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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

Geophysical cave detection with a portable Very Low Frequency (VLF) radio transmitter  

NASA Astrophysics Data System (ADS)

In the past few years several attempts have been made to delineate karstic features as caves with geophysical methods from the surface. Knowledge about the exact position of caves might be of interest for karst hydrogeology, hazard estimation or even touristy purposes. However, interpretation of data from indirect approaches as geophysics naturally always holds a certain degree of ambiguity. A geophysical field experiment at the Swiss Jura Mountains is presented, which shows the possibility for precise lateral position delineation of an accessible cave at a depth varying from 10 to about 60 meters below surface in Mesozoic limestone. For this purpose, a portable Very Low Frequency radio transmitter prototype with a loop diameter of about one meter is placed along a 150 meter long profile at several positions inside the cave with vertical transmitter loop axis orientation. In order to delineate the transmitter locations from the surface, a Radio-Magnetotelluric (RMT) receiver prototype is used simply by triangulation of the zero-signal from the transmitter loop. The zero signal of the emitted EM field should coincide with the transmitter loop axis in case of an undistorted EM field. As in-situ proof, the transmitter positions additionally have been speleologically mapped. The results of the experiment show that the lateral positions found from the surface by combined application of a VLF transmitter and RMT receiver coincide extremely well with the locations speleologically mapped. At the deepest part of the cave (about 60 meters below surface) lateral deviation between EM- and speleological results is only about one meter. Therefore, this technique for instance enables positioning of drilling locations aiming on entering cave galleries.

Bosch, Frank P.; Gurk, Marcus; Jeannin, Pierre-Yves; Müller, Imre

2010-05-01

3

System efficiency analysis for high power solid state radio frequency transmitter.  

PubMed

This paper examines some important relationships, related with the system efficiency, for very high power, radio frequency solid-state transmitter; incorporating multiple solid-state power amplifier modules, power combiners, dividers, couplers, and control/interlock hardware. In particular, the characterization of such transmitters, at the component as well as the system level, is discussed. The analysis for studying the influence of the amplitude and phase imbalance, on useful performance parameters like system efficiency and power distribution is performed. This analysis is based on a scattering parameter model. This model serves as a template for fine-tuning the results, with the help of a system level simulator. For experimental study, this approach is applied to a recently designed modular and scalable solid-state transmitter, operating at the centre frequency of 505.8?MHz and capable of delivering a continuous power of 75 kW. Such first time presented, system level study and experimental characterization for the real time operation will be useful for the high power solid-state amplifier designs, deployed in particle accelerators. PMID:24593383

Jain, Akhilesh; Sharma, D K; Gupta, A K; Lad, M R; Hannurkar, P R; Pathak, S K

2014-02-01

4

System efficiency analysis for high power solid state radio frequency transmitter  

NASA Astrophysics Data System (ADS)

This paper examines some important relationships, related with the system efficiency, for very high power, radio frequency solid-state transmitter; incorporating multiple solid-state power amplifier modules, power combiners, dividers, couplers, and control/interlock hardware. In particular, the characterization of such transmitters, at the component as well as the system level, is discussed. The analysis for studying the influence of the amplitude and phase imbalance, on useful performance parameters like system efficiency and power distribution is performed. This analysis is based on a scattering parameter model. This model serves as a template for fine-tuning the results, with the help of a system level simulator. For experimental study, this approach is applied to a recently designed modular and scalable solid-state transmitter, operating at the centre frequency of 505.8 MHz and capable of delivering a continuous power of 75 kW. Such first time presented, system level study and experimental characterization for the real time operation will be useful for the high power solid-state amplifier designs, deployed in particle accelerators.

Jain, Akhilesh; Sharma, D. K.; Gupta, A. K.; Lad, M. R.; Hannurkar, P. R.; Pathak, S. K.

2014-02-01

5

SHIELDED-NEEDLE TECHNIQUE FOR SURGICALLY IMPLANTING RADIO-FREQUENCY TRANSMITTERS IN FISH  

EPA Science Inventory

Protruding whip antenna radio transmitters were implanted in fish with abdominal pelvic fins. This surgical technique enables the transmitter to be positioned anywhere in the peritoneal cavity without piercing vital organs through the use of a shielded needle to guide an antenna ...

6

Radio frequency detection assembly and method for detecting radio frequencies  

DOEpatents

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

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

2010-03-16

7

EFFECTS OF EXTERNAL RADIO TRANSMITTERS ON FISH  

EPA Science Inventory

Yellow perch (Perca flavescens) and largemouth bass (Micropterus salmoides) were studied to determine the effects of externally attached radio transmitter tags. Perch that had been tagged with dummy radio tags were more susceptible to predation and more sensitive to environmental...

8

Miniature Low Frequency Acoustic Transmitter.  

National Technical Information Service (NTIS)

A miniature lightweight transmitter that mechanically generates low- frequency acoustic energy is described, wherein one or more miniature balloons filled with air are positioned at the center of a pressure vessel filled with water and tethered in place. ...

A. A. Ruffa

2006-01-01

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

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

11

Radio frequency interference mitigation in radio astronomy  

NASA Astrophysics Data System (ADS)

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

Boonstra, Albert-Jan

2005-12-01

12

The Frequency Spectrum Radio.  

ERIC Educational Resources Information Center

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

Howkins, John, Ed.

1979-01-01

13

Radio Link Frequency Assignment  

Microsoft Academic Search

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

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

1999-01-01

14

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

15

47 CFR 95.629 - LPRS transmitter frequencies.  

Code of Federal Regulations, 2013 CFR

...629 LPRS transmitter frequencies. (a) LPRS transmitters may operate on any frequency listed in paragraphs...750-217.000 MHz band for low power point-to-point...indicates standard band frequencies. The channel...

2013-10-01

16

Effects of radio transmitters on nesting captive mallards  

USGS Publications Warehouse

Radio packages may subtly affect bird behavior and condition, and thus could bias results from studies using this technique. To assess effects on reproduction of mallards (Anas platyrhynchos), we tested 3 types of back-mounted radio packages on captive females. Eight paired females were randomly assigned to each of 4 treatments: 4-g transmitter attached with sutures and glue, 10-g or 18-g transmitter attached with a harness, and no transmitter (control). All mallards were fed ad libitum. No differences were detected among treatments in number of clutches, clutch size, nesting interval, egg mass, or body mass; powers (range = 0.15-0.48) of tests were low. Feather wear and skin irritation around radio packages were minimal. Birds retained sutured transmitters for an average of 43.5 days (range = 3-106 days) and harness transmitters for the duration of the study (106 days). Sutures were not reliable and presently are not recommended as an attachment method. Caution is advised in applying these results to radio-equipped mallards in the wild.

Houston, R. A.; Greenwood, R. J.

1993-01-01

17

Efficacy of using radio transmitters to monitor least tern chicks  

USGS Publications Warehouse

Little is known about Least Tern (Sterna antillarum) chicks from the time they leave the nest until fledging because they are highly mobile and cryptically colored. We evaluated the efficacy of using radiotelemetry to monitor Interior Least Tern (S. a. athalassos) chicks at Salt Plains National Wildlife Refuge, Oklahoma. In 1999, we attached radio transmitters to 26 Least Tern chicks and tracked them for 2-17 days. No adults abandoned their chicks after transmitters were attached. Transmitters did not appear to alter growth rates of transmittered chicks (P = 0.36) or prevent feather growth, although dermal irritation was observed on one chick. However, without frequent reattachment, transmitters generally did not remain on chicks <1 week old for more than 2 days because of feather growth and transmitter removal, presumably by adult terns. Although the presence of transmitters did not adversely affect Least Tern chicks, future assessments should investigate nonintrusive methods to improve retention of transmitters on young chicks and reduce the number of times that chicks need to be handled.

Whittier, J. B.; Leslie, Jr. , D. M.

2005-01-01

18

Transmitter-Oriented Code Assignment for Multihop Packet Radio  

Microsoft Academic Search

Quasi-orthogonal codes are assigned to transmitters in a packet radio network such that interference caused by hidden terminals is eliminated. In addition, a handshaking protocol permits random access between nodes. Simple mathematical models and simulation indicate a potential throughput advantage over slotted ALOHA and CSMA.

TAREK MAKANSI

1987-01-01

19

A Digital LINC Transmitter Architecture for Opportunistic Radio  

Microsoft Academic Search

This paper describes a radio transmitter architecture based on the LINC concept. It associates a digital RF modulator with highly selective compact filters and saturated power amplifiers. Despite its apparent complexity, this mixed digital\\/analogue system guarantees both linearity and high power efficiency while offering increased flexibility, reconfigurability and compactness. As a result, this architecture appears as a relevant choice for

Patrick Wurm

2009-01-01

20

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

21

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

22

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

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 Differential Absorption LIDAR (DIAL) measurements in the field.

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

1996-09-01

24

Radio frequency identification (RFID)  

Microsoft Academic Search

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

C. M. Roberts

2006-01-01

25

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

26

Radio Frequency Interference Mitigation in Radio Astronomy.  

National Technical Information Service (NTIS)

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

A. J. Boonstra

2005-01-01

27

Radio frequency pulse compression  

SciTech Connect

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

Farkas, Z.D.

1988-12-01

28

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

NASA Astrophysics Data System (ADS)

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

Bretteil, S.; Weber, R.

2005-07-01

29

Radio frequency picosecond phototube  

SciTech Connect

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

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

2006-10-01

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

WIND TUNNEL EXPERIMENTS TO ASSESS THE EFFECT OFBACK-MOUNTED RADIO TRANSMITTERS ON BIRD BODY DRAG  

Microsoft Academic Search

SUMMARY The aerodynamic drag of bird bodies was measured in a wind tunnel, with and without back-mounted dummy radio transmitters. Flight performance estimates indicate that the drag of a large transmitter can cause a substantial reduction of a migrant's range, that is, the distance it can cover in non-stop flight. The drag of the transmitter can be reduced by arranging

Holliday H. Obrecht III; C. J. Pennycuick; Mark R. Fuller

32

Externally attached radio transmitters do not affect the parental care behaviour of rock bass  

Microsoft Academic Search

Turning, pectoral fin and caudal fin rates and time spent on the nest of male rock bass Ambloplites rupestris, engaged in parental care, were not affected after the attachment of external radio transmitters. Reproductive success was similar between treatment and control fish. Micro external radio transmitters can be used on small fishes for studying parental care duration and post-care movement

S. J. C OOKE

33

Stabilized radio-frequency quadrupole  

DOEpatents

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

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

1982-09-29

34

Tesla’s multi-frequency wireless radio controlled vessel  

Microsoft Academic Search

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

Aleksandar Marincic; Djuradj Budimir

2008-01-01

35

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.

36

Frequency Allocation; The Radio Spectrum.  

ERIC Educational Resources Information Center

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

Federal Communications Commission, Washington, DC.

37

Effects of antenna length and material on output power and detection of miniature radio transmitters  

USGS Publications Warehouse

The optimal antenna of transmitters used in small aquatic animals is often a compromise between efficient radio wave propagation and effects on animal behavior. Radio transmission efficiency generally increases with diameter and length of the conductor, but increased antenna length or weight can adversely affect animal behavior. We evaluated the effects of changing antenna length and material on the subsequent tag output power, reception, and detection of tagged fish. In a laboratory, we compared the relative signal strengths in water of 150 MHz transmitters over a range of antenna lengths (from 6 to 30 cm) and materials (one weighing about half of the other). The peak relative signal strengths were at 20 and 22 cm, which are approximately one wavelength underwater at the test frequency. The peak relative signal strengths at these lengths were approximately 50% greater than those of 30 cm antennas, a length commonly used in fisheries research. Few significant differences were present in distances for the operator to hear or the telemetry receiver to decode transmitters from a boat-mounted receiving system based on antenna length, but the percent of tagged fish detected passing a hydroelectric dam fitted with an array of receiving systems was significantly greater at the antenna length with peak output power in laboratory tests. This study indicates careful choice of antenna length and material of small transmitters can be used to reduce weight and possible antenna effects on animal behavior, to maximize tag output power and detection, or to balance these factors based on the needs of the application. ?? 2007 Springer Science+Business Media B.V.

Beeman, J. W.; Bower, N.; Juhnke, S.; Dingmon, L.; Van Den, Tillaart, M.; Thomas, T.

2007-01-01

38

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

39

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

PubMed

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

Skotte, J

1984-12-01

40

'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

41

Effect of relative volume on radio transmitter expulsion in subadult common carp  

USGS Publications Warehouse

Expulsion of surgically implanted radio transmitters is a problem in some fish telemetry studies. We conducted a 109-d experiment to test the hypothesis that variation in relative volume of transmitters surgically implanted in subadult common carp Cyprinus carpio would affect transmitter expulsion. We also necropsied fish at the end of the experiment to evaluate histological evidence for the mechanism of expulsion. Survival rate was high during our experiment; all control fish and 88% of the fish subjected to the implantation surgery survived. Expulsion rate was low; of the 23 fish that received transmitters and survived the experiment, only two (9%) expelled the transmitters. One of these expulsions occurred through a rupture of the incision and the other occurred via the intestine. Retained transmitters were all encapsulated by tissue, and most exhibited multiple adhesions to the intestine, gonads, and body wall. Adhesions were more numerous in fish that received larger transmitters. ?? Copyright by the American Fisheries Society 2007.

Penne, C. R.; Ahrens, N. L.; Summerfelt, R. C.; Pierce, C. L.

2007-01-01

42

Measurement of transmitter noise at high frequency through microwave frequencies  

Microsoft Academic Search

A tutorial review of the basis for transmitter noise measurements shows that noise is best described and measured as AM and FM noise. The contribution of AM noise to RF spectrum shape is determined by the power spectral density shape of the AM noise. The contribution of FM noise to the RF spectrum is to make the shape that of

T. A. Barley; G. J. Rast Jr.; J. R. Ashley

1976-01-01

43

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

44

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

45

Investigation of new low-loss and high-power SAW filters for reverse-frequency-allocated cellular radios  

Microsoft Academic Search

Japanese cellular radios employ reverse frequency-allocations of the transmitter and receiver frequency bands. A rather narrowband surface acoustic wave (SAW) transmitter prefilter and a new type of SAW low-loss and high-power transmitter final stage filter-dual configurations to previously developed US cellular radio system filter-have been developed. The dual configurations provide the stopbands for the filter at the lower side of

Mitsutaka Hikita; Toyoji Tabuchi; Nobuhiko Shibagaki

1993-01-01

46

Technique for Predicting the Radio Frequency Field Strength Inside an Enclosure  

NASA Technical Reports Server (NTRS)

This technical memo represents a simple analytical technique for predicting the Radio Frequency (RF) field inside an enclosed volume in which radio frequency occurs. The technique was developed to predict the RF field strength within a launch vehicle fairing in which some payloads desire to launch with their telemetry transmitter radiating. This technique considers both the launch vehicle and the payload aspects.

Hallett, Michael P.; Reddell, Jerry P.

1997-01-01

47

Effects of radio transmitters on the behavior of Red-headed Woodpeckers.  

SciTech Connect

ABSTRACT. Previous studies have revealed that radio-transmitters may affect bird behaviors, including feeding rates, foraging behavior, vigilance, and preening behavior. In addition, depending on the method of attachment, transmitters can potentially affect the ability of cavity-nesting birds to use cavities. Our objective was to evaluate effects of transmitters on the behavior of and use of cavities byRed-headedWoodpeckers (Melanerpes erythrocephalus). Using backpack harnesses, we attached 2.1-g transmitter packages that averaged 3.1% of body weight (range = 2.5–3.6%) to Red-headed Woodpeckers. We observed both radio-tagged (N = 23) and nonradio-tagged (N = 28) woodpeckers and determined the percentage of time spent engaged in each of five behaviors: flight, foraging, perching, preening, and territorial behavior. We found no difference between the two groups in the percentage of time engaged in each behavior. In addition, we found that transmitters had no apparent effect on use of cavities for roosting by radio-tagged woodpeckers (N = 25).We conclude that backpack transmitters weighing less than 3.6% of body weight had no impact on either their behavior or their ability to use cavities.

Vukovich, Mark; Kilgo, John, C.

2009-05-01

48

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

49

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

50

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

51

Influence of transmitter configurations on spatial statistics of radio environment maps  

Microsoft Academic Search

We study the influence of the configuration and distribution of transmitters on radio environment maps. We adopt a statistical approach, treating total received power as a random field characterised with second-order statistics. Using extensive simulations we characterise the effects of changing node counts, distribution of node locations, transmit powers and propagation environments on the studied statistics. We also comment and

Janne Riihijärvi; Petri Mähönen; Shima Sajjad

2009-01-01

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

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

54

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

55

Topic in Depth - Radio Frequency Identification  

NSDL National Science Digital Library

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

2010-09-14

56

Monochromatic radio frequency accelerating cavity  

DOEpatents

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

Giordano, S.

1984-02-09

57

Monochromatic radio frequency accelerating cavity  

DOEpatents

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

Giordano, Salvatore (Port Jefferson, NY)

1985-01-01

58

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

59

Radio-Frequency Plasma Probes  

NASA Astrophysics Data System (ADS)

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

Fernsler, Richard

2011-11-01

60

Luminescent radio frequency radiation dosimetry.  

PubMed

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

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

1999-01-01

61

UWB Impulse Radio Transmitter Using an Electrooptic Phase Modulator Together With a Delay Interferometer  

Microsoft Academic Search

A simple ultra-wideband (UWB) impulse radio transmitter is experimentally demonstrated using an electrooptic phase modulator (PM) and a delay interferometer (DI). By applying an electrical nonreturn-to-zero (NRZ) baseband signal to the PM, a pair of optical Gaussian pulses with opposite polarities is generated at the two output ports of the DI. By properly setting the delay between these two polarity-reversed

Fangzheng Zhang; Songnian Fu; Jian Wu; Nam Quoc Ngo; Kun Xu; Yan Li; Xiaobin Hong; Ping Shum; Jintong Lin

2010-01-01

62

Orbiting Low Frequency Array for radio astronomy  

Microsoft Academic Search

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

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

2011-01-01

63

Effects of Surgically and Gastrically Implanted Radio Transmitters on Growth and Feeding Behavior of Juvenile Chinook Salmon  

Microsoft Academic Search

We examined the effects of surgically and gastrically implanted radio transmitters (representing 2.3–5.5% of body weight) on the growth and feeding behavior of 192 juvenile chinook salmon Oncorhynchus tshawytscha (114–159 mm in fork length). Throughout the 54-d study, the 48 fish with transmitters in their stomachs (gastric fish) consistently grew more slowly than fish with surgically implanted transmitters (surgery fish),

Noah S. Adams; Dennis W. Rondorf; Scott D. Evans; Joseph E. Kelly

1998-01-01

64

Demonstration of space optical transmitter development for multiple high-frequency bands  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

65

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

66

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

67

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

68

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

69

Method of and system for classifying emergency locating transmitters and emergency positions indicating radio beacons  

NASA Technical Reports Server (NTRS)

During a distress call, a distress location transmitter 10 generates a high frequency carrier signal 40 that is modulated by a predetermined distress waveform characteristic 29. The classification of user associated with the distress call is identified by periodically interrupting modulation 42; user classification is determined by the repetition rate of the interruptions, the interruption periods, or both.

Wren, Paul E. (Inventor)

1983-01-01

70

Wind tunnel experiments to assess the effect of back-mounted radio transmitters on bird body drag  

USGS Publications Warehouse

The aerodynamic drag of bird bodies was measured in a wind tunnel, with and without back-mounted dummy radio transmitters. Flight performance estimates indicate that the drag of a large transmitter can cause a substantial reduction of a migrant's range, that is, the distance it can cover in non-stop flight. The drag of the transmitter can be reduced by arranging the components in an elongated shape, so minimizing the frontal area. The addition of a rounded fairing to the front end, and a pointed fairing behind, was found to reduce the drag of the transmitter by about onethird, as compared with an unfaired rectangular box.

Obrecht, H.H., III; Pennycuick, C.J.; Fuller, M.R.

1988-01-01

71

Modeling, Simulation and Implementation of a Non-Coherent Binary- Frequency-Shift-Keying (BFSK) Receiver-Transmitter into a Field Programmable Gate Array (FPGA).  

National Technical Information Service (NTIS)

This thesis presents the use of a field programmable gate array (FPGA) to implement a non-coherent binary-frequency-shift-keyed receiver- transmitter (BFSK-RT) that simulates the modulation of the SINCGARS radio, the RT-1523C. An FPGA successfully, and wi...

J. P. Svenningsen

2005-01-01

72

Block Copolymer Nanoarchitectures for Radio Frequency Applications.  

National Technical Information Service (NTIS)

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

P. Kofinas

2006-01-01

73

Improved fire resistant radio frequency anechoic materials  

NASA Technical Reports Server (NTRS)

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

Robinson, D. A.

1969-01-01

74

Radio Frequency Idenfication Static Discharge Protection.  

National Technical Information Service (NTIS)

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

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

2004-01-01

75

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

76

Frequency Modulation in the Transmittivity of Wave Guides in Elastic-Wave BandGap Materials  

Microsoft Academic Search

It is shown, for the first time, that the transmittivity of wave guides created as rectilinear defects in periodic elastic band-gap materials oscillates as a function of frequency. The results are obtained using the finite difference time domain method for elastic waves propagating in two-dimensional inhomogeneous media. The oscillations of the transmittivity are due to the richness of modes in

M. Kafesaki; M. M. Sigalas; N. García

2000-01-01

77

47 CFR 80.927 - Antenna radio frequency indicator.  

Code of Federal Regulations, 2013 CFR

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

2013-10-01

78

47 CFR 80.1019 - Antenna radio frequency indicator.  

Code of Federal Regulations, 2013 CFR

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

2013-10-01

79

Radio Propagation at Frequencies above 30 Megacycles  

Microsoft Academic Search

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

K. Bullington

1947-01-01

80

Chipless Radio Frequency Identification (RFID) Device  

Microsoft Academic Search

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

Somnath Mukherjee

2007-01-01

81

Microelectromechanical resonators for radio frequency communication applications  

Microsoft Academic Search

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

Joydeep BasuTarun; Tarun Kanti Bhattacharyya

82

Low-frequency radio monitoring of microquasars  

NASA Astrophysics Data System (ADS)

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

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

2007-02-01

83

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

84

Low-frequency radio emissions at Neptune  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

85

Radio Frequency Signals in Jupiter's Atmosphere  

PubMed

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

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

1996-05-10

86

47 CFR 80.209 - Transmitter frequency tolerances.  

Code of Federal Regulations, 2013 CFR

...power of 25 watts or less the frequency tolerance is 10 parts in 10...the bands above 2.4 GHz the frequency at which maximum emission...5/T MHz to the upper and lower limits of the authorized bandwidth...00-14.05 GHz the center frequency must not vary more than...

2013-10-01

87

Adversarial Model for Radio Frequency Identification  

Microsoft Academic Search

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

G. Avoine

2006-01-01

88

Cost cutting using radio frequency inventory control.  

PubMed

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

Weber, J

1992-05-01

89

Radio frequency interference at the geostationary orbit  

NASA Technical Reports Server (NTRS)

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

Sue, M. K.

1981-01-01

90

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

National Technical Information Service (NTIS)

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 juv...

A. E. Welch C. McKinstry M. Theriault R. S. Brown T. J. Carlson

2007-01-01

91

47 CFR 95.655 - Frequency capability.  

Code of Federal Regulations, 2013 CFR

...for use in another radio service for which the frequency is authorized and...Transmitters with frequency capability for the Amateur Radio Services and Military Affiliate Radio System will not... (b) All frequency...

2013-10-01

92

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

93

Digital avionics susceptibility to high energy radio frequency fields  

NASA Technical Reports Server (NTRS)

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

Larsen, William E.

1988-01-01

94

Carbon nanotube composite optoacoustic transmitters for strong and high frequency ultrasound generation  

PubMed Central

We demonstrate carbon nanotube (CNT) composite-based optoacoustic transmitters that generate strong and high frequency ultrasound. The composite consists of CNTs grown on a substrate, which are embedded in elastomeric polymer used as an acoustic transfer medium. Under pulsed laser excitation, the composite generates very strong optoacoustic pressure: 18 times stronger than a Cr film reference and five times stronger than a gold nanoparticle composite with the same polymer. This enhancement persists over a broadband frequency range of up to 120 MHz and is confirmed by calculation. We suggest the CNT-polymer composites as highly efficient optoacoustic transmitters for high resolution ultrasound imaging.

Won Baac, Hyoung; Ok, Jong G.; Park, Hui Joon; Ling, Tao; Chen, Sung-Liang; Hart, A. John; Guo, L. Jay

2010-01-01

95

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

Federal Register 2010, 2011, 2012, 2013

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

2013-03-01

96

Radio-frequency point-contact electrometer  

NASA Astrophysics Data System (ADS)

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

Qin, Hua; Williams, David A.

2006-05-01

97

Graphene radio frequency receiver integrated circuit.  

PubMed

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

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

2014-01-01

98

Graphene radio frequency receiver integrated circuit  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

99

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

100

47 CFR 2.815 - External radio frequency power amplifiers.  

Code of Federal Regulations, 2010 CFR

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

2009-10-01

101

47 CFR 2.815 - External radio frequency power amplifiers.  

Code of Federal Regulations, 2010 CFR

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

2010-10-01

102

Review of radio frequency microelectromechanical systems technology  

Microsoft Academic Search

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

S. Lucyszyn

2004-01-01

103

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

104

A prediction model for personal radio frequency electromagnetic field exposure.  

PubMed

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

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

2009-12-15

105

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

106

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

107

Acquisition signal transmitter  

NASA Technical Reports Server (NTRS)

An encoded information transmitter which transmits a radio frequency carrier that is amplitude modulated by a constant frequency waveform and thereafter amplitude modulated by a predetermined encoded waveform, the constant frequency waveform modulated carrier constituting an acquisition signal and the encoded waveform modulated carrier constituting an information bearing signal, the acquisition signal providing enhanced signal acquisition and interference rejection favoring the information bearing signal. One specific application for this transmitter is as a distress transmitter where a conventional, legislated audio tone modulated signal is transmitted followed first by the acquisition signal and then the information bearing signal, the information bearing signal being encoded with, among other things, vehicle identification data. The acquistion signal enables a receiver to acquire the information bearing signal where the received signal is low and/or where the received signal has a low signal-to-noise ratio in an environment where there are multiple signals in the same frequency band as the information bearing signal.

Friedman, Morton L. (Inventor)

1989-01-01

108

Analysis of resonant coupled coils in the design of radio frequency transcutaneous links  

Microsoft Academic Search

A theory of coupled resonant coils has been developed which makes possible the design of radio frequency transcutaneous links\\u000a of simultaneously high overall efficiency and good displacement tolerance while keeping circuitry simple (particularly in\\u000a the implanted receiver). Series-tuned transmitter coils were used, obtaining high efficiency. In the first example a stimulator\\u000a which has excellent displacement tolerance because it works at

N. de N. Donaldson; T. A. Perkins

1983-01-01

109

Frequency modulation in the transmittivity of wave guides in elastic-wave band-gap materials.  

PubMed

It is shown, for the first time, that the transmittivity of wave guides created as rectilinear defects in periodic elastic band-gap materials oscillates as a function of frequency. The results are obtained using the finite difference time domain method for elastic waves propagating in two-dimensional inhomogeneous media. The oscillations of the transmittivity are due to the richness of modes in the elastic systems and, mainly, due to the periodicity of the potential in the direction of the wave propagation. Results are presented for a periodic array of Pb and Ag cylinders inserted in an epoxy host, as well as for Hg cylinders in an Al host. PMID:11056620

Kafesaki, M; Sigalas, M M; García, N

2000-11-01

110

Frequency Modulation in the Transmittivity of Wave Guides in Elastic-Wave Band-Gap Materials  

SciTech Connect

It is shown, for the first time, that the transmittivity of wave guides created as rectilinear defects in periodic elastic band-gap materials oscillates as a function of frequency. The results are obtained using the finite difference time domain method for elastic waves propagating in two-dimensional inhomogeneous media. The oscillations of the transmittivity are due to the richness of modes in the elastic systems and, mainly, due to the periodicity of the potential in the direction of the wave propagation. Results are presented for a periodic array of Pb and Ag cylinders inserted in an epoxy host, as well as for Hg cylinders in an Al host.

Kafesaki, M.; Sigalas, M. M.; Garcia, N.

2000-11-06

111

Cubesat Missions for Low Frequency Radio Astronomy  

NASA Astrophysics Data System (ADS)

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

Jones, Dayton L.

2013-01-01

112

The Mariner Mars 1971 radio frequency subsystem  

NASA Technical Reports Server (NTRS)

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

Hughes, R. S.

1972-01-01

113

Radio frequency identification applications in hospital environments.  

PubMed

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

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

2006-01-01

114

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

115

A Sub100 $\\\\mu$ W MICS\\/ISM Band Transmitter Based on Injection-Locking and Frequency Multiplication  

Microsoft Academic Search

For fully autonomous implantable or body-worn devices running on harvested energy, the peak and average power dissipation of the radio transmitter must be minimized. Additionally, link symmetry must be maintained for peer-to-peer network applications. We propose a highly integrated 90 W 400 MHz MICS band transmitter with an output power of 20 W, leading to a 22% global efficiency—the highest

Jagdish Pandey; Brian P. Otis

2011-01-01

116

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

NASA Astrophysics Data System (ADS)

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

Ellingson, Steven W.

2005-07-01

117

Distress Transmitter and Receiver  

NASA Technical Reports Server (NTRS)

Identifying distress signals sent and received automatically. Radio transmitter and receiver designed to be used together for location and identification of persons, aircraft, or ships in distress. Modulation of transmitted signal characterized by unique combination of frequencies, repetition rates, and duty cycles, so type or identity of vehicle or person in distress ascertained from signal. Receiver operates manually and monitored aurally in conventional manner: also includes automatic tuning and monitoring features to assist operator in measuring modulation characteristics and in detecting weak signals. Transmitter generates signal characterized by timed sequence of modulating pulses. Receiver automatically locks onto signal and identifies it according to modulation characteristics.

Wren, Paul E.

1987-01-01

118

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

119

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

120

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

NASA Astrophysics Data System (ADS)

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

Richman, Michael; Hoffman, Kara

2011-04-01

121

Surgical implantation of radio transmitters in arctic foxes (Alopex lagopus) on Svalbard, Norway.  

PubMed

Twelve captive wild-caught adult arctic foxes (Alopex lagopus) were anesthetized a total of 24 times for an equal number of surgical procedures involving implantation of heart rate (HR) and core body temperature transmitters (Tb) between October 1995 and April 1997. Xylazine-ketamine and medetomidine-ketamine anesthesia was used, resulting in an unacceptably high death rate. One out of four foxes anesthetized with xylazine-ketamine died, whereas two of nine foxes anesthetized with medetomidine-ketamine died out of a total of 20 surgical procedures. Durations of the surgeries for implantation of Tb transmitters and HR transmitters were 73 +/- 7 min and 95 +/- 13 min, respectively. PMID:12564532

Fuglei, Eva; Mercer, James B; Arnemo, Jon M

2002-12-01

122

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

123

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

124

Nb3Sn for Radio Frequency Cavities  

SciTech Connect

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

Godeke, A.

2006-12-18

125

Radio-frequency low-coherence interferometry.  

PubMed

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

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

2014-06-15

126

Autonomous Measurements of Bridge Pier and Abutment Scour using Motion-Sensing Radio Transmitters, Tech Transfer Summary.  

National Technical Information Service (NTIS)

The main objective of this study is to evaluate the capabilities of Radio Frequency IDentification (RFID) technology in collecting field data and remotely monitoring bridge scour. RFID is a wireless automated identification technology that utilizes waves ...

M. Elhakeem T. N. Papanicolaou

2010-01-01

127

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

128

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

129

Cassini/RPWS: A low frequency radio imager at Saturn  

NASA Astrophysics Data System (ADS)

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

Cecconi, Baptiste; Lamy, Laurent; Zarka, Philippe

2014-05-01

130

Trirotron: triode rotating beam radio frequency amplifier  

DOEpatents

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

Lebacqz, Jean V. (Stanford, CA)

1980-01-01

131

Systems and Methods for Determining Radio Frequency Interference.  

National Technical Information Service (NTIS)

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

K. Johannsen S. Sabaroff V. F. Henry

1976-01-01

132

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

NASA Astrophysics Data System (ADS)

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

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

2004-08-01

133

Experimental radio frequency link for Ka-band communications applications  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

134

Study on dedicated radio frequency for railway use  

Microsoft Academic Search

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

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

2010-01-01

135

Algorithms for the Radio Link Frequency Assignment Problem.  

National Technical Information Service (NTIS)

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

K. Aardal J. K. Lenstra S. Tiourine

1999-01-01

136

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...

137

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...

138

Radio frequency seismic gathering system employing an airborne blimp  

Microsoft Academic Search

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

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

1980-01-01

139

Wideband micromachined microphones with radio frequency detection  

NASA Astrophysics Data System (ADS)

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

Hansen, Sean Thomas

140

Directional Radio-Frequency Identification Tag Reader  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

141

Soviet high-power radio frequency research  

NASA Astrophysics Data System (ADS)

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

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

1988-07-01

142

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

143

A 24mm2 Quad-Band Single-Chip GSM Radio with Transmitter Calibration in 90nm Digital CMOS  

Microsoft Academic Search

The RF transceiver is built on the Digital RF Processor (DRP) technology. The ADPLL-based transmitter uses a polar architecture with all-digital PM-FM and AM paths. The receiver uses a discrete-time architecture in which the RF signal is directly sampled and processed using analog and DSP techniques. A 26 MHz digitally controlled crystal oscillator (DCXO) generates frequency reference (FREF) and has

R. B. Staszewski; D. Leipold; O. Eliezer; M. Entezari; K. Muhammad; I. Bashir; C.-M. Hung; J. Wallberg; P. Cruise; S. Rezeq; S. Vemulapalli; K. Waheed; N. Barton; M.-C. Lee; C. Fernando; K. Maggio; T. Jung; I. Elahi; S. Larson; T. Murphy; G. Feygin; I. Deng; T. Mayhugh; Y.-C. Ho; K.-M. Low; C. Lin; J. Jaehnig; J. Kerr; J. Mehta; S. Glock; T. Almholt; S. Bhatara

2008-01-01

144

Frequency coupling in dual frequency capacitively coupled radio-frequency plasmas  

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

145

Tabu Search for Frequency Assignment in Mobile Radio Networks  

Microsoft Academic Search

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

Jin-kao Hao; Raphaël Dorne; Philippe Galinier

1998-01-01

146

Dynamics Of Ions In A Radio-Frequency Quadrupole Trap  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

147

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

Code of Federal Regulations, 2010 CFR

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

2010-10-01

148

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

Federal Register 2010, 2011, 2012, 2013

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

2013-03-29

149

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

Code of Federal Regulations, 2010 CFR

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

2009-10-01

150

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

Federal Register 2010, 2011, 2012, 2013

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

2012-06-13

151

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

Code of Federal Regulations, 2010 CFR

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

2010-10-01

152

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

Federal Register 2010, 2011, 2012, 2013

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

2010-02-11

153

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

Federal Register 2010, 2011, 2012, 2013

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

2012-12-21

154

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

Federal Register 2010, 2011, 2012, 2013

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

2011-09-15

155

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

Federal Register 2010, 2011, 2012, 2013

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

2011-04-05

156

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

Code of Federal Regulations, 2010 CFR

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

2009-10-01

157

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

Federal Register 2010, 2011, 2012, 2013

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

2013-08-22

158

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

Federal Register 2010, 2011, 2012, 2013

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

2010-09-09

159

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

Code of Federal Regulations, 2010 CFR

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

2010-10-01

160

Ion cyclotron radio frequency systems and performance on the tandem mirror experiment-upgrade (TMX-U)  

SciTech Connect

High power ion cyclotron radio frequency (ICRF) systems are now gaining greater attention than before as prime driver ion heating systems. Lawrence Livermore National Laboratory (LLNL) has installed a 200 kW high frequency (HF) transmitter system on its Tandem Mirror Experiment-Upgrade (TMX-U). This paper describes the system, antenna, controls, and monitoring apparatus. The transmitter operates into a high Q antenna installed in the central cell region of the experiment. It incorporates a dual-port feedback system to automatically adjust the transmitter's output power and allow the maximum consistent with the plasma loading of the antenna. Special techniques have been used to measure, in real-time, the dynamically changing loading values presented by the plasma. From the measurements, the antenna impedance can be optimized for specified plasma density.

Moore, T.L.; Molvik, A.W.; Cummins, W.F.; Pedrotti, L.R.; Henderson, A.L.; Karsner, P.G.; Scofield, D.W.; Brooksby, C.A.

1983-12-01

161

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

162

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

163

Electron density changes in the nighttime D region due to heating by very-low-frequency transmitters  

NASA Technical Reports Server (NTRS)

Modification of the nighttime D region electron density (N(sub e)) due to heating by very-low-frequency (VLF) transmitters is investigated theoretically using a four-species model of the ion chemistry. The effects of a 100 kW, a 265 kW, and a 1000 kW VLF transmitter are calculated for three ambient N(sub e) profiles. Results indicate that N(sub e) is reduced by up to 26% at approximately 80 km altitude over a 1000 kW transmitter.

Rodriguez, Juan V.; Inan, Umran S.

1994-01-01

164

An overview of backscattered radio frequency identification system (RFID)  

Microsoft Academic Search

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

K. V. S. Rao

1999-01-01

165

Radio frequency identification in the UK: opportunities and challenges  

Microsoft Academic Search

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

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

2004-01-01

166

Solar observations with a low frequency radio telescope  

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

167

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

168

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

Microsoft Academic Search

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

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

2010-01-01

169

Security and Privacy in Radio-Frequency Identification Devices  

Microsoft Academic Search

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

Stephen August Weis

2003-01-01

170

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

National Technical Information Service (NTIS)

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

E. C. Macalanda

2006-01-01

171

Final report: In situ radio frequency heating demonstration.  

National Technical Information Service (NTIS)

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

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

1994-01-01

172

Principles and Applications of Radio Frequency Impedance Probes.  

National Technical Information Service (NTIS)

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

S. T. Lai

1981-01-01

173

Propagation Effects at Radio Frequencies on Satellite Navigation Systems.  

National Technical Information Service (NTIS)

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

V. L. Pisacane M. M. Feen

1974-01-01

174

An Investigation of Radio Frequency Auditory Training Units  

ERIC Educational Resources Information Center

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

Matkin, Noel D.; Olsen, Wayne

1973-01-01

175

Low frequency radio synthesis imaging of the galactic center region  

Microsoft Academic Search

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

Michael Evans Nord

2005-01-01

176

Radio frequency electromagnetic fields: mild hyperthermia and safety standards  

Microsoft Academic Search

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

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

2007-01-01

177

Radio frequency interference issues in impulse radio multiple access communication systems  

Microsoft Academic Search

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

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

2002-01-01

178

Planetary and exoplanetary low frequency radio observations from the Moon  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

179

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

180

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

PubMed

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

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

2012-01-01

181

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

182

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

PubMed

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

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

2014-06-01

183

Radio frequency hollow cathodes for the plasma processing technology  

Microsoft Academic Search

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

L. Bárdoš

1996-01-01

184

Radio Frequency Impedance Interrogation monitoring of hemodynamic parameters  

Microsoft Academic Search

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

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

2011-01-01

185

Chipless radio frequency identification by remote measurement of complex impedance  

Microsoft Academic Search

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

S. Mukherjee

2007-01-01

186

Chipless Radio Frequency Identification by Remote Measurement of Complex Impedance  

Microsoft Academic Search

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

S. Mukherjee

2007-01-01

187

Radio astronomical determination of ground state transition frequencies of CH  

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

188

Recent observations of the very low frequency interplanetary radio emission  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

189

System Analysis and Planning Factors for Adjacent Channel Distributed Transmitters at UHF Frequencies  

Microsoft Academic Search

The interference between first adjacent channels N and Nplusmn1 in an environment of distributed on-channel transmitters is analyzed. Channel N uses a single transmitter and the adjacent channels Nplusmn1 use distributed on-channel transmitters. The conditions and planning factors that will permit reliable implementation of ACI-free areas across all applicable signal levels are presented. The effect of antenna gain, height and

Oded Bendov

2006-01-01

190

Characteristics of Radio-Frequency Circuits Utilizing Ferroelectric Capacitors  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

191

The Use of a Solid State Analog Television Transmitter as a Superconducting Electron Gun Power Amplifier  

SciTech Connect

A solid state analog television transmitter designed for 200 MHz operation is being commissioned as a radio frequency power amplifier on the Wisconsin superconducting electron gun cavity. The amplifier consists of three separate radio frequency power combiner cabinets and one monitor and control cabinet. The transmitter employs rugged field effect transistors built into one kilowatt drawers that are individually hot swappable at maximum continuous power output. The total combined power of the transmitter system is 33 kW at 200 MHz, output through a standard coaxial transmission line. A low level radio frequency system is employed to digitally synthesize the 200 MHz signal and precisely control amplitude and phase.

J.G. Kulpin, K.J. Kleman, R.A. Legg

2012-07-01

192

Radio Frequency Interference Suppression Techniques in FMCW Modulated HF Radars  

Microsoft Academic Search

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

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

2007-01-01

193

On MC-CDMA transmission system performance at nonlinear high power amplifier of transmitter over frequency selective fading channel  

Microsoft Academic Search

The study in this paper underlines the importance of correct joint selection of the spreading codes at the transmitter side and detector at the receiver side in the uplink multi-carrier code division multiple access transmission system model (MC-CDMA) in the presence of frequency selective fading environment and nonlinear distortion due to high power amplifier (HPA). For the precise overall performance,

Juraj Gazda; P. Drotar; D. Kocur; P. Galajda

2009-01-01

194

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

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

195

Range and movement of resident holdover and hatchery brown trout tagged with radio transmitters in the Farmington River, Connecticut  

USGS Publications Warehouse

The 5.8-km West Branch Farmington River Trout Management Area (TMA) is one of Connecticut's premier catch-and-release fisheries for brown trout Salmo trutta. However, little is known about the behavior of brown trout in this system and to what extent brown trout emigrate from the TMA. The objectives of this study were to determine the movement, range, and emigration of resident holdover and newly stocked brown trout tagged with radio transmitters in the TMA. Transmitters were implanted into 22 first-year (mean total length = 314 mm) and 25 second-year (mean total length = 432 mm) holdover brown trout. Twenty catchable-size (mean total length = 290 mm) brown trout were also implanted with transmitters and released into the TMA. The mean range (distance between the extreme upstream and downstream locations) was greater for second-year holdover brown trout than for first-year holdover brown trout, and it was greater in fall than in winter. The movement (distance moved between successive locations) of holdover brown trout was greater in fall than in winter. Movement of first-year holdover brown trout was significantly related to discharge, water temperature, and the number of days between successive locations. Newly stocked brown trout exhibited the two largest ranges (5.3 and 4.7 km). The range of newly stocked brown trout was not different between seasons, but movement was greater in spring than in summer. Through 16 weeks poststocking, there was no discernable difference in the percentage of stocked brown trout dispersing in a predominantly upstream or downstream direction. Mean dispersal distances from the stocking location were 0.5 and 0.9 km at 2 and 12 weeks poststocking, respectively. Movement of newly stocked brown trout was positively related to discharge and negatively related to water temperature. A known 6% (4 of 67) of the tagged brown trout emigrated from the TMA, but up to 21% (14 of 67) of tagged fish could have left the study area if all missing fish were emigrants. ?? Copyright by the American Fisheries Society 2005.

Popoff, N. D.; Neumann, R. M.

2005-01-01

196

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

Microsoft Academic Search

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

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

2009-01-01

197

Dual radio frequency plasma source: Understanding via electrical asymmetry effect  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

198

Effective Collision Frequency and Radio Frequency Conductivity in the Magnetosphere.  

National Technical Information Service (NTIS)

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

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

1970-01-01

199

Effect of screening on the variation of transmittance with voltage and frequency for a twisted nematic liquid crystal cell  

NASA Astrophysics Data System (ADS)

The transmittance (T) versus voltage (V) curve for a 90° twisted nematic liquid crystal cell with positive dielectric anisotropic liquid crystal sample is revisited to elucidate the ion charge effect or screening effect. It is shown explicitly why the application of ac voltage is more suitable to enhance the performance of the liquid crystal devices as compared to the dc voltage. The observed variation of transmittance with frequency shows an interesting ``U'' shaped behavior between 10Hz-300 kHz for a fixed ac voltage of 2.5 V (rms value).

Sinha, Subhojyoti; Chatterjee, Sanat Kumar; Meikap, Ajit Kumar

2012-06-01

200

Low Frequency Radio Observations of GRS1915+105 with GMRT  

Microsoft Academic Search

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

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

2005-01-01

201

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

National Technical Information Service (NTIS)

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

R. K. Mclean

2013-01-01

202

Low frequency radio observations of five rich clusters of galaxies  

SciTech Connect

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

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

1980-03-01

203

Low frequency radio synthesis imaging of the galactic center region  

NASA Astrophysics Data System (ADS)

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

Nord, Michael Evans

2005-11-01

204

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

205

A radio-frequency sheath model for complex waveforms  

NASA Astrophysics Data System (ADS)

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

Turner, M. M.; Chabert, P.

2014-04-01

206

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

207

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

208

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

209

Radio frequency interference of electric motors and associated controls  

Microsoft Academic Search

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

M. A. Jabbar; M. A. Rahman

1991-01-01

210

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

211

A Portable Miniature Transistorized Radio-Frequency Coupled Cardiac Pacemaker  

Microsoft Academic Search

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

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

1961-01-01

212

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

213

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

214

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

215

Modification of the DSN radio frequency angular tropospheric refraction model  

NASA Technical Reports Server (NTRS)

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

Berman, A. L.

1977-01-01

216

Radio frequency analog electronics based on carbon nanotube transistors  

Microsoft Academic Search

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

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

2008-01-01

217

Self-consistent simulations of multipacting in superconducting radio frequencies  

Microsoft Academic Search

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

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

2007-01-01

218

Method of making radio frequency ion source antenna  

Microsoft Academic Search

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

Kenneth W. Ehlers; Ka-Ngo Leung

1988-01-01

219

Radio-frequency controllable quantum interference in Mössbauer spectroscopy  

Microsoft Academic Search

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

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

2006-01-01

220

Radio-frequency controllable quantum interference in Mössbauer spectroscopy  

Microsoft Academic Search

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

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

2007-01-01

221

Nanotechnology of transparent metals for radio frequency electromagnetic shielding  

Microsoft Academic Search

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

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

2003-01-01

222

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

NASA Technical Reports Server (NTRS)

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

Wagner, Raymond S.; Barton, Richard J.

2014-01-01

223

Tracked 3D ultrasound in radio-frequency liver ablation  

Microsoft Academic Search

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

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

2003-01-01

224

Tracked 3D Ultrasound in Radio-Frequency Liver Ablation  

Microsoft Academic Search

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

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

2003-01-01

225

Radio-frequency energy in fusion power generation  

SciTech Connect

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

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

1983-01-01

226

Experimental development and theoretical studies of radio-frequency absorbers  

Microsoft Academic Search

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

J. L. L. M. Massa

1991-01-01

227

Operating a radio-frequency plasma source on water vapor  

Microsoft Academic Search

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

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

2009-01-01

228

Radio-frequency Ablation in the Treatment of Hepatic Malignancies  

Microsoft Academic Search

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

Richard HG; Lo FRCR

2004-01-01

229

Global Measurements of Low-Frequency Radio Noise.  

National Technical Information Service (NTIS)

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

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

1992-01-01

230

Global Measurements of Low-Frequency Radio Noise.  

National Technical Information Service (NTIS)

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

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

1995-01-01

231

Thermochemiluminescence as a technique for radio frequency radiation dosimetry  

Microsoft Academic Search

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

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

1998-01-01

232

Localized radio frequency communication using asynchronous transfer mode protocol  

DOEpatents

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

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

2007-08-14

233

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...

234

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...

235

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

236

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

237

Four-Sector Cylindrical Radio-Frequency Ion Trap  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

238

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

239

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

NASA Astrophysics Data System (ADS)

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 ~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.

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

2010-01-01

240

Graphene radio frequency devices on flexible substrate  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

241

Radio-Over-Fiber 16-QAM, 100-km Transmission at 5 Gb\\/s Using DSB-SC Transmitter and Remote Heterodyne Detection  

Microsoft Academic Search

By using a double-sideband suppressed carrier (DSB-SC) optical transmitter and a remote self-heterodyned (RSH) detection method, we experimentally and analytically proved the feasibility of a radio-over-fiber system using a 16-QAM signal at 5 Gb\\/s and 18 GHz, with a transmission distance of 100 km between a mobile service center and a base station. The transmission system performance was carefully analyzed

Chia-Kai Weng; Yu-Min Lin

2008-01-01

242

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

243

Radio-frequency heating plans for CTX  

SciTech Connect

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

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

1981-01-01

244

TORE SUPRA fast reciprocating radio frequency probe  

SciTech Connect

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

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

1995-02-01

245

Performance analysis of a photonic single-hop ATM switch architecture, with tunable transmitters and fixed frequency receivers  

Microsoft Academic Search

We consider a photonic asynchronous transfer mode (ATM) switch based on the single-hop wavelength division multiplexing (WDM) architecture with tunable transmitters and fixed frequency receivers. The switch operates under a schedule that masks the transceiver tuning latency. We analyze approximately a queueing model of the switch in order to obtain the queue-length distribution and the cell-loss probability at the input

Martin W. McKinnon; George N. Rouskas; Harry G. Perros

1998-01-01

246

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

247

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

Federal Register 2010, 2011, 2012, 2013

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

2011-09-20

248

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

249

Remote Sensing: Radio Frequency Detection for High School Physics Students  

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

250

Overview of technical approaches to radio frequency interference mitigation  

NASA Astrophysics Data System (ADS)

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

Briggs, F. H.; Kocz, J.

2005-07-01

251

Adaptive filters revisited: Radio frequency interference mitigation in pulsar observations  

NASA Astrophysics Data System (ADS)

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

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

2005-05-01

252

Radio frequency wave reducing material and methods for manufacturing same  

US Patent & Trademark Office Database

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

2011-10-04

253

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

Federal Register 2010, 2011, 2012, 2013

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

2013-08-14

254

Optical-radio-frequency resonances free from power broadening  

SciTech Connect

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

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

2010-01-15

255

Radio-frequency ablation of renal cell carcinoma  

Microsoft Academic Search

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

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

2002-01-01

256

Pancakes and Cigars - Low Frequency Variability of Extragalactic Radio Sources  

NASA Astrophysics Data System (ADS)

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

Odell, S. L.

257

Development of radio frequency induction plasma generators for neutral beams  

Microsoft Academic Search

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

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

1986-01-01

258

Radio-frequency quadrupole vane-tip geometries  

Microsoft Academic Search

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

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

1983-01-01

259

South Polar in situ radio-frequency ice attenuation  

Microsoft Academic Search

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

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

2005-01-01

260

Division X Working Group on Radio Frequency Interference Mitigation  

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

261

Tests of niobium cathode for the superconducting radio frequency gun  

Microsoft Academic Search

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

Qiang Zhao; Triveni Srinivasan-Rao; M. Cole

2003-01-01

262

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

NASA Astrophysics Data System (ADS)

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

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

2009-09-01

263

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.

264

Experimental development and theoretical studies of radio-frequency absorbers  

NASA Astrophysics Data System (ADS)

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

Massa, J. L. L. M.

1991-04-01

265

Multiplexing of Radio-Frequency Single Electron Transistors  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

266

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

267

Low Frequency Radio Observations of GRS1915+105 with GMRT  

Microsoft Academic Search

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

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

2005-01-01

268

New observations of the low frequency interplanetary radio emissions  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

269

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

Microsoft Academic Search

We examined the effects of surgical and gastric transmitter implantation techniques on the growth, general physiology and\\u000a 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%\\u000a of the body weight of the fish (in air). Individuals were randomly assigned

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

1998-01-01

270

Radio frequency seismic gathering system employing an airborne blimp  

SciTech Connect

The central station of a radio-connected seismic surveying system uses a tethered blimp carrying an antenna and an electronics package including a dc voltage/rf decoupler, a variable dc controlled preamplifier, a p-i-n diode switch for changing the antenna from receive to transmit operation, a transmitter and modulator and a battery. An rf coaxial cable to ground provides means for controlling the preamplifier gain and for switching the central station to the transmit mode by using appropriate dc signals. In the receive mode, the cable carries detected field unit seismic signals, which are detected by the blimp-carried antenna and preamplified by the blimp preamplifier, to the ground for suitable recording and further processing in the ground portion of the central station. An audio channel can also be modulated onto the transmit carrier of approximately 70 mhz to provide voice communications via the blimp electronics, if desired. Both the ground portion and the blimp portion of the central station are packaged for helicopter transporting.

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

1980-11-25

271

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

NASA Astrophysics Data System (ADS)

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

Orienti, M.; Dallacasa, D.

2014-02-01

272

Physical properties of conventional explosives deduced from radio frequency emissions  

SciTech Connect

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

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

2008-01-01

273

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

PubMed

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

Kolokathi, Aikaterini; Rallis, Panagiotis

2013-01-01

274

Hollow metal target magnetron sputter type radio frequency ion source.  

PubMed

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

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

2014-02-01

275

Protein adsorption enhanced radio-frequency heating of silica nanoparticles  

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

276

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

277

The radio-frequency impedance of individual intrinsic Josephson junctions  

SciTech Connect

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

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

2009-12-21

278

Implantable Radio Frequency Identification Sensors: Wireless Power and Communication  

PubMed Central

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

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

2013-01-01

279

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

PubMed

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

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

2008-09-01

280

Nonclassical crystallization of amorphous iron nanoparticles by radio frequency methods  

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

281

Radio-frequency quadrupole: general properties and specific applications  

SciTech Connect

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

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

1980-01-01

282

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

National Technical Information Service (NTIS)

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

C. Redding R. McLean

1998-01-01

283

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

National Technical Information Service (NTIS)

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

A. Adams

2011-01-01

284

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

Code of Federal Regulations, 2013 CFR

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

2013-10-01

285

Radio-frequency probe for bubble size and velocity measurements.  

PubMed

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

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

1979-10-01

286

Radio frequency shielding for a linac-MRI system  

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

287

In situ observations of medium frequency auroral radio emissions  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

288

Fundamental investigations of capacitive radio frequency plasmas: simulations and experiments  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

289

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

290

Effects of intermodulation distortion on the performance of a hybrid radio\\/fiber system employing a self-pulsating laser diode transmitter  

Microsoft Academic Search

A self-pulsating laser is used to generate a multicarrier (five radio frequency (RF) channels) microwave optical signal for use in a hybrid radio\\/fiber system. The self-pulsation is achieved by external light injection into the laser diode. By varying the RF channel spacing, we have been able to estimate the degradation in system performance due to intermodulation distortion (caused by the

A. Kaszubowska; L. P. Barry; P. Anandarajah

2003-01-01

291

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

NASA Astrophysics Data System (ADS)

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

Fridman, P. A.

2008-05-01

292

Solar Corona and plasma effects on Radio Frequency waves  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

293

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

National Technical Information Service (NTIS)

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

E. L. Price

1968-01-01

294

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

National Technical Information Service (NTIS)

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

J. L. L. M. Massa

1991-01-01

295

Extending the ICRF to Higher Radio Frequencies -- Imaging Results  

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

296

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

Microsoft Academic Search

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

M. Georgiopoulos; P. Kazakos

1987-01-01

297

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

Microsoft Academic Search

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

M. Georgiopoulos

1987-01-01

298

Coherent Transmitter Considerations Utilizing Injection Locked Magnetrons  

Microsoft Academic Search

The Radio Frequency (RF) power generation capability of various Ka-band transmitter alternatives are discussed. The coherent magnetron can be a low cost method of producing Ka-band RF power efficiently. Additive FM noise characteristics of commercially available X-band magnetrons were measured and their power combining capability studied. Finally, noise theory for coherent magnetrons is reviewed and an equation to predict FM

W. S. Best; R. W. Laton; V. H. Smith

1984-01-01

299

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

PubMed

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. PMID:20059160

Liang, Xiao; Weimin, Wang

2009-12-01

300

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

PubMed

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

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

2014-05-01

301

Low Frequency Radio Observations of GRS1915+105 with GMRT  

NASA Astrophysics Data System (ADS)

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

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

2005-06-01

302

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

Federal Register 2010, 2011, 2012, 2013

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

2013-07-22

303

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

Federal Register 2010, 2011, 2012, 2013

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

2012-11-14

304

Radio frequency identification enabled wireless sensing for intelligent food logistics.  

PubMed

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

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

2014-01-01

305

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

306

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

307

Security risks associated with radio frequency identification in medical environments.  

PubMed

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

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

2012-12-01

308

Low-frequency radio emissions in the outer heliosphere  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

309

Fiducialization of Superconducting Radio Frequency Cryomodules at Jefferson Lab  

SciTech Connect

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

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

2006-09-26

310

Radio frequency interference effect on PN code sequence lock detector  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

311

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

312

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

313

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

314

The Radio Frequency Health Node Wireless Sensor System  

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

315

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

PubMed

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

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

2014-04-01

316

Optical properties of hexagonal boron nitride thin films deposited by radio frequency bias magnetron sputtering  

NASA Astrophysics Data System (ADS)

The optical properties of hexagonal boron nitride (h-BN) thin films were studied in this paper. The films were characterized by Fourier transform infrared spectroscopy, UV—visible transmittance and reflection spectra. h-BN thin films with a wide optical band gap Eg (5.86 eV for the as-deposited film and 5.97 eV for the annealed film) approaching h-BN single crystal were successfully prepared by radio frequency (RF) bias magnetron sputtering and post-deposition annealing at 970 K. The optical absorption behaviour of h-BN films accords with the typical optical absorption characteristics of amorphous materials when fitting is made by the Urbach tail model. The annealed film shows satisfactory structure stability. However, high temperature still has a significant effect on the optical absorption properties, refractive index n, and optical conductivity ? of h-BN thin films. The blue-shift of the optical absorption edge and the increase of Eg probably result from stress relaxation in the film under high temperatures. In addition, it is found that the refractive index clearly exhibits different trends in the visible and ultraviolet regions. Previous calculational results of optical conductivity of h-BN films are confirmed in our experimental results.

Deng, Jin-Xiang; Zhang, Xiao-Kang; Yao, Qian; Wang, Xu-Yang; Chen, Guang-Hua; He, De-Yan

2009-09-01

317

Radio-frequency superimposed direct current magnetron sputtered Ga:ZnO transparent conducting thin films  

SciTech Connect

The utilization of radio-frequency (RF) superimposed direct-current (DC) magnetron sputtering deposition on the properties of gallium doped ZnO (GZO) based transparent conducting oxides has been examined. The GZO films were deposited using 76.2 mm diameter ZnO:Ga{sub 2}O{sub 3} (5 at. % Ga vs. Zn) ceramic oxide target on heated non-alkaline glass substrates by varying total power from 60 W to 120 W in steps of 20 W and at various power ratios of RF to DC changing from 0 to 1 in steps of 0.25. The GZO thin films grown with pure DC, mixed approach, and pure RF resulted in conductivities of 2200 {+-} 200 S/cm, 3920 {+-} 600 S/cm, and 3610 {+-} 400 S/cm, respectively. X-ray diffraction showed all films have wurtzite ZnO structure with the c-axis oriented perpendicular to the substrate. The films grown with increasing RF portion of the total power resulted in the improvement of crystallographic texture with smaller full-width half maximum in {chi} and broadening of optical gap with increased carrier concentration via more efficient doping. Independent of the total sputtering power, all films grown with 50% or higher RF power portion resulted in high mobility ({approx}28 {+-} 1 cm{sup 2}/Vs), consistent with observed improvements in crystallographic texture. All films showed optical transmittance of {approx}90% in the visible range.

Sigdel, Ajaya K.; Shaheen, Sean E. [Department of Physics and Astronomy, University of Denver, Denver, Colorado 80208 (United States); National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Ndione, Paul F.; Perkins, John D.; Gennett, Thomas; Hest, Maikel F. A. M. van; Ginley, David S.; Berry, Joseph J. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)

2012-05-01

318

Radio-Frequency Superimposed Direct Current Magnetron Sputtered Ga:ZnO Transparent Conducting Thin Films  

SciTech Connect

The utilization of radio-frequency (RF) superimposed direct-current (DC) magnetron sputtering deposition on the properties of gallium doped ZnO (GZO) based transparent conducting oxides has been examined. The GZO films were deposited using 76.2 mm diameter ZnO:Ga{sub 2}O{sub 3} (5 at. % Ga vs. Zn) ceramic oxide target on heated non-alkaline glass substrates by varying total power from 60 W to 120 W in steps of 20 W and at various power ratios of RF to DC changing from 0 to 1 in steps of 0.25. The GZO thin films grown with pure DC, mixed approach, and pure RF resulted in conductivities of 2200 {+-} 200 S/cm, 3920 {+-} 600 S/cm, and 3610 {+-} 400 S/cm, respectively. X-ray diffraction showed all films have wurtzite ZnO structure with the c-axis oriented perpendicular to the substrate. The films grown with increasing RF portion of the total power resulted in the improvement of crystallographic texture with smaller full-width half maximum in {chi} and broadening of optical gap with increased carrier concentration via more efficient doping. Independent of the total sputtering power, all films grown with 50% or higher RF power portion resulted in high mobility ({approx}28 {+-} 1 cm{sup 2}/Vs), consistent with observed improvements in crystallographic texture. All films showed optical transmittance of {approx}90% in the visible range.

Sigdel, A. K.; Ndione, P. F.; Perkins, J. D.; Gennett, T.; van Hest, M. F. A. M.; Shaheen, S. E.; Ginley, D. S.; Berry, J. J.

2012-05-01

319

Characteristics of radio frequency-sputtered ZnS on the flexible polyethylene terephthalate (PET) substrate.  

PubMed

Zinc sulfide (ZnS) thin film was deposited on the flexible polyethylene-terephtalate (PET) polymer substrate by radio frequency (RF) magnetron sputtering system. ZnS film has a critical thickness range affecting crystal structure where it shows preferred orientation with intensity peak of X-ray diffractometer at 28.4 degrees for ZnS thinner than 200 nm while hexagonal wurtzite and cubic zinc-blend (101) are co-existed for film thicker than 200 nm. Optical band gap energy (Eg) decreases with increasing RF-powers, resulting from increase in film thickness. Eg of ZnS films on PET is 3.68-3.86 eV, which is lower than that of ZnS on the rigid substrate by 0.27-0.28 eV. This is attributed to amount of incorporated oxygen to ZnS material as well as residual strain and disorder of grain boundary. Transmittance of ZnS on PET degrades due to surface defects and complex internal structure. Energy dispersive spectroscopy reveals out that ZnS film does not have a unity of Zn to S ratio, but it is close to stoichiometric composition with increasing thickness. PMID:24266145

Yoo, Dongjun; Choi, Moon-Suk; Chung, Chulwon; Heo, Seung Chan; Kim, Dohyung; Choi, Changhwan

2013-12-01

320

Field emission from ZnS nanorods synthesized by radio frequency magnetron sputtering technique  

NASA Astrophysics Data System (ADS)

The field emission property of zinc sulphides nanorods synthesized in the thin film form on Si substrates has been studied. It is seen that ZnS nanorod thin films showed good field emission properties with a low-macroscopic turn-on field (2.9-6.3 V/?m). ZnS nanorods were synthesized by using radio frequency magnetron sputtering of a polycrystalline prefabricated ZnS target at a relatively higher pressure (10 -1 mbar) and at a lower substrate temperature (233-273 K) without using any catalyst. Transmission electron microscopic image showed the formation of ZnS nanorods with high aspect ratio (>60). The field emission data were analysed using Fowler-Nordhiem theory and the nearly straight-line nature of the F-N plots confirmed cold field emission of electrons. It was also found that the turn-on field decreased with the decrease of nanorod's diameters. The optical properties of the ZnS nanorods were also studied. From the measurements of transmittance of the films deposited on glass substrates, the direct allowed bandgap values have been calculated and they were in the range 3.83-4.03 eV. The thickness of the films was ˜600 nm.

Ghosh, P. K.; Maiti, U. N.; Jana, S.; Chattopadhyay, K. K.

2006-11-01

321

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

NASA Technical Reports Server (NTRS)

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

Stull, M. A.; Alexander, G.

1976-01-01

322

Optimal Power Control over Fading Cognitive Radio Channels by Exploiting Primary User CSI  

Microsoft Academic Search

This paper is concerned with spectrum sharing cognitive radio networks, where a secondary user (SU) or cognitive radio link communicates simultaneously over the same frequency band with an existing primary user (PU) link. It is assumed that the SU transmitter has the perfect channel state information (CSI) on the fading channels from SU transmitter to both PU and SU receivers

Rui Zhang

2008-01-01

323

1. BOLINAMARCONI TRANSMITTER SITE, BUILDING #1. ORIGINALLY CONTAINED ALEXANDERSON ALTERNATORS ...  

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

1. BOLINA-MARCONI TRANSMITTER SITE, BUILDING #1. ORIGINALLY CONTAINED ALEXANDERSON ALTERNATORS AND POINT-TO-POINT TRANSMITTERS, LATER MANY SHIP-TO-SHORE TRANSMITTER PARTIALLY EXTANT (DISMANTLES AND VANDALIZED). - Marconi Radio Sites, Transmitting, Point Reyes Station, Marin County, CA

324

Radio-Frequency Tank Eigenmode Sensor for Propellant Quantity Gauging  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

325

Tracking electric field exposure levels through radio frequency dosimetry  

SciTech Connect

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

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

1991-01-01

326

Low energy booster radio frequency cavity structural analysis  

SciTech Connect

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

Jones, K.

1993-04-01

327

Low energy booster radio frequency cavity structural analysis  

SciTech Connect

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

Jones, K.

1993-04-01

328

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

Microsoft Academic Search

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

D. LLANWYN JONES

1974-01-01

329

1.8 GHz Radio Frequency signal radiation effects on human health  

Microsoft Academic Search

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

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

2011-01-01

330

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

Microsoft Academic Search

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

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

2003-01-01

331

Exploring radio frequency identification technology and its impact on business systems  

Microsoft Academic Search

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

Alan D. Smith

2005-01-01

332

Nanoionics-Based Switches for Radio-Frequency Applications  

NASA Technical Reports Server (NTRS)

Nanoionics-based devices have shown promise as alternatives to microelectromechanical systems (MEMS) and semiconductor diode devices for switching radio-frequency (RF) signals in diverse systems. Examples of systems that utilize RF switches include phase shifters for electronically steerable phased-array antennas, multiplexers, cellular telephones and other radio transceivers, and other portable electronic devices. Semiconductor diode switches can operate at low potentials (about 1 to 3 V) and high speeds (switching times of the order of nanoseconds) but are characterized by significant insertion loss, high DC power consumption, low isolation, and generation of third-order harmonics and intermodulation distortion (IMD). MEMS-based switches feature low insertion loss (of the order of 0.2 dB), low DC power consumption (picowatts), high isolation (>30 dB), and low IMD, but contain moving parts, are not highly reliable, and must be operated at high actuation potentials (20 to 60 V) generated and applied by use of complex circuitry. In addition, fabrication of MEMS is complex, involving many processing steps. Nanoionics-based switches offer the superior RF performance and low power consumption of MEMS switches, without need for the high potentials and complex circuitry necessary for operation of MEMS switches. At the same time, nanoionics-based switches offer the high switching speed of semiconductor devices. Also, like semiconductor devices, nanoionics-based switches can be fabricated relatively inexpensively by use of conventional integrated-circuit fabrication techniques. More over, nanoionics-based switches have simple planar structures that can easily be integrated into RF power-distribution circuits.

Nessel, James; Lee, Richard

2010-01-01

333

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

NASA Astrophysics Data System (ADS)

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

Karlický, M.

2014-01-01

334

47 CFR 90.463 - Transmitter control points.  

Code of Federal Regulations, 2013 CFR

...RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Transmitter...employee of the licensee; or the agent of the licensee, appointed... (g) [Reserved] (h) Mobile transmitters shall be assumed...the immediate control of the mobile operator; provided,...

2013-10-01

335

47 CFR 90.463 - Transmitter control points.  

Code of Federal Regulations, 2010 CFR

...RADIO SERVICES PRIVATE LAND MOBILE RADIO SERVICES Transmitter...employee of the licensee; or the agent of the licensee, appointed... (g) [Reserved] (h) Mobile transmitters shall be assumed...the immediate control of the mobile operator; provided,...

2010-10-01

336

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

SciTech Connect

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

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

1993-07-01

337

The Low-frequency Radio Catalog of Flat-spectrum Sources  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

338

Terrestrial VLF transmitter injection into the magnetosphere  

NASA Astrophysics Data System (ADS)

Very Low Frequency (VLF, 3-30 kHz) radio waves emitted from ground sources (transmitters and lightning) strongly impact the radiation belts, driving electron precipitation via whistler-electron gyroresonance, and contributing to the formation of the slot region. However, calculations of the global impacts of VLF waves are based on models of trans-ionospheric propagation to calculate the VLF energy reaching the magnetosphere. Limited comparisons of these models to individual satellite passes have found that the models may significantly (by >20 dB) overestimate amplitudes of ground based VLF transmitters in the magnetosphere. To form a much more complete empirical picture of VLF transmitter energy reaching the magnetosphere, we present observations of the radiation pattern from a number of ground-based VLF transmitters by averaging six years of data from the DEMETER satellite. We divide the slice at ˜700 km altitude above a transmitter into pixels and calculate the average field for all satellite passes through each pixel. There are enough data to see 25 km features in the radiation pattern, including the modal interference of the subionospheric signal mapped upwards. Using these data, we deduce the first empirical measure of the radiated power into the magnetosphere from these transmitters, for both daytime and nighttime, and at both the overhead and geomagnetically conjugate region. We find no detectable variation of signal intensity with geomagnetic conditions at low and mid latitudes (L < 2.6). We also present evidence of ionospheric heating by one VLF transmitter which modifies the trans-ionospheric absorption of signals from other transmitters passing through the heated region.

Cohen, M. B.; Inan, U. S.

2012-08-01

339

Reference antenna techniques for canceling radio frequency interference due to moving sources  

NASA Astrophysics Data System (ADS)

We investigate characteristics of radio frequency interference (RFI) signals that can affect the excision potential of some interference mitigation algorithms. The techniques considered are those that modify signals from auxiliary reference antennas to model and cancel interference from an astronomical observation. These techniques can be applied in the time domain, where the RFI voltage is modeled and subtracted from the astronomy signal path (adaptive noise canceling), or they can be applied to the autocorrelated and cross-correlated voltage spectra in the frequency domain (postcorrelation canceling). For ideal receivers and a single, statistically stationary interfering signal, both precorrelation and postcorrelation filters can result in complete cancellation of the interference from the observation. The postcorrelation method has the advantage of being applied on tens or hundreds of millisecond timescales rather than tens or hundreds of nanosecond timescales. However, this can be a disadvantage if the RFI transmitter location is changing, since the cross-correlated power measurements which link the interference power in the astronomy and reference signal paths can decorrelate. If the decorrelation is not too severe, it can be allowed for, at the expense of a noise increase. The time domain adaptive cancelers are allowed to slightly vary their internal coefficients and adapt to changing phases during the integrations, which means that they avoid the decorrelation problem. However, the freedom to adapt also results in a noise increase. In this paper the ability of both types of cancelers to excise interference originating from a moving source is compared. The cancelers perform well on both observed and simulated data, giving complete cancellation.

Mitchell, D. A.; Robertson, J. G.

2005-07-01

340

The Stabiliy of Radio-Frequency Plasma Treated Polydimethylsiloxane Surface  

PubMed Central

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

Chen, I-Jane

2008-01-01

341

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

342

Three-dimensional effects for radio frequency antenna modeling  

SciTech Connect

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

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

1994-10-15

343

Manufacture of Radio Frequency Micromachined Switches with Annealing  

PubMed Central

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

Lin, Cheng-Yang; Dai, Ching-Liang

2014-01-01

344

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

345

Radio frequency operation of a quantum point contact charge detector  

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

346

Radio Frequency Identification (RFID) technology and patient safety  

PubMed Central

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

Ajami, Sima; Rajabzadeh, Ahmad

2013-01-01

347

Radio-frequency quadrupole vane-tip geometries  

SciTech Connect

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

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

1983-01-01

348

Radio frequency heating of beef rolls from biceps femoris muscle.  

PubMed

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

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

2006-03-01

349

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

350

Ion Dynamics Model for Collisionless Radio Frequency Sheaths  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

351

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

352

Optimization framework for a radio frequency gun based injector  

NASA Astrophysics Data System (ADS)

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

Hofler, Alicia S.

353

Radio frequency coil technology for small-animal MRI.  

PubMed

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

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

2007-05-01

354

Radio-frequency spectroscopy of polarons in ultracold Bose gases  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

355

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

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

356

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

357

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

358

Adhoc electromagnetic compatibility testing of non-implantable medical devices and radio frequency identification  

PubMed Central

Background The use of radiofrequency identification (RFID) in healthcare is increasing and concerns for electromagnetic compatibility (EMC) pose one of the biggest obstacles for widespread adoption. Numerous studies have documented that RFID can interfere with medical devices. The majority of past studies have concentrated on implantable medical devices such as implantable pacemakers and implantable cardioverter defibrillators (ICDs). This study examined EMC between RFID systems and non-implantable medical devices. Methods Medical devices were exposed to 19 different RFID readers and one RFID active tag. The RFID systems used covered 5 different frequency bands: 125–134 kHz (low frequency (LF)); 13.56 MHz (high frequency (HF)); 433 MHz; 915 MHz (ultra high frequency (UHF])) and 2.4 GHz. We tested three syringe pumps, three infusion pumps, four automatic external defibrillators (AEDs), and one ventilator. The testing procedure is modified from American National Standards Institute (ANSI) C63.18, Recommended Practice for an On-Site, Ad Hoc Test Method for Estimating Radiated Electromagnetic Immunity of Medical Devices to Specific Radio-Frequency Transmitters. Results For syringe pumps, we observed electromagnetic interference (EMI) during 13 of 60 experiments (22%) at a maximum distance of 59 cm. For infusion pumps, we observed EMI during 10 of 60 experiments (17%) at a maximum distance of 136 cm. For AEDs, we observed EMI during 18 of 75 experiments (24%) at a maximum distance of 51 cm. The majority of the EMI observed was classified as probably clinically significant or left the device inoperable. No EMI was observed for all medical devices tested during exposure to 433 MHz (two readers, one active tag) or 2.4 GHz RFID (two readers). Conclusion Testing confirms that RFID has the ability to interfere with critical medical equipment. Hospital staff should be aware of the potential for medical device EMI caused by RFID systems and should be encouraged to perform on-site RF immunity tests prior to RFID system deployment or prior to placing new medical devices in an RFID environment. The methods presented in this paper are time-consuming and burdensome and suggest the need for standard test methods for assessing the immunity of medical devices to RFID systems.

2013-01-01

359

A 3.1–4.8 GHz transmitter with a high frequency divider in 0.18 ?m CMOS for OFDM-UWB  

Microsoft Academic Search

A fully integrated low power RF transmitter for a WiMedia 3.1–4.8 GHz multiband orthogonal frequency division multiplexing ultra-wideband system is presented. With a separate transconductance stage, the quadrature up-conversion modulator achieves high linearity with low supply voltage. The co-design of different resonant frequencies of the modulator and the differential to single (D2S) converter ensures in-band gain flatness. By means of

Zheng Renliang; Ren Junyan; Li Wei; Li Ning

2009-01-01

360

SEMICONDUCTOR INTEGRATED CIRCUITS: A 3.1-4.8 GHz transmitter with a high frequency divider in 0.18 mum CMOS for OFDM-UWB  

Microsoft Academic Search

A fully integrated low power RF transmitter for a WiMedia 3.1-4.8 GHz multiband orthogonal frequency division multiplexing ultra-wideband system is presented. With a separate transconductance stage, the quadrature up-conversion modulator achieves high linearity with low supply voltage. The co-design of different resonant frequencies of the modulator and the differential to single (D2S) converter ensures in-band gain flatness. By means of

Zheng Renliang; Ren Junyan; Li Wei; Li Ning

2009-01-01

361

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

362

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

363

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

364

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

PubMed

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

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

2008-12-01

365

Surface Impedance of Superconducting Radio Frequency (SRF) Materials  

NASA Astrophysics Data System (ADS)

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

Xiao, Binping

366

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

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

367

X-ray imaging of superconducting radio frequency cavities  

NASA Astrophysics Data System (ADS)

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

Musser, Susan Elizabeth

368

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

369

Three-dimensional effects for radio frequency antenna modeling  

SciTech Connect

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

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

1993-09-01

370

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

371

H- radio frequency source development at the Spallation Neutron Source  

SciTech Connect

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

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

2012-01-01

372

Pulsed radio frequency therapy of experimentally induced arthritis in ponies.  

PubMed Central

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

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

1991-01-01

373

Radiation effects on communication performance of radio frequency identification tags.  

PubMed

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

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

2010-11-01

374

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

375

A frequency hopping spread spectrum transmission scheme for uncoordinated cognitive radios  

Microsoft Academic Search

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

Xiaohua Li; Juite Hwu

2009-01-01

376

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

Microsoft Academic Search

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

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

2001-01-01

377

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

NASA Astrophysics Data System (ADS)

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

URSI Workshop Session Chairmen

378

Ion species mix and ion density measurements using radio frequency waves  

Microsoft Academic Search

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

George Wilder Watson III

2003-01-01

379

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

ERIC Educational Resources Information Center

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

Boyadzhiev, Khristo N.

2010-01-01

380

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

Microsoft Academic Search

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

I. A. Strukov; D. P. Skulachev

1988-01-01

381

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

382

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

383

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

Microsoft Academic Search

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

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

2003-01-01

384

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

National Technical Information Service (NTIS)

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

J. Jo

2007-01-01

385

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

National Technical Information Service (NTIS)

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

M. Georgiopoulos P. Papantoni-Kazakos

1986-01-01

386

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

National Technical Information Service (NTIS)

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

2001-01-01

387

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

National Technical Information Service (NTIS)

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

R. Crooks W. Chang

2009-01-01

388

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

National Technical Information Service (NTIS)

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

S. Takashima

1965-01-01

389

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

National Technical Information Service (NTIS)

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

2005-01-01

390

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

Federal Register 2010, 2011, 2012, 2013

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

2011-02-22

391

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

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

392

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

393

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

394

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

National Technical Information Service (NTIS)

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

R. J. Turner W. J. Siskaninetz

2008-01-01

395

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

396

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

ERIC Educational Resources Information Center

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

Burgess, Vic; And Others

1979-01-01

397

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...

398

Throughput and packet error probability of cellular frequency-hopped spread-spectrum radio networks  

Microsoft Academic Search

The authors characterize multiple-access interference for cellular mobile networks, in which users are assumed to be Poisson-distributed in the plane and use frequency-hopped spread-spectrum signaling with a transmitter-oriented assignment of frequency-hopping patterns. Exact expressions for the bit error probabilities are derived for binary coherently demodulated systems without coding. Approximations for the packet-error probability are derived for coherent and noncoherent systems

J. W. Gluck; E. Geraniotis

1989-01-01

399

Performance of cellular frequency-hopped spread-spectrum radio networks  

Microsoft Academic Search

Multiple access interference is characterized for cellular mobile networks, in which users are assumed to be Poisson-distributed in the plane and employ frequency-hopped spread-spectrum signaling with transmitter-oriented assignment of frequency-hopping patterns. Exact expressions for the bit error probabilities are derived for binary coherently demodulated systems without coding. Approximations for the packet error probability are derived for coherent and noncoherent systems

Jeffrey W. Gluck; Evaggelos Geraniotis

1989-01-01

400

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

401

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

Microsoft Academic Search

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

Vikas Midha; Demetre J. Economou

1997-01-01

402

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

Microsoft Academic Search

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

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

2010-01-01

403

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

404

The 406 MHz ELT/EPIRBs. [Emergency Locator Transmitters/Emergency Position Indicating Radio Beacons (ELT/EPIRB)  

NASA Technical Reports Server (NTRS)

Specifications for the COSPAS/SARSAT beacons are presented and related design considerations are discussed. Critical design aspects having significant impact on cost and performance are highlighted. Among these is the oscillator, whose frequency drift specifications require stabilization by ovens or digital control. Design options are presented and their impact on cost and performance assessed. Beacon designs developed to meet COSPAS/SARSAT specifications are shown.

Flatow, F. S.; Gal, C.; Hayes, E. J.

1984-01-01

405

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

406

Coincidently Searching for Gravitational Waves and Low Frequency Radio Transients  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

407

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

408

Emergency locating transmitter  

NASA Technical Reports Server (NTRS)

A transmitter generates three signals for sequential transmission. These signal are an unmodulated r.f. carrier, a r.f. carrier amplitude modulated by a first audio frequency waveform and a r.f. carrier amplitude modulated by a second audio frequency waveform which is distinguishable from the first and which may be employed as a means for identifying a particular transmitter. The composite, sequentially transmitted signal may be varied in terms of the individual signal transmission sequence, the duration of the individual signals, overall composite signal repetition rate and the frequency of the second audio waveform. Various combinations of signal variations may be employed to transmit different information.

Wren, Paul E. (inventor)

1991-01-01

409

Spontaneous Radio Frequency Emissions from Natural Aurora. Chapter 4  

NASA Technical Reports Server (NTRS)

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

LaBelle, J.

2009-01-01

410

Depth-focused radio frequency coils for MR imaging.  

PubMed

Surface coils improve signal-to-noise ratios by the simple expedient of reducing field of view. The uniformity of response of these coils is poor, since signal reception is weighted toward the surface of the object, which generally is of least interest. Furthermore, whole-section transmitter coils excite the subject uniformly, so that weak signals are detected from far regions. A dual-coil arrangement permits avoidance of these problems by combining the nonuniform excitation and reception characteristics of two surface coils. PMID:3628778

Carlson, J W; Arakawa, M; Kaufman, L; McCarten, B M; George, C

1987-10-01

411

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

Microsoft Academic Search

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

M. Georgiopoulos

1988-01-01

412

Opportunistic use of radio-frequency spectrum: a network perspective  

Microsoft Academic Search

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

M. E. Steenstrup

2005-01-01

413

Origin of pulsar radio emission. I. High frequency data  

Microsoft Academic Search

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

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

1997-01-01

414

Multi-frequency observations of X-shaped radio galaxies  

Microsoft Academic Search

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

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

1998-01-01

415

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

416

Frequency-domain equalization of mobile radio and terrestrial broadcast channels  

Microsoft Academic Search

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

H. Sari; G. Karam; I. Jeanclaudle

1994-01-01

417

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

418

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

419

Radio-frequency probes of Antarctic ice at South Pole  

NASA Astrophysics Data System (ADS)

Using hardware developed for the ARA (Askaryan Radio Array) particle astrophysics experiment, we herein report on the amplitude and temporal characteristics of polarized surface radar echo data collected in South Polar ice using radio sounding equipment with 0.5-ns echo-time sampling. We observe strong echoes at 6, 9.6, 13.9, 17, and 19 ?s following vertical pulse emission from the surface, corresponding to reflectors in the upper half of the ice sheet. The synchronicity of those echoes for all broadcast azimuthal polarizations affirms the lack of observable birefringence over the upper half of the ice sheet. Of the five strongest echoes, three exhibit an evident amplitude correlation with the local surface ice flow direction, qualitatively consistent with measurements in East Antarctica. Combined with other radio echo sounding data, we conclude that observed birefringent asymmetries at South Pole are generated entirely in the lower half of the ice sheet. By contrast, birefringent asymmetries are observed at shallow depths in East Antarctica.

Besson, D.; Kravchenko, I.

2013-05-01

420

Analysis of a discrete spectrum analyzer for the detection of radio frequency interference  

NASA Technical Reports Server (NTRS)

As the radio frequency spectrum becomes increasingly overcrowded, interference with mission-critical DSN operations is rising at an alarming rate. To alleviate this problem the DSN is developing a wideband surveillance system for on-site detection and identification of potential sources of radio frequency interference (RFI), which will complement the existing frequency coordination activities. The RFI monitoring system is based on a wideband, multi-look discrete spectrum analyzer operating on fast Fourier transform principles. An extensive general statistical analysis is presented of such spectrum analyzers and derives threshold detection performance formulas for signals of interest. These results are then applied to the design of the RFI spectrum analyzer under development.

Levitt, B. K.

1977-01-01

421

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

422

Analysis of Single Pulses from Radio Pulsars at High Observing Frequencies  

NASA Astrophysics Data System (ADS)

Single pulses from eight strong pulsars were studied for the drifting subpulse behaviour. The pulsars were observed at 8.35 GHz at 100-m Effelsberg radio telescope. For almost all the pulsars we identified the features corressponding to the frequencies reported at low observing frequencies.

Honnappa, S.; Kijak, J.; Lewandowski, W.

2012-12-01

423

A random access algorithm for frequency hopped spread spectrum packet radio networks  

Microsoft Academic Search

The authors consider packet radio multi-user spread-spectrum environments, where frequency hopping spread spectrum techniques are deployed for protection against intelligent adversaries. When the users in such environments are mobile and bursty, random access frequency hopping transmission algorithms should be adopted, for efficiency in throughput and delay control. This paper proposes and analyzes such an algorithm, named Collision Resolution Algorithm for

M. Georgiopoulos; P. Papantoni-Kazakos

1986-01-01

424

Deposition of vertically oriented carbon nanofibers in atmospheric pressure radio frequency discharge  

Microsoft Academic Search

Deposition of vertically oriented carbon nanofibers (CNFs) has been studied in an atmospheric pressure radio frequency discharge without dielectric barrier covering the metallic electrodes. When the frequency is sufficiently high so that ions reside in the gap for more than one rf cycle (``trapped ions''), the operating voltage decreases remarkably and the transition from a uniform glow discharge to an

Tomohiro Nozaki; Tomoya Goto; Ken Okazaki; Kuma Ohnishi; Lorenzo Mangolini; Joachim Heberlein; Uwe Kortshagen

2006-01-01

425

Broadband operation of a radio frequency spectrum analyzer based on spectral hole burning  

Microsoft Academic Search

Summary form only given. We recently demonstrated the principle of radio frequency spectrum analysis based on the engraving of multiple monochromatic gratings in a Spectral Hole Burning (SHB) material. This device is considered for applications in radar and sub-millimeter wave astronomy. In the first experiment, the frequency scanning procedure limited the bandwidth to 35 MHz. With a new broadband setup

I. Lorgere; V. Lavielle

2002-01-01

426

Exposure to radio frequency radiation emitted by cell phone and mortality in chick embryos (Gallus domesticus)  

Microsoft Academic Search

The rapidly increasing use of cell phones since late 1990s has caused a general concern on the possible hazardous health effects of exposure to radio frequency electro-magnetic radiation (EMR) emitted by them. While considering the bio- logical effects of EMR on the human body, its intensity, frequency of radiation and duration of exposure are important determinants. Many researchers have reported

I. V. Ingole; S. K. Ghosh

2006-01-01

427

Upgrade of the Westerbork synthesis radio telescope: The multi frequency front end  

Microsoft Academic Search

The performance of a novel front end system, the Multi Frequency Front End (MEFE), for use in a synthesis radio telescope is discussed. This front end covers 9 frequency bands in the range from 250 MHz to 8600 MHz. All receivers are based on the double superheterodyne principle. Each receiver has two channels which are connected to dual polarized feed

G H Tan

1996-01-01

428

Electrical Properties of Radio Frequency Glow Discharges in Air at Atmospheric Pressure.  

National Technical Information Service (NTIS)

Gas discharges maintained by radio frequency power were examined in the frequency range 1-25 Mc/s. The discharges were maintained in air at atmospheric pressure between water cooled metal electrodes. The discharges were made symmetric by using two electro...

H. A. Schwab

1967-01-01

429

Gas Breakdown of Radio Frequency Glow Discharges in Helium at near Atmospheric Pressure  

NASA Astrophysics Data System (ADS)

A one-dimensional self-consistent fluid model was developed for radio frequency glow discharge in helium at near atmospheric pressure, and was employed to study the gas breakdown characteristics in terms of breakdown voltage. The effective secondary electron emission coefficient and the effective electric field for ions were demonstrated to be important for determining the breakdown voltage of radio frequency glow discharge at near atmospheric pressure. The constant of A was estimated to be 64±4 cm-1Torr-1, which was proportional to the first Townsend coefficient and could be employed to evaluate the gas breakdown voltage. The reduction in the breakdown voltage of radio frequency glow discharge with excitation frequency was studied and attributed to the electron trapping effect in the discharge gap.

Liu, Xinkun; Xu, Jinzhou; Cui, Tongfei; Guo, Ying; Zhang, Jing; Shi, Jianjun

2013-07-01

430

Radio frequency interference mitigation with phase-only adaptive beam forming  

NASA Astrophysics Data System (ADS)

Connected radio interferometers are sometimes used in the tied array mode: signals from antenna elements are coherently added and the sum signal applied to a very long baseline interferometry (VLBI) back-end or pulsar-processing machine. Usually, there is no computer-controlled amplitude weighting in the existing radio interferometer facilities. Radio frequency interference (RFI) mitigation with phase-only adaptive beam forming is proposed for this mode of observation. Small phase perturbations are introduced in each of the antenna's signals. The values of these perturbations are optimized in such a way that the signal from a radio source of interest is preserved and RFI signals are suppressed. An evolutionary programming algorithm is used for this task. Computer simulations, made for both one-dimensional and two-dimensional array setups, show considerable suppression of RFI and acceptable changes to the main array beam in the radio source direction.

Fridman, P. A.

2005-05-01

431

Offset, tilted dipole models of Uranian smooth high-frequency radio emission  

NASA Technical Reports Server (NTRS)

The smooth high-frequency (SHF) component of the radio emission detected during the Voyager 2 encounter with Uranus (January 1986) is studied. An offset tilted dipole (OTD) investigation of the SHF emission at L shells is carried out within the range of the bursty source locations. A viable high L shell model is presented. It is suggested that Miranda, which reaches a minimum L shell at L = 5, may be related to the timing of several types of radio emissions.

Schweitzer, Andrea E.; Romig, Joseph H.; Evans, David R.; Sawyer, Constance B.; Warwick, James W.

1990-01-01

432

Offset, tilted dipole models of Uranian smooth high-frequency radio emission  

NASA Astrophysics Data System (ADS)

The smooth high-frequency (SHF) component of the radio emission detected during the Voyager 2 encounter with Uranus (January 1986) is studied. An offset tilted dipole (OTD) investigation of the SHF emission at L shells is carried out within the range of the bursty source locations. A viable high L shell model is presented. It is suggested that Miranda, which reaches a minimum L shell at L = 5, may be related to the timing of several types of radio emissions.

Schweitzer, Andrea E.; Romig, Joseph H.; Evans, David R.; Sawyer, Constance B.; Warwick, James W.

1990-09-01

433

Frequency effects on the electron density and {alpha}-{gamma} mode transition in atmospheric radio frequency discharges  

SciTech Connect

In this paper, a one-dimensional model is explored to investigate the frequency effects on the characteristics of atmospheric radio frequency discharges at a given power. The simulation data and analytical results show that the improvement of electron density can be observed with better discharge stability by increasing excitation frequency in an appropriate range. Using the analytical equations deduced from the model, the mean electron density could be inferred by means of the measured parameters. The {alpha}-{gamma} mode transition especially in high frequency discharges is also analytically discussed based on the theoretical equations.

Zhang Yuantao [Shandong Provincial Key Lab of UHV Technology and Gas Discharge Physics, School of Electrical Engineering, Shandong University, Jinan, Shandong Province 250061 (China); Cui Shaoyan [School of Mathematics and Information, Ludong University, Yantai, Shandong Province 264025 (China)

2011-08-15

434

Radio frequency science considerations. [technology utilization of telecommunications system  

NASA Technical Reports Server (NTRS)

Use of the 400 MHz telecommunications system to obtain scientific information, to provide backup information for the experiments flown, and to obtain measurements which aid in designing future probes is considered. Recommended objectives of such a program are summarized and include: measure 400 MHz amplitude to determine adsorption and perhaps scintillation (if data rate permits); measure noise strength near 400 MHz to reexamine 400 MHz choice and to observe thermal, cosmic, and local synchrotron noise trends; probe VSWR sensing to monitor integrity of system, icing, and possible plasma effects; after the probe is finished, have the bus radio occultation in the same region where the probe fell to evaluate the occultation.

Croft, T. A.

1974-01-01

435

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

Microsoft Academic Search

The author corrects the approach followed in the above-titled paper (see ibid., vol.36, no.6, p.720-3, 1988) to compute packet error probabilities in frequency-hopped spread-spectrum packet radio networks with memoryless frequency-hopping patterns. The nature of the error is that the sequence of symbol errors is not Markov, so that a formula which is instrumental for the computation of packet error probabilities,

M. Georgiopoulos

1991-01-01

436

Optical fiber sensor based on a radio frequency Mach-Zehnder interferometer.  

PubMed

This Letter proposes an optical fiber radio frequency (RF) Mach-Zehnder interferometer (MZI) for sensing applications. An RF modulated laser source is injected into an optical fiber RF-MZI and collected by a photodiode. The interference pattern is observed in the RF domain by sweeping the frequency using a network analyzer. The proposed sensor has a linear response to applied temperature change. In addition, the sensitivity, observation frequency range, and the length of the sensing arm are discussed. PMID:22344135

Wei, Tao; Huang, Jie; Lan, Xinwei; Han, Qun; Xiao, Hai

2012-02-15

437

Tunable Atomic Magnetometer for Detection of Radio-Frequency Magnetic Fields  

Microsoft Academic Search

We describe an alkali-metal magnetometer for detection of weak magnetic fields in the radio-frequency (rf) range. High sensitivity is achieved by tuning the Zeeman resonance of alkali atoms to the rf frequency and partially suppressing spin-exchange collisions in the alkali-metal vapor. We demonstrate magnetic field sensitivity of 2 fT\\/Hz¹² at a frequency of 99 kHz with a resonance width of

I. M. Savukov; S. J. Seltzer; M. V. Romalis; K. L. Sauer

2005-01-01

438

Tunable Atomic Magnetometer for Detection of Radio-Frequency Magnetic Fields  

Microsoft Academic Search

We describe an alkali-metal magnetometer for detection of weak magnetic fields in the radio-frequency (rf) range. High sensitivity is achieved by tuning the Zeeman resonance of alkali atoms to the rf frequency and partially suppressing spin-exchange collisions in the alkali-metal vapor. We demonstrate magnetic field sensitivity of 2 fT\\/Hz1\\/2 at a frequency of 99 kHz with a resonance width of

I. M. Savukov; S. J. Seltzer; M. V. Romalis; K. L. Sauer

2005-01-01

439

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

440

High Power RF Transmitters for ICRF Applications on EAST  

NASA Astrophysics Data System (ADS)

An Ion Cyclotron Range of Frequency (ICRF) system with a radio frequency (RF) power of 4 × 1.5 MW was developed for the Experimental Advanced Superconducting Tokamak (EAST). High RF power transmitters were designed as a part of the research and development (R&D) for an ICRF system with long pulse operation at megawatt levels in a frequency range of 25 MHz to 70 MHz. Studies presented in this paper cover the following parts of the high power transmitter: the three staged high power amplifier, which is composed of a 5 kW wideband solid state amplifier, a 100 kW tetrode drive stage amplifier and a 1.5 MW tetrode final stage amplifier, and the DC high voltage power supply (HVPS). Based on engineering design and static examinations, the RF transmitters were tested using a matched dummy load where an RF output power of 1.5 MW was achieved. The transmitters provide 6 MW RF power in primary phase and will reach a level up to 12 MW after a later upgrade. The transmitters performed successfully in stable operations in EAST and HT-7 devices. Up to 1.8 MW of RF power was injected into plasmas in EAST ICRF heating experiments during the 2010 autumn campaign and plasma performance was greatly improved.

Mao, Yuzhou; Yuan, Shuai; Zhao, Yanping; Zhang, Xinjun; Chen, Gen; Kumazawa, R.; Cheng, Yan; Wang, Lei; Ju, Songqing; Deng, Xu; Qin, Chengming; Yang, Lei

2013-03-01

441

Oblique Heating of the Auroral Ionosphere by LF/MF Transmitters.  

National Technical Information Service (NTIS)

The generation of extremely low frequency (ELF) signals due to oblique heating of the auroral ionosphere by signals from ELF modulated LF/MF radio transmitters is described. A part from signals of natural origin, timing signals (six pips which occurred on...

P. S. Cannon M. J. Rycroft T. Turunen

1990-01-01

442

Non-detection at Venus of high-frequency radio signals characteristic of terrestrial lightning.  

PubMed

The detection of impulsive low-frequency (10 to 80 kHz) radio signals, and separate very-low-frequency (approximately 100 Hz) radio 'whistler' signals provided the first evidence for lightning in the atmosphere of Venus. Later, a small number of impulsive high-frequency (100 kHz to 5.6 MHz) radio signals, possibly due to lightning, were also detected. The existence of lightning at Venus has, however, remained controversial. Here we report the results of a search for high-frequency (0.125 to 16 MHz) radio signals during two close fly-bys of Venus by the Cassini spacecraft. Such signals are characteristic of terrestrial lightning, and are commonly heard on AM (amplitude-modulated) radios during thunderstorms. Although the instrument easily detected signals from terrestrial lightning during a later fly-by of Earth (at a global flash rate estimated to be 70 s(-1), which is consistent with the rate expected for terrestrial lightning), no similar signals were detected from Venus. If lightning exists in the venusian atmosphere, it is either extremely rare, or very different from terrestrial lightning. PMID:11201733

Gurnett, D A; Zarka, P; Manning, R; Kurth, W S; Hospodarsky, G B; Averkamp, T F; Kaiser, M L; Farrell, W M

2001-01-18

443

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

444

Radio frequency controlled synthetic wavelength sweep for absolute distance measurement by optical interferometry  

SciTech Connect

We present a new technique applied to the variable optical synthetic wavelength generation in optical interferometry. It consists of a chain of optical injection locking among three lasers: first a distributed-feedback laser is used as a master to injection lock an intensity-modulated laser that is directly modulated around 15 GHz by a radio frequency generator on a sideband. A second distributed-feedback laser is injection locked on another sideband of the intensity-modulated laser. The variable synthetic wavelength for absolute distance measurement is simply generated by sweeping the radio frequency over a range of several hundred megahertz, which corresponds to the locking range of the two slave lasers. In this condition, the uncertainty of the variable synthetic wavelength is equivalent to the radio frequency uncertainty. This latter has a relative accuracy of 10{sup -7} or better, resulting in a resolution of {+-}25 {mu}m for distances exceeding tens of meters. The radio frequency generator produces a linear frequency sweep of 1 ms duration (i.e., exactly equal to one absolute distance measurement acquisition time), with frequency steps of about 1 MHz. Finally, results of absolute distance measurements for ranges up to 10 m are presented.

Le Floch, Sebastien; Salvade, Yves; Mitouassiwou, Rostand; Favre, Patrick

2008-06-01

445

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

446

Propagation of Radio Frequency Waves in a Weakly Ionized Gas  

NASA Astrophysics Data System (ADS)

Long distance communication and diagnostics of the space environment rely on an understanding of the refraction, phase alteration and attenuation of electromagnetic waves in the ionosphere and plasmasphere. The nature of wave propagation in a spatially inhomogeneous plasma was explored using a numerical implementation of the eikonal approach(L. D. Landau and E. M. Lifshitz, Electrodynamics of Continuous Media), (Pergamon Press 1960), pp. 269-279. . The calculation was validated by comparing numerical results with analytic solutions( K. G. Budden, Radio Waves In the Ionosphere), (Cambridge University Press, 1966), pp. 179-182. for a horizontally stratified plasma with linear and exponential variations in the density. The treatment was extended to treat arbitrary plasma distributions. Ray trajectories and attentuation are presented for typical ionospheric profiles, exhibiting non-monotonic density variations, and profiles associated with a plasma generated by injection of a relativistic electron beam. USE ONLY)

Lockwood, Nathaniel P.; Bailey, Wm. F.

2000-10-01

447

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

448

Radio frequency operation of clocked quantum-dot cellular automata latch  

NASA Astrophysics Data System (ADS)

The radio frequency operation of a single-electron latch based on Al-AlOx-Al tunnel junctions is presented. By capacitively coupling the latch to a radio frequency single electron transistor, charge switching on the microsecond timescale is demonstrated. The fast switching and high repeatability of the latch response indicates that high speed operation of pipelines, signal fan-outs, and more complex logic devices are possible with this technology. The experimental technique developed is also promising for enabling the investigation of the intrinsic switching speed in electronic quantum-dot cellular automata-based circuits.

Tang, Yong; Orlov, Alexei O.; Snider, Gregory L.; Fay, Patrick J.

2009-11-01

449

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

Microsoft Academic Search

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

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

2011-01-01

450

Routing in frequency-hop packet radio networks with partial-band jamming  

NASA Astrophysics Data System (ADS)

This paper describes research in adaptive, decentralized routing for frequency-hop packet radio networks with mobile partial-band jamming. A new routing technique, called least-resistance routing (LRR) is developed, and various versions of this routing method are examined. LRR uses a quantitative assessment of the interference environment experienced by a radio's receiver to determine a resistance value for that radio. Two components for the interference environment are considered: transmissions from other radios and partial-band jamming. The resistances for each of the radios in a particular path are combined to form the path resistance, and packets are forwarded on the path with the smallest resistance. Comparisons are made between different versions of LRR and between LRR and previously developed adaptive routing techniques. It is found that LRR is an effective way for dealing with mobile jamming in a frequency-hop packet radio network. Significant increases in throughput and end-to-end probability of success are obtained by use of LRR.

Pursley, Michael B.; Russell, Harlan B.

1993-07-01

451

47 CFR 80.203 - Authorization of transmitters for licensing.  

Code of Federal Regulations, 2013 CFR

...controls of a maritime station transmitter must be...in Appendix 18 of the international Radio Regulations...in Appendix 18 of the international Radio Regulations must...VHF maritime radio station transmitters capable...use in the INMARSAT space segment must...

2013-10-01

452

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

453

Radio frequency studies in the NASA Lewis Bumpy Torus  

NASA Technical Reports Server (NTRS)

The fluctuations in potential of the plasma in the NASA Lewis Bumpy Torus are observed using capacitive probes over frequencies from 1 kHz to 25 MHz and a wide range of operating conditions. The spectra are found to differ greatly above and below a background gas pressure of .000034 torr deuterium. Above this pressure, the spectrum is dominated by the ion spoke frequency and a spectral index may be defined. Below this pressure, the spectrum below 200 kHz is lower in amplitude by a factor of ten and no spectral index can be defined. At these lower pressures, fluctuations appearing to be ion spokes are observed, but have a dependence of frequency on operating conditions which is previously unreported.

Gerdin, G. A.

1974-01-01

454

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

455

Network protocols for frequency-hop packet radios with decoder side information  

NASA Astrophysics Data System (ADS)

Reliable data distribution within spread-spectrum packet radio networks requires high performance from the network protocols. This paper describes research in forwarding and routing protocols that are designed specifically for slow-frequency hop (SFH) packet radio networks in which some of the radios are subjected to excessive interference. It is shown that information extracted from the decoder can be used to aid the network protocols. New metrics are introduced that use this information to give a quantitative assessment of the interference environment experienced by the receiver in an SFH radio. Forwarding protocols are developed that can react quickly to local sources of interference, and the metrics that are introduced permit the routing algorithm to react to changes in the interference conditions in the network.

Pursley, Michael B.; Russell, Harlan B.

1994-05-01

456

Deriving Kinetic Luminosity Functions from the Low-Frequency Radio Luminosity Functions of FRII Sources  

NASA Astrophysics Data System (ADS)

FRII radio galaxies are relatively simple systems which can be used to determine the influence of jets on their environments. Even simple analytical models of FRII evolution can link the observed lobe luminosities and sizes to fundamental properties such as jet power and density of the ambient medium; these are crucial for understanding AGN feedback. However, due to strong flux selection effects interpreting FRII samples is not straightforward. To overcome this problem we construct Monte Carlo simulations to create artificial samples of radio galaxies. We explore jet power and external density distributions by using them as the simulation input parameters. Further, we compute radio luminosity functions (RLF) and fit them to the observed low-frequency radio data that cover redshifts up to z 2, which gives us the most plausible distributions of FRIIs' fundamental properties. Moreover, based on these RLFs, we obtain the kinetic luminosity functions of these powerful sources.

Kapinska, Anna D.; Uttley, P.; Kaiser, C. R.

2010-02-01

457

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

458

Temperature responsive transmitter  

NASA Technical Reports Server (NTRS)

A temperature responsive transmitter is provided in which frequency varies linearly with temperature. The transmitter includes two identically biased transistors connected in parallel. A capacitor, which reflects into the common bases to generate negative resistance effectively in parallel with the capacitor, is connected to the common emitters. A crystal is effectively in parallel with the capacitor and the negative resistance. Oscillations occur if the magnitude of the absolute value of the negative resistance is less than the positive resistive impedance of the capacitor and the inductance of the crystal. The crystal has a large linear temperature coefficient and a resonant frequency which is substantially less than the gain-bandwidth product of the transistors to ensure that the crystal primarily determines the frequency of oscillation. A high-Q tank circuit having an inductor and a capacitor is connected to the common collectors to increase the collector current flow which in turn enhances the radiation of the oscillator frequency by the inductor.

Kleinberg, Leonard L. (Inventor)

1987-01-01

459