Showing papers on "Radio frequency published in 1983"

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

Abstract: A theory of coupled resonant coils has been developed which makes possible the design of radio frequency transcutaneous links of simultaneously high overall efficiency and good displacement tolerance while keeping circuitry simple (particularly in the implanted receiver). Series-tuned transmitter coils were used, obtaining high efficiency. In the first example a stimulator which has excellent displacement tolerance because it works at critical coupling is designed. The second example shows how the theory was used when the voltage in the implant was regulated. The design process involvesad hoc compromises between disparate quantities (e.g. efficiency against voltage transfer ratio), rendering a standard design procedure unsuitable. Fortunately, the derived theoretical formulae are simple enough for every design to be considered from fundamentals, based on coil parameters. Extensive coil loss data are presented here for the frequency band 0·2 to 20 MHz.

rf stabilization of an axisymmetric tandem mirror

Abstract: Plasma with significant central-cell beta can be sustained in a tandem mirror composed of three axisymmetric simple mirror cells by the use of ion-cyclotron resonant heating. Radial ponderomotive force due to the rf electric field opposes the centrifugal force due to the field-line curvature to ensure interchange stability. This is indicated by the sensitive dependence of the plasma stability on the sign of the difference between the rf frequency and the ion-cyclotron frequency.

Dual frequency heart rate monitor utilizing doppler radar

Abstract: A heart rate monitor for use where direct contact with a patient cannot be made utilizes two continuous radio frequency (RF) signals, one of relatively low frequency and one of relatively high frequency directed toward the patient whose heart is to be determined. Doppler shifted signals are reradiated by the patient back to the monitor. The reradiated low RF signal has doppler components due to bodily motion caused by respiration and heartbeat. The reradiated high RF signal has doppler components due to patient bodily movement caused by respiration. Doppler components due to heartbeat if any, are of substantially lower value than those associated with the low RF signal. The heart rate monitor includes a difference amplifier which effectively subtracts the doppler signal associated with the high RF frequency from the doppler signal associated with the low RF frequency to obtain a signal which contains only components due to the heartbeat of the patient.

Crossed beam high frequency anti-theft system

Abstract: An article surveillance system employs a label or tag containing a non-linear impedance element, such as a semiconductor diode, connected to a metal antenna loop configured to pick up two distinct radio frequency transmissions displaced on either side of a selected center frequency. The non-linear impedance element connects opposing sides of a closed loop section at one end of the antenna to form a tuned tank circuit having a resonant frequency twice that of the selected center frequency. A first transmitter generates a tone modulated radio frequency displaced on one side of the center frequency, and a second transmitter generates a continuous wave radio frequency displaced from the center frequency on the other side. Both transmitter signals are fed separately to respective radiating antennae located adjacent to a surveillance area. The antennae are chosen to produce circularly polarized transmission of both frequencies within the surveillance area. The two different frequencies picked up by the transponder antenna are mixed by the non-linear impedance causing the tank circuit to resonate at a single higher frequency equal to their sum, which is double the center frequency; that resonant frequency is reradiated to be picked up by a receiver antenna or antennae suitably placed with respect to the surveillance zone to be detected by a very narrow band receiver responsive to the sum frequency. The modulating tone signal is derived from the received signal to produce a gradually increasing charge that is compared against a preselected threshold level to trigger an alarm for a fixed interval only when the detected signal is of a sufficient strength and duration.

A 30‐W radio frequency excited waveguide CO2 laser

Abstract: We describe the design and preliminary performance characteristics of a compact sealed, transverse rf discharge excited waveguide CO2 laser which is capable of output powers of 30 W and a peak efficiency of 13% from a 37‐cm discharge length.

Design and Performance of W-Band Broad-Band Integrated Circuit Mixers

Abstract: Broad-band integrated circuit mixers rising a crossbar suspended stripline configuration and a finline configuration were developed with GaAs beamlead diodes. For the crossbar suspended stripline balanced mixer, less than 7.5-dB conversion loss for 15-GHz instantaneous, IF bandwidth was achieved with the LO at 75 GHz and the RF swept from 76 to 91 GHz. With the LO at 90 GHz, a conversion loss of less than 7.8 dB was achieved over a 14-GHz instantaneous bandwidth as the RF is swept from 92 to 105 GHz. For the finline balanced mixer, a conversion loss of 8 to 12 dB over a 32-GHz instantaneous IF bandwidth was achieved as the RF is swept from 76 to 108 GHz. Integrated circuit building blocks, such as filters, broadside couplers, matching circuits, and varions transitions, were also developed.

Radio frequency sputtering—the significance of power input

Abstract: Radio frequency (rf) sputtering is used for the deposition and etching of thin layers. In both cases the target etch rate must be controlled, and often power input has been used as one of the controlling parameters. An earlier paper has shown that the applied rf target voltage (V pp) was a more useful parameter, and here new data is presented which indicates that the peak‐to‐peak voltage remains the preferable parameter for both etch rate control and in transferring between machines. However, a new method is described here which obtains the discharge power by subtracting losses from the total power reading. This discharge power is shown to be related to etch rates, and can thus be used as an aid in the scaling of system sizes. In addition, this discharge power exhibits interesting behavior as the pressure is varied, at constant applied rf voltage. Three main regions are evident when etching Si with CF4: at low pressures directional ion‐induced etching is obtained; in an intermediate region the input power rises rapidly with pressure and the etching is less directional resulting in overhang profiles; and at high pressures an isotropic etching component results in undercut profiles. The two extreme regions correlate with the commonly identified regimes of: (a) low power input, low pressure reactive sputter etching, and (b) high power input, high pressure plasma etching.

V-band Low-noise Integrated Circuit Receiver

Abstract: A compact low-noise V-band integrated circuit receiver has been developed for space communication systems, The receiver accepts an RF input of 60-63 GHz and generates an IF output of 3-6 GHz. A Gunn oscillator at 57 GHz is phaselocked to a low-frequency reference source to achieve high stability and low FM noise. The receiver has an overall single sideband noise figure of less than 10.5 dB and an RF to IF gain of 40 dB over a 3-GHz RF bandwidth. All RF circuits are fabricated in integrated circuits on a Duroid substrate.

RF Interferometer/Doppler target location system

Abstract: A radio frequency interferometer/Doppler target location system comprising in one embodiment a wave source on a target vehicle which is tracked by a radio frequency interferometer located at a known situs. The radio frequency interferometer generates signals representing the azimuth angle, elevational angle and Doppler shift of the source. The Doppler shift is a direct measurement of the velocity of the target vehicle in wavelengths per second and therefore if the Doppler cycles are counted from the time the target vehicle is launched, its range can be determined at any desired time. The azimuth angle signal, elevation angle signal and the Doppler shift signal are then transmitted to a processor where the information is converted into any desired format to indicate the position of the tracked vehicle.

Adaptive quadrature combining apparatus

Abstract: A quadrature combiner circuit is provided which employs a quadrature coupler to split an input radio frequency signal into split radio frequency signals which are amplified by respective amplifiers and recombined in a second quadrature coupler in such a manner as to minimize intermodulation distortion products. A feedback loop is employed to assure that the split amplified radio frequency signals incident upon the second quadrature combiner are maintained in quadrature relationship to assure intermodulation product cancellation.

Method and apparatus for eliminating interference due to spurious signals generated in synthesized receivers

Abstract: A synthesizer radio frequency (RF) signal receiver (FIG. 1) for single sideband radios is described that can eliminate interference due to internally generated spurious signals, commonly referred to as "whistler spurs". The unique receiver includes first and second mixers (102 and 106), which are intercoupled by a 75 mHz crystal filter (104) having a 20 kHz passband, and which are each coupled to signals from voltage controlled oscillators (120 and 140). The first IF frequency provided by the first mixer (102) varies about 75 mHz, and the second IF frequency provided by the second mixer (106) is fixed at 11.4 mHz. The second mixer (106) is coupled to 11.4 mHz stages (108) which have a 2.7 kHz passband. The 11.4 mHz stages (108) are followed by another mixer (110) and audio stages (112) for demodulating audio signals from the received RF signal, which are then applied to a speaker (114). The frequency of the VCO (120) coupled to the first mixer (102) can be varied by changing the divisor N of a programmable divider (123), and the frequency of the VCO (140) coupled to the second mixer (106) likewise can be varied by changing the divisor M of a programmable divider (133). When interference due to a whistler spur is present, activation of an IF pushbutton (160) enables a microcomputer (170), which changes divisors N and M for varying the frequencies of the two VCO's (120 and 140) by a multiple of 3.2 kHz, which in turn shifts the first IF frequency by 3.2 kHz. The frequency change also shifts the whistler spur outside of the 2.7 kHz passband of the 11.4 mHz stages (108) and greatly attenuates it. If the whistler spur is not sufficiently attenuated, the IF pushbutton (160) can be activated a second time.

Codeable identifying tag and method of identification thereof

Abstract: A tag is receptive of two radio frequencies (RF signals) for mixing the two frequencies and radiating a signal which is either or both the sum and difference of the two RF frequencies. A uniquely identifiable tag includes, in addition to the mixer one or more filters for radiating a signal only when the sum or difference of the two signals is a pre-specified value or only when the RF signals are each of pre-selected values.

Double conversion tuner for broadcast and cable television channels

Abstract: In a double conversion tuner intended to tune UHF broadcast channels as well as VHF broadcast and cable channels, the frequency range of the first intermediate signal produced by the first mixer is selected to correspond to that of UHF channel 37. The frequency range of UHF channel 37 is reserved for radio astronomy and is, therefore, not used for the broadcast of television information. The tuner includes provisions for inhibiting interference from the RF signals corresponding to channels 36 and 38 which are adjacent to channel 37 and which are used for the broadcast of television information.

SiO2 Planarization by Two Step RF Bias Sputtering

Abstract: A new angled‐surface‐moving model for surface planarization by rf bias sputtering is proposed. This planarization is achieved by angular selective etching of SiO2 films on top of metal stripes. A two‐step rf bias‐sputtering technique was developed, based on the new model. In this technique, the substrate bias voltage was changed in two steps during bias sputtering. The first step was to fill gaps without microcracks. The second step was to planarize at higher substrate bias. The planarized SiO2 layer surface, deposited on thermally oxidized Si wafers with Mo stripe patterns, had good flatness. A planarized 4‐level metallization test structure was fabricated by the two‐step rf bias‐sputtering.

Apparatus for generating or detecting field components in a magnetic resonance system

Abstract: Apparatus for generating and detecting magnetic field components oscillating at a radio frequency in a direction transverse to a static magnetic field in a nuclear-magnetic-resonance (NMR) system. The apparatus has a plurality of conductive elements spaced from one another and from the axis along which the static magnetic field is directed. The relative amplitudes of alternating currents in the conductive elements are controlled to generate a spatially uniform field. A preferred embodiment uses a standing wave in a coil assembly to control relative current amplitudes, which takes advantage of the current-phase characteristics of such waves. Detection of RF magnetic fields results from an EMF generated in the coil assembly in response to the time-varying magnetic field; the high Q of the coil assembly enhances detection properties.

Modified time-division transmission technique for digital mobile radio systems

Abstract: The present invention relates to a time-division radio transmission technique which uses a modified full-duplex arrangement where two channels are assigned to each two-way link. Simultaneous two-way transmission includes sequential digital symbol bursts between two remote transceivers which alternate between a first and a second channel centered on a first and a second radio frequency, respectively, with each transceiver using a different one of the channels at any instant of time.

Method and apparatus for the conveying and radio frequency processing of dielectric materials

Abstract: Particulate dielectric material is provided by radio frequency (RF) energy while being simultaneously conveyed from an inlet (42) to an outlet (18) by disposing the transmitting (62) and receiving (58) electrodes of an RF generator (74) diametrically opposite each other on the outside of a conveyor tube (16) containing a screw conveyor (44) both the tube and screw being made of dielectric material. A fiberoptic probe (76) is located at one end to sense the temperature of the particulate material in the conveyor tube and is connected at the opposite end to an infrared sensor (82), which provides an electric output signal proportional to the sensed temperature. This output signal is coupled to a set point controller (84) which provides an electric output signal representing a small temperature range above and below a selected set point temperature, and the latter output signal is coupled to a duty cycle regulator (92) which operates to regulate the "on" time of the RF generator.

Reduction of the Apparent Impedance of Wide Band Accelerating Cavities by RF Feedback

Abstract: In the CERN SPS proton synchrotron the four accelerating cavities are of the travelling wave structure type. At the 10 GeV/c injection energy the cavities present to the beam an impedance very similar to that of a detuned RLC cavity with the result that strong dipole and quadrupole instabilities occur. The SPS accelerated beam current was limited by the combined action of these two effects to 2.5 X 10/sup 13/ protons which resulted in capture losses increasing with the injected beam intensity. Among the solutions possible for this problem, the RF feedback, which would alleviate both transient beam loading and instability effects, looked to the authors to be the most promising. In such a system the total voltage seen by the beam is reinjected into the feedback cavity via its power amplifier. Without any delay in the system the cavity impedance seen by the beam could be greatly reduced. Unfortunately the long delay in the system severely limits the bandwidth and the RF feedback could hardly correct more than the n = O beam loading component. The authors circumvented this problem by observing that they needed a large gain only in the vicinities of the RF frequencies. Outside these bandsmore » the phase rotation due to the long delay is unimportant if the gain is made low enough. If, in addition, the total delay of the system is made exactly equal to one machine turn, the open loop phase of the feedback system is always zero for each RF frequency. The two ingredients needed to make the RF feedback work for n not too small are therefore a transfer function with comb filter shape and a total delay of one machine turn. In this paper these ingredients are derived.« less

Radio frequency induction heating device

Abstract: A radio frequency induction heater for locally heating a metallic work piece. The induction heater comprises an elongated conductor surrounded by a core of magnetic material having a narrow slot formed therein serving as the inductor core air gap. The conductor is connected across a source of radio frequency current. The induction heater is located adjacent the metallic work piece with the inductor core air gap very near (and preferably in contact with) that portion of the metallic work piece to be heated. When the radio frequency current is caused to pass through the conductor, the gap concentrates the flux entering the work piece, inducing voltages in the work piece resulting in eddy currents which flow in the work piece along and parallel to the gap. This, in turn, results in the rapid local heating of a narrow band of the work piece.

Radio‐frequency amplifier based on a dc superconducting quantum interference device

Abstract: A dc superconducting quantum interference device used as a radio‐frequency amplifier has achieved a power gain of 19.5±0.5 dB and a noise temperature of 1.0±0.4 K at a frequency of 100 MHz and an operating temperature of 1.5 K.

Radio frequency signal direction finding apparatus

Abstract: A system for determining the difference in phase between a pair of radio frequency signals wherein quadrature components of one of such pair of signals are alternatively combined with the other one of such pair of radio frequency signals to provide sum and difference signals thereof. Alternative ones of such sum and different signals are alternatively coupled to an output to provide a composite signal having a phase related to the difference in phase between the pair of radio frequency signals. The composite signal is then amplified and the phase of the amplified radio frequency signal is detected to determine the difference in phase between the pair of radio frequency signals.

Radio frequency network having plural electrically interconnected field effect transistor cells

Abstract: A radio frequency network is provided having a plurality of field effect transistor cells, each one of such cells having a reactive element, and coupling means for electrically interconnecting the plurality of field effect transistor cells, such coupling means having an impedance in accordance with the reactance of the reactive elements of the cells to provide such radio frequency network with a predetermined characteristic impedance related to the impedance of an input circuit which feeds radio frequency energy to an input one of the plurality of cells. With such arrangement the coupling means and the plurality of field effect transistor cells provide the radio frequency network with a predetermined characteristic impedance which is related to the impedance of the input circuit.

Effects of Diffraction on Measurements of the Frequency-Dependent Ultrasonic Attenuation

Abstract: Using a one-dimensional model of wave propagation, the ultrasonic attenuation can be estimimated from spectral analysis of RF A-scans. The results of computer modeling studies and measurements on tissue equivalent phantoms indicate that spectral analysis methods are accurate only in the regime where a one-dimensional model is adequate. In the near field of a typical B-scan transducer, a one-dimenional model is not an accurate description of wave propagation. A simple processing method is presented that minimizes near field diffraction effects on estimates of the slope of the attenuation coefficient as a function of frequency.

The velocity and the density spectrum of the solar wind from simultaneous three-frequency IPS observations

Abstract: Density inhomogeneities in the solar wind cause fluctuations regarding the emission of small diameter radio sources. Such fluctuations are called interplanetary scintillation (IPS). IPS has been studied to obtain information on both the solar wind and on the radio sources. In the present investigation it is attempted to extract information about the solar wind from simultaneous IPS observations at three radio frequencies and a single antenna. Data were recorded at frequencies of 270 MHz, 340 MHz, and 470 MHz on a 91 m telescope. Five different radio sources were observed. The observations are compared with theoretical predictions for spectra, cross-spectra, and cross-correlations using weak scattering theory and various models for the wavenumber spectrum of density inhomogeneities in the solar wind. Good fits are obtained over the observed wavenumbers to a spectrum modeled as a power law.

An Implantable Electric-Field Probe of Submillirneter Dimensions

Abstract: Many areas of biological research await the development of practical electric (E)-field probes with submillimeter dimensions for in situ measurements of RF electromagnetic fields. This paper reports on the design, fabrication, and testing of such a probe. The probe consists of a 0.6-mm dipole antenna zero-bias Schottky barrier diode and a unique highly resistive output lead structure. Experimental results indicate the probe does not perturb the field under investigation and is linear over a range of field strengths from less than 60 to over 1200 V/m. The probe has been designed so as to he independent of the media in which measurements are being made.

Optimum design of n + -n-n + InP devices in the millimeter-range frequency limitation—RF performances

Abstract: Systematic simulations of n+-n-n+InP millimeter-wave transferred-electron devices have been performed in order to define the frequency limitation of the fundamental accumulation transmit mode, as well as the maximum RF performance of these devices The simulations indicate that the use of n+-n-n+InP devices yields significant net output powers and efficiencies up to 160 GHz, according to the present state of technology

Biological effects and dosimetry of nonionizing radiation : radiofrequency and microwave energies

Abstract: History of the Genesis and Development of the Study of Effects of Low Energy Electromagnetic Fields.- Sources and Applications of Radio Frequency and Microwave Energy.- Fundamentals of the Classical Theory of Electromagnetic Fields.- Fundamentals of the Interactions of Radio-Frequency and Microwave Energies with Matter.- Instrumentation of Measurement of Electromagnetic Fields: Equipment, Calibrations and Selected Applications.- Dosimetry of Radio Frequency and Microwave Radiation: Theoretical Analyses.- Molecular Interpretation of the Dielectric Behaviour of Biological Material.- Dielectric Properties of Biological Tissue and Cells at RF- and MW-Frequencies.- Biophysics of the Interaction of Electromagnetic Energy with Cells and Membranes.- Broadband MM-Wave Spectroscopy on Biological Samples.- Theory of Resonant Effects of RF and MW Energy.- Experimental RF and MW Resonant Nonthermal Effects.- Biological Effects of RF and MW Energy at Molecular and Cellular Level.- Interactions of Electromagnetic Fields with Living Cells and Molecular Systems.- Biological Effects and Health Hazards of RF and MW Energy: Fundamentals and Overall Phenomenology.- Biological Effects of Low Energy Electromagnetic Fields on the Central Nervous System.- Behavioural Effects of Radiofrequency Energy.- Neuroendocrine Response to Microwave/Radiofrequency Energies.- Radiofrequency and Microwave Effects on Immunological and Hematopoietic Systems.- Mutagenic and Developmental Effects of Microwave Radiofrequency (MW/ RF) Energies.- Cataractogenesis Induced by RF and MW Energy.- Interaction of RF and MW with the Living Systems: Research and Experience in China.- Differentiation Between Biological Effects and Health Hazards: Scaling from Animals.- Dielectric Properties of Biological Tissues and Cells at ELF-Frequencies.- Some Fundamental Aspects of Biological Effects of Extremely Low Frequency (ELF).- Power Frequency Electric Fields: Dosimetry.- Analysis of Experimental and Epidemiological Data from Exposure to Microwave/Radiofrequency (MW/RF) Energies.- Development of Standards - Assessment of Health Hazards and Other Factors.- Assessment of Health Hazard and Standard Promulgation in China.- Microwave/Radiofrequency Protection Guide and Standard.- Lecturers.- Participants.