-01

99

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

100

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

101

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

102

Phase manipulation for efficient radio frequency transmission  

E-print Network

Power amplifiers (PAs) for microwave communications are generally the most power-hungry element of a transmitter. High linearity is required for modern digital communications standards, and often is achieved at the expense ...

Barton, Taylor Wallis

2012-01-01

103

Assessment of Barotrauma Resulting from Rapid Decompression of Depth Acclimated Juvenile Chinook Salmon Bearing Radio Telemetry Transmitters  

SciTech Connect

A multifactor study was conducted by Battelle for the US Army Corps of Engineers to assess the significance of the presence of a radio telemetry transmitter on the effects of rapid decompression from simulated hydro turbine passage on depth acclimated juvenile run-of-the-river Chinook salmon. Study factors were: (1) juvenile chinook salmon age;, subyearling or yearling, (2) radio transmitter present or absent, (3) three transmitter implantation factors: gastric, surgical, and no transmitter, and (4) four acclimation depth factors: 1, 10, 20, and 40 foot submergence equivalent absolute pressure, for a total of 48 unique treatments. Exposed fish were examined for changes in behavior, presence or absence of barotrauma injuries, and immediate or delayed mortality. Logistic models were used to test hypotheses that addressed study objectives. The presence of a radio transmitter was found to significantly increase the risk of barotrauma injury and mortality at exposure to rapid decompression. Gastric implantation was found to present a higher risk than surgical implantation. Fish were exposed within 48 hours of transmitter implantation so surgical incisions were not completely healed. The difference in results obtained for gastric and surgical implantation methods may be the result of study design and the results may have been different if tested fish had completely healed surgical wounds. However, the test did simulate the typical surgical-release time frame for in-river telemetry studies of fish survival so the results are probably representative for fish passing through a turbine shortly following release into the river. The finding of a significant difference in response to rapid decompression between fish bearing radio transmitters and those not implies a bias may exist in estimates of turbine passage survival obtained using radio telemetry. However, the rapid decompression (simulated turbine passage) conditions used for the study represented near worst case exposure for fish passing through turbines. At this time, insufficient data exist about the distribution of river-run fish entering turbines, and particularly, the distribution of fish passing through turbine runners, to extrapolate study findings to the population of fish passing through FCRPS turbines. This study is the first study examining rapid decompression study to include acclimation depth as an experimental factor for physostomous fish. We found that fish acclimated to deeper depth were significantly more vulnerable to barotrauma injury and death. Insufficient information about the distribution of fish entering turbines and their depth acclimation currently exists to extrapolate these findings to the population of fish passing through turbines. However, the risk of barotrauma for turbine-passed fish could be particularly high for subyearling Chinook salmon that migrate downstream at deeper depths late in the early summer portion of the outmigration. Barotrauma injuries led to immediate mortality delayed mortality and potential mortality due to increased susceptibility to predation resulting from loss of equilibrium or swim bladder rupture.

Brown, Richard S.; Carlson, Thomas J.; Welch, Abigail E.; Stephenson, John R.; Abernethy, Cary S.; McKinstry, Craig A.; Theriault, Marie-Helene

2007-09-06

104

Polarimetric Observations at Low Radio Frequencies  

NASA Astrophysics Data System (ADS)

Magnetic fields play a fundamental role in the evolution of astrophysical systems. These fields can be studied through wide-field spectropolarimetry, which allows for faint polarised signals to be detected at relatively low radio frequencies. An interferometric polarisation mode has recently become available at the Giant Metrewave Radio Telescope (GMRT). A detailed analysis of the GMRT's instrumental response is presented. The findings are used to create a polarisation pipeline, which in combination with rotation measure (RM) Synthesis is used for the detection of extended linearly polarised emission at 610 MHz. A number of compact sources are detected and their Faraday depth and polarisation fraction are reported. New holography observations of the GMRT's primary beam are presented. Instantaneous off-axis polarisation is substantial and scales with the Stokes I beam. The developed beam models are used to reduce direction-dependent instrumental polarisation, and the Stokes I beam is shown to deviate from circular symmetry. A new technique for electric vector polarisation angle calibration is developed that removes the need for known sources on the sky, eliminates ionospheric effects, and avoids a flaw in current methods which could erroneously yield multiple Faraday components for sources that are well-parameterised by a single RM. A sample of nine galaxies from two Southern Compact Groups are then presented, with constraints being placed on the polarised fraction, RM, spectral index, star formation rate, companion sources, and hydrodynamical state. One galaxy has a displaced peak of radio emission that is extended beyond the disk in comparison to the near-IR disk - suggesting the radio disturbance may be a consequence of ram pressure stripping. Linear polarisation is detected from the core of NGC 7552 at 610 MHz, while another three galaxies ESO 0353-G036, NGC 7590, and NGC 7599 are found to be unpolarised. An analysis of additional extended sources allows for an FR-I and an FR-II radio source to be morphologically classified. Finally, spatial spectral variations are identified in the youngest known Galactic supernova remnant G1.9+0.3, with flatter spectra in the NW and SE. Models of cosmic ray acceleration at oblique shocks suggest the variation is most consistent with an ambient B field perpendicular to the axis of bilateral symmetry. For the first time, the presence of polarised emission is detected. There is increased ordering of the B field in the NW and strong Faraday depolarisation must also be present. An intrinsically radially-oriented field could be provided by a systematic gradient in RM of 140 rad m-2 from N to S and can also explain the depolarisation. Such a gradient may be caused by an anisotropic regular magnetic field within the remnant or in an intervening Faraday screen.

Farnes, J. S.

2012-06-01

105

Circuits and passive components for radio-frequency power conversion  

E-print Network

This thesis focuses on developing technology for high efficiency power converters operating at very high frequencies. The work in the thesis involves two aspects of such converters: rf (radio-frequency) power circuit design ...

Han, Yehui, Ph. D. Massachusetts Institute of Technology

2010-01-01

106

Radio Frequency Identification for Educational Gaming using Mobile Devices  

Microsoft Academic Search

Radio Frequency Identification (RFID) is a location determination technology that has been receiving a lot of commercial attention in recent times, especially in the areas of asset tracking and supply chain management. The technology makes use of radio frequency communication to transfer data between the two key components of an RFID system, the tag and the reader. Location based gaming,

Kevin Curran; Martin Porter

2009-01-01

107

CITY OF PRINCE GEORGE: RADIO FREQUENCY TREATMENT OF PARTIALLY  

E-print Network

#12;CITY OF PRINCE GEORGE: RADIO FREQUENCY TREATMENT OF PARTIALLY DIGESTED/DEWATERED BIOSOLIDS/DEWATERED BIOSOLIDS FINAL REPORT SUMMARY The City of Prince George recently proposed to investigate the possibility of applying radio frequency (RF) technology to partially digested/dewatered biosolids from domestic wastewater

108

Radio-frequency scanning tunnelling microscopy U. Kemiktarak1  

E-print Network

LETTERS Radio-frequency scanning tunnelling microscopy U. Kemiktarak1 , T. Ndukum3 , K. C. Schwab3-year period since its invention, the STM has helped uncover a wealth of phenomena in diverse physical measurementsinmesoscopicelectronicsandmechanics. Broadband noise measurements across the tunnel junction using this radio-frequency STM

109

Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD)  

E-print Network

Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD) Kurt Alexander Polzin;Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD) Prepared by: Kurt Alexander Polzin Dr. Michael R. LaPointe Dissertation Reader #12;c Copyright by Kurt Alexander Polzin, 2006. All

Choueiri, Edgar

110

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...

111

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...

112

IN SITU AND SOIL DECONTAMINATION BY RADIO FREQUENCY HEATING  

EPA Science Inventory

In situ radio frequency heating is performed by applying electromagnetic energy in the radio frequency band to an array of electrodes placed in bore holes drilled through the contaminated soil. he process removes organic contaminants from large volumes of soil by volatilization, ...

113

Solar radioastronomy with the LOFAR (LOw Frequency ARray) radio telescope  

E-print Network

Solar radioastronomy with the LOFAR (LOw Frequency ARray) radio telescope Stephen M. White Array (LOFAR) will be a radio astronomy interferometric array operating in the approximate fre­ quency of high solar activity the Sun will be a prominent (and highly variable) feature of the low­frequency sky

White, Stephen

114

Solar radioastronomy with the LOFAR (LOw Frequency ARray) radio telescope  

E-print Network

Solar radioastronomy with the LOFAR (LOw Frequency ARray) radio telescope Stephen M. Whitea, Namir, USA bRemote Sensing Div., Naval Research Lab., Washington D.C., USA ABSTRACT The Low Frequency Array (LOFAR) will be a radio astronomy interferometric array operating in the approximate fre- quency range 10

115

Reception conditions of low frequency (LF) transmitter signals onboard DEMETER micro-satellite  

NASA Astrophysics Data System (ADS)

We analyze the flux density variation associated to low frequency (LF) broadcasting transmitters observed by the ICE electric field experiment onboard DEMETER micro-satellite. We select five stations localised around the Mediterranean and the black seas: Tipaza (252 kHz, 02°28'E, 36°33'N, Algeria), Roumoules (216 kHz, 06°08'E, 43°47'N, Monte Carlo), Polatli (180 kHz, 32°25'E, 39°45'N, Turkey), Nador (171 kHz, 02°55'W, 35°02'N, Morocco) and Brasov (153 kHz, 25°36'E,45°40', Romania). The detection of the LF transmitter signals by DEMETER micro-satellite is found to depend on the radiated power, the emitted frequency, and the orbit paths with regard to the location of the stations. This leads us to characterise the reception condition of the LF signals and to define time intervals where the detection probability is high. We firstly discuss the dependence of the reception conditions on the ionospheric disturbances due to the geomagnetic and solar activities, and we secondly attempt to estimate the global electric environment above the Mediterranean and the black seas.

Boudjada, Mohammed Y.; Biagi, Pier F.; Sawas, Sami; Galopeau, Patrick H. M.; Besser, Bruno; Wolbang, Daniel; Prattes, Gustav; Eichelberger, Hans; Stangl, Günter; Parrot, Michel; Schwingenschuh, Konrad

2014-05-01

116

Radio Frequency Plasma Applications for Space Propulsion  

SciTech Connect

Recent developments in solid-state radio frequency (RF) power technologies allow for the practical consideration of RF heated plasmas for space propulsion. These technologies permit the use of any electrical power source, de-couple the power and propellant sources, and allow for the effcient use of both the propellant mass and power. Effcient use of the propellant is obtained by expelling the rocket exhaust at the highest possible velocity, which can be orders of magnitude higher than those achieved in chemical rockets. Handling the hot plasma exhaust requires the use of magnetic nozzles, and the basic physics of ion detachment from the magnetic #12;eld is discussed. The plasma can be generated by RF using helicon waves to heat electrons. Further direct heating of the ions helps to reduce the line radiation losses, and the magnetic geometry is tailored to allow ion cyclotron resonance heating. RF #12;eld and ion trajectory calculations are presented to give a reasonably self-consistent picture of the ion acceleration process.

Baity, F.W., Jr.; Barber, G.C.; Carter, M.D.; Chang-Diaz, F.R.; Goulding, R.H.; Ilin, A.V.; Jaeger, E.F.; Sparks, D.O.; Squire, J.P.

1999-09-13

117

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

118

Radio-frequency plasma spraying of ceramics  

SciTech Connect

This study was aimed at developing a novel spraying process using a radio-frequency (rf) plasma. Experiments of Al{sub 2}O{sub 3} and ZrO{sub 2} {minus} 8 wt% Y{sub 2}O{sub 3} spraying showed that the initial powder size was the most important parameter for depositing dense coatings. The optimum powder sizes of Al{sub 2}O{sub 3} and ZrO{sub 2} {minus} 8 wt% Y{sub 2}O{sub 3} were considered to be around 100 and 80 {mu}m, respectively. The use of such large-size powders compared with those used by conventional dc plasma spraying made it possible to deposit adherent ceramics coatings of 150 to 300 {mu}m on as-rolled SS304 substrates. It was also shown that low particle velocity of about 10 m/s, which is peculiar to rf plasma spraying, was sufficient for particle deformation, though it imposed a severe limitation on the substrate position. These experimental results prove that rf plasma spraying is an effective process and a strong candidate to open new fields of spraying applications.

Okada, T.; Hamatani, H.; Yoshida, T. (Dept. of Metallurgy and Materials Science, Faculty of Engineering, The Univ. of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113 (JP))

1989-11-01

119

Method and apparatus for radio frequency ceramic sintering  

DOEpatents

Radio frequency energy is used to sinter ceramic materials. A coaxial waveguide resonator produces a TEM mode wave which generates a high field capacitive region in which a sample of the ceramic material is located. Frequency of the power source is kept in the range of radio frequency, and preferably between 60-80 MHz. An alternative embodiment provides a tunable radio frequency circuit which includes a series input capacitor and a parallel capacitor, with the sintered ceramic connected by an inductive lead. This arrangement permits matching of impedance over a wide range of dielectric constants, ceramic volumes, and loss tangents.

Hoffman, Daniel J. (Oak Ridge, TN); Kimrey, Jr., Harold D. (Knoxville, TN)

1993-01-01

120

Method and apparatus for radio frequency ceramic sintering  

DOEpatents

Radio frequency energy is used to sinter ceramic materials. A coaxial waveguide resonator produces a TEM mode wave which generates a high field capacitive region in which a sample of the ceramic material is located. Frequency of the power source is kept in the range of radio frequency, and preferably between 60-80 MHz. An alternative embodiment provides a tunable radio frequency circuit which includes a series input capacitor and a parallel capacitor, with the sintered ceramic connected by an inductive lead. This arrangement permits matching of impedance over a wide range of dielectric constants, ceramic volumes, and loss tangents. 6 figures.

Hoffman, D.J.; Kimrey, H.D. Jr.

1993-11-30

121

Selection of radio transmitter and attachment method for post-release monitoring of captive-bred reintroduced Red-billed Curassow Crax blumenbachii , Brazil  

Microsoft Academic Search

Long-term monitoring of reintroduced individuals is a central component of many endangered species reintroduction programs.\\u000a Radio-telemetry techniques are rarely used to monitor reintroduced captive-bred Cracids and few data exist regarding possible adverse effects of radio-tagging Cracids. In this study, we identify an appropriate radio transmitter design and develop a suitable attachment method that minimizes\\u000a anthropogenic influence and enables long-term, post-release

Christine Steiner S. Bernardo; Brian Cresswell; Huw Lloyd; Roberto Azeredo; James Simpson

2011-01-01

122

Adaptive radio frequency interference mitigation for HF surface wave radar  

Microsoft Academic Search

The paper analyses the characteristics of radio frequency interference (RFI) in HF surface wave radar (HFSWR) which adopt the linear frequency modulated interrupted continuous wave (FMICW). RFI will influence all the range cells including all the positive and negative frequency, and that the negative frequency range cells contain only the interference information. Based on the above characteristics, we introduce and

Wan Xianrong; Wen Biyang; Ke Hengyu

2004-01-01

123

Assessment of gaseous CO2 and AQUI-S as anesthetics when surgically implanting radio transmitters into cutthroat trout  

USGS Publications Warehouse

Tricaine methanesulfonate (MS-222) and CO2 are anesthetics that can be legally used in fisheries work in the United States, but they are limited in their field applications. A mandatory 21-d withdrawal period is required for fish exposed to MS-222. Carbon dioxide is not approved by the U.S. Food and Drug Administration, but it is a "low regulatory priority drug" that can be used legally for fish anesthesia. However, stressful induction and lengthy recovery times have been associated with CO2. AQUI-S is a clove oil derivative that has the potential to become an approved anesthetic without the limitations of MS-222 or CO2. We compared the efficacy of CO2 with that of AQUI-S when surgically implanting radio transmitters into cutthroat trout Oncorhynchus clarkii. A 20% survival rate was observed when CO2 was used in combination with silk sutures, but a 100% survival rate was observed when CO2 was used in combination with surgical staples to shorten the duration of the surgical procedure. A 100% survival rate was observed when AQUI-S was used in combination with either silk sutures or surgical staples. Carbon dioxide in combination with surgical staples seemed to provide a reasonable option when surgically implanting radio transmitters into cutthroat trout, but AQUI-S may be the preferred anesthesia because high pH and dissolved oxygen levels and low free-CO2 concentrations are maintained during surgical procedures.

Sanderson, T. B.; Hubert, W. A.

2007-01-01

124

Radio-Frequency Radiation Exposure from AM Radio Transmitters and Childhood Leukemia and Brain Cancer  

Microsoft Academic Search

Leukemia and brain cancer patients under age 15 years, along with controls with respiratory illnesses who were matched to cases on age, sex, and year of diagnosis (1993-1999), were selected from 14 South Korean hospitals using the South Korean Medical Insurance Data System. Diagnoses were confirmed through the South Korean National Cancer Registry. Residential addresses were obtained from medical records.

Mina Ha; Hyoungjune Im; Mihye Lee; Hyun Joo Kim; Byung-Chan Kim; Yoon-Myoung Gimm; Jeong-Ki Pack

2007-01-01

125

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

126

47 CFR 2.805 - Operation of radio frequency products prior to equipment authorization.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Operation of radio frequency products prior to equipment authorization...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...AND REGULATIONS Marketing of Radio-frequency Devices § 2.805 Operation of...

2013-10-01

127

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

Code of Federal Regulations, 2013 CFR

...2013-10-01 false External radio frequency power amplifiers and antenna modifications...COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators § 15.204 External radio frequency power amplifiers and antenna...

2013-10-01

128

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

Federal Register 2010, 2011, 2012, 2013

...COMMISSION [Docket No. 2941] Certain Radio Frequency Identification (``RFID'') Products...received a complaint entitled Certain Radio Frequency Identification (``RFID'') Products...States after importation of certain radio frequency identification (``RFID'')...

2013-03-01

129

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

Code of Federal Regulations, 2012 CFR

...2012-10-01 false Marketing of radio frequency devices prior to equipment authorization...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...AND REGULATIONS Marketing of Radio-frequency Devices § 2.803 Marketing of...

2012-10-01

130

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

Code of Federal Regulations, 2012 CFR

...false External radio frequency power amplifiers and antenna modifications. 15.204...204 External radio frequency power amplifiers and antenna modifications. ...any external radio frequency power amplifier or amplifier kit intended for use...

2012-10-01

131

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

132

Radio frequency analog electronics based on carbon nanotube transistors  

E-print Network

Radio frequency analog electronics based on carbon nanotube transistors Coskun Kocabas*, Hoon band with power gains as high as 14 dB. As a demon- stration, we fabricated nanotube transistor radios technologies. The invention of the transistor in 1947 represents the birth of the solid state electronics age

Rogers, John A.

133

DEMONSTRATION BULLETIN: RADIO FREQUENCY HEATING - IIT RESEARCH INSTITUTE  

EPA Science Inventory

Radio frequency heating (RFH) is a process that uses electromagnetic energy generated by radio waves to heat soil in situ, thereby potentially enhancing the performance of standard soil vapor extraction (SVE) technologies. An RFH system developed by the IIT Research Institute ...

134

An overview of DREV's activities on pulsed CO2 laser transmitters: Frequency stability and lifetime aspects  

NASA Astrophysics Data System (ADS)

After introducing the desired features in a transmitter for laser radar applications, the output characteristics of several configurations of frequency-stable TEA-CO2 lasers are reviewed. Based on work carried out at the Defence Research Establishment Valcartier (DREV), output pulses are examined from short cavity lasers, CW-TEA hybrid lasers, and amplifiers for low power pulses. It is concluded that the technique of injecting a low-power laser beam into a TEA laser resonator with Gaussian reflectivity mirrors should be investigated because it appears well adapted to producing high energy, single mode, low chirp pulses. Finally, a brief report on tests carried out on catalysts composed of stannic oxide and noble metals demonstrates the potential of these catalysts, operating at close to room temperature, to provide complete closed-cycle laser operation.

Cruickshank, James; Pace, Paul; Mathieu, Pierre

1987-04-01

135

An overview of DREV's activities on pulsed CO2 laser transmitters: Frequency stability and lifetime aspects  

NASA Technical Reports Server (NTRS)

After introducing the desired features in a transmitter for laser radar applications, the output characteristics of several configurations of frequency-stable TEA-CO2 lasers are reviewed. Based on work carried out at the Defence Research Establishment Valcartier (DREV), output pulses are examined from short cavity lasers, CW-TEA hybrid lasers, and amplifiers for low power pulses. It is concluded that the technique of injecting a low-power laser beam into a TEA laser resonator with Gaussian reflectivity mirrors should be investigated because it appears well adapted to producing high energy, single mode, low chirp pulses. Finally, a brief report on tests carried out on catalysts composed of stannic oxide and noble metals demonstrates the potential of these catalysts, operating at close to room temperature, to provide complete closed-cycle laser operation.

Cruickshank, James; Pace, Paul; Mathieu, Pierre

1987-01-01

136

Adaptive radio frequency interference mitigation for HF surface wave radar  

Microsoft Academic Search

The paper analyses the characteristics of radio frequency interference (RFI) in HF surface wave radar (HF-SWR) which adopts\\u000a the linear frequency modulated interrupted continuous wave (FMICW). RFI will influence all the range cells including all the\\u000a positive frequency and negative frequency, and the negative frequency range cells contain only the interference information.\\u000a Based on the above characteristics, we introduce and

Wan Xian-rong; Ke Heng-yu; Cheng Feng

2005-01-01

137

Terrestrial VLF transmitter injection into the magnetosphere M. B. Cohen1  

E-print Network

Frequency (VLF, 3­30 kHz) radio waves emitted from ground sources (transmitters and lightning) strongly for surface ships and submerged sub- marines. VLF transmitters were also utilized for geo-location prior to the advent of the Global Positioning System [Swanson, 1983]. Today, there are $20 powerful VLF transmitters

138

Two signaling schemes for improving the error performance of frequency division duplex (FDD) transmission systems using transmitter antenna diversity  

Microsoft Academic Search

We propose two signaling schemes that exploit the availability of multiple (N) antennas at the transmitter to provide diversity benefit to the receiver. This is typical of cellular radio systems where a mobile is equipped with only one antenna while the base station is equipped with multiple antennas. We further assume that the mobile-to-base and base-to-mobile channel variations are statistically

N. Seshadri; Jack H. Winters

1994-01-01

139

Radio frequency overview of the high explosive radio telemetry project  

SciTech Connect

High explosive radio telemetry (HERT) is a project that is being developed jointly by Los Alamos National Laboratory and AlliedSignal Federal Manufacturing and Technologies. The ultimate goal is to develop a small, modular telemetry system capable of high-speed detection of explosive events, with an accuracy on the order of 10 nanoseconds. The reliable telemetry of this data, from a high-speed missile trajectory, is a very challenging opportunity. All captured data must be transmitted in less than 20 microseconds of time duration. This requires a high bits/Hertz microwave telemetry modulation code to insure transmission of the data with the limited time interval available.

Bracht, R. [Los Alamos National Lab., NM (United States); Dimsdle, J.; Rich, D.; Smith, F. [AlliedSignal Federal Manufacturing and Technologies, Kansas City, MO (United States)

1998-12-31

140

Numerical modelling of a radio-frequency micro ion thruster  

E-print Network

A simple performance model is developed for an inductively-coupled radio-frequency micro ion thruster. Methods of particle and energy balance are utilized for modeling the chamber plasma discharge. A transformer model is ...

Tsay, Michael Meng-Tsuan

2006-01-01

141

RFIDSim : a discrete event simulator for Radio Frequency Identification systems  

E-print Network

This thesis presents RFIDSim, a discrete event process-oriented simulator designed to model Radio Frequency Identification (RFID) communication. The simulator focuses on the discovery and identification process of passive ...

Yu, Kenneth Kwan-Wai, 1979-

2003-01-01

142

Radio-frequency spectroscopy of ultracold atomic Fermi gases  

E-print Network

This thesis presents experiments investigating the phase diagram of ultracold atomic Fermi gases using radio-frequency spectroscopy. The tunability of many experimental parameters including the temperature, the interparticle ...

Schirotzek, Andre

2010-01-01

143

Radio frequency identification (RFID) applications in semiconductor manufacturing  

E-print Network

Radio frequency identification (RFID) has an enormous potential impact within the semiconductor supply chain, especially within semiconductor manufacturing. The end benefit of RFID will be in the mass serialization, and ...

Cassett, David Ian, 1971-

2004-01-01

144

Visible and Controllable RFID Tags Radio frequency identification (RFID) tags containing  

E-print Network

;Introduction and Motivation Since its invention in the early 20th century, radio frequency identification (RFIDVisible and Controllable RFID Tags Abstract Radio frequency identification (RFID) tags containing

Greenberg, Saul

145

Searching for Low-Frequency Radio Transients from Supernovae  

NASA Astrophysics Data System (ADS)

Supernovae events may be accompanied by prompt emission of a low-frequency electromagnetic transient. These transient events are created by the interaction of a shock wave of charged particles created by SN core-collapse with a stars ambient magnetic field. Such events can be detected in low-frequency radio array. Here we discuss an ongoing search for such events using two radio arrays: the Long Wavelength Array (LWA) and Eight-meter-wavelength Transient Array (ETA).

Tsai-Wei, Jr.; Cutchin, Sean; Kothari, Manthan; Schmitt, Christian; Kavic, Michael; Simonetti, John

2011-10-01

146

RADIO-CONTROLLED CYBORG BEETLES: A RADIO-FREQUENCY SYSTEM FOR  

E-print Network

-yet unmatched flight performance and increasingly understood muscular and nervous systems [2]. AdditionallyRADIO-CONTROLLED CYBORG BEETLES: A RADIO-FREQUENCY SYSTEM FOR INSECT NEURAL FLIGHT CONTROL H. Sato1 were accomplished by optic lobe stimulation while muscular stimulation of either right or left basalar

Maharbiz, Michel

147

Adaptive filter technique for suppression of wideband or offset narrowband radio frequency interference  

NASA Astrophysics Data System (ADS)

The adaptive filter for frequency modulation of the present invention utilizes an audio tone multiplexed into the baseband modulation spectrum as a pilot tone to control and determine the amount of adaptation of the effective and variable bandwidth of the filter for optimum selectivity and rejection of wideband interference or narrowband offset interference. The multiplexed tone is detected and the filter is adjusted according to the signal-to-noise ratio of the detected tone. A continuous and adaptive decrease or increase in bandwidth is produced to accommodate the actual signal bandwidth to achieve rejection of interference with minimum distortion. Additionally, the filter compensates for transmitter drift of center frequency. This filter may be used at radio or intermediate frequencies.

Miller, Jeffry J.

1992-03-01

148

Supplying the Power Requirements to a Sensor Network Using Radio Frequency Power Transfer  

PubMed Central

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

149

Multi-dimensional ultra-high frequency passive radio frequency identification tag antenna designs  

E-print Network

In this thesis, we present the design, simulation, and empirical evaluation of two novel multi-dimensional ultra-high frequency (UHF) passive radio frequency identification (RFID) tag antennas, the Albano-Dipole antenna ...

Delichatsios, Stefanie Alkistis

2006-01-01

150

The Current Status of Low Frequency Radio Astronomy from Space  

NASA Astrophysics Data System (ADS)

Ground-based radio astronomy is severely limited by the Earth's ionosphere. Below 15 -- 20 MHz, space-based radio observations are superior or even mandatory. Three different areas of astronomical research manifest themselves at low radio frequencies: solar, planetary, and galactic-extragalactic. Space-based observations of solar phenomena at low frequencies are a natural extension of high-frequency ground-based observations that have been carried out since the beginnings of radio astronomy. Measurements of known solar phenomena such as Types II and III bursts have been extended from the few solar radii altitude range reachable by ground-based techniques out to 1 AU and beyond. These space-based solar measurements have become critical in our developing an understanding of ``space weather." In contrast, non-thermal planetary radio emissions are almost exclusively a space radio astronomy phenomenon. With the exception of two components of Jupiter's complex radio spectrum, the magnetospheric and Auroral radio emissions of Earth, Jupiter, Saturn, Uranus, and Neptune have all been discovered by space radio astronomy techniques. For astrophysical applications, the lack of angular resolution from space at low frequencies has thwarted progress such that most areas still remain to be fully exploited. Results to date have only included overall cosmic background spectra and extremely crude (~1 steradian resolution) ``maps." In this overview we will briefly summarize the current status of science in the three areas of research and outline some future concepts for low-frequency, space-based instruments for solar, planetary, and astrophysical problems.

Kaiser, M. L.; Weiler, K. W.

151

Power Supplies and Radio Frequency Department at Culham  

E-print Network

Power Supplies and Radio Frequency Department at Culham Culham Centre for Fusion Energy #12;WeMW 800tonne flywheel-driven generators, high current and high voltage DC switches in pulsed supplies frequency generators. We have an ongoing need for power electrical engineers and technicians across a range

152

Spectrum Sensing in Cognitive Radios Based on Multiple Cyclic Frequencies  

Microsoft Academic Search

Cognitive radios sense the radio spectrum in order to find unused frequency\\u000abands and use them in an agile manner. Transmission by the primary user must be\\u000adetected reliably even in the low signal-to-noise ratio (SNR) regime and in the\\u000aface of shadowing and fading. Communication signals are typically\\u000acyclostationary, and have many periodic statistical properties related to the\\u000asymbol

Jarmo Lundén; Visa Koivunen; Anu Huttunenand; H. Vincent Poor

2007-01-01

153

Cosmic Radio-Frequency Radiation Near One Megacycle  

Microsoft Academic Search

Observations of cosmic radio-frequency radiation on frequencies of 2130 kc\\/sec, 1435 kc\\/sec, 900 kc\\/sec, and 520 kc\\/sec have been made, using a method of recording which effectively reduces interference from atmospherics. At these frequencies, the intensity of the radiation is approximately 10 - watt per square metre per cycle per second** per steradian. The ionospheric effects associated with observations near

Grote Reber; G. R. Ellis

1956-01-01

154

Radio frequency dc-dc power conversion  

E-print Network

THIS THESIS addresses the development of system architectures and circuit topologies for dc-dc power conversion at very high frequencies. The systems architectures that are developed are structured to overcome limitations ...

Rivas, Juan, 1976-

2007-01-01

155

Radio frequency interference measurements in Indonesia. A survey to establish a radio astronomy observatory  

NASA Astrophysics Data System (ADS)

We report the first measurements of radio frequency spectrum occupancy performed at sites aimed to host the future radio astronomy observatory in Indonesia. The survey is intended to obtain the radio frequency interference (RFI) environment in a spectral range from low frequency 10 MHz up to 8 GHz. The measurements permit the identification of the spectral occupancy over those selected sites in reference to the allocated radio spectrum in Indonesia. The sites are in close proximity to Australia, the future host of Square Kilometre Array (SKA) at low frequency. Therefore, the survey was deliberately made to approximately adhere the SKA protocol for RFI measurements, but with lower sensitivity. The RFI environment at Bosscha Observatory in Lembang was also measured for comparison. Within the sensitivity limit of the measurement equipment, it is found that a location called Fatumonas in the surrounding of Mount Timau in West Timor has very low level of RFI, with a total spectrum occupancy in this measured frequency range being about 1 %, mostly found at low frequency below 20 MHz. More detailed measurements as well as a strategy for a radio quiet zone must be implemented in the near future.

Hidayat, Taufiq; Munir, Achmad; Dermawan, Budi; Jaelani, Anton Timur; Léon, Stéphane; Nugroho, Dading Hadi; Suksmono, Andriyan Bayu; Mahasena, Putra; Premadi, Premana Wardayanti; Herdiwijaya, Dhani; Kunjaya, Chatief; Dupe, Zadrach Ledoufij; Brahmantyo, Budi; Mandey, Denny; Yusuf, Muhammad; Tri Wulandari, Hesti Retno; Arief, Falahuddin; Irfan, Muhammad; Puri Jatmiko, Agus Triono; Akbar, Evan Irawan; Sianturi, Hery Leo; Tanesib, Jehunias Leonidas; Warsito, Ali; Utama, Judhistira Aria

2014-02-01

156

Black phosphorus radio-frequency transistors.  

PubMed

Few-layer and thin film forms of layered black phosphorus (BP) have recently emerged as a promising material for applications in high performance nanoelectronics and infrared optoelectronics. Layered BP thin films offer a moderate bandgap of around 0.3 eV and high carrier mobility, which lead to transistors with decent on-off ratios and high on-state current densities. Here, we demonstrate the gigahertz frequency operation of BP field-effect transistors for the first time. The BP transistors demonstrated here show respectable current saturation with an on-off ratio that exceeds 2 × 10(3). We achieved a current density in excess of 270 mA/mm and DC transconductance above 180 mS/mm for hole conduction. Using standard high frequency characterization techniques, we measured a short-circuit current-gain cutoff frequency fT of 12 GHz and a maximum oscillation frequency fmax of 20 GHz in 300 nm channel length devices. BP devices may offer advantages over graphene transistors for high frequency electronics in terms of voltage and power gain due to the good current saturation properties arising from their finite bandgap, thus can be considered as a promising candidate for the future high performance thin film electronics technology for operation in the multi-GHz frequency range and beyond. PMID:25347787

Wang, Han; Wang, Xiaomu; Xia, Fengnian; Wang, Luhao; Jiang, Hao; Xia, Qiangfei; Chin, Matthew L; Dubey, Madan; Han, Shu-Jen

2014-11-12

157

Calcium, calpain, and calcineurin in low-frequency depression of transmitter release.  

PubMed

Low-frequency depression (LFD) of transmitter release occurs at phasic synapses with stimulation at 0.2 Hz in both isolated crayfish (Procambarus clarkii) neuromuscular junction (NMJ) preparations and in intact animals. LFD is regulated by presynaptic activity of the Ca(2+)-dependent phosphatase calcineurin (Silverman-Gavrila and Charlton, 2009). Since the fast Ca(2+) chelator BAPTA-AM inhibits LFD but the slow chelator EGTA-AM does not, the Ca(2+) sensor for LFD may be close to a Ca(2+) source at active zones. Calcineurin can be activated by the Ca(2+)-activated protease calpain, and immunostaining showed that both proteins are present at nerve terminals. Three calpain inhibitors, calpain inhibitor I, MDL-28170, and PD150606, but not the control compound PD145305, inhibit LFD both in the intact animal as shown by electromyograms and by intracellular recordings at neuromuscular junctions. Analysis of mini-EPSPs indicated that these inhibitors had minimal postsynaptic effects. Proteolytic activity in CNS extract, detected by a fluorescent calpain substrate, was modulated by Ca(2+) and calpain inhibitors. Western blot analysis of CNS extract showed that proteolysis of calcineurin to a fragment consistent with the constitutively active form required Ca(2+) and was blocked by calpain inhibitors. Inhibition of LFD by calpain inhibition blocks the reduction in phosphoactin and the depolymerization of tubulin that normally occurs in LFD, probably by blocking the dephosphorylation of cytoskeletal proteins by calcineurin. In contrast, high-frequency depression does not involve protein phosphorylation- or calpain-dependent mechanisms. LFD may involve a specific pathway in which local Ca(2+) signaling activates presynaptic calpain and calcineurin at active zones and causes changes of tubulin cytoskeleton. PMID:23365236

Silverman-Gavrila, Lorelei B; Praver, Moshe; Mykles, Donald L; Charlton, Milton P

2013-01-30

158

Dual radio frequency plasma source: Understanding via electrical asymmetry effect  

SciTech Connect

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 ({xi}), ourstudies also predict local maxima for odd integer values of 2{xi} as a consequence of the electrical asymmetry effect produced by dual frequency voltage sources.

Bora, B. [Departamento de Plasma Termonuclear, Comision Chilena de Energia Nuclear (CCHEN), Casilla 188-D, Santiago (Chile); Departamento de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Bhuyan, H.; Favre, M.; Wyndham, E. [Departamento de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Wong, C. S. [Plasma Technology Research Centre, Physics Department, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia)

2013-04-21

159

A Radio-Frequency-over-Fiber link for large-array radio astronomy applications  

NASA Astrophysics Data System (ADS)

A prototype 425-850 MHz Radio-Frequency-over-Fiber (RFoF) link for the Canadian Hydrogen Intensity Mapping Experiment (CHIME) is presented. The design is based on a directly modulated Fabry-Perot (FP) laser, operating at ambient temperature, and a single-mode fiber. The dynamic performance, gain stability, and phase stability of the RFoF link are characterized. Tests on a two-element interferometer built at the Dominion Radio Astrophysical Observatory for CHIME prototyping demonstrate that RFoF can be successfully used as a cost-effective solution for analog signal transport on the CHIME telescope and other large-array radio astronomy applications.

Mena, J.; Bandura, K.; Cliche, J.-F.; Dobbs, M.; Gilbert, A.; Tang, Q. Y.

2013-10-01

160

76 FR 12995 - In the Matter of Certain Radio Control Hobby Transmitters and Receivers and Products Containing...  

Federal Register 2010, 2011, 2012, 2013

...Transmitters and Receivers and Products Containing Same; Notice of Investigation AGENCY: U...transmitters and receivers and products containing same by reason of infringement of certain claims...transmitters and receivers and products containing same that infringe one or more of claims...

2011-03-09

161

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

162

The solar elongation distribution of low-frequency radio bursts  

NASA Technical Reports Server (NTRS)

Over 500 days of low-frequency (less than 1 MHz) radio observations from the IMP-6 spacecraft have been accumulated to produce a two-dimensional map (frequency vs elongation) of solar type III burst occurrences. This map indicates that most solar bursts in this frequency range are observed at the second harmonic of the plasma frequency, rather than the fundamental. The map also shows that the solar wind electron density varies as an inverse power of heliocentric distance, with the exponent somewhat less than 2 to perhaps 3 or higher.

Kaiser, M. L.

1975-01-01

163

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

164

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

165

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

166

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

167

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

168

Fabrication of the APS storage ring radio frequency accelerating cavities  

Microsoft Academic Search

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

K. Primdahl; J. Bridges; F. DePaola; R. Kustom; D. Snee

1993-01-01

169

Radio frequency telemetry system for sensors and actuators  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

170

Radio Frequency Telemetry System for Sensors and Actuators  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

171

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

172

Energy Saving Glass Lamination via Selective Radio Frequency Heating  

Microsoft Academic Search

Ceralink Inc. developed FastFuse, a rapid, new, energy saving process for lamination of glass and composites using radio frequency (RF) heating technology. The Inventions and Innovations program supported the technical and commercial research and development needed to elevate the innovation from bench scale to a self-supporting technology with significant potential for growth. The attached report provides an overview of the

Shawn M. Allan; Patricia M. Strickland; Holly S. Shulman

2009-01-01

173

Radio frequency and infrared drying of sized textile warp yarns  

SciTech Connect

Drying sized textile warp yarns without contacting the warp is easily accomplished by either radio frequency or infrared techniques. Although the process is more expensive than conventional drying, the substantial savings accrued during subsequent weaving and finishing of the cloth can help keep the US textile industry competitive and support electrical load. 5 refs., 8 figs., 14 tabs.

Ruddick, H.G. (West Point Foundry and Machine Co., GA (USA))

1990-11-01

174

Low-frequency radio maps and spectra of supernova remnants  

NASA Technical Reports Server (NTRS)

Low-frequency radio maps of 18 supernova remnants have been constructed from observations made at the Arecibo Observatory. The integrated flux densities have been combined with others in the literature to show that most of the sources have simple power-law spectra. None of the sources show features which would suggest changes in the spectrum spatially across the given source.

Dickel, J. R.; Denoyer, L. K.

1975-01-01

175

Image transmission in tactical radio frequency shared network propagation environments  

Microsoft Academic Search

The need to transmit images across tactical radio frequency (rf) links has been identified in army digitization applications. For example, military doctrine requires that tactical functions like identification of battlefield entities as potential targets and battle damage assessment be performed by the soldier. Currently, a key input to these processes is imagery. Therefore, the quality and timeliness of the image

Kent H. White; Kerry A. Wagner; Scott O'Hanian

1997-01-01

176

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

177

Radio frequency identification and food retailing in the UK  

Microsoft Academic Search

Purpose – This paper aims to offer an outline of the characteristics of radio frequency identification (RFID) technology and briefly discusses some of its perceived benefits and challenges for food retailers in the UK. Design\\/methodology\\/approach – The paper draws material largely from trade and practitioner sources and illustrates general themes with specific retail examples. Findings – The paper suggests that

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

2005-01-01

178

Radio-frequency quadrupole: General properties and specific applications  

NASA Astrophysics Data System (ADS)

The general properties of radio frequency quadrupole accelerators are reviewed and beam dynamics simulation results are presented for their use in a variety of accelerating systems. 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 are included.

Stokes, R. H.; Crandall, K. R.; Hamm, R. W.; Humphry, F. J.; Jameson, R. A.; Knapp, E. A.; Potter, J. M.; Rodenz, G. W.; Stovall, J. E.; Swenson, D. A.

1980-07-01

179

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...

180

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...

181

DETECTION OF TRANSIENT IN RADIO FREQUENCY FINGERPRINTING USING SIGNAL PHASE  

E-print Network

of the transient can be delayed. In addition, the performance of the Bayesian Step Change Detector mayDETECTION OF TRANSIENT IN RADIO FREQUENCY FINGERPRINTING USING SIGNAL PHASE Jeyanthi Hall Michel wireless devices. It es- sentially involves the detection of the transient signal and the extraction

Barbeau, Michel

182

Celestial Reference Frame Realizations at Multiple Radio Frequency Bands  

NASA Astrophysics Data System (ADS)

The International Celestial Reference Frame (ICRF) was adopted by the IAU in 1997 based on VLBI measurements at S/X - band (2.3/8.4 GHz) and complemented by HIPPARC OS measurements at optical frequencies. At that time, the IAU encouraged the astrometric community to extend the ICRF to additional frequency bands. In response, VLBI measurements have been made at 24, 32, and 43 GHz. Meanwhile, the 8.4 GHz work has been greatly improved with the release of the ICRF - 2 in 2009. This paper will discuss the programmatic and scientific motivations for extending the ICRF to these higher radio bands. Results to date will be summarized including evidence that these new high frequency frames are rapidly approaching the accuracy of the 8.4 GHz ICRF - 2. We will discuss the current limiting errors and prospects for the future accuracy of radio reference frames. In particular, we will discuss using multiple radio frames to characterize t he frequency dependent systematic noise floor from extended source morphology and core shift. Finally, given the potential of the Gaia optical mission for state - of - the - art astrometry, we will discuss simulations which show the potential for a radio - optical frame tie at the 10 - 15 ?as level of precision (1 - sigma). The research described in this paper was done under contract with NASA. Government sponsorship acknowledged. ©2012 California Institute of Technology.

Jacobs, Chris

2012-08-01

183

Radio frequency power sensor based on MEMS technology  

Microsoft Academic Search

We present the first measurement results of a power sensor for radio frequency (rf) signals (50 kHz - 40 GHz) with almost no dissipation during the measurement. This sensor is, therefore, a 'through' power sensor, that means that the rf signal is available during the measurement of its power. The power detection has been realized by measuring capacitively the movement

Luis J. Fernandez; Eelke Visser; Javier Sesé; Remco Wiegerink; Jaap Flokstra; Henri Jansen; Miko Elwenspoek

2003-01-01

184

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

185

Optical, thermal, and electrical monitoring of radio-frequency tissue modification.  

PubMed

Radio-frequency (rf) tissue fusion involves the sealing of tissue between two electrodes delivering rf currents. Applications include small bowel fusion following anastomosis. The mechanism of adhesion is poorly understood, but one hypothesis is that rf modification is correlated to thermal damage and dehydration. A multimodal monitoring system capable of acquiring tissue temperature, electrical impedance, and optical transmittance at 1325-nm wavelength during rf delivery by a modified Ligasure fusion tool is presented. Measurements carried out on single layers of ex vivo porcine small bowel tissue heated at approximately 500-kHz frequency are correlated with observation of water evaporation and histological studies on full seals. It is shown that the induced current generates a rapid quasilinear rise of temperature until the boiling point of water, that changes in tissue transmittance occur before impedance control is possible, and that a decrease in transmission occurs at typical denaturation temperatures. Experimental results are compared with a biophysical model for tissue temperature and a rate equation model for thermal damage. PMID:20210489

Floume, Timmy; Syms, Richard R A; Darzi, Ara W; Hanna, George B

2010-01-01

186

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

187

LOFAR: A new radio telescope for low frequency radio observations: Science and project status  

E-print Network

LOFAR, the Low Frequency Array, is a large radio telescope consisting about 100 soccer field sized antenna stations spread over a region of 400 km in diameter. It will operate in the frequency range from ~10 to 240 MHz, with a resolution at 240 MHz of better than an arcsecond. Its superb sensitivity will allow for a broad range of astrophysical studies. In this contribution we first discuss four major areas of astrophysical research in which LOFAR will undoubtedly make important contributions: reionisation, distant galaxies and AGNs, transient radio sources and cosmic rays. Subsequently, we will discuss the technical concept of the instrument and the status of the LOFAR project

H. Rottgering; A. G. de Bruyn; R. P. Fender; J. Kuijpers; M. P. van Haarlem; M. Johnston-Hollitt; G. K Miley

2003-07-11

188

Radio Frequency Spectra of 388 Bright 74 MHz Sources  

E-print Network

As a service to the community, we have compiled radio frequency spectra from the literature for all sources within the VLA Low Frequency Sky Survey (VLSS) that are brighter than 15 Jy at 74 MHz. Over 160 references were used to maximize the amount of spectral data used in the compilation of the spectra, while also taking care to determine the corrections needed to put the flux densities from all reference on the same absolute flux density scale. With the new VLSS data, we are able to vastly improve upon previous efforts to compile spectra of bright radio sources to frequencies below 100 MHz because (1) the VLSS flux densities are more reliable than those from some previous low frequency surveys and (2) the VLSS covers a much larger area of the sky (declination >-30 deg.) than many other low frequency surveys (e.g., the 8C survey). In this paper, we discuss how the spectra were constructed and how parameters quantifying the shapes of the spectra were derived. Both the spectra and the shape parameters are made available here to assist in the calibration of observations made with current and future low frequency radio facilities.

J. F. Helmboldt; N. E. Kassim; A. S. Cohen; W. M. Lane; T. J. Lazio

2007-07-23

189

Preening behavior of adult gyrfalcons tagged with backpack transmitters  

USGS Publications Warehouse

Radio transmitters provide data that enhance understanding of raptor biology (Walls and Kenward 2007) and are now used to answer a multitude of research questions (Meyburg and Fuller 2007). However, transmitters affect the birds that carry them (Barron et al. 2010), and it is important to document and evaluate such effects (Casper 2009). For example, decreased survival has been documented in Prairie Falcons (Falco mexicanus; Steenhof et al. 2006), Northern Goshawks (Accipiter gentilis; Reynolds et al. 2004), and Spotted Owls (Strix occidentalis; Paton et al. 1991) tagged with radio transmitters. However, no such effects were reported for Peregrine Falcons (Falco peregrinus; Fuller et al. 1998, McGrady et al. 2002) and a number of other species (Kenward 2001). White and Garrott (1990) noted that in general, animals tagged with radio transmitters often altered their behaviors for 1–14 d after release during an adjustment period that included increased preening and grooming frequencies. Although more than 90 Gyrfalcons (Falco rusticolus) have been tagged with radio transmitters (e.g., Burnham 2007, McIntyre et al. 2009, T. Booms unpubl. data), the effects of transmitters on this species are not well documented. Anecdotal information suggests some Gyrfalcons might be negatively affected by radio-tagging (Booms et al. 2008). As part of a study investigating Gyrfalcon breeding biology, we conducted opportunistic, focused observations on two radio-tagged adult female Gyrfalcons and their unmarked mates. We here describe and quantify preening behavior of Gyrfalcons shortly after radio-tagging.

Booms, T.L.; Schempf, P.F.; Fuller, M.R.

2011-01-01

190

Exploring the magnetized cosmic web through low frequency radio emission  

E-print Network

Recent improvements in the capabilities of low frequency radio telescopes provide a unique opportunity to study thermal and non-thermal properties of the cosmic web. We argue that the diffuse, polarized emission from giant radio relics traces structure formation shock waves and illuminates the large-scale magnetic field. To show this, we model the population of shock-accelerated relativistic electrons in high-resolution cosmological simulations of galaxy clusters and calculate the resulting radio synchrotron emission. We find that individual shock waves correspond to localized peaks in the radio surface brightness map which enables us to measure Mach numbers for these shocks. We show that the luminosities and number counts of the relics strongly depend on the magnetic field properties, the cluster mass and dynamical state. By suitably combining different cluster data, including Faraday rotation measures, we are able to constrain some macroscopic parameters of the plasma at the structure formation shocks, such as models of turbulence. We also predict upper limits for the properties of the warm-hot intergalactic medium, such as its temperature and density. We predict that the current generation of radio telescopes (LOFAR, GMRT, MWA, LWA) have the potential to discover a substantially larger sample of radio relics, with multiple relics expected for each violently merging cluster. Future experiments (SKA) should enable us to further probe the macroscopic parameters of plasma physics in clusters.

N. Battaglia; C. Pfrommer; J. L. Sievers; J. R. Bond; T. A. Ensslin

2008-06-19

191

A simple, tunable, and highly sensitive radio-frequency sensor  

PubMed Central

We report a radio frequency (RF) sensor that exploits tunable attenuators and phase shifters to achieve high-sensitivity and broad band frequency tunability. Three frequency bands are combined to enable sensor operations from ?20?MHz to ?38?GHz. The effective quality factor (Qeff) of the sensor is as high as ?3.8?×?106 with 200??l of water samples. We also demonstrate the measurement of 2-proponal-water-solution permittivity at 0.01 mole concentration level from ?1?GHz to ?10?GHz. Methanol-water solution and de-ionized water are used to calibrate the RF sensor for the quantitative measurements. PMID:24023393

Cui, Yan; Sun, Jiwei; He, Yuxi; Wang, Zheng; Wang, Pingshan

2013-01-01

192

Surveying abandoned mine shafts with Remote Radio Transmitter EM methods and Selfpotential  

NASA Astrophysics Data System (ADS)

Abandoned near subsurface mining constructions from the 19th and early 20th century in urbanized areas placed upon former ore mines near the city of Aachen (Germany), as well as in many other regions of the world, provide hazardous risks concerning possible collapses. In many cases, the exact locations of such constructions are not known anymore. For instance, to map covered shafts of one meter diameter on large survey areas, high resolution methods with rapid measurement progress are necessary. Enhanced developments of the traditional Very Low Frequency (VLF) technique such as VLF-gradient and Radiomagnetotellurics (RMT) fulfill these requirements. Continuous ground-contactless VLF-gradient survey quickly provides maps indicating the lateral electric resistivity heterogeneity distribution. Inversions of RMT data provide 2D-resistivity-depth sections and also the interpretation of Self-Potential data gives information about the nature of the VLF-gradient anomalies. The successful combination of the three methods for detecting mineshafts near to the city if Aachen is presented for both an electromagnetic undisturbed and noisy location.

Bosch, F. P.; Gurk, M.

2009-04-01

193

Hidden Mine Shaft Detection With Remote Radio Transmitter Electromagnetics and Self- Potential Method  

NASA Astrophysics Data System (ADS)

Abandoned near subsurface mining constructions from the 19th and early 20th century in urbanized areas placed upon former ore mines near the city of Aachen (Germany), and in many other regions of the world, provide hazardous risks concerning possible collapses. In many cases, the exact locations of such constructions are not known anymore. For instance, to map covered shafts of one meter diameter on large survey areas, high resolution methods with rapid measurement progress are necessary. Enhanced developments of the traditional Very Low Frequency (VLF) technique such as VLF-gradient and Radiomagnetotellurics (RMT) fulfill these requirements. Continuous ground-contactless VLF-gradient survey quickly provides maps indicating the lateral electric resistivity heterogeneity distribution. Inversions of RMT data provide 2D-resistivity-depth sections and also the interpretation of Self-Potential data gives information about the nature of the VLF-gradient anomalies. The successful combination of the three methods for detecting mineshafts is presented for both an electromagnetic undisturbed and noisy location.

Bosch, F. P.; Gurk, M.

2008-12-01

194

Low Frequency Radio Astronomical Antennas for the Lunar Environment  

NASA Astrophysics Data System (ADS)

Low radio frequencies (? MHz) represent the last of the relatively unexplored wavebands in the electromagnetic spectrum for astrophysics. Such observations are very challenging from the surface of the Earth because of an abundance of human-made radio interference (e.g., FM bands, TV channels) and because of ionospheric refraction. The lunar farside presents a unique opportunity to fully open this cosmic window because of the demonstrated radio-quiet environment. The ultimate science goal of a lunar farside low frequency telescope is to explore a new frontier in cosmology, the so-called Dark Ages. This era occurs between Recombination (at z 1100) when the universe first becomes transparent (producing what we observe today as the CMB) and Reionization when the first stars and galaxies form (at z 10-20). During the Dark Ages, the universe was unlit by any star and the only detectable signal is likely to arise from neutral hydrogen absorption against the CMB (from the collapse of the first structures). Observing this absorption signal would be a powerful probe of fundamental cosmology. During the Dark Ages (z 20 - 150), when the 21-cm (1.4 GHz) neutral hydrogen line is redshifted into the low frequency radio band (10-30 MHz, 10-30 m), the absorption signal has the potential to be the richest of all cosmological data sets. In this poster, we will discuss the opportunities and options for low frequency radio antennas in both lunar orbit and on the lunar surface. We are investigating a novel concept to deploy a large number of low-mass antennas deposited on sheets of polyimide film. We will also describe results of laboratory vacuum testing at U. Colorado on polyimide film cycled between -150 C and 100 C, and exposed to far-ultraviolet light, with conditions like those on the lunar surface.

Burns, Jack O.; Lazio, J.; ROLSS DALI Teams

2009-01-01

195

Dowsing can be interfered with by radio frequency radiation.  

PubMed

The soil radiation, watercourses and ores have been located for centuries by sensitive persons, dowsers. An ideomotoric explanation of the dowsing reaction, with no physical interaction, has been accepted. Our present re-analyses of some such results have shown, that there could be a physical phenomenon connecting the human reactions in field experiments, where the test subjects walked or were sitting in a slow-moving car, with the windows covered, and a dowsing rod in their hands was recorded. The correlations between the reaction points by test subjects in the moving car and the points by walking along the same path were highly significant. The correlation was not seen in all test locations. The distance between the test location and the radio tower, and the incidence angle of the transmitted radio wave, possibly had an effect on results. We hypothesize that the experiments carried out in the 20th century were interfered with by man-made radio frequency radiation, mainly FM radio and TV broadcasting, as test subjects' bodies absorbed the radio waves and unconscious hand movement reactions took place following the standing waves or intensity variations due to multipath propagation. PMID:22365422

Huttunen, Paavo; Niinimaa, Ahti; Myllylä, Risto

2012-04-01

196

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

197

Controller design issues in the feedback control of radio frequency plasma processing reactors  

E-print Network

Controller design issues in the feedback control of radio frequency plasma processing reactors the potential for improving the reliability and performance of radio frequency rf plasma processing reactors feedback control of inductively coupled plasma processing reactors for polysilicon etching and

Kushner, Mark

198

Radio frequency analog electronics based on carbon nanotube transistors  

PubMed Central

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 analog electronic devices, such as narrow band amplifiers operating in the VHF frequency band with power gains as high as 14 dB. As a demonstration, we fabricated nanotube transistor radios, in which SWNT devices provide all of the key functions, including resonant antennas, fixed RF amplifiers, RF mixers, and audio amplifiers. These results represent important first steps to practical implementation of SWNTs in high-speed analog circuits. Comparison studies indicate certain performance advantages over silicon and capabilities that complement those in existing compound semiconductor technologies. PMID:18227509

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

2008-01-01

199

Predictions for high-frequency radio surveys of extragalactic sources  

E-print Network

We present detailed predictions of the contributions of the various source populations to the counts at frequencies of tens of GHz. New evolutionary models are worked out for flat-spectrum radio quasars, BL Lac objects, and steep-spectrum sources. Source populations characterized by spectra peaking at high radio frequencies, such as extreme GPS sources, ADAF/ADIOS sources and early phases of gamma-ray burst afterglows are also dealt with. The counts of different populations of star-forming galaxies (normal spirals, starbursts, high-z galaxies detected by SCUBA and MAMBO surveys, interpreted as proto-spheroidal galaxies) are estimated taking into account both synchrotron and free-free emission, and dust re-radiation. Our analysis is completed by updated counts of Sunyaev-Zeldovich effects in clusters of galaxies and by a preliminary estimate of galactic-scale Sunyaev-Zeldovich signals associated to proto-galactic plasma.

Gianfranco De Zotti; Roberto Ricci; Dino Mesa; Laura Silva; Pasquale Mazzotta; Luigi Toffolatti; Joaquin Gonzalez-Nuevo

2004-10-28

200

Radio frequency communication system utilizing radiating transmission lines  

DOEpatents

A radio communication system for use in tunnels, mines, buildings or other shielded locations in which a pair of radiating transmission lines (30), (31) extend through such location in spaced coextensive relation to each other. Each transmission line (30), (31) has at least one unidirectional amplifier (32), (33) interposed therein with the sense of the unidirectional amplifier (32) of one transmission line (30) being opposite to the sense of the unidirectional amplifier (33) of the other transmission line (31). Each of the amplifiers (32), (33) has a gain which is less than the coupling loss between the transmission lines (30), (31). Two or more mobile transceivers (35) in the location served by the system are coupled to the transmission lines (30), (31) by electromagnetic wave propagation in space in order to communicate directly with each other at a given radio frequency within the frequency range of the system.

Struven, Warren C. (San Carlos, CA)

1984-01-01

201

Hermetic aluminum radio frequency interconnection and method for making  

Microsoft Academic Search

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

R. D. Kilgo; L. Kovacic; R. K. Brow

2000-01-01

202

Terahertz bandwidth integrated radio frequency spectrum analyzer via nonlinear optics  

E-print Network

We report an integrated all-optical radio frequency spectrum analyzer based on a ~ 4cm long doped silica glass waveguide, with a bandwidth greater than 2.5 THz. We use this device to characterize the intensity power spectrum of ultrahigh repetition rate mode-locked lasers at repetition rates up to 400 GHz, and observe dynamic noise related behavior not observable with other techniques.

Ferrera, Marcello; Pasquazi, Alessia; Peccianti, Marco; Clerici, Matteo; Caspani, Lucia; Chu, Sai T; Little, Brent E; Morandotti, Roberto; Moss, David J

2014-01-01

203

Tunable (LSMO) Ferromagnetic Thin Films for Radio Frequency Applications  

Microsoft Academic Search

In this letter, an original work in tunable (La,Sr)MnO3 (LSMO) ferromagnetic thin film materials for radio frequency applications is presented. 400 nm thick LSMO thin film is formed by the chemical solution deposition on the top of indium tin oxide (ITO)\\/SiO2\\/Si heterostructure. Interdigitated capacitor structures are used to study the behavior of LSMO thin film materials when a dc electrostatic

M. Al Ahmad; Young Taek Lee; Chae Il Cheon; Eui-Jung Yun; R. Plana

2009-01-01

204

CARS spectroscopy of radio-frequency discharge plasma in hydrogen  

Microsoft Academic Search

The population of the vibrational and rotational levels of hydrogen is studied by the narrow-and broadband CARS spectroscopy in capacitive and inductive-capacitive radio-frequency discharge plasmas. Computational codes are developed to analyze and process CARS spectra of hydrogen obtained under conditions of disturbance of thermodynamic equilibrium over internal degrees of freedom of molecules. To interpret the measurement results, a model is

V. A. Shakhatov; O. A. Gordeev

2007-01-01

205

CARS spectroscopy of radio-frequency discharge plasma in hydrogen  

Microsoft Academic Search

The population of the vibrational and rotational levels of hydrogen is studied by the narrow-and broadband CARS spectroscopy\\u000a in capacitive and inductive-capacitive radio-frequency discharge plasmas. Computational codes are developed to analyze and\\u000a process CARS spectra of hydrogen obtained under conditions of disturbance of thermodynamic equilibrium over internal degrees\\u000a of freedom of molecules. To interpret the measurement results, a model is

V. A. Shakhatov; O. A. Gordeev

2007-01-01

206

Longitudinal capture in the radio-frequency-quadrupole structure  

SciTech Connect

The radio-frequency-quadrupole (RFQ) linac structure not only can attain easily transverse focusing in the low-beta region, but also can obtain very high capture efficiency because of its low beta-lambda and low-particle rigidity. An optimization study of the zero space-charge longitudinal capture in an RFQ linac that yields configurations with large capture efficiency is described.

Inagaki, S.

1980-03-01

207

Perforated-Layer Implementation Of Radio-Frequency Lenses  

NASA Technical Reports Server (NTRS)

Luneberg-type radio-frequency dielectric lenses made of stacked perforated circular dielectric sheets, according to proposal. Perforation pattern designed to achieve required spatial variation of permittivity. Consists of round holes distributed across face of each sheet in "Swiss-cheese" pattern, plus straight or curved slots that break up outer parts into petals in "daisy-wheel" pattern. Holes and slots made by numerically controlled machining.

Dolgin, Benjamin P.

1996-01-01

208

Spectral Occupancy at VHF: Implications for Frequency-Agile Cognitive Radios  

E-print Network

Spectral Occupancy at VHF: Implications for Frequency-Agile Cognitive Radios Steven W. Ellingson Blacksburg, VA 24061 Email: ellingson@vt.edu Abstract-- Frequency-agile cognitive radio is a potential solu. I. INTRODUCTION Frequency-agile cognitive radio is a potential solution to the problem

Ellingson, Steven W.

209

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.

210

The radio-frequency design of an iris-type coupler for the CPHS radio-frequency quadrupole  

NASA Astrophysics Data System (ADS)

The Compact Pulsed Hadron Source (CPHS) project is a university-based proton accelerator platform (13 MeV, 16 kW, 50 mA peak current, 0.5 ms pulse width at 50 Hz) for multi-disciplinary neutron and proton applications. The CPHS linac consists of a 3 MeV radio-frequency quadrupole (RFQ) linac and a 13 MeV drift tube linac (DTL). Both the RFQ and DTL share a 325 MHz, 2.1 MW klystron source. A single iris-type radio-frequency (RF) coupler is used to feed 537 kW of RF power to the RFQ cavity. Three-dimensional electromagnetic models of the ridge-loaded tapered waveguide (RLWG) and the coupler-cavity system are presented, and the design process and results of the RLWG and iris plate are described in detail.

Xiong, Zheng-Feng; Zheng, Shu-Xin; Xing, Qing-Zi; Guan, Xia-Ling

2012-01-01

211

Optical frequency comb technology for ultra-broadband radio-frequency photonics  

E-print Network

The outstanding phase-noise performance of optical frequency combs has led to a revolution in optical synthesis and metrology, covering a myriad of applications, from molecular spectroscopy to laser ranging and optical communications. However, the ideal characteristics of an optical frequency comb are application dependent. In this review, the different techniques for the generation and processing of high-repetition-rate (>10 GHz) optical frequency combs with technologies compatible with optical communication equipment are covered. Particular emphasis is put on the benefits and prospects of this technology in the general field of radio-frequency photonics, including applications in high-performance microwave photonic filtering, ultra-broadband coherent communications, and radio-frequency arbitrary waveform generation.

Torres-Company, Victor

2014-01-01

212

Polycrystalline silicon carbide films deposited by low-power radio-frequency plasma decomposition of SiF4CF4-H2 gas mixtures  

Microsoft Academic Search

Polycrystalline silicon carbide thin films have been deposited on amorphous substrates by radio-frequency plasma-assisted decomposition of tetrafluoro silane, tetrafluoro methane, and hydrogen gas mixtures using low-power density and deposition temperatures. The material is shown to possess the ?-SiC structure using transmission electron microscopy. It has highly visible transmittance and exhibits bands due to silicon carbide as well as fluorine bonded

Gautam Ganguly; Subal C. De; Swati Ray; A. K. Barua

1991-01-01

213

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

214

Ross Ice Shelf in situ radio-frequency ice attenuation  

E-print Network

We have measured the in situ average electric field attenuation length for radio-frequency signals broadcast vertically through the Ross Ice Shelf. We chose a location, Moore Embayment, south of Minna Bluff, known for its high reflectivity at the ice-sea interface. We confirmed specular reflection and used the return pulses to measure the average attenuation length from 75-1250 MHz over the round-trip distance of 1155 m. We find the average electric field attenuation length to vary from 500 m at 75 MHz to 300 m at 1250 MHz, with an experimental uncertainty of 55 to 15 m. We discuss the implications for neutrino telescopes that use the radio technique and include the Ross Ice Shelf as part of their sensitive volume.

Barrella, Taylor; Saltzberg, David

2010-01-01

215

A very low frequency radio astronomy observatory on the Moon  

NASA Technical Reports Server (NTRS)

Because of terrestrial ionospheric absorption, very little is known of the radio sky beyond 10 m wavelength. An extremely simple, low cost very low frequency radio telescope is proposed, consisting of a large array of short wires laid on the lunar surface, each wire equipped with an amplifier and a digitizer, and connected to a common computer. The telescope could do simultaneous multifrequency observations of much of the visible sky with high resolution in the 10 to 100 m wavelength range, and with lower resolution in the 100 to 1000 m range. It would explore structure and spectra of galactic and extragalactic point sources, objects, and clouds, and would produce detailed quasi-three-dimensional mapping of interstellar matter within several thousand parsecs of the Sun.

Douglas, James N.; Smith, Harlan J.

1988-01-01

216

Ross Ice Shelf in situ radio-frequency ice attenuation  

E-print Network

We have measured the in situ average electric field attenuation length for radio-frequency signals broadcast vertically through the Ross Ice Shelf. We chose a location, Moore Embayment, south of Minna Bluff, known for its high reflectivity at the ice-sea interface. We confirmed specular reflection and used the return pulses to measure the average attenuation length from 75-1250 MHz over the round-trip distance of 1155 m. We find the average electric field attenuation length to vary from 500 m at 75 MHz to 300 m at 1250 MHz, with an experimental uncertainty of 55 to 15 m. We discuss the implications for neutrino telescopes that use the radio technique and include the Ross Ice Shelf as part of their sensitive volume.

Taylor Barrella; Steven Barwick; David Saltzberg

2010-11-02

217

Comparative Study of Frequency Agile Data Transmission Schemes for Cognitive Radio Transceivers  

E-print Network

Comparative Study of Frequency Agile Data Transmission Schemes for Cognitive Radio Transceivers agile data transmission schemes employed by cognitive radio transceivers for use in dynamic spectrum requirements and conditions1 are known as cognitive radios [4]. With re- cent developments in cognitive radio

Kansas, University of

218

High-resolution radio study of SNR IC443 at low radio frequencies  

E-print Network

We investigated in detail the morphology at low radio frequencies of the supernova remnant IC443 and accurately established its radio continuum spectral properties. We used the VLA in multiple configurations to produce high resolution radio images of IC443 at 74 and 330 MHz. The changes with position in the radio spectral index were correlated with data in near infrared from 2MASS, in gamma-rays from VERITAS, and with the molecular 12^CO line emission. The new image at 74 MHz has HPBW=35", rms=30 mJy/beam and at 330 MHz HPBW= 17" and rms=1.7 mJy/beam. The integrated flux densities for the whole SNR are S_74MHz=470+/-51 Jy and S_330MHz=248+/-15 Jy. For the pulsar wind nebula associated with the compact source CXOUJ061705.3+222127, we calculated S_330MHz=0.23+/-0.05 Jy, S_1420MHz=0.20+/-0.04 Jy, and alpha~0.0. Substantial variations are observed in spectral index between 74 and 330 MHz across IC443. The flattest spectral components (-0.25< alpha<-0.05) coincide with the brightest parts of the SNR along th...

Castelletti, G; Clarke, T; Kassim, N E

2011-01-01

219

Radio-frequency ablation electrode displacement elastography: A phantom study  

PubMed Central

This article describes the evaluation of a novel method of tissue displacement for use in the elastographic visualization of radio-frequency (rf) ablation-induced lesions. The method involves use of the radio-frequency ablation electrode as a displacement device, which provides localized compression in the region of interest. This displacement mechanism offers the advantage of easyin vivo implementation since problems such as excessive lateral and elevational displacements present when using external compression are reduced with this approach. The method was tested on a single-inclusion tissue-mimicking phantom containing a radio-frequency ablation electrode rigidly attached to the inclusion center. Full-frame rf echo signals were acquired from the phantom before and after electrode displacements ranging from 0.05 to 0.2 mm. One-dimensional cross-correlation analysis between pre-and postcompression signals was used to measure tissue displacements, and strains were determined by computing the gradient of the displacement. The strain contrast, contrast-to-noise ratio, and signal-to-noise ratio were estimated from the resulting strain images. Comparisons are drawn between the elastographically measured dimensions and those known a priori for the single-inclusion phantom. Electrode displacement elastography was found to slightly underestimate the inclusion dimensions. The method was also tested on a second tissue-mimicking phantom and on in vitro rf-ablated lesions in canine liver tissue. The results validate previous in vivo findings that electrode displacement elastography is an effective method for monitoring rf ablation. PMID:18649476

Bharat, Shyam; Varghese, Tomy; Madsen, Ernest L.; Zagzebski, James A.

2008-01-01

220

Occupational exposure to radio-frequency electromagnetic fields  

SciTech Connect

The paper considers occupational exposure to radio-frequency (RF) electromagnetic (EM) fields in industrial processes in near-field situations where electric and magnetic field strengths are monitored to assess the health hazard. Plastic materials are joined by an RF machine whose electrodes are not shielded and which may produce high level RF fields in the immediate vicinity, exceeding the ANSI standard. A physiotherapist may be exposed to high E and H fields using RF shortwave therapy, the maintenance personnel in FM/TV broadcast towers are subject to intense RF fields, and induction heating equipment used for forging, annealing and brazing can expose operators' hands to magnetic fields.

Mild, K.H.

1980-01-01

221

Moving target indication in the presence of radio frequency interference  

NASA Astrophysics Data System (ADS)

Moving target indication (MTI) is greatly complicated by the presence of radio frequency interference (RFI) which 'rings' the MTI filter causing false alarms. This effect is particularly important in radars with a limited number of coherent bursts on target. A subclutter RFI processing (SRP) technique has been developed to allow effective MTI processing in the presence of impulsive RFI. This technique does not have the sensitivity gap characteristic of conventional 'RFI detectors'. Thus, RFI induced false alarms can be effectively eliminating while still maintaining useful subclutter target visibility. The SRP technique has been analyzed by Monte Carlo simulation and by experiments conducted with recorded coherent radar signals.

Fong, E.; Walker, J. A.; Bath, W. G.

222

Towards optimization of probe placement for radio-frequency ablation.  

PubMed

We present a model for the optimal placement of mono- and bipolar probes in radio-frequency (RF) ablation. The model is based on a numerical computation of the probe's electric potential and of the steady state of the heat distribution during RF ablation. The optimization is performed by minimizing a temperature based objective functional under these constraining equations. The paper discusses the discretization and implementation of the approach. Finally, applications of the optimization to artificial data and a comparison to a real RF ablation are presented. PMID:17354926

Altrogge, Inga; Kröger, Tim; Preusser, Tobias; Büskens, Christof; Pereira, Philippe L; Schmidt, Diethard; Weihusen, Andreas; Peitgen, Heinz-Otto

2006-01-01

223

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

224

Primary lung cancer: treatment with radio-frequency thermal ablation.  

PubMed

Primary lung cancer is the most frequently diagnosed malignancy in the world and the leading cause of death from cancer [1]. When the initial diagnosis is made, most cases are inoperable or the patients' condition does not permit surgical interventions [2]. For patients with inoperable lung cancer, percutaneous radio-frequency thermal ablation (RFA) under CT guidance represents an alternative and minimally invasive treatment. It can also be applied in combination with radiation therapy and chemotherapy. We report three cases treated by percutaneous CT-guided RF ablation, from which two had post-operative recurrent tumor and one was inoperable. PMID:14666377

Thanos, L; Mylona, S; Pomoni, M; Kalioras, V; Zoganas, L; Batakis, N

2004-05-01

225

Development of a radio frequency surface contour mapping system  

SciTech Connect

A radio-frequency based system is being developed for imaging the top surface of the contents of vessels used in coal processes including lockhoppers, gasifiers, and mixing chambers. The system will be designed to image a minimum of 25 pixels with a depth resolution of {+-}1 inch over ranges of 4 to 30 feet. The system must tolerate harsh environments as found in coal gasifiers with temperatures up to 1800 F and pressures up to 600 psig. The system will provide both a visual readout of the contour of the upper surface of a vessel`s contents via a computer monitor and a data interface to the process control system.

Buttermore, W.H.; Weber, W.H.; Straszheim

1994-10-01

226

Plasma sheath thickness in radio-frequency discharges  

NASA Astrophysics Data System (ADS)

The radio-frequency glow discharges of several kinds of gases were examined to measure the ion sheath thickness at the cathode electrode. At intermediate gas pressures around 0.05- 0.5 Torr, the sheath thickness d depends on the pressure P in the expression P1/2d=K0 for almost all of the discharges examined. It was also pointed out that the constant K0 value decreased linearly against a mass of the predominant ion in the plasma. The discrepancy between the sheath thickness measured in this work and by theoretical solution was discussed for the argon discharge.

Mutsukura, Nobuki; Kobayashi, Kenji; Machi, Yoshio

1990-09-01

227

Detection of NMR signals with a radio-frequency atomic magnetometer I.M. Savukov 1  

E-print Network

Detection of NMR signals with a radio-frequency atomic magnetometer I.M. Savukov 1 , S.J. Seltzer of proton NMR signals with a radio-frequency (rf) atomic magnetometer tuned to the NMR frequency of 62 kHz. High-frequency operation of the atomic magnetometer makes it relatively insensitive to ambient magnetic

Romalis, Mike

228

Practical Frequency Synchronization Scheme in an Open Software Radio TD-SCDMA System  

Microsoft Academic Search

This paper concerns how to achieve the initial frequency acquisition and frequency tracking in an open software radio TD-SCDMA platform, which consists of several common PCs and universal software radio peripheral. In this proposal, at the stage of frequency acquisition, the frequency difference between the base station and the terminal can be reduced step by step, by adjusting the size

Lin Huang; Hanwen Cao; Kan Zheng; G. Decarreau

2007-01-01

229

arXiv:astro-ph/0309647v123Sep2003 Hydra A at Low Radio Frequencies  

E-print Network

arXiv:astro-ph/0309647v123Sep2003 Hydra A at Low Radio Frequencies W.M. Lane Naval Research Lab present new, low-frequency images of the powerful FR I radio galaxy Hydra A (3C 218). Images were made: galaxies 1. Introduction Hydra A (3C 218) is a high luminosity Fanaroff- Riley type I (FR I) radio galaxy

Taylor, Greg

230

Vandermonde-subspace Frequency Division Multiplexing for Two-Tiered Cognitive Radio  

E-print Network

Vandermonde-subspace Frequency Division Multiplexing for Two-Tiered Cognitive Radio Networks--Vandermonde-subspace frequency division multi- plexing (VFDM) is an overlay spectrum sharing technique for cognitive radio. VFDM/Hz over cognitive radio systems based on unused band detection. We also present some key design parameters

Paris-Sud XI, Université de

231

Jupiter's low-frequency radio spectrum from Cassini\\/Radio and Plasma Wave Science (RPWS) absolute flux density measurements  

Microsoft Academic Search

We apply the calibration method developed by Dulk et al. [2001] to the data from the Cassini\\/Radio and Plasma Wave Science (RPWS) High-Frequency Receiver in order to derive flux density measurements of six components of the Jovian low-frequency radio spectrum over the full frequency range of the instrument (3.5 kHz to 16.1 MHz). The estimated accuracy is better than 50%,

P. Zarka; B. Cecconi; W. S. Kurth

2004-01-01

232

The Siple VLF transmitter as a multi-frequency probe of the earth-ionosphere waveguide  

NASA Astrophysics Data System (ADS)

Receptions of subionospheric signals radiated from Siple, Antarctic in 1983 to stations at Palmer, Halley, and South Pole are reported which are shown to be strongly dependent upon azimuth and signal frequency. The results indicate that antenna properties favor the endfire direction (toward Halley) at the third harmonic of the antenna half wave resonance frequency, and in general demonstrate greater efficiency at higher frequencies. The present effects provide a means of extending the effective frequency range of the narrowband Siple antenna system and of selectively probing certain regions of the earth-ionosphere waveguide.

Carpenter, D. L.; Bell, T. F.; Smith, A. J.

1988-02-01

233

Nonlinear frequency coupling in dual radio-frequency driven atmospheric pressure plasmas  

SciTech Connect

Plasma ionization, and associated mode transitions, in dual radio-frequency driven atmospheric pressure plasmas are governed through nonlinear frequency coupling in the dynamics of the plasma boundary sheath. Ionization in low-power mode is determined by the nonlinear coupling of electron heating and the momentary local plasma density. Ionization in high-power mode is driven by electron avalanches during phases of transient high electric fields within the boundary sheath. The transition between these distinctly different modes is controlled by the total voltage of both frequency components.

Waskoenig, J.; Gans, T. [Centre for Plasma Physics, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland (United Kingdom)

2010-05-03

234

Hermetic aluminum radio frequency interconnection and method for making  

SciTech Connect

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 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, R.D.; Kovacic, L.; Brow, R.K.

2000-03-14

235

Antarctic Radio Frequency Albedo and Implications for Cosmic Ray Reconstruction  

E-print Network

From an elevation of ~38 km, the balloon-borne ANtarctic Impulsive Transient Antenna (ANITA) is designed to detect the up-coming radio frequency (RF) signal resulting from a sub-surface neutrino-nucleon collision. Although no neutrinos have been discovered thus far, ANITA is nevertheless the only experiment to self-trigger on radio frequency emissions from cosmic-ray induced atmospheric air showers. In the majority of those cases, down-coming RF signals are observed via their reflection from the Antarctic ice sheet and back up to the ANITA interferometer. Estimating the energy scale of the incident cosmic rays therefore requires an estimate of the fractional power reflected at the air-ice interface. Similarly, inferring the energy of neutrinos interacting in-ice from observations of the upwards-directed signal refracting out to ANITA also requires consideration of signal coherence across the interface. By comparing the direct Solar RF signal intensity measured with ANITA to the surface-reflected Solar signal ...

Besson, D Z; Sullivan, M; Allison, P; Barwick, S W; Baughman, B M; Beatty, J J; Belov, K; Bevan, S; Binns, W R; Chen, C; Chen, P; Clem, J M; Connolly, A; De Marco, D; Dowkontt, P F; DuVernois, M; Goldstein, D; Gorham, P W; Grashorn, E W; Hill, B; Hoover, S; Huang, M; Israel, M H; Javaid, A; Kowalski, J; Learned, J; Liewer, K M; Matsuno, S; Mercurio, B C; Miki, C; Mottram, M; Nam, J; Naudet, C J; Nichol, R J; Palladino, K; Romero-Wolf, A; Ruckman, L; Saltzberg, D; Seckel, D; Shang, R Y; Stockham, M; Varner, G S; Vieregg, A G; Wang, Y

2013-01-01

236

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

237

Design and characterization of a radio-frequency dc/dc power converter  

E-print Network

The use of radio-frequency (RF) amplifier topologies in dc/dc power converters allows the operating frequency to be increased by more than two orders of magnitude over the frequency of conventional converters. This enables ...

Jackson, David A. (David Alexander)

2005-01-01

238

2-microm Doppler lidar transmitter with high frequency stability and low chirp.  

PubMed

A coherent Doppler lidar system was frequency stabilized in a master-slave configuration by a phase-modulation technique. The short-term frequency stability, ~0.2 MHz rms, was maintained in a vibrational environment on a ship during a field campaign in the tropical Pacific Ocean. The long-term frequency stability was <2.6 kHz/h. Thus, in many applications, shot-to-shot frequency correction can be disregarded, which will result in increased speed and simplicity of the data-acquisition system. A frequency chirp could not be detected. These properties permit Doppler wind measurements with high efficiency and duty cycles to be made, even on airborne and spaceborne platforms. PMID:18066175

Wulfmeyer, V; Randall, M; Brewer, A; Hardesty, R M

2000-09-01

239

Humeral remodeling and soft tissue injury of the wings caused by backpack harnesses for radio transmitters in New Zealand Takah? (Porphyrio hochstetteri).  

PubMed

Backpack harnesses are commonly used to attach radio and satellite transmitters to a wide range of bird species for research and conservation management. They are an integral part of the conservation management of the New Zealand Takah? (Porphyrio hochstetteri), an endangered flightless rail. Radio transmitters mounted on backpack harnesses enable the birds to be tracked in their remaining native range of remote, mountainous Fiordland, New Zealand. We evaluated 26 Takah? retrospectively at necropsy by gross examination, radiography, and computed tomography to assess damage from the backpack harness. Ten birds that had never worn a harness had no evidence of wing injury. Of the 16 birds that had worn a harness, 10 (63%) had superficial soft tissue injury to skin or patagium or more severe injury, such as remodeling of the distal humerus at the harness cord-wing interface, or pathologic fractures. Such injuries are hypothesized to be associated with discomfort, increased risk of infection or fracture, and therefore reduced fitness. These findings have implications for all avian species deployed with backpack harnesses. PMID:23778604

Michael, Sarah; Gartrell, Brett; Hunter, Stuart

2013-07-01

240

New synchronization method of arbitrary different radio frequencies in accelerators  

NASA Astrophysics Data System (ADS)

In electron accelerator facilities, radio frequencies for a linac accelerator and a circular accelerator including a booster synchrotron ring and a storage ring are completely different. In order to improve the beam transmission efficiency from a linac to a circular accelerator, and to make the beam intensity constant, both rf's are generally synchronized. This method is well known and uses a common subharmonic frequency of around 10 MHz. The rf's used are generated by using a frequency multiplier from the common frequency, and they are continuously generated. We paid attention to the fact that the electron beam from a linac accelerator is always pulsed, and the rf of the linac requires only a moment during beam emission and acceleration. Taking this fact into account, we invented a new synchronization method for the rf's of both the linac and the circular accelerators. The new method is explained by describing a concrete example at the synchrotron radiation facility, SPring-8 (Super Photon ring 8 GeV). A 2856 MHz rf for the linac is generated by 508.58 MHz rf of the storage ring for a short duration of about 290 ?s. Thus, the phase difference between the two rf's is automatically fixed. This method can be applied to any combination of arbitrary different rf's.

Kawashima, Y.; Asaka, T.; Takashima, T.

2001-08-01

241

A radio-frequency source using direct digital synthesis and field programmable gate array for nuclear magnetic resonance  

NASA Astrophysics Data System (ADS)

A radio-frequency (rf) source for nuclear magnetic resonance (NMR) is described. With the application of direct digital synthesis (DDS), the rf source has the ability to yield rf pulses with short switching time and high resolution in frequency and phase. To facilitate the generation of a soft pulse, a field programmable gate array (FPGA) cooperating with a pulse programmer is used as the auxiliary controller of the DDS chip. Triggered by the pulse programmer, the FPGA automatically controls the DDS to generate soft pulse according to predefined parameters, and the operation mode of the pulse programmer is optimized. The rf source is suitable for being used as transmitter in low-field (<1 T) NMR applications, for example, magnetic resonance imaging and relaxation measurement. As a compact and low-cost module, the rf source is of general use for constructing low-field NMR spectrometer.

Liang, Xiao; Weimin, Wang

2009-12-01

242

analysis and design of metal-surface mounted radio frequency identification (RFID) transponders  

Microsoft Academic Search

With the development of the radio frequency integrated circuit (RFIC), contactless radio frequency identification (RFID) technology, as one of the fastest growing sectors of automatic identification procedures (Auto-ID), gains broad application in tracking assets in supply chain management. However, one of the largest challenges for the RFID industry is that the ultra high frequency (UHF) RFID transponder doesn't function well

Sanyi Zhan

2008-01-01

243

High Q radio frequency circuits employing a superconductive layer on a thermally matched aggregate metallic substrate  

Microsoft Academic Search

High Q radio frequency circuits such as reference cavity resonators for frequency standards and coupled cavity circuits for linear accelerators are disclosed. Such circuits comprise a radio frequency wave supporting structure formed by a superconductive layer deposited upon or otherwise formed on a metallic substrate member. The substrate is matched to the coefficient of linear thermal expansion of the superconductive

1969-01-01

244

Subfemtotesla radio-frequency atomic magnetometer for detection of nuclear quadrupole resonance  

E-print Network

Subfemtotesla radio-frequency atomic magnetometer for detection of nuclear quadrupole resonance S 20 November 2006 A radio-frequency tunable atomic magnetometer is developed for detection of nuclearHz 14 N NQR frequency of ammonium nitrate. A potential application of the magnetometer is detection

Romalis, Mike

245

Controlling the electromagnetically induced transparency frequency tuning range by radio-frequency field  

NASA Astrophysics Data System (ADS)

The Electromagnetically Induced Transparency (EIT) is associated with a ? three-level system and the spectral position of EIT window can be changed by varying the frequency of the coupling field, however, at large detuning the EIT will evolve into a dispersion-like feature and transparency property of EIT become less obvious. In this paper, it is shown that we can perform EIT frequency tuning by a radio-frequency (rf) field. In the cascade quasic-? four-level system, the absorption profile of probe field is calculated by solving the equations of motion of the density matrix. It is shown that the Autler-Townes doublet originates from the rf-field induced dynamic Stark effect and the spectral position of EIT window is determined by the frequency detuning of the coupling field. When the frequency detuning of the coupling field is half of the rf Rabi frequency, the EIT feature remain its absorptive profile. The frequency tuning rang of EIT is determined by the rf Rabi frequency, and can be explained using a dressed-state analysis. Therefore, frequency tuning range of EIT can be controlled by the rf Rabi frequency.

Zhang, Lianshui; Zhuang, Zhonghong; Wang, Jian; Feng, Xiaomin; Yang, Lijun

2008-01-01

246

Very low frequency radio astronomy from lunar orbit  

NASA Astrophysics Data System (ADS)

This paper discusses the use of very low frequency aperture synthesis as a probe of astrophysical phenomena. Specifically, the science achievable with the Lunar Observer Radio Astronomy Experiment (LORAE) is discussed. The density distribution and the degree of turbulence of the galactic plasma can be determined from its effect on background radio sources. These same absorption phenomena can be used to determine magnetic field strengths within astrophysical plasmas. Detection of unabsorbed synchrotron emission can provide information on the relativistic plasma component. The detection of new pulsars may prove feasible because of their steep spectra. Observations of planets in the solar system will be used to study their interaction with the solar wind. VLF studies of the sun will provide new information on the outer layers of its atmosphere and magnetic field as well as provide insight on the propagation of MHD disturbances through the corona. The plasma in the earth's magnetic field can be observed in detail and as a function of time. This will prove invaluable in understanding auroral phenomena end reconnection events.

Duric, Nebojsa

247

Low Frequency Radio Observations of GRS1915+105 with GMRT  

E-print Network

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.

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

2005-12-02

248

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

249

Superconducting radio-frequency modules test faciilty operating experience  

SciTech Connect

Fermilab is heavily engaged and making strong technical contributions to the superconducting radio-frequency research and development program (SRF R&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 Fermilab SRF R&D needs. The first stage of the project 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 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.; /Fermilab

2007-07-01

250

Superconducting Radio-Frequency Modules Test Facility Operating Experience  

NASA Astrophysics Data System (ADS)

Fermilab is heavily engaged and making strong technical contributions to the superconducting radio-frequency research and development program (SRF R&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&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.

2008-03-01

251

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

252

NbN thin films for superconducting radio frequency cavities  

NASA Astrophysics Data System (ADS)

NbN thin films have the potential to be incorporated into radio frequency cavities in a multilayer coating to overcome the fundamental field gradient limit of 50 MV m-1 for the bulk niobium based technology that is currently implemented in particle accelerators. In addition to having a larger critical field value than bulk niobium, NbN films develop smoother surfaces which are optimal for cavity performance and lead to fewer losses. Here, we present a study on the correlation of film deposition parameters, surface morphology, microstructure, transport properties and superconducting properties of NbN thin films. We have achieved films with bulk-like lattice parameters and superconducting transition temperatures. These NbN films have a lower surface roughness than similarly grown niobium films of comparable thickness. The potential application of NbN thin films in accelerator cavities is discussed.

Roach, W. M.; Skuza, J. R.; Beringer, D. B.; Li, Z.; Clavero, C.; Lukaszew, R. A.

2012-12-01

253

Radio-frequency quadrupole: A new linear accelerator  

NASA Astrophysics Data System (ADS)

The radio frequency quadrupole (RFQ) linear accelerator is discussed. In the RFQ, the use of RF electric fields for radial focusing, combined with special programming of the bunching, allows high current dc beams to be captured and accelerated with only small beam loss and low radial emittance growth. Advantages of the RFQ linac include a low injection energy (20 to 50 keV for protons) and a final energy high enough so the beam can be further accelerated with high efficiency in a Wideroee or Alvarez linac. The beam dynamics parameters of three RFQ systems are described. These are the final design for the prototype test of the Fusion Materials Irradiation Test accelerator, the final design for the prototype test of the Pion Generator for Medical Irradiations, and an improved low velocity linac for heavy ion fusion.

Stokes, R. H.; Wangler, T. P.; Crandall, K. R.

254

Microcalorimetry of dust particles in a radio-frequency plasma  

NASA Astrophysics Data System (ADS)

The internal temperature of rhodamine B-dyed dust particles (2rp=1.2 ?m) immersed in radio-frequency (rf) plasmas has been measured for various plasma conditions. For this purpose, the dye has been excited with an argon-ion laser and the fluorescent emission of the particles has been recorded with an optical multichannel analyzer system. The temperature has been determined after comparison with calibration curves. In argon, the particle temperature increases with rf power and is independent of pressure. In oxygen, an increase with rf power is observed, too. However, the energy flux towards the particles includes also heating by atom recombination (association) and exothermic combustion reactions. These temperature measurements have been compared with calculations based on the thermal balance, where measurements of gas temperature, electron density, and electron temperature have been used. A good agreement between theory and experiment has been found.

Swinkels, G. H. P. M.; Kersten, H.; Deutsch, H.; Kroesen, G. M. W.

2000-08-01

255

Stabilization of Fundamental-Frequency Microwave Oscillators for Radio-Relay Systems (Panel)  

Microsoft Academic Search

Frequency tolerances for microwave communications are presently under study within the International Telecommunications Union (ITU). This is being carried out in preparation for the World Administrative Radio Conference, 1979 (WAKC-79), which will revise the existing Radio Regulations. The International Radio Consultative Committee (CCIR) will hold in the Autumn of 1978, its Special Preparatory Meeting (SPM) for the WARC-79. So far,

F. Ivanek

1978-01-01

256

Glass-based confined structures fabricated by sol-gel and radio frequency sputtering  

NASA Astrophysics Data System (ADS)

Some of the main results obtained in the field of glass-based photonic crystal (PC) systems using complementary techniques, such as radio frequency (RF) sputtering and sol-gel route, are presented. Initially, rare earth-activated one-dimensional PCs fabricated by RF-sputtering technique will be discussed, specifically the cavity is constituted by an Er-doped SiO active layer inserted between two Bragg reflectors consisting of 10 pairs of SiO2/TiO2 layers. Moreover, from near infrared, transmittance and variable angle reflectance spectra have verified the presence of a stop band from 1500 to 2000 nm with a cavity resonance centered at 1749 nm at 0 deg and quality factor of 890. In the second case, a composite system based on polystyrene colloidal nanoparticles assembled and embedded in an elastomeric matrix will be presented in detail. This system has been designed as a structure that displays an iridescent green color that can be attributed to the PC effect. This feature has been exploited to create a chemical sensor; in fact optical measurements have evidenced that this system presents a different optical response as a function of the solvent applied on the surface, showing: (1) high sensitivity, (2) fast response, and (3) reversibility of the signal change.

Chiappini, Andrea; Armellini, Cristina; Carpentiero, Alessandro; Vasilchenko, Iustyna; Lukowiak, Anna; Risti?, Davor; Varas, Stefano; Normani, Simone; Mazzola, Maurizio; Chiasera, Alessandro

2014-07-01

257

Latitudinal beaming of Jupiter's low frequency radio emissions  

NASA Technical Reports Server (NTRS)

By comparing RAE-1 and IMP-6 satellite measurements of Jupiter's radio emission near 1MHz with recent Voyager-1 and 2 observations in the same frequency range, the properties of the low frequency radiation pattern over a 10 deg range of latitudes with respect to the Jovian rotation equator can be studied. These observations, which cover a wider latitudinal range than is possible from the earth, are consistent with many aspects of earlier ground-based measurements used to infer a sharp beaming pattern for the decameter wavelength emissions. Marked, systematic changes are found in the statistical occurrence probability distributions with system 3 central meridian longitude as the jovigraphic latitude of the observer changes over this range. Simultaneous observations by the two Voyager spacecraft suggest that the instantaneous beam width may be no more than a few degrees at times. The new hectometer-wave results can be interpreted in terms of a narrow, curved sheet at a fixed magnetic latitude into which the emission is beamed to escape the planet.

Alexander, J. K.; Desch, M. D.; Kaiser, M. L.; Thieman, J. R.

1979-01-01

258

Enhancement of electromagnetic propagation through complex media for Radio Frequency Identification  

E-print Network

In this thesis, I present and examine the fundamental limitations involved in Radio Frequency Identification (RFID) as well as provide a means to improve reader-tag communication in ultra high frequency RFID systems. The ...

Marti, Uttara P

2005-01-01

259

Chapter 7: Radio-Frequency Wave Physics in the FTU  

SciTech Connect

This chapter reports the main physics results obtained with three radio-frequency-injection systems. The frequency of 8 GHz for the lower hybrid (LH) current drive (CD) (LHCD) system was chosen to explore CD at high density: full CD has been demonstrated for central densities up to 1.4 x 10{sup 20} m{sup -3} at 0.5 MA with an applied power up to 2.0 MW. The Frascati Tokamak Upgrade (FTU) database shows CD efficiencies from 0.1 to 0.3 x 10{sup 20} AW{sup -1} m{sup -2}. In combined experiments with electron cyclotron (EC) waves (140 GHz, up to 1.2 MW), a suprathermal absorption by the fast electron tail generated by LHCD has been observed in both downshifted and upshifted interaction regimes, with the resulting electron cyclotron current drive (ECCD) ranging from 20 to 100 kA, depending on experimental conditions. With pure EC resonance heating, the narrowness of the radial power deposition profile has been exploited, resulting in strong local electron heating. Results in high-density regimes are also presented. The third system (433 MHz, 0.5 MW) is the first to test ion Bernstein wave (IBW) coupling with a waveguide antenna. The experiment operates at high frequency, avoiding the occurrence of nonlinear phenomena at the edge. Improved confinement regimes resulting in a central peaking of the pressure profiles have been achieved with P{sub IBW} up to 0.4 MW. Modeling and experimental results are summarized.

Granucci, G. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Airoldi, A. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Barbato, E. [Associazione EURATOM-ENEA sulla Fusione (Italy); Bruschi, A. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Cardinali, A. [Associazione EURATOM-ENEA sulla Fusione (Italy); Castaldo, C. [Associazione EURATOM-ENEA sulla Fusione (Italy); Cesario, R. [Associazione EURATOM-ENEA sulla Fusione (Italy); Cirant, S. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Esposito, B. [Associazione EURATOM-ENEA sulla Fusione (Italy); Farina, D. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Gandini, F. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Giruzzi, G. [Association EURATOM-CEA sur la Fusion (France); Gormezano, C. [Associazione EURATOM-ENEA sulla Fusione (Italy); Leigheb, M. [Associazione EURATOM-ENEA sulla Fusione (Italy); Marinucci, M. [Associazione EURATOM-ENEA sulla Fusione (Italy); Mirizzi, F. [Associazione EURATOM-ENEA sulla Fusione (Italy); Nowak, S. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Panaccione, L. [Associazione EURATOM-ENEA sulla Fusione (Italy); Pericoli-Ridolfini, V. [Associazione EURATOM-ENEA sulla Fusione (Italy); Podda, S. [Associazione EURATOM-ENEA sulla Fusione (Italy); Ramponi, G. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Ravera, G.L. [Associazione EURATOM-ENEA sulla Fusione (Italy); Saveliev, A.N. [A. F. Ioffe Physico-Technical Institute (Russian Federation); Simonetto, A. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Sozzi, C. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Tuccillo, A.A. [Associazione EURATOM-ENEA sulla Fusione (Italy); Zonca, F. [Associazione EURATOM-ENEA sulla Fusione (Italy)

2004-05-15

260

Charge dynamics in capacitively coupled radio frequency discharges  

NASA Astrophysics Data System (ADS)

In a capacitively coupled radio frequency (CCRF) discharge the number of positive and negative charges lost to each electrode must balance within one RF period to ensure a constant total uncompensated charge in the discharge, Qtot, on time average. This balance is the result of a compensation of electron and ion fluxes at each electrode within one RF period. Although Qtot is constant on temporal average, it is time dependent on time scales shorter than one RF period, since it results from a balance of the typically constant ion flux and the strongly time dependent electron flux at each electrode. Nevertheless, Qtot is assumed to be constant in various models. Here the dynamics of Qtot is investigated in a geometrically symmetric CCRF discharge operated in argon at 13.56 and 27.12 MHz with variable phase shift ? between the driving voltages by a PIC simulation and an analytical model. Via the electrical asymmetry effect (EAE) a variable dc self-bias is generated as a function of ?. It is found that Qtot is not temporally constant within the low frequency period, but fluctuates by about 10% around its time average value. This modulation is understood by an analytical model. It is demonstrated that this charge dynamics leads to a phase shift of the dc self-bias not captured by models neglecting the charge dynamics. This dynamics is not restricted to dual frequency discharges. It is a general phenomenon in all CCRF discharges and can generally be described by the model introduced here. Finally, Qtot is split into the uncompensated charges in each sheath. The sheath charge dynamics and the self-excitation of non-linear plasma series resonance oscillations of the RF current via the EAE at low pressures of a few pascals are discussed.

Schulze, J.; Schüngel, E.; Donkó, Z.; Czarnetzki, U.

2010-06-01

261

Automatic calibration of modulated fractional-N frequency synthesizers  

E-print Network

The focus of this research has been the development of a low power, radio frequency transmitter architecture. Specifically, a technique for in service automatic calibration of a modulated phase locked loop (PLL) frequency ...

McMahill, Dan

2001-01-01

262

Room temperature femtotesla radio-frequency atomic magnetometer W. Chalupczak,1  

E-print Network

Room temperature femtotesla radio-frequency atomic magnetometer W. Chalupczak,1 R. M. Godun,1 S online 12 June 2012) A radio-frequency tunable atomic magnetometer with a sensitivity of about 1 fT/Hz1/2 in a range of 10�500 kHz is demonstrated. The magnetometer is operated in the orientation configuration

263

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

Code of Federal Regulations, 2013 CFR

...Marketing of radio frequency products prior to equipment authorization...Marketing of radio frequency products prior to equipment authorization...includes sale or lease, or offering for sale or lease...selling or leasing or offering for sale or lease...1) Activities under product development and...

2013-10-01

264

Nonlinear Exothermic Contributions to RadioFrequency Bonding of Adhesives 1  

E-print Network

Nonlinear Exothermic Contributions to Radio­Frequency Bonding of Adhesives 1 H.T. Banks 2 S and Department of Mathematics, Box 8205, North Car­ olina State University, Raleigh, NC 27695­8205. 3 Lord This work describes an effort to model the radio­frequency curing of epoxy adhesives in bonding

265

Exascale Real-Time Radio Frequency Interference Mitigation  

NASA Astrophysics Data System (ADS)

Radio Frequency Interference (RFI) mitigation is extremely important to take advantage of the vastly improved bandwidth, sensitivity, and field-of-view of exascale telescopes. For current instruments, RFI mitigation is typically done offline, and in some cases (partially) manually. At the same time, it is clear that due to the high bandwidth requirements, RFI mitigation will have to be done automatically, and in real-time, for exascale instruments. In general, real-time RFI mitigation will be less precise than offline approaches. Due to memory constraints, there is much less data to work with, typically only in the order of one second or less, as opposed to the entire observation. In addition, we can record only limited statistics of the past. Moreover, we will typically have only few frequency channels locally available at each compute core. Finally, the amount of processing that can be spent on RFI mitigation is extremely limited due to computing and power constraints. Nevertheless, there are potential benefits as well, which include the possibility of working on higher time and frequency resolutions before any integration is done, leading to more accurate results. Most importantly, we can remove RFI before beam forming, which combines data from all receivers. The RFI that is present in the data streams from the separate receivers is also combined, effectively taking the union of all RFI. Thus, the RFI from all receivers pollutes all beams. Therefore, it is essential to do real-time RFI mitigation before the beam former. This is particularly important for pulsar surveys, for instance. modes. Although our techniques are generic, we describe how we implemented real-time RFI mitigation for one of the SKA pathfinders: The Low Frequency Array (LOFAR). The RFI mitigation algorithms and operations we introduce here are extremely fast, and the computational requirements scale linearly in the number of samples and frequency channels. We evaluate the quality of the algorithms with real LOFAR pulsar observations. By comparing the signal-to-noise ratios of the folded pulse profiles, we can quantitatively compare the impact of real-time RFI mitigation, and compare different algorithms.

van Nieuwpoort, Rob; Lofar Team

2014-04-01

266

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

267

Low Frequency Radio Signal Polarisation Sensor with Applications in Attitude Estimation  

E-print Network

. I. INTRODUCTION Measurement of a system’s attitude (its orientation relative to a reference coordinate frame) is essential in a range of applications, from simple smartphone tilt measurement to inertial navigation and attitude control. Within... for numerous commercial radio stations, navigation beacons and timing signals. Signals travel mainly by direct line-of-sight transmission and by ground- wave (surface wave), which allows LF signals to be received over very large distances. Transmitters...

Maguire, Sean; Robertson, Paul

2014-01-01

268

Post-growth annealing study of heavily Ga-doped zinc oxide grown by radio frequency magnetron sputtering  

NASA Astrophysics Data System (ADS)

Heavily doped Ga-doped ZnO (resistivity ˜8 × 10-4 ? cm and optical transmittance 96%) were fabricated by radio frequency magnetron sputtering. Post-growth annealing studies in H2-Ar and pure Ar atmospheres were conducted. No noticeable thermal-induced change in the Ga depth profile or in the Ga chemical state was found in both atmospheres up to 600 °C. The Burstein-Moss effect was exhibited in the effective optical band gap, and the cathodoluminescence (CL) photon energy of the near band edge emission. CL emission related to VZn persisted after the 600 °C annealing. The thermal evolutions of the carrier concentrations were nearly identical for both annealing atmospheres. The carrier mobility increased upon annealing in H2/Ar and remained effectively unchanged in pure Ar. The observed changes in carrier concentration and mobility were tentatively associated with VZn, or other compensating defects, which have concentrations as high as 1019-1020 cm-3.

Pak, C. M.; Su, S. C.; Ling, C. C.; Lu, Y. M.; Zhu, D. L.

2013-04-01

269

Optical and electrical properties of Mg-doped zinc tin oxide films prepared by radio frequency magnetron sputtering  

NASA Astrophysics Data System (ADS)

In this study, magnesium (Mg)-doped zinc tin oxide (ZTO) films were deposited by radio frequency (RF) magnetron sputtering. The Mg was selected as an electron suppressor for the ZTO films. X-ray diffraction (XRD) was carried out to observe the crystallinity of the films. The Mg-doping effects on the elemental properties of the films were investigated by X-ray photoelectron spectroscopy (XPS). The optical properties, such as transmittance, optical band gap, Urbach energy, and refractive index, were compared as a function of Mg content. Bottom-gate transparent thin-film transistors (TTFTs) were fabricated on N+ Si wafers. The turn-off voltage, threshold voltage, and mobility variation as a function of Mg content were studied.

Ma, Tae Young; Choi, Mu Hee

2013-12-01

270

From T.H. Lee, The Design of CMOS Radio-Frequency Integrated Circuits A Nonlinear History of Radio 1998 Cambridge University Press Page 1 of 34  

E-print Network

From T.H. Lee, The Design of CMOS Radio-Frequency Integrated Circuits A Nonlinear History of Radio ©1998 Cambridge University Press Page 1 of 34 A Nonlinear History of Radio 1.0 Introduction Integrated history of radio touches briefly on just some of the main stories, and provides pointers to the literature

Lee, Thomas H.

271

Energy Saving Glass Lamination via Selective Radio Frequency Heating  

SciTech Connect

Ceralink Inc. developed FastFuse™, a rapid, new, energy saving process for lamination of glass and composites using radio frequency (RF) heating technology. The Inventions and Innovations program supported the technical and commercial research and development needed to elevate the innovation from bench scale to a self-supporting technology with significant potential for growth. The attached report provides an overview of the technical and commerical progress achieved for FastFuse™ during the course of the project. FastFuse™ has the potential to revolutionize the laminate manufacturing industries by replacing energy intensive, multi-step processes with an energy efficient, single-step process that allows higher throughput. FastFuse™ transmits RF energy directly into the interlayer to generate heat, eliminating the need to directly heat glass layers and the surrounding enclosures, such as autoclaves or vacuum systems. FastFuse™ offers lower start-up and energy costs (up to 90% or more reduction in energy costs), and faster cycles times (less than 5 minutes). FastFuse™ is compatible with EVA, TPU, and PVB interlayers, and has been demonstrated for glass, plastics, and multi-material structures such as photovoltaics and transparent armor.

Shawn M. Allan; Patricia M. Strickland; Holly S. Shulman

2009-11-11

272

Manufacture of radio frequency micromachined switches with annealing.  

PubMed

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. PMID:24445415

Lin, Cheng-Yang; Dai, Ching-Liang

2013-01-01

273

Radio-frequency measurement of an asymmetric single electron transistor  

NASA Astrophysics Data System (ADS)

Since the invention of the radio-frequency single-electron transistor (RF-SET) by Schoelkopf et al.,[1] most measurements have focused on the symmetric single electron transistor. It has been shown, however, that the symmetric SET has a rather low measurement efficiency in its normal working regime.[2][3] Recently, it has been pointed out that an asymmetric SET can be considerably more efficient than a symmetric SET as a quantum amplifier. In this case the measurement efficiency of the asymmetric SET becomes similar to that of the quantum point contact (QPC) detector which can approach the quantum limit. We investigate the asymmetric SET by fabricating Al/AlOx SETs with junction areas 40x40 nm^2 and 40x80nm^2 and total resistance of about 25k?. The results of RF and DC characterization of such asymmetric SETs will be discussed. [1] R. J. Schoelkopf, P. Wahlgren, A. A. Kozhevnikov, P. Delsing, D. E. Prober, Science, 280, 1242 (1998). [2] A. N. Korotkov, Phys. Rev. B, 63, 085312 (2001); 63, 115403 (2001). [3] D. Mozyrsky, I. Martin, and M. B. Hastings, Phys. Rev. Lett., 92, 018303 (2004). [4] S. A. Gurvitz and G. P. Berman, Phys. Rev. B, 72 , 073303(2005).

Ji, Zhongqing; Xue, Weiwei; Rimberg, A. J.

2007-03-01

274

A Graphical Approach to Radio Frequency Quadrupole Design  

E-print Network

The design of a radio frequency quadrupole, an important section of all ion accelerators, and the calculation of its beam dynamics properties can be achieved using the existing computational tools. These programs, originally designed in 1980s, show effects of aging in their user interfaces and in their output. The authors believe there is room for improvement in both design techniques using a graphical approach and in the amount of analytical calculations before going into CPU burning finite element analysis techniques. Additionally an emphasis on the graphical method of controlling the evolution of the relevant parameters using the drag-to-change paradigm is bound to be beneficial to the designer. A computer code, named DEMIRCI, has been written in C++ to demonstrate these ideas. This tool has been used in the design of Turkish Atomic Energy Authority (TAEK)'s 1.5 MeV proton beamline at Saraykoy Nuclear Research and Training Center (SANAEM). DEMIRCI starts with a simple analytical model, calculates the RFQ b...

Turemen, G; Yasatekin, B

2014-01-01

275

Radio-frequency plasma transducer for use in harsh environments.  

PubMed

We describe a compact transducer used to generate and modulate low-intensity radio-frequency atmospheric pressure plasma (RF-APP) for high temperature gap measurement and generation of air-coupled ultrasound. The new transducer consists of a quarter-wave transmission line where the ground return path is a coaxial solenoid winding. The RF-APP is initiated at the open end of the transmission line and stabilized by passive negative feedback between the electrical impedance of the plasma and the energy stored in the solenoid. The electrical impedance of the plasma was measured at the lower-voltage source end of the transducer, eliminating the need to measure kilovolt-level voltages near the discharge. We describe the use of a 7 MHz RF-APP prototype as a harsh-environment clearance sensor to demonstrate the suitability of plasma discharges for a common nondestructive inspection application. Clearance measurements of 0-5 mm were performed on a rotating calibration target with a measurement precision of 0.1 mm and a 20 kHz sampling rate. PMID:17979443

May, Andrew; Andarawis, Emad

2007-10-01

276

Image transmission in tactical radio frequency shared network propagation environments  

NASA Astrophysics Data System (ADS)

The need to transmit images across tactical radio frequency (rf) links has been identified in army digitization applications. For example, military doctrine requires that tactical functions like identification of battlefield entities as potential targets and battle damage assessment be performed by the soldier. Currently, a key input to these processes is imagery. Therefore, the quality and timeliness of the image directly impact tactical performance. The military is investigating the employment of remote sensors and advanced communications systems to meet this requirement as part of its digitization effort. Army communications systems exist that partially meet this requirement. However, many existing solutions employ these legacy systems in the context of a point-to-point communications architecture. Solutions to the problem of transmitting images across a rf network have not been fully explored. The term network implies that the rf transmission media is common to and shared by multiple subscribers. It is a suite of capabilities that collectively manage media access and information transfer for its subscribers thus providing substantial improvements in effectiveness, efficiency, and robustness. This paper discusses the challenges of transmitting images using one army legacy communications system in a tactical rf network, presents a conceptual framework for attacking the problem, and discusses one solution.

White, Kent H.; Wagner, Kerry A.; O'Hanian, Scott

1997-06-01

277

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

278

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. PMID:17279784

Chen, I-Jane

2008-01-01

279

Operating a radio-frequency plasma source on water vapor.  

PubMed

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(i) approximately = n(e), where n(i) is the positive ion density. But in the electronegative water plasma, quasineutrality requires n(i+) = n(i-) + n(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. PMID:19725651

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

2009-08-01

280

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

281

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

282

Radio-frequency plasma transducer for use in harsh environments  

SciTech Connect

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

May, Andrew; Andarawis, Emad [GE Global Research, 1 Research Circle, Niskayuna, New York 12309 (United States)

2007-10-15

283

Controlled radio frequency vessel sealing system for surgical applications  

NASA Astrophysics Data System (ADS)

A radio frequency tissue welding system has been developed for occlusion of vessels during surgery. The system is designed to replace commonly used mechanical clip and suture ligation techniques. Other energy based ligation techniques are limited to use on small structures (

Kennedy, Jenifer S.; Buysse, Steve; Chandler, James; Eggleston, Jeff; Taylor, Kenneth D.; Thomsen, Sharon L.

1998-04-01

284

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

285

47 CFR 101.129 - Transmitter location.  

Code of Federal Regulations, 2010 CFR

...101.129 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES Technical Standards § 101.129 Transmitter location. (a) The applicant must...

2010-10-01

286

47 CFR 87.133 - Frequency stability.  

Code of Federal Regulations, 2010 CFR

... 13 30 Radionavigation stations 20 20 Differential GPS 2 (6) Band-137 to 470MHz: Aeronautical stations...20 Hz. (d) For radar transmitters, except non-pulse signal radio altimeters, the frequency at which maximum...

2010-10-01

287

Growth and physiological responses to surgical and gastric radio transmitter implantation techniques in subyearling chinook salmon (Oncorhynchus tshawytscha)  

USGS Publications Warehouse

We examined the effects of surgical and gastric transmitter implantation techniques on the growth, general physiology and behavior of 230 subyearling chinook salmon (Oncorhynchus tshawytscha, Walbaum) (100 mm-154 mm fork length). The transmitter weighed 1.3 g in air (0.9 g in water) and comprised, on average, 6% of the body weight of the fish (in air). Individuals were randomly assigned to an experimental group (control, surgical or gastric) and a sampling period (day 5 or day 21). Relative growth rate was expressed as% body weight gained/day. General condition was assessed by necropsy. Physiological response variables included hematocrit, leucocrit and plasma protein concentration. The mean relative growth rates of control, surgical and gastric fish were not significantly different at day 5. By day 21, the gastric group had a significantly lower relative growth rate (1.3%) as compared to the surgical group (1.8%) and the control group (1.9%) (P = 0.0001). Mean hematocrit values were significantly lower in the surgical (41.8%) and gastric (42.2%) groups as compared to controls (47.3%) at day 5 (P = 0.01), but all were within normal range for salmonids. No significant differences in hematocrit values were detected at day 21. Leucocrit values for all groups were ??? 1% in 99% of the fish. Both tagged groups had significantly lower mean plasma protein levels as compared to controls at day 5 (P = 0.001) and day 21 (P = 0.0001). At day 21 the gastric group (64.4 g 100 m1-1) had significantly lower mean plasma protein levels than the surgical group (68.8 g 100 ml-1) (P = 0.0001). Necropsies showed decreasing condition of gastrically tagged fish over time, and increasing condition of surgical fish. Paired releases of surgically and gastrically implanted yearling chinook salmon in the lower Columbia River in spring, 1996 revealed few significant differences in migration behavior through two reservoirs. We conclude that gastrically implanted fish show decreased growth and condition over a 21 d period. We recommend a surgical implantation method for long-term studies of juvenile salmonids, however, gastric implantation may be suitable for short-term studies.

Martinelli, T. L.; Hansel, H. C.; Shively, R. S.

1998-01-01

288

Radio frequency sputtered Al:ZnO-Ag transparent conductor: A plasmonic nanostructure with enhanced optical and electrical properties  

NASA Astrophysics Data System (ADS)

Optimization of metal-based transparent conductors (MTCs) made of silver and aluminium-doped zinc oxide (AZO) prepared by radio-frequency (r.f.) sputtering has been carried out through tuning of metal film properties. The influence of morphology and related plasmonic features of AZO/Ag/AZO MTCs on their optical and electrical performance is demonstrated and it is shown that the nominal thickness of the silver layer itself is not the most crucial value determining the MTC performance. The MTC performance has been optimized by a search of deposition conditions ensuring fractal-type metal layer formation up to a certain coalescence state that enables full gaining from silver optical properties, including its plasmonic features. For 150 W- and 200 W-deposited silver, MTCs with maximum transmittance as high as 83.6% have been obtained. These coatings have a figure of merit as good as 0.01 ?-1 and a remarkably wide spectral transparency region: transmittance higher than 70% down to 1200 nm for 200W-samples. Modelling of the MTC coatings is proposed additionally, based on variable angle spectroscopic ellipsometric measurements, which takes into account the variation of the optical properties of silver when deposited in various conditions and embedded in a semiconductor stack.

Sytchkova, Anna; Luisa Grilli, Maria; Rinaldi, Antonio; Vedraine, Sylvain; Torchio, Philippe; Piegari, Angela; Flory, François

2013-09-01

289

Unveiling the nature of the unidentified gamma-ray sources: blazar counterparts at low radio frequencies  

NASA Astrophysics Data System (ADS)

About one third of the gamma-ray sources detected by Fermi have still no firmly established counterpart at lower energies. Here we propose a new approach to find candidate counterparts for the unidentified gamma-ray sources (UGSs) based on the 325 MHz radio survey performed with Westerbork Synthesis Radio Telescope (WSRT) in the northern hemisphere. First we investigate the low-frequency radio properties of blazars, the largest known population of gamma-ray sources; then we search for sources with similar radio properties combining the information derived from the Westerbork Northern Sky Survey (WENSS) with those of the NRAO VLA Sky survey (NVSS). We present a list of candidate counterparts for 32 UGSs with at least one counterpart in the WENSS. We also performed an extensive research in literature to look for infrared and optical counterparts of the gamma-ray blazar candidates selected with the low-frequency radio observations to confirm their nature. On the basis of our multifrequency research we identify 23 new gamma-ray blazar candidates out of 32 UGSs investigated. I will also present the first analysis of very low frequency radio emission of blazars based on the recent Very Large Array Low-Frequency Sky Survey (VLSS) at 74 MHz. I show that blazars present radio flat spectra when evaluated at 74 MHz, about an order of magnitude in frequency lower than previous analyses. The implications of these findings in the contest of the blazars - radio galaxies connection will be discussed.

Massaro, Francesco; D'Abrusco, R.; Giroletti, M.; Paggi, A.; Masetti, N.; Tosti, G.

2014-07-01

290

Radio Frequency Characteristics of Printed Meander Inductors and Interdigital Capacitors  

NASA Astrophysics Data System (ADS)

Radio frequency (RF) characterizations of printed silver ink inductors manufactured at low (150 °C) and high (850 °C) temperatures and interdigital capacitors manufactured at high (850 °C) temperatures were carried out in the 500 MHz to 6 GHz range. The S-parameter responses of the components were measured with a probe station and an Agilent 8510C network analyzer. Electrical parameters such as inductance, capacitance, and a quality factor were estimated from experimental results and numerical calculation. Component parameters are dependent on physical dimensions and material properties. The components were created in a 4 ×4 mm2 area with line widths/gaps of 500/500, 250/250, and 200/200 µm. Windings in the coils varied from 2 to 5 turns and finger counts in the capacitors, from 5 to 11 within the defined area and line widths. As a result, low-T-cured (150 °C) silver ink meander line inductors achieved 8 to 18 nH inductances at 1 and 2 GHz with a quality value of 10-25. High-T-cured (850 °C) silver ink meander line inductors had 6-15 nH inductances and quality values were around 100, indicating a conductivity challenge with low-T-cured inks. Interdigital capacitors with 1 to 4 pF capacitances and sufficient quality values were created. A low-loss BaTiO3 coating was printed over the interdigital capacitors; they exhibited suitable electrical characteristics to allow decreasing the physical size of the component.

Myllymaki, Sami; Teirikangas, Merja; Nelo, Mikko; Tulppo, Joel; Soboci?ski, Maciej; Juuti, Jari; Jantunen, Heli; Sloma, Marcin; Jakubowska, Malgorzata

2013-05-01

291

Scattering of radio frequency waves by blobs in tokamak plasmasa)  

NASA Astrophysics Data System (ADS)

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.; Hizanidis, Kyriakos; Kominis, Yannis

2013-05-01

292

Radio frequency needle hyperthermia of normal and cancerous animal tissue  

NASA Astrophysics Data System (ADS)

Capacitative radio frequency (RF) was met with little success when used to treat human cancer. Conductive rf needle hyperthermia (RFNH) is used successfully for human tissue ablation in neurosurgery, cardiology, and recently in urology. RFNH ablates tissue by causing thermal damage limited to the vicinity of the rf needle. We conducted a series of studies to evaluate the effect of RFNH on cancerous and normal tissue. RFNH was applied to normal porcine livers during open surgery. Liver function tests were elevated two days post treatment, then returned to normal. Pigs were sequentially sacrificed. RFNH induced lesions were found to be maximal in size on days 2 - 4 post treatment and later became smaller as liver regenerated. Phase 2 included mice bearing two subcutaneous murine bladder tumors (MBT2). The rf needle was inserted into both tumors of each mouse, but rf current was applied to one tumor only. Energies of 3 to 7.5 watts were applied for 30 seconds to 5 minutes using a 0.02 inch needle. Mice were sacrificed 0, 1, and 3 days after treatment. Necrotic lesions 0.5 - 1.2 cm in diameter were found within the treated tumors. In phase 3, mice bearing a single 8 - 18 mm subcutaneous tumor were treated by RFNH aiming for complete tumor destruction. All control mice died of huge tumors within 31 days. Treated mice were alive with no signs of tumor when sacrificed 60 days after treatment. In phase 3 RFNH is capable of complete tumor eradication with little damage to surrounding normal tissue. It may have clinical applications for percutaneous endoscopic and laparoscopic treatment of tumors.

Shalhav, Arieh; Ramon, J.; Goldwasser, Benad; Nativ, Ofer; Cherniack, Ramy; Zajdel, Liliana

1994-12-01

293

Radio-Frequency Plasma Cleaning of a Penning Malmberg Trap  

NASA Technical Reports Server (NTRS)

Radio-frequency-generated plasma has been demonstrated to be a promising means of cleaning the interior surfaces of a Penning-Malmberg trap that is used in experiments on the confinement of antimatter. {Such a trap was reported in Modified Penning-Malmberg Trap for Storing Antiprotons (MFS-31780), NASA Tech Briefs, Vol. 29, No. 3 (March 2005), page 66.} Cleaning of the interior surfaces is necessary to minimize numbers of contaminant atoms and molecules, which reduce confinement times by engaging in matter/antimatter-annihilation reactions with confined antimatter particles. A modified Penning-Malmberg trap like the one described in the cited prior article includes several collinear ring electrodes (some of which are segmented) inside a tubular vacuum chamber, as illustrated in Figure 1. During operation of the trap, a small cloud of charged antiparticles (e.g., antiprotons or positrons) is confined to a spheroidal central region by means of a magnetic field in combination with DC and radiofrequency (RF) electric fields applied via the electrodes. In the present developmental method of cleaning by use of RF-generated plasma, one evacuates the vacuum chamber, backfills the chamber with hydrogen at a suitable low pressure, and uses an RF-signal generator and baluns to apply RF voltages to the ring electrodes. Each ring is excited in the polarity opposite that of the adjacent ring. The electric field generated by the RF signal creates a discharge in the low-pressure gas. The RF power and gas pressure are adjusted so that the plasma generated in the discharge (see Figure 2) physically and chemically attacks any solid, liquid, and gaseous contaminant layers on the electrode surfaces. The products of the physical and chemical cleaning reactions are gaseous and are removed by the vacuum pumps.

Sims, William Herbert, III; Martin, James; Pearson, J. Boise; Lewis, Raymond

2005-01-01

294

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

295

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

296

Development of a superconducting radio frequency photoelectron injector  

NASA Astrophysics Data System (ADS)

A superconducting radio frequency (RF) photoelectron injector (SRF gun) is under development at the Research Center Dresden-Rossendorf. This project aims mainly at replacing the present thermionic gun of the superconducting electron linac ELBE. Thereby the beam quality is greatly improved. Especially, the normalized transverse emittance can be reduced by up to one order of magnitude depending on the operating conditions. The length of the electron bunches will be shortened by about two orders of magnitude making the present bunchers in the injection beam line dispensable. The maximum obtainable bunch charge of the present thermionic gun amounts to 80 pC. The SRF gun is designed to deliver also higher bunch charge values up to 2.5 nC. Therefore, this gun can be used also for advanced facilities such as energy recovery linacs (ERLs) and soft X-ray FELs. The SRF gun is designed as a 3{1}/{2} cell cavity structure with three cells basically TESLA cells supplemented by a newly developed gun cell and a choke filter. The exit energy is projected to be 9.5 MeV. In this paper, we present a description of the design of the SRF gun with special emphasis on the physical and technical problems arising from the necessity of integrating a photocathode into the superconducting cavity structure. Preparation, transfer, cooling and alignment of the photocathode are discussed. In designing the SRF gun cryostat for most components wherever possible the technical solutions were adapted from the ELBE cryostat in some cases with major modifications. As concerns the status of the project the design is finished, most parts are manufactured and the gun is being assembled. Some of the key components are tested in special test arrangements such as cavity warm tuning, cathode cooling, the mechanical behavior of the tuners and the effectiveness of the magnetic screening of the cavity.

Arnold, A.; Büttig, H.; Janssen, D.; Kamps, T.; Klemz, G.; Lehmann, W. D.; Lehnert, U.; Lipka, D.; Marhauser, F.; Michel, P.; Möller, K.; Murcek, P.; Schneider, Ch.; Schurig, R.; Staufenbiel, F.; Stephan, J.; Teichert, J.; Volkov, V.; Will, I.; Xiang, R.

2007-07-01

297

H- radio frequency source development at the Spallation Neutron Sourcea)  

NASA Astrophysics Data System (ADS)

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.

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

298

Analytical model for the radio-frequency sheath.  

PubMed

A simple analytical model for the planar radio-frequency (rf) sheath in capacitive discharges is developed that is based on the assumptions of a step profile for the electron front, charge exchange collisions with constant cross sections, negligible ionization within the sheath, and negligible ion dynamics. The continuity, momentum conservation, and Poisson equations are combined in a single integro-differential equation for the square of the ion drift velocity, the so called sheath equation. Starting from the kinetic Boltzmann equation, special attention is paid to the derivation and the validity of the approximate fluid equation for momentum balance. The integrals in the sheath equation appear in the screening function which considers the relative contribution of the temporal mean of the electron density to the space charge in the sheath. It is shown that the screening function is quite insensitive to variations of the effective sheath parameters. The two parameters defining the solution are the ratios of the maximum sheath extension to the ion mean free path and the Debye length, respectively. A simple general analytic expression for the screening function is introduced. By means of this expression approximate analytical solutions are obtained for the collisionless as well as the highly collisional case that compare well with the exact numerical solution. A simple transition formula allows application to all degrees of collisionality. In addition, the solutions are used to calculate all static and dynamic quantities of the sheath, e.g., the ion density, fields, and currents. Further, the rf Child-Langmuir laws for the collisionless as well as the collisional case are derived. An essential part of the model is the a priori knowledge of the wave form of the sheath voltage. This wave form is derived on the basis of a cubic charge-voltage relation for individual sheaths, considering both sheaths and the self-consistent self-bias in a discharge with arbitrary symmetry. The externally applied rf voltage is assumed to be sinusoidal, although the model can be extended to arbitrary wave forms, e.g., for dual-frequency discharges. The model calculates explicitly the cubic correction parameter in the charge-voltage relation for the case of highly asymmetric discharges. It is shown that the cubic correction is generally moderate but more pronounced in the collisionless case. The analytical results are compared to experimental data from the literature obtained by laser electric field measurements of the mean and dynamic fields in the capacitive sheath for various gases and pressures. Very good agreement is found throughout. PMID:24483571

Czarnetzki, Uwe

2013-12-01

299

Radio-frequency single-electron transistor: Toward the shot-noise limit A. Aassime,a)  

E-print Network

to a few kHz. With the invention of the radio-frequency SET rf-SET ,5 the SET was made fast and veryRadio-frequency single-electron transistor: Toward the shot-noise limit A. Aassime,a) D. Gunnarsson is embedded. We measured the charge sensitivity of this radio-frequency single-electron transistor to be 3

300

Calculation of frequency and spatial separation regulations for fixed service receiving stations and radio facilities of other services  

Microsoft Academic Search

In the process of transmission of fixed service radio links it is important to provide the required frequency and spatial separation between fixed service receiving stations and radio facilities of other services operating in the same frequency band as fixed service stations. According to radio regulations, the frequency bands assigned to the fixed service are in most cases also used

A. K. Meteisky; V. I. Mordachev; V. M. Kozel

2001-01-01

301

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

302

An in situ measurement of the radio-frequency attenuation in ice at Summit Station, Greenland  

E-print Network

We report an in situ measurement of the electric field attenuation length at radio frequencies for the bulk ice at Summit Station, Greenland, made by broadcasting radio-frequency signals vertically through the ice and measuring the relative power in the return ground bounce signal. We find the depth-averaged field attenuation length to be 947 +92/-85 meters at 75 MHz. While this measurement has clear radioglaciological applications, the radio clarity of the ice also has implications for the detection of ultra-high energy (UHE) astrophysical particles via their radio emission in dielectric media such as ice. The measured attenuation length at Summit Station is comparable to previously measured radio-frequency attenuation lengths at candidate particle detector sites around the world, and strengthens the case for Summit Station as the most promising northern site for UHE neutrino detection.

Avva, J; Miki, C; Saltzberg, D; Vieregg, A G

2014-01-01

303

An in situ measurement of the radio-frequency attenuation in ice at Summit Station, Greenland  

E-print Network

We report an in situ measurement of the electric field attenuation length at radio frequencies for the bulk ice at Summit Station, Greenland, made by broadcasting radio-frequency signals vertically through the ice and measuring the relative power in the return ground bounce signal. We find the depth-averaged field attenuation length to be 947 +92/-85 meters at 75 MHz. While this measurement has clear radioglaciological applications, the radio clarity of the ice also has implications for the detection of ultra-high energy (UHE) astrophysical particles via their radio emission in dielectric media such as ice. The measured attenuation length at Summit Station is comparable to previously measured radio-frequency attenuation lengths at candidate particle detector sites around the world, and strengthens the case for Summit Station as the most promising northern site for UHE neutrino detection.

J. Avva; J. M. Kovac; C. Miki; D. Saltzberg; A. G. Vieregg

2014-09-18

304

2010 Raj JainCSE574sWashington University in St. Louis Radio FrequencyRadio Frequency  

E-print Network

openers use RFID Implants in human, horses, fishes, animals Animal ID Standards ISO 11784 and 11785 use, Radio receiver, radio modulator, control logic, memory and a power system Power Source: Passive Tags. Designed to be implanted in humans. Identify patients. Semi-passive RFIDs used in E-Z Pass toll collection

Jain, Raj

305

Assessment of radio frequency exposures in schools, homes, and public places in belgium.  

PubMed

Characterization of exposure from emerging radio frequency (RF) technologies in areas where children are present is important. Exposure to RF electromagnetic fields (EMF) was assessed in three "sensitive" microenvironments; namely, schools, homes, and public places located in urban environments and compared to exposure in offices. In situ assessment was conducted by performing spatial broadband and accurate narrowband measurements, providing 6-min averaged electric-field strengths. A distinction between internal (transmitters that are located indoors) and external (outdoor sources from broadcasting and telecommunication) sources was made. Ninety-four percent of the broadband measurements were below 1 V m. The average and maximal total electric-field values in schools, homes, and public places were 0.2 and 3.2 V m (WiFi), 0.1 and 1.1 V m (telecommunication), and 0.6 and 2.4 V m (telecommunication), respectively, while for offices, average and maximal exposure were 0.9 and 3.3 V m (telecommunication), satisfying the ICNIRP reference levels. In the schools considered, the highest maximal and average field values were due to internal signals (WiFi). In the homes, public places, and offices considered, the highest maximal and average field values originated from telecommunication signals. Lowest exposures were obtained in homes. Internal sources contributed on average more indoors (31.2%) than outdoors (2.3%), while the average contributions of external sources (broadcast and telecommunication sources) were higher outdoors (97.7%) than at indoor positions (68.8%). FM, GSM, and UMTS dominate the total downlink exposure in the outdoor measurements. In indoor measurements, FM, GSM, and WiFi dominate the total exposure. The average contribution of the emerging technology LTE was only 0.6%. PMID:25353235

Verloock, Leen; Joseph, Wout; Goeminne, Francis; Martens, Luc; Verlaek, Mart; Constandt, Kim

2014-12-01

306

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

307

Multi-frequency radio observations of a solar eclipse  

Microsoft Academic Search

The main results of radio observations of the Feb. 16, 1980 eclipse carried out in Yunnan are summarized. The authors have found: The radius of the radio sun in solar maximum year amounts to 1.007, 1.013, 1.040, 1.067 and 1.090 R_sun; at 0.86 cm, 2.0 cm, 3.2 cm, 8.2 cm and 21 cm respectively. The flux density spectra of the

Q.-J. Fu; S.-C. Ji; X.-H. Luo; Z.-M. Gao; X.-M. Mun

1983-01-01

308

Low Frequency Radio Transients in the Galactic Center  

Microsoft Academic Search

We report the detection of a new radio transient source, GCRT J1746-2757, located only 1.1 degrees north of the Galactic center. Consistent with other radio transients toward the Galactic center, this source brightened and faded on a time scale of a few months. No X-ray counterpart was detected, but upper limits suggest that GCRT J1746-2757 may have been a \\

S. D. Hyman; A. L. Bartleson; T. J. W. Lazio; N. E. Kassim

2001-01-01

309

Preliminary analysis of investigation Radio Frequency Interference (RFI) profile analysis at Universiti Teknologi MARA  

Microsoft Academic Search

In this paper, we have identified some important Radio Frequency Interference (RFI) sources that can potentially be a problem for any future radio astronomical observations in Universiti Teknologi MARA (UiTM) and possibly in Malaysia as a whole. Analysis is done by classifying and characterizing the strength of the sources' RFI profiles. Comparison of the RFI profiles between the indoor (Faculty

Z. S. Hamidi; Z. Z. Abidin; Z. A. Ibrahim; N. N. M. Shariff; Ungku Ferwani Salwa Ungku Ibrahim; R. Umar

2011-01-01

310

Sleep EEG alterations: effects of pulsed magnetic fields versus pulse-modulated radio frequency electromagnetic fields.  

PubMed

Studies have repeatedly shown that electroencephalographic power during sleep is enhanced in the spindle frequency range following radio frequency electromagnetic field exposures pulse-modulated with fundamental frequency components of 2, 8, 14 or 217 Hz and combinations of these. However, signals used in previous studies also had significant harmonic components above 20 Hz. The current study aimed: (i) to determine if modulation components above 20 Hz, in combination with radio frequency, are necessary to alter the electroencephalogram; and (ii) to test the demodulation hypothesis, if the same effects occur after magnetic field exposure with the same pulse sequence used in the pulse-modulated radio frequency exposure. In a randomized double-blind crossover design, 25 young healthy men were exposed at weekly intervals to three different conditions for 30 min before sleep. Cognitive tasks were also performed during exposure. The conditions were a 2-Hz pulse-modulated radio frequency field, a 2-Hz pulsed magnetic field, and sham. Radio frequency exposure increased electroencephalogram power in the spindle frequency range. Furthermore, delta and theta activity (non-rapid eye movement sleep), and alpha and delta activity (rapid eye movement sleep) were affected following both exposure conditions. No effect on sleep architecture and no clear impact of exposure on cognition was observed. These results demonstrate that both pulse-modulated radio frequency and pulsed magnetic fields affect brain physiology, and the presence of significant frequency components above 20 Hz are not fundamental for these effects to occur. Because responses were not identical for all exposures, the study does not support the hypothesis that effects of radio frequency exposure are based on demodulation of the signal only. PMID:22724534

Schmid, Marc R; Murbach, Manuel; Lustenberger, Caroline; Maire, Micheline; Kuster, Niels; Achermann, Peter; Loughran, Sarah P

2012-12-01

311

Radio-Frequency Conversion and Synthesis (for a 115mW GPS Receiver)  

E-print Network

at the antenna (PS -130dBm, PN -110dBm) · Large processing gain (GPS data bit, Tb = 20ms; C/A code chip, Tc 1Radio-Frequency Conversion and Synthesis (for a 115mW GPS Receiver) Arvin Shahani Stanford University #12;Overview · GPS Overview · Frequency Conversion · Frequency Synthesis · Conclusion #12;GPS

Lee, Thomas H.

312

Extending the ICRF to Higher Radio Frequencies: 24 and 43 GHz Astrometry  

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-band) 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.

Jacobs, Christopher S.; Charlot, Patrick; Fomalont, Ed B.; Gordon, David; Lanyi, Gabor E.; Ma, Chopo; Naudet, Charles J.; Sovers, Ojars J.; Zhang, Li-Wei D.

2004-01-01

313

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

314

Encoding, application and association of radio frequency identification tags on high speed manufacturing lines  

E-print Network

One of the entry points of radio frequency identification technology in supply chain applications is at the manufacturing line, after production, as packaged goods leave for the next link of the network of suppliers, ...

Fonseca, Herbert Moreti, 1973-

2004-01-01

315

REGENERATION AND REACTIVATION OF CARBON ADSORBENTS BY RADIO FREQUENCY INDUCTION HEATING  

EPA Science Inventory

1. Electrical Properties of Adsorbents: We measured the electric permittivity of four commercially available carbon adsorbents (supplied by Wesvaco Inc) over the radio frequency range (1 to 40 MHz). Westvaco is by far the largest volume supplier of activated carbon...

316

The Universe at Low Radio Frequencies ASP Conference Series, Vol. XXX , 2000  

E-print Network

The Universe at Low Radio Frequencies ASP Conference Series, Vol. XXX , 2000 A. Pramesh Rao et al.3% to 16.8%. Deep red CCD images do not reveal any optical object with a brightness and/or position typical

Roy, Alan

317

Integrating Radio Frequency Identification (RFID) data with Electronic Data Interchange (EDI) business processes  

E-print Network

Radio Frequency Identification (RFID) technology, an important component in the enterprise IT infrastructure, must be integrated into the legacy IT system. This thesis studies how RFID technology can be integrated into the ...

Chen, Yan (Yan Henry), 1976-

2005-01-01

318

A systems approach to the evaluation of Radio Frequency Identification (RFID) in the defense industry  

E-print Network

Radio Frequency Identification (RFID) is a wireless technology with possible applications in the supply chain. RFID tags' fast read rates, non-line-of-sight identification and large storage capacity may revolutionize supply ...

Shah, Ronak R

2005-01-01

319

A Dedicated Search for Low Frequency Radio Transient Astrophysical Events using ETA  

E-print Network

Frequency Radio Transients, Eight-meter-wavelength Transient Array, Crab Giant Pulses, Gamma Ray Bursts-annihilation of primordial black holes (PBHs), gamma ray bursts (GRBs), and supernovae are expected to produce single

Ellingson, Steven W.

320

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

321

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

322

Potential health effects of video display terminals and radio frequency heaters and sealers  

NASA Astrophysics Data System (ADS)

Video display terminals and radio frequency heaters and sealers have wide industrial applications. Both of these technologies involve the use of nonionizing radiation. Radiation leakages from these devices and their potential health effects are investigated.

323

Radio Frequency Identification of Katrina Hurricane Victims Rajit Gadh and B.S. Prabhu  

E-print Network

1 Radio Frequency Identification of Katrina Hurricane Victims Rajit Gadh and B.S. Prabhu Recently of the hurricane Katrina. Motivated by the interest generated by this news, in what follows we comment

California at Los Angeles, University of

324

Use of Radio Frequency Identification for Targeted Advertising: A Collaborative Filtering Approach Using Bayesian Networks  

E-print Network

This article discusses a potential application of radio frequency identification (RFID) and collaborative filtering for targeted advertising in grocery stores. Every day hundreds of items in grocery stores are marked down ...

Cinicioglu, Esma N.; Shenoy, Prakash P.; Kocabasoglu, Canan

2007-07-01

325

Computer simulation of a novel technique for Radio-Frequency Ablation of ventricular arrhythmias  

E-print Network

Ventricular Tachycardia (VT) is a rapid arrhythmia, most commonly due to reentrant electrical activity in the heart. A common treatment for VT is Radio-Frequency Ablation (RFA), which is minimally invasive, but requires ...

Rosbury, Tamara S

2006-01-01

326

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...

327

Measurement of radio-frequency magnetic fluctuations in the VTF magnetic reconnection experiment  

E-print Network

In this thesis work, I designed, fabricated, and calibrated, a radio-frequency magnetic probe, subsequently used to measure magnetic turbulance in the reconnecting plasmas of the Versatile Toroidal Facility (VTF). Reconnecting ...

Whitney, John Peter, 1982-

2004-01-01

328

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

329

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

330

Faraday accelerator with radio-frequency assisted discharge (FARAD)  

NASA Astrophysics Data System (ADS)

A new electrodeless accelerator concept, called Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD), that relies on an RF-assisted discharge to produce a plasma, an applied magnetic field to guide the plasma into the acceleration region, and an induced current sheet to accelerate the plasma, is presented. The presence of a preionized plasma allows for current sheet formation at lower discharge voltages and energies than those found in other pulsed inductive accelerator concepts. A proof-of-concept experiment, supported by optical and probe diagnostics, was constructed and used to demonstrate the main features of the FARAD and to gain physical insight into the low-voltage, low-energy current sheet formation and acceleration processes. Magnetic field data indicate that the peak sheet velocity in this unoptimized configuration operating at a pulse energy of 78.5 J is 12 km/s. It is found that changes in the background gas pressure and applied field affect the initial preionized plasma distribution which, in turn, affects the sheet's initial location, relative magnetic impermeability and subsequent velocity history. The results of the experimental investigation motivated further theoretical and numerical investigations of pulsed inductive plasma acceleration. A model consisting of a set of coupled circuit equations and a one-dimensional momentum equation was nondimensionalized leading to the identification of several scaling parameters. Numerical analysis revealed the benefits of underdamped current waveforms and led to an efficiency maximization criterion that requires matching the external circuit's natural period to the acceleration timescale. Predictions of the model were compared to experimental measurements and were found to be in good qualitative agreement and reasonable quantitative agreement for most quantities. A set of design rules aimed at producing a high-performance FARAD thruster are derived using the modeling results and physical insights. The rules concern the optimization of each of the major processes in FARAD: plasma acceleration, current sheet formation, applied field generation, and mass injection and preionization, and are cast as specific prescriptions for the dynamic impedance, inductance change, circuit damping, plasma collisionality (or magnetization), magnetic field strength and topology, and intra-pulse sequencing.

Polzin, Kurt Alexander

331

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

332

Investigation of inherent radio frequency oscillation and minor switching in amorphous chalcogenide semiconductors  

E-print Network

INVESTIGATION OF INHERENT RADIO FREQUENCY OSCILLATION AND MINOR SWITCHING IN AMORPHOUS CHALCOGENIDE SEMICONDUCTORS A Thesis by ROBERT WAYNE GILL JR. Submitted to the Graduate College of Texas AAM University in partial fulfillment... of the requirement for the degree of MASTER OF SCIENCE August 1971 Major Subject: Electrical Engineering INVESTIGATION OF INHERENT RADIO FREQUENCY OSCILLATION AND MINOR SWITCHING IN AMORPHOUS CHALCOGENIDE SEMICONDUCTORS A Thesis by ROBERT WAYNE GILL JR...

Gill, Robert Wayne

2012-06-07

333

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

334

Radio-frequency tag with optoelectronic interface for distributed wireless chemical and biological sensor applications  

Microsoft Academic Search

A battery-free, wireless optical chemical sensor with integral contactless power and data link is demonstrated. The chemical sensor and its optoelectronic interface form an integral part of a radio-frequency tag which we have developed specifically for use as a wireless chemical and biological sensor, and which is compatible with the International Standards Organisation ISO15693 radio-frequency identification (RFID) protocol. The chemical

Ivana Murkovi? Steinberg; Matthew D. Steinberg

2009-01-01

335

High-frequency radio-wave ablation of osteoid osteoma in the lumbar spine  

Microsoft Academic Search

The authors report on the first known application in the spine of percutaneous ablation of osteoid osteoma using radio-frequency\\u000a waves. The technique involves a CT-guided biopsy of the lesion followed by introduction of a 1-mm probe connected to a radio-frequency\\u000a lesion generator. The procedure was performed on an outpatient basis and the patient experienced immediate relief of his symptoms.\\u000a No

O. L. Osti; R. Sebben

1998-01-01

336

Radio frequency sensing measurements and methods for location classification in wireless networks  

NASA Astrophysics Data System (ADS)

The wireless radio channel is typically thought of as a means to move information from transmitter to receiver, but the radio channel can also be used to detect changes in the environment of the radio link. This dissertation is focused on the measurements we can make at the physical layer of wireless networks, and how we can use those measurements to obtain information about the locations of transceivers and people. The first contribution of this work is the development and testing of an open source, 802.11b sounder and receiver, which is capable of decoding packets and using them to estimate the channel impulse response (CIR) of a radio link at a fraction of the cost of traditional channel sounders. This receiver improves on previous implementations by performing optimized matched filtering on the field-programmable gate array (FPGA) of the Universal Software Radio Peripheral (USRP), allowing it to operate at full bandwidth. The second contribution of this work is an extensive experimental evaluation of a technology called location distinction, i.e., the ability to identify changes in radio transceiver position, via CIR measurements. Previous location distinction work has focused on single-input single-output (SISO) radio links. We extend this work to the context of multiple-input multiple-output (MIMO) radio links, and study system design trade-offs which affect the performance of MIMO location distinction. The third contribution of this work introduces the "exploiting radio windows" (ERW) attack, in which an attacker outside of a building surreptitiously uses the transmissions of an otherwise secure wireless network inside of the building to infer location information about people inside the building. This is possible because of the relative transparency of external walls to radio transmissions. The final contribution of this dissertation is a feasibility study for building a rapidly deployable radio tomographic (RTI) imaging system for special operations forces (SOF). We show that it is possible to obtain valuable tracking information using as few as 10 radios over a single floor of a typical suburban home, even without precise radio location measurements.

Maas, Dustin C.

337

High efficiency LTE transmitter considering a polar PWM architecture and RF front-end blocks  

Microsoft Academic Search

This paper presents validation of a high efficiency multi-radio transmitter applied to the LTE transmission features. Our design takes into account the influence of RF components, such as frequency synthesizer, switched-mode power amplifier and RF band-pass filter. Architecture of the transmitter is based on the Envelope Elimination and Restoration (EER) principle and uses a Pulse Width Modulator (PWM) to code

M. L. S. Penaloza; V. Valenta; G. Baudoin; M. Villegas; R. Mars?a?lek

2010-01-01

338

Emergency and operational low and medium frequency band radio communications system for underground mines  

SciTech Connect

This paper reports on a minewide low- and medium-frequency radio system has been developed and installed in coal and metalliferous mines. The radio system established reliable emergency communications between mine personnel on the surface, in working areas, or traveling in designated escapeway. The system also provides operational communications to improve coordination among working groups in the underground mining complex. The radio system utilizes two robust radio signal transmission modes to establish underground radio coverage areas. The seam transmission mode occurs when layers of coal, trona, potash, quartzite, or gilsonite are surrounded by more electrically conductive sediment layers. The layering forms a natural waveguide for transmission of medium-frequency (MF) band (300 to 23 000 kHz) radio signals. The conductor transmission line mode waveguide occurs when electrical conductors, such as ac power distribution cable, conveyor belt structures, steel pipe, and rail are in place in mine passageways. The conductor transmission waveguide attenuation rate is lowest in the low-frequency and (30 to 300 kHz). Safety is inherent in the system design since robust radio signal transmission modes are likely to survive events such as rock falls, fire, or explosion. Since the conductor utilities are necessary parts of the underground mine infrastructure, transmission line installation and maintenance cost can be avoided in the radio system.

Stolarczyk, L.G. (Stolar, Inc., Raton, NM (US))

1991-07-01

339

Encoding many channels in the same frequency through radio vorticity: first experimental test  

E-print Network

We have shown experimentally that it is possible to propagate and use the properties of twisted non-monochromatic incoherent radio waves to simultaneously transmit to infinity more radio channels on the same frequency band by encoding them in different orbital angular momentum states. This novel radio technique allows the implementation of, at least in principle, an infinite number of channels on one and the same frequency, even without using polarization or dense coding techniques. An optimal combination of all these physical properties and techniques represents a solution for the problem of radio band congestion. Our experimental findings show that the vorticity of each twisted electromagnetic wave is preserved after the propagation, paving the way for entirely new paradigms in radio communication protocols.

Tamburini, Fabrizio; Sponselli, Anna; Romanato, Filippo; Thidé, Bo; Bianchini, Antonio; Palmieri, Luca; Someda, Carlo G

2011-01-01

340

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

341

Secular decrease of the radio emission flux density of Cassiopeia A at the 38-MHz frequency  

NASA Astrophysics Data System (ADS)

The radio emission flux density of Cassiopeia A relative to Cygnus A was measured with the DKR-1000 radio telescope in 1987, 1988, and 1991. The mean rate of the secular flux-density decline at the 7.9-m wavelength during 1956-1991 is determined, on the basis of earlier published data, to be 0.70 +/- 0.19 percent/yr. This value is half that extrapolated to the 38-MHz frequency, which was obtained from frequency dependences of the secular decrease rate for Cassiopeia A radio emission.

Vinyajkin, E. N.; Volodin, A. G.; Koval'Chuk, O. M.

1992-09-01

342

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

343

Imaging interplanetary CMEs at radio frequency from solar polar orbit  

Microsoft Academic Search

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

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

2011-01-01

344

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

345

Energy Saving Glass Lamination via Selective Radio Frequency Heating  

SciTech Connect

This project focused on advancing radio-frequency (RF) lamination technology closer to commercial implementation, in order to reduce the energy intensity of glass lamination by up to 90%. Lamination comprises a wide range of products including autoglass, architectural safety and innovative design glass, transparent armor (e.g. bullet proof glass), smart glass, mirrors, and encapsulation of photovoltaics. Lamination is also the fastest growing segment of glass manufacturing, with photovoltaics, architectural needs, and an anticipated transition to laminated side windows in vehicles. The state-of-the-art for glass lamination is to use autoclaves, which apply heat and uniform gas pressure to bond the laminates over the course of 1 to 18 hours. Laminates consist of layers of glass or other materials bonded with vinyl or urethane interlayers. In autoclaving, significant heat energy is lost heating the chamber, pressurized air, glass racks, and the glass. In RF lamination, the heat is generated directly in the vinyl interlayer, causing it to heat and melt quickly, in just 1 to 10 minutes, without significantly heating the glass or the equipment. The main purpose of this project was to provide evidence that low energy, rapid RF lamination quality met the same standards as conventionally autoclaved windows. The development of concepts for laminating curved glass with RF lamination was a major goal. Other primary goals included developing a stronger understanding of the lamination product markets described above, and to refine the potential benefits of commercial implementation. The scope of the project was to complete implementation concept studies in preparation for continuation into advanced development, pilot studies, and commercial implementation. The project consisted of 6 main tasks. The first dealt with lamination with poly-vinyl butyral (PVB) interlayers, which prior work had shown difficulties in achieving good quality laminates, working with Pilkington North America. The second task dealt with a study of current lamination processes in the various laminate industries, and development of concepts for integrating RF lamination into new or existing processes. The third task explored the use of a non-destructive technique for analyzing laminate adhesion with the University of Illinois at Urbana-Champaign. The fourth task focused on developing concepts for curved glass lamination using RF lamination. The fifth and sixth tasks together comprised an analysis of laminate product markets, ranking for applicability and commercialization potential, and the development of commercialization strategies for those products. In addition, throughout the project as new experimental data and conventional process data were obtained, the benefits analysis of RF lamination was refined. The goals of the project described above were achieved, positioning RF lamination for the next stage growth envisioned in the original Industrial Grand Challenge proposal. Working with Pilkington North America, lamination of flat autoglass with PVB was achieved, meeting all 16 stringent industry tests. In particular, PVB laminates made with RF lamination passed environmental tests including the high temperature, 120 C bake test, without significant formation of bubbles (defects). The adhesion of PVB to glass was measured using the pummel method. Adhesion values ranging from 1 to 7 out of 10 were obtained. The significant process parameters affecting the environmental and adhesion performance were identified through a designed experiment. Pre-lamination process variables including PVB storage humidity and the de-airing process (vacuum or nip rolling) were significant, as well as the level of pressure applied to the laminate during the RF process. Analysis of manufacturing with RF lamination equipment, based on the processes developed indicated that 3 RF presses could replace a typical auto-industry autoclave to achieve equal or greater throughput with possibly less capital cost and smaller footprint. Concepts for curved lamination identifying castable molds for

Allan, Shawn M.

2012-02-27

346

Energy Saving Glass Lamination via Selective Radio Frequency Heating  

SciTech Connect

This project focused on advancing radio-frequency (RF) lamination technology closer to commercial implementation, in order to reduce the energy intensity of glass lamination by up to 90%. Lamination comprises a wide range of products including autoglass, architectural safety and innovative design glass, transparent armor (e.g. bullet proof glass), smart glass, mirrors, and encapsulation of photovoltaics. Lamination is also the fastest growing segment of glass manufacturing, with photovoltaics, architectural needs, and an anticipated transition to laminated side windows in vehicles. The state-of-the-art for glass lamination is to use autoclaves, which apply heat and uniform gas pressure to bond the laminates over the course of 1 to 18 hours. Laminates consist of layers of glass or other materials bonded with vinyl or urethane interlayers. In autoclaving, significant heat energy is lost heating the chamber, pressurized air, glass racks, and the glass. In RF lamination, the heat is generated directly in the vinyl interlayer, causing it to heat and melt quickly, in just 1 to 10 minutes, without significantly heating the glass or the equipment. The main purpose of this project was to provide evidence that low energy, rapid RF lamination quality met the same standards as conventionally autoclaved windows. The development of concepts for laminating curved glass with RF lamination was a major goal. Other primary goals included developing a stronger understanding of the lamination product markets described above, and to refine the potential benefits of commercial implementation. The scope of the project was to complete implementation concept studies in preparation for continuation into advanced development, pilot studies, and commercial implementation. The project consisted of 6 main tasks. The first dealt with lamination with poly-vinyl butyral (PVB) interlayers, which prior work had shown difficulties in achieving good quality laminates, working with Pilkington North America. The second task dealt with a study of current lamination processes in the various laminate industries, and development of concepts for integrating RF lamination into new or existing processes. The third task explored the use of a non-destructive technique for analyzing laminate adhesion with the University of Illinois at Urbana-Champaign. The fourth task focused on developing concepts for curved glass lamination using RF lamination. The fifth and sixth tasks together comprised an analysis of laminate product markets, ranking for applicability and commercialization potential, and the development of commercialization strategies for those products. In addition, throughout the project as new experimental data and conventional process data were obtained, the benefits analysis of RF lamination was refined. The goals of the project described above were achieved, positioning RF lamination for the next stage growth envisioned in the original Industrial Grand Challenge proposal. Working with Pilkington North America, lamination of flat autoglass with PVB was achieved, meeting all 16 stringent industry tests. In particular, PVB laminates made with RF lamination passed environmental tests including the high temperature, 120 ���°C bake test, without significant formation of bubbles (defects). The adhesion of PVB to glass was measured using the pummel method. Adhesion values ranging from 1 to 7 out of 10 were obtained. The significant process parameters affecting the environmental and adhesion performance were identified through a designed experiment. Pre-lamination process variables including PVB storage humidity and the de-airing process (vacuum or nip rolling) were significant, as well as the level of pressure applied to the laminate during the RF process. Analysis of manufacturing with RF lamination equipment, based on the processes developed indicated that 3 RF presses could replace a typical auto-industry autoclave to achieve equal or greater throughput with possibly less capital cost and smaller footprint. Concepts for curved lamination id

Allan, Shawn M.; Baranova, Inessa; Poley, Joseph; Reis, Henrique

2012-02-27

347

Low-Frequency Radio Observations of X-Ray Ghost Bubbles in A2597: A History of Radio Activity in the Core  

Microsoft Academic Search

A previous analysis of the Chandra X-ray image of the center of the cooling core cluster A2597 showed two ``ghost holes'' in the X-ray emission to the west and northeast of the central radio galaxy PKS 2322-123. Previous radio observations did not detect any radio emission coming from the interior of the X-ray holes. We present new low-frequency radio observations

T. E. Clarke; C. L. Sarazin; E. L. Blanton; D. M. Neumann; N. E. Kassim

2005-01-01

348

Space Shuttle and Space Station Radio Frequency (RF) Exposure Analysis  

NASA Technical Reports Server (NTRS)

This paper outlines the modeling techniques and important parameters to define a rigorous but practical procedure that can verify the compliance of RF exposure to the NASA standards for astronauts and electronic equipment. The electromagnetic modeling techniques are applied to analyze RF exposure in Space Shuttle and Space Station environments with reasonable computing time and resources. The modeling techniques are capable of taking into account the field interactions with Space Shuttle and Space Station structures. The obtained results illustrate the multipath effects due to the presence of the space vehicle structures. It's necessary to include the field interactions with the space vehicle in the analysis for an accurate assessment of the RF exposure. Based on the obtained results, the RF keep out zones are identified for appropriate operational scenarios, flight rules and necessary RF transmitter constraints to ensure a safe operating environment and mission success.

Hwu, Shian U.; Loh, Yin-Chung; Sham, Catherine C.; Kroll, Quin D.

2005-01-01

349

Modified transmitter attachment method for adult ducks  

USGS Publications Warehouse

The value of radio telemetry for waterfowl research depends on the availability of suitable methods of attaching transmitters. In previous studies, external transmitters attached to adult Mallards (Anas platyrhynchos) with sutures and glue did not stay on birds reliably. In an attempt to improve transmitter retention, a method of attachment was tested in which 4-g transmitters were attached mid-dorsally with sutures and with a stainless steel anchor-shaped wire inserted subcutaneously (anchor transmitters). Field tests indicated that all of 26 female Mallards and 63 of 65 female Gadwalls (Anas strepera) retained their anchor transmitters during 4369 bird-days of monitoring during nesting and brood rearing. Survival rates of females with anchor transmitters compared favorably with those reported from other studies. In this study, females with and without anchor transmitters did not differ with respect to survival rates of their ducklings. The anchor transmitter may be suitable for a variety of field studies on numerous species.

Pietz, P. J.; Brandt, D. A.; Krapu, G. L.; Buhl, D. A.

1995-01-01

350

2006 Raj JainCSE574sWashington University in St. Louis Radio FrequencyRadio Frequency  

E-print Network

door openers use RFID ! Implants in human, horses, fishes, animals Animal ID Standards ISO 11784, radio modulator, control logic, memory and a power system ! Power Source: " Passive Tags: Powered. Designed to be implanted in humans. Identify patients. " Semi-passive RFIDs used in E-Z Pass toll

Jain, Raj

351

Radio frequency polyphase filter design in 0.13-?m CMOS for wireless communications  

Microsoft Academic Search

Polyphase filters are an efficient solution for high image rejection and great accuracy quadrature generation in radio frequency (RF) receivers. Analytical modeling of passive polyphase filter suitable for RF front-end applications operating in 2.4 GHz frequency band is dealt with. This analytical analysis has been used to calibrate the optimal values of passive components in order to obtain the maximum

F. Haddad; R. Bouchakour; W. Rahajandraibe; L. Zaid; O. Frioui

2007-01-01

352

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

353

Frequency planning and system design of wide-area coverage cellular radio systems  

Microsoft Academic Search

A cellular-based approach to frequency planning and system design in wide-area-coverage radio systems is presented. The basic cellular theory is described; appropriate frequency allocation methods are discussed; and performance planning criteria are detailed with respect to ESKOM's experience in VHF and UHF systems. The use of computerized propagation prediction tools in the design process is discussed

A. R. Johnson

1992-01-01

354

Comparison of Pulsed Sinusoid Radio Frequency Interference Detection Algorithms Using Time and  

E-print Network

Comparison of Pulsed Sinusoid Radio Frequency Interference Detection Algorithms Using Time (ROC) for pulsed sinusoid RFI. Downlink data bandwidth is one of the major design factors-11]. RFI is often localized in time and frequency, relative to the integration times and pre

Ruf, Christopher

355

Automatic radio-transmission monitor  

NASA Technical Reports Server (NTRS)

System continuously monitors radio transmissions stored in memory. If spectrum deviates beyond present limits, alarm is tripped and spectrum is transferred to long-term storage for later analysis. Monitor can be useful in ensuring proper power level and spectral quality and in finding cause of failure. It might also be used to monitor radio-frequency interference or power levels of citizen's-band transmitters.

Bernstein, A. J.

1978-01-01

356

Effects of solar and geomagnetic activities on the sub-ionospheric very low frequency transmitter signals received by the DEMETER micro-satellite  

NASA Astrophysics Data System (ADS)

In the framework of seismic precursor electromagnetic investigations, we analyzed the very low frequency (VLF) amplitude signals recorded by the Instrument Champ Electrique (ICE) experiment on board the DEMETER micro-satellite. The sun-synchronous orbits of the micro-satellite allowed us to cover an invariant latitude of between -65° and +65° in a time interval of about 40 min. We considered four transmitter signals emitted by stations in Europe (France, FTU, 18.3 kHz; Germany, DFY, 16.58 kHz),Asia (Japan, JP, 17.8 kHz) and Australia (Australia, NWC, 19.8 kHz). We studied the variations of these VLF signals, taking into consideration: the signal-to-noise ratio, sunspots, and the geomagnetic activity. We show that the degree of correlation in periods of high geomagnetic and solar activities is, on average, about 40%. Such effects can be fully neglected in the period of weak activity. We also find that the solar activity can have a more important effect on the VLF transmitter signal than the geomagnetic activity. Our data are combined with models where the coupling between the lithosphere, atmosphere and ionosphere is essential to explain how ionospheric disturbances scatter the VLF transmitter signal.

Boudjada, Mohammed Yahia; Schwingenschuh, Konrad; Al-Haddad, Emad; Parrot, Michel; Galopeau, Patrick H. M.; Besser, Bruno; Stangl, Guenter; Voller, Wolfgang

2012-04-01

357

Dielectric properties of salmon ( Oncorhynchus keta) and sturgeon ( Acipenser transmontanus) caviar at radio frequency (RF) and microwave (MW) pasteurization frequencies  

Microsoft Academic Search

Radio frequency (RF) and microwave (MW) heating provide an important advantage of more rapid heat penetration in pasteurization processes for heat labile high value foods, which to date, have only been pasteurized by conductive heating. The objectives of this work were to determine the dielectric constant, loss factor and power penetration depth for salmon (0.8% and 2.3% total salt) and

Murad Al-Holy; Yifen Wang; Juming Tang; Barbara Rasco

2005-01-01

358

Observation of solar radio bursts using swept-frequency radiospectrograph in 20-40 MHz Band  

NASA Astrophysics Data System (ADS)

A new station for the observation of solar decametric radio bursts has been developed at Miyagi Vocational Training College in Tsukidate, Miyagi, Japan. Using the swept frequency radiospectrograph covering a frequency range from 20 MHz to 40 MHz within 200 msec, with bandwidth of 30 KHz, the radio outbursts from the sun have been currently monitored with colored dynamic spectrum display. After July 1982, successful observations provide the data which include all types of solar radio bursts such as type I, II, III, IV and V in the decametric wavelength range. In addition to these typical radio bursts, rising tone bursts with fast drift rate followed by strong type III bursts and a series of bursts repeating rising and falling tone bursts with slow drift rate have been observed.

Aoyama, Takashi; Oya, Hiroshi

359

Limits on low frequency radio emission from southern exoplanets with the Murchison Widefield Array  

E-print Network

We present the results of a survey for low frequency radio emission from 17 known exoplanetary systems with the Murchison Widefield Array. This sample includes 13 systems that have not previously been targeted with radio observations. We detected no radio emission at 154 MHz, and put 3 sigma upper limits in the range 15.2-112.5 mJy on this emission. We also searched for circularly polarised emission and made no detections, obtaining 3 sigma upper limits in the range 3.4-49.9 mJy. These are comparable with the best low frequency radio limits in the existing literature and translate to luminosity limits of between 1.2 x 10^14 W and 1.4 x 10^17 W if the emission is assumed to be 100% circularly polarised. These are the first results from a larger program to systematically search for exoplanetary emission with the MWA.

Murphy, Tara; Kaplan, David L; Gaensler, B M; Offringa, Andre R; Lenc, Emil; Hurley-Walker, Natasha

2014-01-01

360

Dynamic link\\/frequency selection in multi-hop cognitive radio networks for delay sensitive applications  

Microsoft Academic Search

Regarding the dynamic nature of cognitive radio networks and the delay of the central decision algorithms due to collecting necessary information in a multi-hop wireless network, distributed resource allocation algorithms are of crucial importance. In this paper we propose a new distributed resource allocation algorithm that properly selects link\\/frequency in a multi-hop cognitive radio network for delay sensitive applications. This

Behrouz Jashni; A. A. Tadaion; Farid Ashtiani

2010-01-01

361

Plasma production using microwave and radio frequency sources  

SciTech Connect

The initial breakdown of neutral fill gas is an important issue for stellarators where ionization of the neutral gas prefill is necessary before other auxiliary power can be coupled to the system. Microwaves with frequencies at the fundamental electron cyclotron resonance can be used for this purpose because they couple to electrons through linear wave-particle interactions. In addition, microwave applications at twice the electron cyclotron frequency typically have a strong enough nonlinear coupling to initiate breakdown with reasonable agreement between theory and experiment. Nonlinear couplings at higher harmonics are progressively weaker, and the possibilities of using the third harmonic are discussed. A difficulty can arise when microwave sources are used for plasma production because it is often too expensive to support the frequency ranges needed to obtain breakdown at arbitrary static magnetic field values. Thus, devices that rely exclusively on microwave sources to obtain target plasmas may be limited in their operational range by their microwave source frequencies. Alternatively, rf sources possessing a broad band of tunable frequencies are often available in the megahertz frequency range. The use of these types of power sources to produce target plasmas could add to the operational limits of many devices. Waves with frequencies of a few megahertz have been used to produce plasmas at the Institute of Physics and Technology at Kharkov (KFTI) for many years. The technique and mechanism by which the neutral gas is broken down in the very early phases of these discharges are presented.

Carter, M.D.

1989-01-01

362

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

363

Radio-Frequency Inverters With Transmission-Line Input Networks  

E-print Network

A soft-switching inverter topology (the Class Phi ) is presented which draws dc source current through a transmission line or a lumped-network approximation of a distributed line. By aligning the inverter switching frequency ...

Phinney, Joshua W.

364

47 CFR 80.911 - VHF transmitter.  

Code of Federal Regulations, 2011 CFR

...transmitter must be certificated to transmit between 20 watts and 25 watts, on each of the frequencies 156.300 MHz, 156...The transmitter output power must be not less than 15 watts. (5) For primary supply voltages, measured...

2011-10-01

365

47 CFR 80.911 - VHF transmitter.  

Code of Federal Regulations, 2012 CFR

...transmitter must be certificated to transmit between 20 watts and 25 watts, on each of the frequencies 156.300 MHz, 156...The transmitter output power must be not less than 15 watts. (5) For primary supply voltages, measured...

2012-10-01

366

47 CFR 80.911 - VHF transmitter.  

Code of Federal Regulations, 2013 CFR

...transmitter must be certificated to transmit between 20 watts and 25 watts, on each of the frequencies 156.300 MHz, 156...The transmitter output power must be not less than 15 watts. (5) For primary supply voltages, measured...

2013-10-01

367

47 CFR 80.911 - VHF transmitter.  

Code of Federal Regulations, 2010 CFR

...transmitter must be certificated to transmit between 20 watts and 25 watts, on each of the frequencies 156.300 MHz, 156...The transmitter output power must be not less than 15 watts. (5) For primary supply voltages, measured...

2010-10-01

368

Omega Transmitter Outages January to December 1979.  

National Technical Information Service (NTIS)

An investigation of Omega transmitter outages during 1979 was conducted with emphasis on the occurrence of simultaneous downtimes. Data presented includes frequency and duration of outages and total yearly percentage shutdown for each transmitter, with sc...

L. Rzonca

1980-01-01

369

Health aspects of radio-frequency radiation accidents. Part II: A proposed protocol for assessment of health effects in radio-frequency radiation accidents  

SciTech Connect

A protocol is proposed for the assessment of health effects following a radio-frequency radiation accident. The protocol is intended to ensure uniform recording of exposure and medical data. This should meet the requirements of the individuals exposed as well as contributing to scientific knowledge. Difficult aspects about the collection of exposure and medical data are discussed and the need to consider the feelings of the exposed individual(s) is emphasized.

Hocking, B.; Joyner, K.

1988-01-01

370

Observations of Low Frequency Solar Radio Bursts from the Rosse Solar-Terrestrial Observatory  

NASA Astrophysics Data System (ADS)

The Rosse Solar-Terrestrial Observatory (RSTO; http://www.rosseobservatory.ie) was established at Birr Castle, Co. Offaly, Ireland (53°05'38.9?, 7°55'12.7?) in 2010 to study solar radio bursts and the response of the Earth's ionosphere and geomagnetic field. To date, three Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy in Transportable Observatory (CALLISTO) spectrometers have been installed, with the capability of observing in the frequency range of 10 - 870 MHz. The receivers are fed simultaneously by biconical and log-periodic antennas. Nominally, frequency spectra in the range of 10 - 400 MHz are obtained with four sweeps per second over 600 channels. Here, we describe the RSTO solar radio spectrometer set-up, and present dynamic spectra of samples of type II, III and IV radio bursts. In particular, we describe the fine-scale structure observed in type II bursts, including band splitting and rapidly varying herringbone features.

Zucca, P.; Carley, E. P.; McCauley, J.; Gallagher, P. T.; Monstein, C.; McAteer, R. T. J.

2012-10-01

371

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

372

Measurements of time average series resonance effect in capacitively coupled radio frequency discharge plasma  

NASA Astrophysics Data System (ADS)

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.; Kakati, M.

2011-10-01

373

Numerical analysis of radio-frequency sheath-plasma interactions in the ion cyclotron range of frequencies  

SciTech Connect

A new finite element numerical scheme for analyzing self-consistent radio-frequency (RF) sheath-plasma interaction problems in the ion cyclotron range of frequencies is applied to various problems represented by simplified models for the tokamak scrape-off layer. The present code incorporates a modified boundary condition, which is called a sheath boundary condition, that couples the radio-frequency waves and sheaths at the material boundaries by treating the sheath as a thin vacuum layer. A series of numerical analyses in one- and two-dimensional domains show several important physical properties, such as the existence of multiple roots, hysteresis effects, presence and characteristics of the sheath-plasma waves, and the phase shift of a reflected slow wave, some of which are newly identified by introducing a spatially varying plasma density and background magnetic field.

Kohno, H. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Myra, J. R.; D'Ippolito, D. A. [Lodestar Research Corporation, 2400 Central Avenue P-5, Boulder, Colorado 80301 (United States)

2012-01-15

374

Detection of NMR signals with a radio-frequency atomic magnetometer  

E-print Network

We demonstrate detection of proton NMR signals with a radio frequency atomic magnetometer tuned to the NMR frequency of 62 kHz. High-frequency operation of the atomic magnetometer makes it relatively insensitive to ambient magnetic field noise. We obtain magnetic field sensitivity of 7 fT/Hz$^{1/2}$ using only a thin aluminum shield. We also derive an expression for the fundamental sensitivity limit of a surface inductive pick-up coil as a function of frequency and find that an atomic rf magnetometer is intrinsically more sensitive than a coil of comparable size for frequencies below about 50 MHz.

Savukov, I M; Seltzer, S J

2006-01-01

375

Radio astronomy with the European Lunar Lander: Opening up the last unexplored frequency regime  

NASA Astrophysics Data System (ADS)

The Moon is a unique location in our solar system and provides important information regarding the exposure to free space that is essential for future human space exploration to mars and beyond. The active broadband (100 kHz-100 MHz) tripole antenna now envisaged to be placed on the European Lunar Lander located at the Lunar South Pole allows for sensitive measurements of the exosphere and ionosphere, and their interaction with the Earths magnetosphere, solar particles, wind and CMEs and studies of radio communication on the Moon, that are essential for future lunar human and science exploration. In addition, the Lunar South Pole provides an excellent opportunity for radio astronomy. Placing a single radio antenna in an eternally dark crater or behind a mountain at the South (or North) pole would potentially provide perfect shielding from man-made radio interference (RFI), absence of ionospheric distortions, and high temperature and antenna gain stability that allows detection of the 21 cm wave emission from pristine hydrogen formed after the Big Bang and into the period where the first stars formed. A detection of the 21 cm line from the Moon at these frequencies would allow for the first time a clue on the distribution and evolution on mass in the early universe between the Epoch of Recombination and Epoch of Reionization (EoR). Next to providing a cosmological breakthrough, a single lunar radio antenna would allow for studies of the effect of solar flares and coronal mass ejections (CMEs) on the solar wind at distances close to Earth (space weather) and would open up the study of low frequency radio events (flares and pulses) from planets such as Jupiter and Saturn, which are known to emit bright (kJy-MJy) radio emission below 30 MHz (Jester and Falcke, 2009). Finally, a single radio antenna on the lunar lander would pave the way for a future large lunar radio interferometer; not only will it demonstrate the possibilities for lunar radio science and open up the last unexplored radio regime, but it will also allow a determination of the limitations of lunar radio science by measuring the local radio background noise.

Klein Wolt, Marc; Aminaei, Amin; Zarka, Philippe; Schrader, Jan-Rutger; Boonstra, Albert-Jan; Falcke, Heino

2012-12-01

376

Advances in magnetospheric radio wave analysis and tomography  

Microsoft Academic Search

A number of experiments have been accomplished in which the Radio Plasma Imager (RPI) on the IMAGE spacecraft was used as a low frequency radio wave transmitter and the WAVES instrument on WIND and the Wide-band instruments on all four CLUSTER spacecraft as receivers. These transmissions\\/receptions provide a unique opportunity to test a number of important magnetospheric measurement techniques. For

J. Green; S. Cummer; B. Reinisch; S. Fung; M. Kaiser; R. Mutel; J. Pickett; I. Christopher; D. Gurnett

2002-01-01

377

Ionospheric irregularities causing scintillation of GHz frequency radio signals  

NASA Technical Reports Server (NTRS)

Consideration of the recently observed phenomenon of scintillation of satellite signals at GHz frequency range. Based on the scintillation data and results from in situ measurements, several ionospheric irregularity models with different power spectra are studied. Scintillation index is computed for the various models and compared with observed results. Both magnitude and frequency dependence of the scintillation index are investigated. It is found that a thick irregularity slab of the order of 200 km with an electron density fluctuation of about 20 per cent of its background value and with a nonmonotonic power spectrum may account for the maximum observed values of the scintillation index as well as its frequency dependence. Some future observations and measurements are suggested.

Wernik, A. W.; Liu, C. H.

1974-01-01

378

Theory study on a photonic-assisted radio frequency phase shifter with direct current voltage control  

NASA Astrophysics Data System (ADS)

A photonic-assisted radio frequency phase shifter with direct current voltage control is proposed using a polymer-based integrated Mach—Zehnder modulator. A closed-form expression of radio frequency (RF) signal power and phase is given. Theoretical calculation reveals that by carefully setting the bias voltages, RF signal power variation lower than 1-dB and phase accuracy less than 3° can be achieved and are not degraded by perturbation of modulation index once the bias voltage drift is kept within −3% ~ 3%.

Li, Jing; Ning, Ti-Gang; Pei, Li; Jian, Wei; You, Hai-Dong; Wen, Xiao-Dong; Chen, Hong-Yao; Zhang, Chan; Zheng, Jing-Jing

2014-10-01

379

Single shot time stamping of ultrabright radio frequency compressed electron pulses  

NASA Astrophysics Data System (ADS)

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.; Jiang, Y.; Kassier, G. H.; Dwayne Miller, R. J.

2013-07-01

380

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

381

Frequency Dependence of Pulse Width for 150 Radio Normal Pulsars  

NASA Astrophysics Data System (ADS)

The frequency dependence of the pulse width is studied for 150 normal pulsars, mostly selected from the European Pulsar Network, for which the 10% multifrequency pulse widths can be well fit with the Thorsett relationship W 10 = A?? + W 10, min. The relative fraction of pulse width change between 0.4 GHz and 4.85 GHz, ? = (W 4.85 – W 0.4)/W 0.4, is calculated in terms of the best-fit relationship for each pulsar. It is found that 81 pulsars (54%) have ? < –10% (group A), showing considerable profile narrowing at high frequencies, 40 pulsars (27%) have –10% <=? <= 10% (group B), meaning a marginal change in pulse width, and 29 pulsars (19%) have ? > 10% (group C), showing a remarkable profile broadening at high frequencies. The fractions of the group-A and group-C pulsars suggest that the profile narrowing phenomenon at high frequencies is more common than the profile broadening phenomenon, but a large fraction of the group-B and group-C pulsars (a total of 46%) is also revealed. The group-C pulsars, together with a portion of group-B pulsars with slight pulse broadening, can hardly be explained using the conventional radius-to-frequency mapping, which only applies to the profile narrowing phenomenon. Based on a recent version of the fan beam model, a type of broadband emission model, we propose that the diverse frequency dependence of pulse width is a consequence of different types of distribution of emission spectra across the emission region. The geometrical effect predicting a link between the emission beam shrinkage and spectrum steepening is tested but disfavored.

Chen, J. L.; Wang, H. G.

2014-11-01

382

The modification of a radio frequency Cockcroft Walton generator  

E-print Network

-Naiton penerator, 17 The $M ko exciter had to satisfy the requf. resents that it be vsriblo in frequency ao as co pornN optitun aiiysnonc of tho r f crsnsfoneer, anal thee it deliver tho required driving power of approximately a$ watts to tho r~f anplifier...-Naiton penerator, 17 The $M ko exciter had to satisfy the requf. resents that it be vsriblo in frequency ao as co pornN optitun aiiysnonc of tho r f crsnsfoneer, anal thee it deliver tho required driving power of approximately a$ watts to tho r~f anplifier...

Holt, Joseph Marion

2012-06-07

383

Radio frequency circuits for wireless receiver front-ends  

E-print Network

. This can be hard to do, especially at RF frequencies where lead inductance and capacitance make short and open circuits di?cult to obtain. Active devices, such as transistors and tunnel diode, very often can not be connected in stable short or open circuit.... This can be hard to do, especially at RF frequencies where lead inductance and capacitance make short and open circuits di?cult to obtain. Active devices, such as transistors and tunnel diode, very often can not be connected in stable short or open circuit...

Xin, Chunyu

2005-11-01

384

Excitation of a magnetospheric maser through modification of the Earth's ionosphere by high-power HF radio emission from a ground-based transmitter  

SciTech Connect

A method for controlled excitation of a magnetospheric maser through the production of artificial density ducts by high-power HF radio emission from the Earth's surface has been proposed and implemented in an in-situ experiment. Artificial density ducts allow one to affect the maser resonator system and the excitation and propagation of low-frequency electromagnetic waves in a disturbed magnetic flux tube. The experimental data presented here were obtained at the mid-latitude Sura heating facility. The characteristics of electromagnetic and plasma disturbances at outer-ionosphere altitudes were measured using the onboard equipment of the DEMETER satellite as it passed through the magnetic flux tube rested on the region of intense generation of artificial ionospheric turbulence.

Markov, G. A., E-mail: markov@rf.unn.ru; Belov, A. S., E-mail: alexis-belov@yandex.ru [Lobachevsky Nizhni Novgorod State University (Russian Federation); Frolov, V. L.; Rapoport, V. O. [Radiophysical Research Institute (Russian Federation); Parrot, M. [Environment Physics and Chemistry Laboratory (France)

2010-01-15

385

Introduction The rapid growth of wireless systems at radio frequencies  

E-print Network

) typically represent the device in 1D or 2D. When solved, the system of equations results in a Jacobian matrix of size (2H+1)N x (2H+1)N ­­ indeed a potentially huge numerical problem (typical N in 2D is more requirements for communications systems necessitate accurate analysis of harmonic content with frequency dif

Dutton, Robert W.

386

Introduction The rapid growth of wireless systems at radio frequencies  

E-print Network

the DC compo- nent. Those nodes (or grid) typically represent the device in 1D or 2D. When solved numerical problem (typical N in 2D is more than 3000, and H can easily e xceed 100). The effi- cient requirements for communications systems necessitate accurate analysis of harmonic content with frequency dif

Dutton, Robert W.

387

RADIO-FREQUENCY BACKSCATTER OF ARTIFICIAL ELECTRON CLOUDS  

Microsoft Academic Search

Backscatter and forward-scatter reflection properties of chemically ; created electron clouds were measured throughout the HF spectrum. The ; measurements included radar cross sections, signal fading characteristics, and ; frequency-time-dependence. These quantities led to certain conclusions regarding ; the cloud model that describes in general the chemical releases. The model so ; presented appears to be a limited coherent type

Philip B. Gallagher; R. A. Barnes

1963-01-01

388

Electromagnetic compatibility between radio links and frequency agile radars  

Microsoft Academic Search

Some recent advances in radar technology, such as pulse compression techniques, frequency agility and other sophisticated electronic counter counter measures, together with the constant escalation in peak output powers, have resulted in the advent of a new generation of high performance radars. The increased capabilities of modern radars, however, almost invariably correspond also to an increased occupation and pollution of

E. Chiarucci; R. Esposito

1975-01-01

389

Motivation and possibilities of affordable low-frequency radio interferometry in space  

E-print Network

The motivation to build spaceborne interferometric arrays for low-frequency radio astronomy is widely recognised because frequencies below the ionospheric cutoff are inaccessible for ground-based radio telescopes. We discuss the theoretical possibilities to use low-frequency spacecraft arrays to detect signals from magnetized extrasolar planets, including earthlike ones. A major uncertainty that prohibits us from knowing if it is possible to detect exoplanet cyclotron maser signals is the incomplete knowledge of the properties of the interstellar plasma. We also present some ideas of how to construct efficient and affordable space-based radio telescopes. We discuss two possibilities, a log-periodic antenna in the spin plane and a two-spacecraft concept where one spacecraft holds a large parabolic wire mesh reflector and the other one contains the receiver. In the latter case, the effective area could be of the order of 1 km$^2$. The purpose of the paper is to stress once more the importance of spaceborne low-frequency measurements by bringing in the intriguing possibility of detecting earthlike exoplanet radio emissions and to demonstrate that building even very large low-frequency antennas in space is not necessarily too expensive.

P. Janhunen; A. Olsson; R. Karlsson; J. -M. Griessmeier

2003-05-23

390

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

391

47 CFR 95.628 - MedRadio transmitters in the 413-419 MHz, 426-432 MHz, 438-444 MHz, and 451-457 MHz and 2360-2400...  

Code of Federal Regulations, 2013 CFR

...a Medical Body Area Network (MBAN). (a) Operating...a Medical Micropower Network. (1) Frequency...for Medical Body Area Networks. A MedRadio programmer...extend the range of spectrum occupied over space...MedRadio systems. (f) Measurement procedures....

2013-10-01

392

Radio emission of RRAT-pulsars at a frequency of 111 MHz  

NASA Astrophysics Data System (ADS)

We will report about our resalts concerning the observations of a number of Rotating Radio Transient (RRAT) pulsars .These observations have been carried out at Large Phased Array of P.N. Lebedev Physical Institute at 111 MHz during 2010-2013 years. RRAT- pulsars were first discovered in archive Parkes Multibeam Pulsar Survey [1,2]and Arecibo Pulsar Survey[3] at higher frequency 1400 MHz and some pulsars were discovered at frequency of 350 MHz with Green Bank Telescope[4]. A characteristic feature of these pulsars is sporadic radio emission in rare active phase and no radio emission for a long time making it difficult to find periodicity .Fast Folding Algorithm processing of observations at 111 MHz shows that even in passive phase RRAT-pulsars generate weak radio emission with the period corresponding to the period of sporadic radio pulses observed in the active phase. The flux density of the radio emission of these pulsars in passive phase is rather small even at low frequency 111 MHz, that greatly complicates its registration at high frequencies since flux density of the RRAT- pulsars decreases with increasing frequency.\\ ?nterline{References}\\ 1.McLaughlin M.A., Lyne A.G., Lorimer D.R. et al., 2006, Nature,439,817. 2.Keane E.F., Ludovici D.A., Eatough E.P. et al., 2010, MNRAS,401,1057. 3.Deneva J.S., Cordes J.M., McLaughlin M.A. et al., 2009,ApJ,703,2259. 4.Keane E.F.,McLaughlin M.A., Bull.Astr.Soc.India, 2011,39,1.

Losovsky, Boris; Dmitry Dumsky, Mr/.

393

Optimized Trigger for Ultra-High-Energy Cosmic-Ray and Neutrino Observations with the Low Frequency Radio Array  

E-print Network

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 e?cient trigger implementation for LOFAR optimized for the observation of short radio pulses.

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

2011-01-01

394

Borehole induction coil transmitter  

DOEpatents

A borehole induction coil transmitter which is a part of a cross-borehole electromagnetic field system that is used for underground imaging applications. The transmitter consists of four major parts: 1) a wound ferrite or mu-metal core, 2) an array of tuning capacitors, 3) a current driver circuit board, and 4) a flux monitor. The core is wound with several hundred turns of wire and connected in series with the capacitor array, to produce a tuned coil. This tuned coil uses internal circuitry to generate sinusoidal signals that are transmitted through the earth to a receiver coil in another borehole. The transmitter can operate at frequencies from 1-200 kHz and supplies sufficient power to permit the field system to operate in boreholes separated by up to 400 meters.

Holladay, Gale (Livermore, CA); Wilt, Michael J. (Walnut Creek, CA)

2002-01-01

395

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

396

Nonlinear nonresonant forces by radio-frequency waves in plasmas  

SciTech Connect

Nonresonant forces by applied rf waves in plasmas are analyzed. Along the background dc magnetic field, the force arises from the gradient of the ponderomotive potential. Only when the dc magnetic field is straight, however, is this parallel force completely consistent with that from the single particle picture, where the ponderomotive force depends on the gradients of rf fields only. Across the dc magnetic field, besides the ponderomotive force from the particle picture, additional Reynolds stress and polarization stress contribute to the total force. For waves with frequency much lower than the cyclotron frequency, the perpendicular forces from the particle and fluid pictures can have opposite signs. In plasmas with a symmetry angle (e.g., toroidal systems), nonresonant forces cannot drive net flow or current in the flux surface, but the radial force may influence macroscopic behavior of plasma. Moreover, nonresonant forces may drive flow or current in linear plasmas or in a localized region of toroidal plasmas.

Gao Zhe; Fisch, Nathaniel J.; Qin, Hong; Myra, J. R. [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Lodestar Research Corporation, Boulder, Colorado 80301 (United States)

2007-08-15

397

47 CFR 90.473 - Operation of internal transmitter control systems through licensed fixed control points.  

Code of Federal Regulations, 2010 CFR

... false Operation of internal transmitter control systems through licensed fixed control points. 90.473 Section 90.473 Telecommunication...PRIVATE LAND MOBILE RADIO SERVICES Transmitter Control Internal Transmitter Control Systems §...

2010-10-01

398

47 CFR 90.461 - Direct and remote control of transmitters.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 false Direct and remote control of transmitters. 90.461 Section 90...PRIVATE LAND MOBILE RADIO SERVICES Transmitter Control § 90.461 Direct and remote control of transmitters. (a) In...

2010-10-01

399

Low Frequency Radio Observations of X-ray Ghost Bubbles in Abell 2597: A History of Radio Activity in the Core  

Microsoft Academic Search

A previous analysis of the Chandra X-ray image of the center of the cooling\\u000acore cluster Abell 2597 showed two ``ghost holes'' in the X-ray emission to the\\u000awest and northeast of the central radio galaxy PKS 2322-123. Previous radio\\u000aobservations did not detect any radio emission coming from the interior of the\\u000aX-ray holes. We present new low frequency

T. E. Clarke; C. L. Sarazin; E. L. Blanton; D. M. Neumann; N. E. Kassim

2005-01-01

400

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

401

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

402

Coupling effects in inductive discharges with radio frequency substrate biasing  

NASA Astrophysics Data System (ADS)

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.; Schüngel, E.; Czarnetzki, U.

2012-01-01

403

Low-power radio-frequency capacitively coupled plasma in air: an alternative spectral source?  

Microsoft Academic Search

The low power radio frequency capacitively coupled plasma sustained in air at atmospheric pressure is described with the aim of using it as spectral source for atomic emission spectroscopy of pneumatically nebulized liquid samples and the direct analysis of non-conductive solid samples. The plasma was generated at a frequency of 13.56 MHz, absorbed RF powers of 20-70 W and air

Sorin Anghel; Alpar Simon; Tiberiu Frentiu; Emil A. Cordos

2000-01-01

404

Source location of the smooth high-frequency radio emissions from Uranus  

NASA Technical Reports Server (NTRS)

The source location of the smooth high-frequency radio emissions from Uranus has been determined. Specifically, by fitting the signal dropouts which occurred as Voyager traversed the hollow center of the emission pattern to a symmetrical cone centered on the source magnetic field direction at the cyclotron frequency, a southern-hemisphere (nightside) source was found at approximately 56 deg S, 219 deg W. The half-angle for the hollow portion of the emission pattern was found to be 13 deg.

Farrell, W. M.; Calvert, W.

1989-01-01

405

Goniopolarimetric study of the revolution 29 perikrone using the Cassini Radio and Plasma Wave Science instrument high-frequency radio receiver  

Microsoft Academic Search

We present goniopolarimetric (also known as direction finding) results of the Saturn kilometric radiation (SKR), using the Cassini Radio and Plasma Wave Science instrument high-frequency radio receiver data. Tools to retrieve the characteristics of the SKR sources have been developed that allow us to measure their 3-D location and beaming angle relative to the magnetic field in the source and,

B. Cecconi; L. Lamy; P. Zarka; R. Prangé; W. S. Kurth; P. Louarn

2009-01-01

406

Radio Frequency Identification Technology and the Risk Society: A Preliminary Review and Critique for Justice Studies  

Microsoft Academic Search

Radio Frequency Identification (RFID) technology promises to revolutionize the way in which citizens interact with society, guaranteeing heightened security and increased protection speculatively critiques the soundness of this logic, especially mindful of the risk society thesis. Relevant historical background on RFID is provided, several notable applications in the corporate and governmental sectors are delineated, and the ethical and

Brian Sellers

2009-01-01

407

NORMAL CONDUCTING RADIO FREQUENCY X-BAND DEFLECTING CAVITY FABRICATION AND VALIDATION*  

E-print Network

NORMAL CONDUCTING RADIO FREQUENCY X-BAND DEFLECTING CAVITY FABRICATION AND VALIDATION* R. Agustsson- picosecond ultra-relativistic electron beams. The device is optimized for the 100 MeV electron beam will be presented. INTRODUCTION Some of the most compelling and demanding applications in high-energy electron beam

Brookhaven National Laboratory

408

NORMAL CONDUCTING RADIO FREQUENCY X-BAND DEFLECTING CAVITY FABRICATION AND VALIDATION*  

E-print Network

NORMAL CONDUCTING RADIO FREQUENCY X-BAND DEFLECTING CAVITY FABRICATION AND VALIDATION* R. Agustsson of the sub- picosecond ultra-relativistic electron beams. The device is optimized for the 100 MeV electron will be presented. INTRODUCTION Some of the most compelling and demanding applications in high-energy electron beam

Brookhaven National Laboratory

409

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

E-print Network

Understanding Pound-Drever-Hall locking using voltage controlled radio-frequency oscillators controlled oscillator to a cavity resonance at 800 MHz using the Pound-Drever-Hall method. This technique of microwave oscillators, and adapted to the optical domain by Drever et al.2 In brief, the source

Le Roy, Robert J.

410

Method for Automated Monitoring of Hand Hygiene Adherence without Radio-Frequency Identification  

PubMed Central

Many efforts to automatically measure hand hygiene activity depend on radio-frequency identification equipment or similar technology that can be expensive to install. We have developed a method for automatically tracking the use of hand hygiene dispensers before healthcare workers enter (or after they exit) patient rooms that is easily and quickly deployed without permanent hardware. PMID:20973724

Polgreen, Philip M.; Hlady, Christopher S.; Severson, Monica A.; Segre, Alberto M.; Herman, Ted

2011-01-01

411

New optical and radio frequency angular tropospheric refraction models for deep space applications  

NASA Technical Reports Server (NTRS)

The development of angular tropospheric refraction models for optical and radio frequency usage is presented. The models are compact analytic functions, finite over the entire domain of elevation angle, and accurate over large ranges of pressure, temperature, and relative humidity. Additionally, FORTRAN subroutines for each of the models are included.

Berman, A. L.; Rockwell, S. T.

1976-01-01

412

High-rate chemical vapor deposition of nanocrystalline silicon carbide films by radio frequency thermal plasma  

E-print Network

thermal plasma F. Liao a , S. Park a , J.M. Larson b , M.R. Zachariah a , S.L. Girshick a,* a Department were deposited by radio frequency thermal plasma chemical vapor deposition (CVD) at rates up to several; Nanomaterials; Silicon carbide; Thermal plasmas; Thin films; Si tetrachlorine precursor Silicon carbide has

Zachariah, Michael R.

413

A radio frequency tracing experiment of bedload transport in a small braided mountain stream  

Microsoft Academic Search

Radio frequency identification technology is used for monitoring the displacement of coarse particles in streams since the beginning of the 2000s. Passive integrated transponders (PIT tags) are small, cheap and long-lasting electronic tags that can be programmed with their own identification code. Initially used in environmental research for animal tracking, they have been deployed successfully in a variety of fluvial

F. Liebault; M. Chapuis; H. Bellot; M. Deschatres

2009-01-01

414

Intelligent tire monitor system of aerial vehicles based on radio frequency technology  

Microsoft Academic Search

A low power consuming intelligent monitor system of tire based on radio frequency technology is designed in this paper. The low consuming power unit, the measurement unit, the agreement of timestamp and the protocol of chain layers are presented in details. The main program flow charts of the measuring terminal and host terminal are given. he tire is the only

Kai-rui Zhao; Shicheng Xu; Qing Ye; Yan Li

2011-01-01

415

IMPROVED TECHNIQUE FOR MONITORING ELECTROCARDIOGRAMS DURING EXPOSURE TO RADIO-FREQUENCY RADIATION  

EPA Science Inventory

Studies were conducted which examined the effects of radio frequency (RF) radiation on heart rate (HR), deep body temperature (TEMP), and electrocardiographic (ECG) waveform parameters in anesthetized rats. One group of animals was exposed to two power levels of continuous wave R...

416

Low-power radio frequency circuit architectures for portable wireless communications  

Microsoft Academic Search

Ultra-low-power implementations of radio-frequency integrated circuits are benefiting from rapid improvements in integrated circuit technology, circuit architecture techniques and wireless system innovations. Some of the key technological developments driving this field are discussed, in addition to new approaches for the realization of next generation wireless circuits and systems that dissipate very little dc power

Lawrence E. Larson

1998-01-01

417

A Low Power Radio Telemetry Achieving Very High Data Rates at Biocompatible Frequencies  

Microsoft Academic Search

This papers reports a solution for a low power, high data rate telemetry, intended to be used in capsule endoscopy. The system is taking advantage of the small absorption of radio waves of low frequencies, around 120 MHz, to allow a telemetry up to a million bit per second of raw data, while keeping the power consumption to 6 mW.

D. Turgis; R. Puers

2007-01-01

418

Radio frequency (rf) plasma spheroidized HA powders: powder characterization and spark plasma sintering behavior  

Microsoft Academic Search

The present study describes the synthesis of spheroidized hydroxyapatite (HA) powders using a radio frequency (rf) inductively coupled plasma (ICP) torch. The spheroidized powders were consolidated through a spark plasma sintering (SPS) system. The microstructure and crystallographic phases in the synthesized powders were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD) and Raman spectrometry. Results

J. L. Xu; K. A. Khor; Y. W. Gu; R. Kumar; P. Cheang

2005-01-01

419

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

E-print Network

vapor infiltration (CVI) has emerged as one of the leading techniques for the fabrication of fiber was developed and used to simulate chemical vapor infil- tration of fiber-reinforced composite materials-consistently the power absorbed by the preform from a radio frequency induction coil. The model equations were solved

Economou, Demetre J.

420

Radio frequency identification in retailing and privacy and public policy issues  

Microsoft Academic Search

Outlines the characteristics of Radio Frequency Identification (RFID) technology and shows the growth of retail interest in the technology’s introduction in the UK. Discusses privacy and public policy issues that are associated with RFID. Concludes that retailers have to address a series of privacy and public liberties, associated with RFID.

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

2004-01-01

421

Epidemiological studies of radio-frequency radiation: current status and areas of concern  

Microsoft Academic Search

These comments deal with the possible impact on human populations of intense sources of radio-frequency radiation, and not the much lower level of the usual sources of such radiation associated, for example with household appliances. These intense sources were developed and extensively used first in World War II (1940–1945). Much of the health evaluation has been done by, and for,

John R. Goldsmith

1996-01-01

422

Fast simulation of nonlinear radio frequency ultrasound images in inhomogeneous nonlinear media: CREANUIS  

E-print Network

Fast simulation of nonlinear radio frequency ultrasound images in inhomogeneous nonlinear media et traitement de l'image pour la sant´e, 7 avenue Jean Capelle, Bat Blaise Pascal, 69621 Villeurbanne, Nantes, France 91 #12;The simulation of ultrasound images is usually based on two main strategies: either

Paris-Sud XI, Université de

423

A radio frequency identification-based quality evaluation system design for the wine industry  

Microsoft Academic Search

In the wine industry, how to evaluate the quality of wine in objective ways has been a thorny problem. The invention of radio frequency identification (RFID) has provided an effective tool to manage wine production. This article reports on the design and the use of an RFID-based quality evaluation system to monitor the whole supply chain of wine. With the

Lixing Wang; S. K. Kowk; W. H. Ip

2012-01-01

424

A radio frequency identification-based quality evaluation system design for the wine industry  

Microsoft Academic Search

In the wine industry, how to evaluate the quality of wine in objective ways has been a thorny problem. The invention of radio frequency identification (RFID) has provided an effective tool to manage wine production. This article reports on the design and the use of an RFID-based quality evaluation system to monitor the whole supply chain of wine. With the

Lixing Wang; S. K. Kowk; W. H. Ip

2011-01-01

425

Design, Fabrication and Testing of Two Dimensional Radio-Frequency Metamaterials.  

National Technical Information Service (NTIS)

This project focused on radio frequency (RF) metamaterials (MTM) structures using two different methods: wet etching copper (Cu) on insulating glass reinforced epoxy resin (FR4) and silver nano-particle ink printed SRR meta-atoms on photo paper (Ag on pap...

R. P. Krones

2014-01-01

426

PHOTONIC SYNTHESIS AND HARDWARE CORRELATIONS OF ULTRABROADBAND RADIO-FREQUENCY WAVEFORMS AND POWER  

E-print Network

PHOTONIC SYNTHESIS AND HARDWARE CORRELATIONS OF ULTRABROADBAND RADIO-FREQUENCY WAVEFORMS AND POWER Jiang and F.S. Toong. Many thanks to Hsiao-Kuan Yuan and my other friends from Purdue who always love ..........................................18 3.1.3 Equalized RF Waveforms............................................23 3.2 Power Spectra

Purdue University

427

Pulsed Discharge Effects on Bacteria Inactivation in Low-Pressure Radio-Frequency Oxygen Plasma  

Microsoft Academic Search

The sporicidal effects of low-pressure radio frequency (RF) discharges in oxygen, produced by the application of continuous and pulsed RF power, were evaluated. For all cases, the survival curves showed a biphasic evolution. The maximum efficiency for bacteria sterilization was obtained when the RF power was injected in the continuous wave mode, while in the pulsed mode the lowest treatment

Dragos Vicoveanu; Yasunori Ohtsu; Hiroharu Fujita

2008-01-01

428

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

Microsoft Academic Search

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

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

2011-01-01

429

Development of structural materials exhibiting dielectric and magnetic loss at radio frequencies  

Microsoft Academic Search

This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The reduction of radio frequency (RF) return from military assets has been of critical interest for the last twenty years. New materials are required that not only provide a reduction in specular and travelling wave RF energy, but also

J. R. Jr. Duke; P. G. Apen; M. Hoisington

1996-01-01

430

Quasilinear theory of collisionless electron heating in radio frequency gas discharges  

E-print Network

to be a collisionless one rather than the conven- tional Joule heating dominant for higher pressures. The problemQuasilinear theory of collisionless electron heating in radio frequency gas discharges Yu. M. Aliev heating of rf discharges is treated for characteristic scale lengths of the heating field much shorter

Kaganovich, Igor

431

Stochastic electron heating in bounded radio-frequency plasmas I. D. Kaganovich,a)  

E-print Network

the mean-free-path is small as compared to and to colli- sional Joule heating. In region B, L, electrons plasma boundary at x L. But contrary to the Joule heating, this hybrid heating is nonlocal: the placeStochastic electron heating in bounded radio-frequency plasmas I. D. Kaganovich,a) V. I. Kolobov

Kaganovich, Igor

432

Ultrasound radio-frequency time series for finding malignant breast lesions  

E-print Network

to augment the Breast Imaging-Reporting and Data System (BI-RADS). Breast ultrasound is used as a supplement 050 051 052 053 Ultrasound radio-frequency time series for finding malignant breast lesions Anonymous-based solutions for breast lesion characterization to reduce the patient recall rate after mammography screening

de Freitas, Nando

433

A radio frequency controlled microvalve for biomedical applications  

NASA Astrophysics Data System (ADS)

In this paper we propose the use of a RF controlled microvalve for implementation on a PZT substrate for biomedical applications. Such device has a huge range of applications such as parallel mixing of photo-lithographically defined nanolitre volumes, flow control in pneumatically driven microfluidic systems and lab-on-chip applications. The microvalve makes use of direct actuation mechanisms at the microscale level to allow its use in vivo applications. A number of acoustic propagation modes are investigated and their suitability for biomedical applications, in terms of the required displacement, device size and operation frequency. A theoretical model of the Surface Acoustic Wave (SAW) device is presented and its use in micro-valve application was evaluated using ANSYS tools. Furthermore, the wireless aspect of the device is considered through combining the RF antenna with the microvalve simulation by assuming a high carrier frequency with a small peak-to-peak signal. A new microvalve structure which uses a parallel type piezoelectric bimorph actuator was designed and simulated using ANSYS tools. Then, further optimization of the device was carried out to achieve a better coupling between electrical signal and mechanical actuation within the SAW device.

Dissanayake, Don W.; Tikka, Ajay C.; Al-Sarawi, Said F.; Abbott, Derek

2007-01-01

434

A new simplified high radio frequency power amplifier  

SciTech Connect

In order to simplify a present standard high rf power amplifier of ion cyclotron range of frequency plasma heating system, a new amplifier arrangement composed of a tetrode with a grounded cathode and a field effect transistor (FET) switching circuit providing an input rf power is proposed. The FET switching circuit is so small that it can be installed close to the tetrode in one cubicle. It might be called a single tube high rf power amplifier. A test amplifier composed of the tetrode (8F76R) and the FET (2SK-1310) switching circuit is constructed. The maximum output rf power of 8.5 kW was stably obtained at 70 MHz. The feasibility of the single tube high rf power amplifier was experimentally proved.

Ogawa, Y.; Okutsu, H.; Kobayashi, N.; Hayakawa, A. [Advanced System Design and Engineering Department, Toshiba Corporation, Shinsugita-cho 8, Isogo-ku, Yokohama-shi 235-8523 (Japan)

2004-10-01

435

Efficient use of the Earth exploration-satellite service radio frequency allocation in 8025-8400 MHz  

Microsoft Academic Search

The radio frequency spectrum (9 kHz-275 GHz) is a limited finite resource for which many radio services compete. Most of the 525 radio frequency bands are shared by two or more of the 30 recognized services. Worldwide, except for some individual country differences, in the 8025-8400 MHz range, often referred to as the X-band, the Earth exploration-satellite service (EESS) shares

David F. McGinnis Jr.; Wayne A. Whyte Jr.; Edward M. Davison

2005-01-01

436

Variable Temperature Rate Studies for the Reaction H3O+ Measured with a Coaxial Molecular Beam Radio Frequency Ring  

E-print Network

Beam Radio Frequency Ring Electrode Ion Trap Mark A. Smith,*,,,§ Bing Yuan, and Andrei Sanov+ are determined using a coaxial molecular beam radio frequency ring electrode ion trap (CoMB-RET). The H3O association reaction at 300 K using the Canterbury selected ion flow tube (SIFT) system in 1996,4 and the rate

Sanov, Andrei

437

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

E-print Network

and opportunities for multi-functional oxide thin films for voltage tunable radio frequency/microwave componentsChallenges and opportunities for multi-functional oxide thin films for voltage tunable radio frequency/microwave components Guru Subramanyam, M. W. Cole, Nian X. Sun, Thottam S. Kalkur, Nick M

Chen, Long-Qing

438

Transvaginal Radio Frequency Treatment of the Endopelvic Fascia: A Prospective Evaluation for the Treatment of Genuine Stress Urinary Incontinence  

Microsoft Academic Search

PurposeWe evaluate the safety and efficacy of a new treatment modality for genuine stress urinary incontinence which was a transvaginal radio frequency applicator to deliver radio frequency energy to the endopelvic fascia. The purported mechanism of effect for this therapy is shrinkage of the collagenated tissue which composes the endopelvic fascia that supports the bladder neck and proximal urethra, thus

ROGER R. DMOCHOWSKI; MARK AVON; JAMES ROSS; JAY M. COOPER; RICHARD KAPLAN; BEVERLY LOVE; NEERAJ KOHLI; DAVID ALBALA; BRUCE SHINGLETON

2003-01-01

439

Extraction of negative ions from pulsed electronegative inductively coupled plasmas having a radio-frequency substrate bias  

E-print Network

Extraction of negative ions from pulsed electronegative inductively coupled plasmas having a radio ions into features. By modulating power in inductively coupled plasmas ICPs , the plasma potential coupled plasmas ICPs powered at radio frequency rf where the carrier frequency the power is square wave

Kushner, Mark

440

The electrical asymmetry effect in capacitively coupled radio-frequency discharges  

NASA Astrophysics Data System (ADS)

We present an analytical model to describe capacitively coupled radio-frequency (CCRF) discharges and the electrical asymmetry effect (EAE) based on the non-linearity of the boundary sheaths. The model describes various discharge types, e.g. single and multi-frequency as well as geometrically symmetric and asymmetric discharges. It yields simple analytical expressions for important plasma parameters such as the dc self-bias, the uncompensated charge in both sheaths, the discharge current and the power dissipated to electrons. Based on the model results the EAE is understood. This effect allows control of the symmetry of CCRF discharges driven by multiple consecutive harmonics of a fundamental frequency electrically by tuning the individual phase shifts between the driving frequencies. This novel class of capacitive radio-frequency (RF) discharges has various advantages: (i) A variable dc self-bias can be generated as a function of the phase shifts between the driving frequencies. In this way, the symmetry of the sheaths in geometrically symmetric discharges can be broken and controlled for the first time. (ii) Almost ideal separate control of ion energy and flux at the electrodes can be realized in contrast to classical dual-frequency discharges driven by two substantially different frequencies. (iii) Non-linear self-excited plasma series resonance oscillations of the RF current can be switched on and off electrically even in geometrically symmetric discharges. Here, the basics of the EAE are introduced and its main applications are discussed based on experimental, simulation, and modeling results.

Czarnetzki, U.; Schulze, J.; Schüngel, E.; Donkó, Z.

2011-04-01

441

Process for preparing superconducting films by radio-frequency generated aerosol-plasma deposition in atmosphere  

SciTech Connect

This patent describes a process for coating a layer of superconductive material with a thickness of from about 0.1 to about 500 microns onto a substrate at a deposition rate of from about 0.01 to about 10 microns per minute per 335 square centimeters of substrate surface. It comprises: providing a solution comprised of an yttrium compound, a barium compound, and a copper compound; subjecting the solution to ultrasonic sound waves at a frequency in excess of 20,000 hertz; providing a radio frequency plasma reactor; generating a hot plasma within the radio frequency reactor; contacting the aerosol with the hot plasma gas within the plasma reactor while subjecting the aerosol to a substantially atmospheric pressure of from about 600 to about 1,000 millimeters of mercury and to a radio frequency alternating current at a frequency of from about 100 kilohertz to about 30 megahertz, thereby forming a vapor; providing a substrate disposed outside of the plasma reactor; providing a substrate holder in contact with the substrate; electrically grounding the substrate holder; and contacting the vapor with the substrate; thereby forming a superconductive film in the as deposited state.

Snyder, R.L.; Wang, X.; Zhong, H.

1992-10-20

442

Low-frequency study of two giant radio galaxies: 3C 35 and 3C 223  

NASA Astrophysics Data System (ADS)

Aims: Radio galaxies with a projected linear size ?1 Mpc are classified as giant radio sources. According to the current interpretation these are old sources which have evolved in a low-density ambient medium. Because radiative losses are negligible at low frequency, extending spectral aging studies in this frequency range will allow us to determine the zero-age electron spectrum injected and then to improve the estimate of the synchrotron age of the source. Methods: We present Very Large Array images at 74 MHz and 327 MHz of two giant radio sources: 3C 35 and 3C 223. We performed a spectral study using 74, 327, 608 and 1400 GHz images. The spectral shape is estimated in different positions along the source. Results: The radio spectrum follows a power-law in the hotspots, while in the inner region of the lobe the shape of the spectrum shows a curvature at high frequencies. This steepening agrees with synchrotron aging of the emitting relativistic electrons. In order to estimate the synchrotron age of the sources, the spectra were fitted with a synchrotron model of emission. They show that 3C 35 is an old source of 143 ± 20 Myr, while 3C 223 is a younger source of 72 ± 4 Myr.

Orrù, E.; Murgia, M.; Feretti, L.; Govoni, F.; Giovannini, G.; Lane, W.; Kassim, N.; Paladino, R.

2010-06-01

443

Frequency dependence of the evolution of the radio emission of the supernova remnant Cas A  

NASA Astrophysics Data System (ADS)

Many-year measurements of the radio flux of the young supernova remnant Cassiopeia A relative to the radio galaxy Cygnus A were continued at 290 and 151.5 MHz. The new data are used together with previously published observations carried out at decameter, meter, centimeter, and millimeter wavelengths to derive the frequency dependence of the secular variation of the radio flux density of Cas A: . The observed slowing of the secular variations with decreasing frequency at decameter wavelengths can be explained by a decrease in the optical depth of a remnant HII zone around Cas A with time due to recombination of hydrogen atoms. The new derived frequency dependence for the rate of the secular decrease, absolute and relative measurements of the radio flux density of Cas A carried out over the last 25 years, and the absolute spectrum of Cyg A are used to construct the spectrum of Cas A in the range 5-250 000 MHz predicted for epoch 2015.5.

Vinyaikin, E. N.

2014-09-01

444

Relations among low ionosphere parameters and high frequency radio wave absorption  

NASA Technical Reports Server (NTRS)

Charged particle conductivities measured in the very low ionosphere at White Sands Missile Range, New Mexico, and Wallops Island, Virginia, are compared with atmospheric parameters and high frequency radio wave absorption measurements. Charged particle densities are derived from the conductivity data. Between 33 and 58 km, positive conductivity correlated well with neutral atmospheric temperature, with temperature coefficients as large as 4.6%/deg K. Good correlations were also found between HF radio wave absorption and negative conductivity at altitudes as low as 53 km, indicating that the day-to-day absorption variations were principally due to variations in electron loss rate.

Cipriano, J. P.

1973-01-01

445

A new approach to multi-frequency synthesis in radio interferometry  

E-print Network

We present a new approach to multi-frequency synthesis in radio astronomy. Using Bayesian inference techniques, the new technique estimates the sky brightness and the spectral index simultaneously. In principle, the bandwidth of a wide-band observation can be fully exploited for sensitivity and resolution, currently only limited by higher order effects like spectral curvature. Employing this new approach, we further present a multi-frequency extension to the imaging algorithm RESOLVE. In simulations, this new algorithm outperforms current multi-frequency imaging techniques like MS-MF-CLEAN.

Junklewitz, H; Enßlin, T

2014-01-01

446

Response of radio frequency superconducting quantum interference devices to electromagnetic interference  

SciTech Connect

A number of applications of high-temperature superconductor radio frequency superconducting quantum interference devices (rf SQUIDs) require a certain immunity of these sensors against electromagnetic interference (EMI). We have investigated effects of electromagnetic radiation in the high-frequency and ultrahigh-frequency range on various types of rf SQUIDs. It has been found that EMI of sufficient field strength reduces the voltage versus flux transfer function, and thus increases the flux noise of the SQUIDs. SQUIDs with a wire wound tank circuit coil have been found to be more sensitive to EMI than SQUIDs integrated into a superconducting microstrip resonator. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Mueck, M.; Dechert, J.; Gail, J.; Kreutzbruck, M.; Schoene, S.; Weidl, R. [Institut fuer Angewandte Physik, Justus-Liebig-Universitaet Giessen, Heinrich-Buff-Ring 16, 35392 Giessen (Germany)] [Institut fuer Angewandte Physik, Justus-Liebig-Universitaet Giessen, Heinrich-Buff-Ring 16, 35392 Giessen (Germany)

1995-09-01

447

Linear transmitter design for MSAT terminals  

NASA Technical Reports Server (NTRS)

One of the factors that will undoubtedly influence the choice of modulation format for mobile satellites, is the availability of cheap, power-efficient, linear amplifiers for mobile terminal equipment operating in the 1.5-1.7 GHz band. Transmitter linearity is not easily achieved at these frequencies, although high power (20W) class A/AB devices are becoming available. However, these components are expensive and require careful design to achieve a modest degree of linearity. In this paper an alternative approach to radio frequency (RF) power amplifier design for mobile satellite (MSAT) terminals using readily-available, power-efficient, and cheap class C devices in a feedback amplifier architecture is presented.

Wilkinson, Ross; Macleod, John; Beach, Mark; Bateman, Andrew

1990-01-01

448

NASA's Radio Frequency Bolt Monitor: A Lifetime of Spinoffs  

NASA Technical Reports Server (NTRS)

This story begins in the 1970s, when Dr. Joseph Heyman, a young scientist at NASA s Langley Research Center, was asked to support the investigation of a wind tunnel accident at a sister center. Although the work was outside of his physics background, it sparked a research focus that guided his lengthy NASA career and would earn him a slew of accolades, including NASA s highest award medals for Exceptional Leadership, Exceptional Achievement, and Exceptional Service; the coveted Silver Snoopy Astronaut Award for Space Shuttle Return to Flight; and the Arthur Fleming Award for being one of the Top Ten Federal Scientists in Government Service. He won 30 additional NASA awards, including the Agency s Invention of the Year and the Agency s highest award for technology transfer, and was the only person to ever win 4 R&D 100 Awards. Back in 1973, though, Heyman was a young civil servant with a background in physics who was asked to sit on an accident review panel. The panel met at Ames Research Center, in Moffet Field, California, and after considerable investigation, concluded that a high-pressure pebble heater used for heating gas had failed, due to improperly tightened bolts in a 1,000-pound gate valve control section. The accident showered the facility with incendiary ceramic spheres and nearly a ton of metal, but, luckily, caused no injuries. Heyman returned to Langley and began work on a solution. He developed an ultrasonic device that would measure bolt elongation, as opposed to torque, the factor typically measured in testing bolt preload or tension. Torque measurement can lead to load errors, with miscalculations as high as 80 percent that can be passed over during installation. Bolt stretch, however, is nearly always accurate to 1 percent or better. Within 1 month, he had an acoustic resonance solution that accurately determined bolt elongation. He assumed his work on this project had ended, but it was actually the start of nearly 15 years of work perfecting, improving, inventing, and modifying the "bolt monitor", all the while, filing numerous patents, presenting papers, and holding demonstrations as the technology matured. Industry engineers challenged Heyman s inventiveness, and reminded the physicist that most bolts are not perfect resonators, and that early devices required that the bolt have reasonably flat and parallel faces. The U.S. Geological Survey asked NASA for help in determining the load in mine roof bolts, which are 8- to 10-feet-long and rough cut. To solve that problem, Heyman modified the original device to operate at a lower frequency and to generate propagation modes that could be used to "lock" the instrument on a particular mode. Further work in this vein led to the development of the Pulsed Phase Locked Loop (P2L2) that worked on the mine bolts. The next set of problems involved high-strength bolts with head markings. For this solution, Heyman invented a modified P2L2 that tracked a specific phase point in the measurement wave. This class of instrumentation, well suited to measuring small changes in acoustic velocity, won the NASA "Invention of the Year" award in 1982. Other scientists and engineers have continued the evolution of this technology both inside NASA and outside of the Agency. Within NASA, the technology has been improved for medical applications, with a particular focus on intercranial pressure (ICP) monitoring.

2005-01-01

449

New Antennas and Methods for the Low Frequency Stellar and Planetary Radio Astronomy  

NASA Astrophysics Data System (ADS)

According to the special Program of the National Academy of Sciences of Ukraine, creation of the new giant Ukrainian radio telescope (GURT) was started a few years ago on the UTR-2 radio telescope observatory. The main goal is to reach maximum band at the lowest frequencies (10-70 MHz), effective area (step-by-step up to 100,000 sq.m), and high interference immunity for resolving many astrophysical tasks when the sensitivity is less limited by the confusion effects. These tasks include stellar radio astronomy (the Sun, solar wind, flare stars, pulsars, transients) and planetary one (Jupiter, planetary lightnings, Earth ionosphere, the Moon, exoplanets). This array should be complementary to the LOFAR, E-LOFAR systems. The first stages of the GURT (6 x 25 cross dipole active elements) and broad-band digital registration of the impulsive and sporadic events were tested in comparison with the existing largest decameter array UTR-2.

Konovalenko, A. A.; Falkovich, I. S.; Rucker, H. O.; Lecacheux, A.; Zarka, Ph.; Koliadin, V. L.; Zakharenko, V. V.; Stanislavsky, A. A.; Melnik, V. N.; Litvinenko, G. V.; Gridin, A. A.; Bubnov, I. N.; Kalinichenko, N. N.; Reznik, A. P.; Sidorchuk, M. A.; Stepkin, S. V.; Mukha, D. V.; Nikolajenko, V. S.; Karlsson, R.; Thide, B.

450

First Spectroscopic Imaging Observations of the Sun at Low Radio Frequencies with the Murchison Widefield Array Prototype  

NASA Astrophysics Data System (ADS)

We present the first spectroscopic images of solar radio transients from the prototype for the Murchison Widefield Array, observed on 2010 March 27. Our observations span the instantaneous frequency band 170.9- 201.6 MHz. Though our observing period is characterized as a period of "low" to "medium" activity, one broadband emission feature and numerous short-lived, narrowband, non-thermal emission features are evident. Our data represent a significant advance in low radio frequency solar imaging, enabling us to follow the spatial, spectral, and temporal evolution of events simultaneously and in unprecedented detail. The rich variety of features seen here reaffirms the coronal diagnostic capability of low radio frequency emission and provides an early glimpse of the nature of radio observations that will become available as the next generation of low-frequency radio interferometers come online over the next few years.

Oberoi, Divya; Matthews, Lynn D.; Cairns, Iver H.; Emrich, David; Lobzin, Vasili; Lonsdale, Colin J.; Morgan, Edward H.; Prabu, T.; Vedantham, Harish; Wayth, Randall B.; Williams, Andrew; Williams, Christopher; White, Stephen M.; Allen, G.; Arcus, Wayne; Barnes, David; Benkevitch, Leonid; Bernardi, Gianni; Bowman, Judd D.; Briggs, Frank H.; Bunton, John D.; Burns, Steve; Cappallo, Roger C.; Clark, M. A.; Corey, Brian E.; Dawson, M.; DeBoer, David; De Gans, A.; deSouza, Ludi; Derome, Mark; Edgar, R. G.; Elton, T.; Goeke, Robert; Gopalakrishna, M. R.; Greenhill, Lincoln J.; Hazelton, Bryna; Herne, David; Hewitt, Jacqueline N.; Kamini, P. A.; Kaplan, David L.; Kasper, Justin C.; Kennedy, Rachel; Kincaid, Barton B.; Kocz, Jonathan; Koeing, R.; Kowald, Errol; Lynch, Mervyn J.; Madhavi, S.; McWhirter, Stephen R.; Mitchell, Daniel A.; Morales, Miguel F.; Ng, A.; Ord, Stephen M.; Pathikulangara, Joseph; Rogers, Alan E. E.; Roshi, Anish; Salah, Joseph E.; Sault, Robert J.; Schinckel, Antony; Udaya Shankar, N.; Srivani, K. S.; Stevens, Jamie; Subrahmanyan, Ravi; Thakkar, D.; Tingay, Steven J.; Tuthill, J.; Vaccarella, Annino; Waterson, Mark; Webster, Rachel L.; Whitney, Alan R.

2011-02-01

451

SAR transmitter  

NASA Astrophysics Data System (ADS)

In the follow-on of the ESA contract 4122/79 it was intended to demonstrate on breadboard the feasibility of a modular EPC supplied by a multibus for a KLYSTRON power transmitter. The aim of this final report is to give details on the design and on test results of the electronics required to drive a KLYSTRON for a SAR system. The concept utilized for the DC/DC conversion is a Series Resonant type (SCHWARZ Converter). An elegant Breadboard of 2 Modules (over 4 required for the complete EPC) has been realized and the tests have demonstrated the envisaged feasibility of an active redundancy with modular EPC both for output voltage generation and for output power. Also the concept of the multibus has been implemented (2 bus over 4) and verified in the EPC breadboard.

1983-06-01

452

Detection of Traveling Ionospheric Disturbances by Medium Frequency Doppler Sounding Using AM Radio Transmissions  

NASA Astrophysics Data System (ADS)

Nighttime traveling ionosphere disturbances (TIDs) propagating in the lower F region of the ionosphere were detected from time variations in the Doppler shifts of commercial AM radio broadcast stations. Three separately deployed receivers, components of the Intercepted Signals for Ionospheric Science (ISIS) Array software radio instrumentation network, recorded signals from two radio stations during eleven nights in March-April, 2012. Combining these measurements established that variations in the frequencies of the received signals, with amplitudes up to a few tenths of a Hertz, resulted from Doppler shifts produced by the ionosphere. At times, TIDs were detected as large amplitude variations in the Doppler shift with approximately 40-minute period correlated across the array. For one study interval, 0000-0400 UT on April 13, 2012, simultaneous GPS-TEC, digisonde, and superDARN coherent backscatter radar measurements confirmed the detection of TIDs with the same period. Detection of the AM signals at widely spaced receivers allowed the phase velocity and wavelength of the TIDs to be inferred, with some limitations due to differing reflection heights for the different frequencies. These measurements will be compared to phase velocities and wavelengths determined from combining an array of GPS receivers; discrepancies due to the altitude sensitivity of the techniques or other effects will be discussed. These results demonstrate that AM radio signals can be used for detection of nighttime TIDs.

Chilcote, M. A.; Labelle, J. W.; Lind, F. D.; Coster, A. J.; Galkin, I. A.; Miller, E.; Weatherwax, A. T.

2013-12-01

453

Influence of growth temperature on electrical, optical, and plasmonic properties of aluminum:zinc oxide films grown by radio frequency magnetron sputtering  

NASA Astrophysics Data System (ADS)

We have investigated the responsible mechanism for the observation of metallic conductivity at room temperature and metal-semiconductor transition (MST) at lower temperatures for aluminum-doped zinc oxide (AZO) films. AZO films were grown on glass substrates by radio-frequency magnetron sputtering with varying substrate temperatures (Ts). The films were found to be crystalline with the electrical resistivity close to 1.1 × 10-3 ? cm and transmittance more than 85% in the visible region. The saturated optical band gap of 3.76 eV was observed for the sample grown at Ts of 400 °C, however, a slight decrease in the bandgap was noticed above 400 °C, which can be explained by Burstein-Moss effect. Temperature dependent resistivity measurements of these highly conducting and transparent films showed a MST at ˜110 K. The observed metal-like and metal-semiconductor transitions are explained by taking into account the Mott phase transition and localization effects due to defects. All AZO films demonstrate crossover in permittivity from positive to negative and low loss in the near-infrared region, illustrating its applications for plasmonic metamaterials, including waveguides for near infrared telecommunication region. Based on the results presented in this study, the low electrical resistivity and high optical transmittance of AZO films suggested a possibility for the application in the flexible electronic devices, such as transparent conducting oxide film on LEDs, solar cells, and touch panels.

Dondapati, Hareesh; Santiago, Kevin; Pradhan, A. K.

2013-10-01

454

Plasma Parameters of SRF Cavities for Radio-Frequency Discharge Processing  

NASA Astrophysics Data System (ADS)

Superconducting radio frequency (SRF) cavities of bulk Niobium are accelerating field-generating components of particle accelerators. Cavities are designed to support TM modes at a resonant frequency, which usually serve as their identifier. RF plasma surface modification dry-etching technology as an alternative to the currently existing wet etching technology requires a different RF coupling regime. The choice of power generator frequency greatly affects the field and plasma parameters distribution over the cavity. These are adjusted by a coaxial centerline antenna to provide for optimum level of plasma sheath uniformity. In the search for best etching conditions, we are opting for radio frequency (13.56 MHz, 100 MHz) and microwave frequency plasma (2.45 GHz) in Ar/Cl2 gas mixture. We have developed five optical probes for simultaneous spectroscopic measurements of the plasma properties at five points inside the cavity. The electron temperature and density measurement at the same set of points will be also measured with a Langmuir probe. The measurement of plasma parameters at different pressure and power for the chosen frequency set with varying chlorine content will be presented.

Upadhyay, Janardan; Popovic, Svetozar; Vuskovic, Lepsha; Valente-Feliciano, Anne-Marie; Phillips, Larry

2012-10-01

455

Discharge characteristics of atmospheric-pressure radio-frequency glow discharges with argon/nitrogen  

SciTech Connect

In this letter, atmospheric-pressure glow discharges in {gamma} mode with argon/nitrogen as the plasma-forming gas using water-cooled, bare copper electrodes driven by radio-frequency power supply at 13.56 MHz are achieved. The preliminary studies on the discharge characteristics show that, induced by the {alpha}-{gamma} coexisting mode or {gamma} mode discharge of argon, argon-nitrogen mixture with any mixing ratios, even pure nitrogen, can be employed to generate the stable {gamma} mode radio-frequency, atmospheric-pressure glow discharges and the discharge voltage rises with increasing the fraction of nitrogen in the argon-nitrogen mixture for a constant total gas flow rate.

Wang Huabo; Sun Wenting; Li Heping; Bao Chengyu; Gao Xing; Luo Huiying [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); School of Public Health and Family Medicine, Capital University of Medical Sciences, Beijing 100069 (China); Beijing Center for Diseases Control and Prevention, Beijing 100013 (China)

2006-10-16

456

Using a Satellite Swarm for building a Space-based Radio Telescope for Low Frequencies  

NASA Astrophysics Data System (ADS)

In radio astronomy, as in astronomy in general, a wide range of frequencies is observed as each spectral band offers a unique window to study astrophysical phenomena. In the recent years, new observatories have been designed and built at the extreme limits of the radio spectrum. For the low frequencies several Earth-based radio telescopes are constructed at this moment. In the Netherlands, the Low Frequency Array (LOFAR) is being constructed at this moment and will be operational later this year. LOFAR observes the sky between 30 and 240 MHz. Observing at even lower frequencies is very interesting, but, due to the influence of the Earth's ionosphere this is not possible from Earth. Thus, the only option to observe low frequencies is a telescope in space. In the past several studies have been conducted on a low-frequency space-based radio tele-scope. In the recent ESA project Distributed Aperture Array for Radio Astronomy in Space (DARIS), such a mission was studied in detail. The study focused on a moderate-size three-dimensional satellite constellation operating as a coherent large-aperture synthesis array. The DARIS project is presented in a separate conference contribution. In the DARIS project the focus was on technology available at this moment, with an outlook and technological development plan/roadmap to be exploited for the future. Using current-day technologies, a space-based low-frequency array would be bulky and, thus, costly. A logical next step would be to investigate possibilities to miniaturize the electronics and use very small satellites, perhaps even nano satellites with masses between 1-10 kg to build the radio tele-scope. The approach is to use a swarm of satellites to establish a virtual telescope to perform the astronomical task. This is investigated in the NWO/STW-funded OLFAR (Orbiting Low Frequency Array) project. The OLFAR radio telescope will be composed of an antenna array based on satellites deployed at a location where the Earth's interference is limited, and where the satellites can be maintained in a three-dimensional configuration with a maximum diameter of 100 km. A Moon orbit could be suitable option. Each individual satellite will consist of deployable antennas. The sky signals will be amplified using an integrated ultra-low power direct sampling receiver and digitizer. Using digital fil-tering, any subband within the LNA passband can be selected. The data will be distributed over the available nodes in space. On-board signal processing will filter the data, invoke RFI mitigation algorithms (if necessary), and finally, correlate the data in a phased array mode. If more satellites are available, they will automatically join the array. The final correlated or beam-formed data will be sent to Earth as part of the telemetry data using a radio link. As the satellites will be far away from Earth, communication to and from Earth will require diversity communication schemes, using all the individual satellites together. In this paper, the design parameters for the satellites and the swarm will be discussed and status of the OLFAR project will be reported. Details will be given about the system and the signals that are expected.

Bentum, Mark; Boonstra, A. J.; Verhoeven, C. J. M.; van der Veen, A. J.; Gill, E. K. A.; Saks, N.; Falcke, H.; Klein-Wolt, M.; Rajan, R. T.; Wijnholds, S. J.; Arts, M.; van't Klooster, K.; Beliün, F.; Meijerink, A.; Monna, B.; Rotteveel, J.; Boer, M. A.; Bongers, E.; Boom, E.; van Tuijl, E.; van Staveren, A.

457

Radio Frequency Scanning Tunneling Spectroscopy for Single-Molecule Spin Resonance  

NASA Astrophysics Data System (ADS)

We probe nuclear and electron spins in a single molecule even beyond the electromagnetic dipole selection rules, at readily accessible magnetic fields (few mT) and temperatures (5 K) by resonant radio-frequency current from a scanning tunneling microscope. We achieve subnanometer spatial resolution combined with single-spin sensitivity, representing a 10 orders of magnitude improvement compared to existing magnetic resonance techniques. We demonstrate the successful resonant spectroscopy of the complete manifold of nuclear and electronic magnetic transitions of up to ?Iz=±3 and ?Jz=±12 of single quantum spins in a single molecule. Our method of resonant radio-frequency scanning tunneling spectroscopy offers, atom-by-atom, unprecedented analytical power and spin control with an impact on diverse fields of nanoscience and nanotechnology.

Müllegger, Stefan; Tebi, Stefano; Das, Amal K.; Schöfberger, Wolfgang; Faschinger, Felix; Koch, Reinhold

2014-09-01

458

Radio frequency scanning tunneling spectroscopy for single-molecule spin resonance.  

PubMed

We probe nuclear and electron spins in a single molecule even beyond the electromagnetic dipole selection rules, at readily accessible magnetic fields (few mT) and temperatures (5 K) by resonant radio-frequency current from a scanning tunneling microscope. We achieve subnanometer spatial resolution combined with single-spin sensitivity, representing a 10 orders of magnitude improvement compared to existing magnetic resonance techniques. We demonstrate the successful resonant spectroscopy of the complete manifold of nuclear and electronic magnetic transitions of up to ?I_{z}=±3 and ?J_{z}=±12 of single quantum spins in a single molecule. Our method of resonant radio-frequency scanning tunneling spectroscopy offers, atom-by-atom, unprecedented analytical power and spin control with an impact on diverse fields of nanoscience and nanotechnology. PMID:25302884

Müllegger, Stefan; Tebi, Stefano; Das, Amal K; Schöfberger, Wolfgang; Faschinger, Felix; Koch, Reinhold

2014-09-26

459

Effect of radio frequency fields on the radical pair magnetoreception model  

NASA Astrophysics Data System (ADS)

Although the radical pair (RP) model is widely accepted for birds' orientation, the physical mechanism of it is still not fully understood. In this paper we consider the RP model in the total angular-momentum representation and clearly show a detailed mechanism for orientation. When only the vertical hyperfine (HF) coupling component is considered, analytical expressions of singlet yield angular profiles are obtained with and without considering the radio frequency field, and when the horizontal HF coupling components are considered, a numerical calculation of the singlet yield is given. Based on these analytical and numerical results we present a detailed account of the following issues: how the HF coupling induces the singlet-triplet conversion; why the vertical radio frequency field can disorient the birds, while the parallel one cannot; and why the birds are able to "train" to different field strengths. Finally, we consider a multinuclei RP model.

Xu, Bao-Ming; Zou, Jian; Li, Hai; Li, Jun-Gang; Shao, Bin

2014-10-01

460

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

NASA Technical Reports Server (NTRS)

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

Few, A. A., Jr.

1981-01-01