Showing papers on "Radio frequency published in 1982"

Measurement of Radio Frequency Permittivity of Biological Tissues with an Open-Ended Coaxial Line: Part I

Abstract: An open-ended coaxial line is analyzed as a sensor for in vivo measurement of the complex permittivity of biological substances. The measurement system, based on two computerized network analyzers operating at frequencies from 10 MHz to 1 GHz, is described. Experimental results are presented in a companion paper.

Dual mode radio frequency-infrared frequency system

Abstract: A combined RF/IR system in which a common surface is used in the dual modes of radiating and absorbing RF energy and of reflecting and focusing IR energy. The common surface is structured, configured, and used as the slotted array antenna for the RF energy and as the primary mirror of a Cassegrain optical subsystem for the IR energy.

Cochannel Interference Considerations in Frequency Reuse Small-Coverage-Area Radio Systems

Abstract: Frequency reuse small-coverage-area radio systems having hexagonal and square coverage areas are compared. Comparison is made on the basis of average signal to average interference (\bar{S}/\bar{I}) in the corners of the areas and on the basis of the expected probability of S/I exceeding some system threshold for at least one base station that is eligible to provide service. The difference in performance between square and hexogonal systems is small, smaller than the usual uncertainties in the propagation parameters needed in the performance estimates. Results suggest that, even if the signal strength decreases as slowly as the inverse cube of the distance and the standard deviation of the large scale signal variation is as large as 10 dB, good service probabilities (on the order of 99 percent) can be provided in small-coverage-area radio systems using 30-40 channel sets.

Planar receiver antenna coil for programmable electromedical pulse generator

Abstract: An implantable programmable pulse generator provides electrical stimulation signals to the heart of a patient. The operating parameters of the pulse generator, such as stimulation rate, refractory period duration, and operating mode are programmable by a physician after the pulse generator has been implanted surgically in the patient. An external programmer device includes a transmitter of coded radio frequency (RF) signals. The pulse generator includes a receiver antenna for receiving the coded RF signals. The receiver antenna includes a first wire-wound, air core, planar coil antenna carried on a flexible insulating substrate adjacent an inner wall of a first major side surface of the pulse generator housing and a second wire-wound, air core, planar coil antenna carried on the flexible insulating substrate adjacent an inner wall of a second major side surface of the pulse generator housing. The planar coils are series additive connected to the programmable pulse generator circuit so that the RF signals will be received regardless of the orientation of the pulse generator when it is implanted in the patient. The planar receiver coil antenna provides reliable reception of the RF signal even when the transmitter coil of the programmer is slightly misaligned or tilted with respect to the receiver coil antenna. In addition, the antenna provides a shallow Q factor so that individual high tolerance tuning of the receiver circuits of the pulse generator is not required.

Electronic intelligence : the analysis of radar signals

Abstract: Signal-to-Noise-Ratio Considerations for Analog and Digital Systems Signal Power Polarization Beam Analysis Antenna Scan Analysis Intrapulse Analysis Pulse Repetition Interval (PRI) Analysis Radio Frequency (RF) Analysis Deinterleaving Pulse Trains Determining ELINT Parameter Limits ELINT Data Files

Radio frequency current generation by waves in toroidal geometry

Abstract: The quasilinear generation of current by rf wave fields is investigated in toroidal geometry. A general expression is derived for the amount of current generated for a given wave‐induced flux of particles. This expression should be of great practical value in assessing the various competing effects on current generation in toroidal geometry and is well‐suited for implementation in a toroidal ray tracing code.

A theory of currents induced by radio-frequency waves in toroidal plasmas

Abstract: A Fokker-Planck treatment of the plasma electron current driven by radio-frequency waves is presented for the electron cyclotron and Landau damping wave absorption mechanisms. Electron-electron collisions are taken into account using the full Fokker-Planck collision operator which leads to an integro-differential equation for the perturbation of the electron distribution function produced by the wave. This equation is solved analytically in the Lorentz gas approximation and numerically in its full form. Efficient current drive is predicted for high phase velocity waves in the electron cyclotron scheme while Landau damping is efficient at both high and low phase velocities. The reduction of the current due to trapping of electrons in a Tokamak field configuration is calculated and a dramatic suppression of the current is predicted for low phase velocities. The efficiency of driving currents with waves is found to be comparable with that obtained using fast ion beams but much less than that using steady electric fields. A comparison with an idealised wave shows that the two practical schemes considered are far from optimum.

Automated acousto-optic infrared analyzer system

Abstract: An automated acousto-optic tunable filter infrared analyzer system useable in a variety of industrial and commercial control applications. The system relies upon a narrow band pass tunable acousto-optic filter which is selectively tuned by predetermined rf frequency signals to selectively transmit the narrow band pass of interest which corresponds to a specific molecular species for identification and analysis. The system includes a microcomputer and associated memory function to measure and compare detected signals from an infrared detector which converts the filtered infrared signal to an electrical signal. The memory provides control signals for the computer and for controlling the sequence and frequency of rf energy applied to tune the filter. In this way, the near to mid range infrared can be analyzed for absorption bands corresponding to predetermined molecular species such as combustion product gases, and a feedback signal generated to control the combustion process.

Multiple modulation for optical pump-probe spectroscopy

Abstract: A system built largely from readily available amateur radio gear which uses radio frequency and audio modulation of pump and probe light beams allows the detection of very weak signals (rms noise ∼3×10−11W for a 10 s time constant) even in the presence of a much larger (3.6×10−2 W) background of pump and probe light.

Global positioning system receiver

Abstract: In a Global Positioning System type of navigation system, a biphase modulated radio frequency input signal is applied to the "front end" (11) of a double heterodyne receiver having a second intermediate frequency stage which operates in the audio frequency range. The audio output signal is phase locked to a 1 KHz reference signal and is applied to a microprocessor (24) for processing via an interface circuit which includes a relatively simple amplitude detector (51) and a biphase detector (54). The microprocessor (24) also controls the phase shifting of a pseudorandom noise code generator (70) whose output is modulated with the output of the first intermediate frequency stage of the receiver.

Microstrip notch antenna

Abstract: A broadband radiating element design is disclosed which provides a smooth, continuous transition from a microstrip feed configuration to a flared notch antenna for transmitting or receiving radio frequency signals.

Variable frequency ultrasonic system

Abstract: The ultrasonographer changes the frequency of ultrasound pulses emitted from an ultrasonic transducer as a result of adjusting the RF frequency of the transmitter burst exciting the broadband transducer; this adjustment takes place between pulse transmissions, while examining the patient. In a phased array imager utilizing baseband processing of received echo signals, the same adjustment supplies the corresponding frequency to the demodulator circuits. An alternative method of changing the system spectrum is to have a narrow bandwidth receiver whose center frequency is varied over the available bandwidth.

Multiport radio frequency signal combiner

Abstract: A multiport radio frequency (RF) signal combiner is described for combining three or more RF signals for application to an antenna. The combiner includes an input port for each RF signal, an output port coupled to the antenna, and a tuning port coupled to a tuning transmission line. The input ports, output port and tuning port are connected to a terminating element. The tuning transmission line is terminated by a fixed or adjustable short-circuit impedance for substantially eliminating the capacitive discontinuity created by interconnecting the input ports. The RF signal combiner can be advantageously utilized in any radio system where it is necessary to multiplex the RF signals from three or more transmitters to a single antenna.

Optical RF downconverter

Abstract: An optical downconverter with very wide bandwidth operable to separately ically downconvert individual spectrum sections of an RF spectrum, comprising the steps of modulating an optical carrier with the RF spectral width to be downconverted, spatially separating via optical gratings the different sections of the spectrum of the optical carrier sidebands into a plurality of optical channels, generating a different phase-coherent optical local oscillator signal for each optical channel at an appropriate frequency such that the difference between the LO frequency and the particular spectrum section on the given optical channel is equal to a predetermined difference frequency; and mixing each optical channel with its appropriate frequency L.O. and detecting the difference frequency resulting therefrom.

Radio frequency communication system utilizing radiating transmission lines

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

Propagation of electrostatic upper‐hybrid emission and Z mode waves at the geomagnetic equatorial plasmapause

Abstract: A theory proposed for the generation of terrestrial myriametric radiation (nonthermal continuum) invokes the linear conversion of electrostatic upper-hybrid emissions to escaping left-hand polarized ordinary (L-O) waves by virtue of propagation primarily in a plasma density gradient. The electrostatic waves first become electromagnetic Z mode waves and these subsequently escape by propagating through the radio window where the wave frequency equals the electron plasma frequency. A realistic model of the plasmapause based on spacecraft data is adopted and the electrostatic wave ray paths are computed by using Poeverlein's construction. The electromagnetic Z and L-O rays are obtained by using a full ray-tracing program. The accessibility of the radio window to the waves is discussed and possible inferences concerning the portion of the wave dispersion branch on which the initial instability occurs are considered.

Characteristics of RF Resulting from Dielectric Discharges

Abstract: This paper presents measurements of the electromagnetic radiation pulses and the replacement current pulses which result from the breakdown of Mylar and Kapton samples. The observed dependence of the characteristics of the replacement current pulse as a function of electron beam energy is discussed. The characteristics of the electromagnetic radiation pulses are also analysed in the text of this paper. The source of the irradiating electrons is a monoenergetic electron beam whose energy was varied from 12.5 KeV to 25 KeV.

Laser pumped by X-band microwaves

Abstract: A laser device pumped by RF microwaves at frequencies in the range of 8 to 12 GHz (X-band). An optical cavity containing a lasing medium is located within an RF cavity resonant at a frequency in the X-band. X-band RF energy is supplied from an RF source to a waveguide. A coupling plate, forming a common wall between the waveguide and the RF cavity, couples the RF energy from the waveguide into the cavity to produce a standing wave pattern therein which excites the lasing medium. Various coupling plate designs are disclosed. In an alternative embodiment, a plurality of separate optical cavities containing separate lasing media are located within the RF cavity and are commonly excited by the microwave energy.

Method and apparatus for mitigation of radio frequency electric field peaking in controlled heat processing of hydrocarbonaceous formations in situ

Abstract: The effects of radio frequency electric field peaking in the earth formations surrounding a conductor excited by radio frequency energy in the controlled in situ heat processing of hydrocarbonaceous earth formations are mitigated by providing an inert buffer region around the conductor to which radio frequency electromagnetic energy is supplied to produce an electric field within the earth formations A portion of the earth formations is removed to accommodate insertion of the conductor at a desired location in the earth formations and to provide a buffer region between the conductor and the surrounding earth formations The conductor is supported at the desired location in spaced relationship to the surrounding earth formations, the buffer region encompassing the principal region of the electric field enhancement region around the conductor where the probability of breakdown in the earth formations over the period of application of the radio frequency energy would be above a tolerable level The buffer region is filled with dielectric material having an electric field breakdown level greater than that of the surrounding earth formation medium such that the probability of breakdown in the buffer region over the period of application of the radio frequency energy is tolerable Preferably the filler medium has a power dissipation characteristic less than that of the surrounding earth formations

Radio-frequency hazards in the VLF to MF band

Abstract: The body currents induced in a human in conductive contact with various ungrounded metallic objects like cars, trucks, fences, etc, are calculated for the frequency band 10 kHz to 10 MHz The calculated incident E-fields required to produce thershold perception and let-go currents indicate that the recently proposed ANSI guideline of 100 mW/cm2(∼615 V/m) in the frequency band 03 to 30 MHz may result in a potential for RF burns

Radio frequency signal combining/sorting apparatus

Abstract: A unique RF signal combining/sorting apparatus is disclosed that includes first and second filters each comprised of one or more bandstop/bandpass filters intercoupled by transmission lines. The bandstop/bandpass filters include a shunt inductor or capacitor and a dielectric block having an input electrode plated on its top surface and a hole located at predetermined distance from the input electrode. The dielectric material is preferably a ceramic comprised of BaO, TiO 2 and ZrO 2 . The dielectric block is entirely plated with copper or silver except for a portion of the top surface surrounding the hole and electrode and is essentially a capacitively coupled, short-circuited coaxial transmission line. Each of the first and second filters is tuned to pass the frequencies of one signal and attenuate the frequencies of the signal passed by the other. The unique RF signal combining/sorting apparatus can be configured as a multi-signal combiner, multi-signal sorter, or multi-signal combiner/sorter. This feature of the unique RF signal combining/sorting apparatus renders it particularly well suited for use as an antenna duplexer for radio transmitters and receivers.

Stabilized radio frequency quadrupole

Abstract: 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.

Apparatus for and method of impedance matching

Abstract: An rf load is matched to an rf source by a matching network having series and shunt impedances connected between the source and load. A network coupled to the load derives a first rf signal responsive to rf energy reflected from the load. Another network responsive to the first rf signal derives plural rf signals, each having an amplitude that is a different function of the magnitude and phase angle of the reflected energy. In response to the amplitudes of the plural rf signals, the values of the series and shunt impedances are controlled.

Radio frequency apparatus for measuring moisture content of materials as a function of dielectric constant

Abstract: Apparatus for measuring moisture content of gypsum board and like products as a function of dielectric constant comprising an rf signal source, an antenna disposed for rf field coupling to a test material, first and second reference inpedances, and a control circuit for selectively connecting the reference and antenna impedances to the output of the rf source. A rectifier is responsive to source output for providing the corresponding d.c. signal to measurement electronics. The measurement electronics first subtract a first reference signal indicative of the reference impedances from both a differing second reference signal indicative of the reference impedances and from a signal indicative of impedance at the antenna. Moisture content is then determined as a function of the ratio of the differences. A threshold detector is responsive to the difference between the antenna and reference signals for indicating the presence of test material adjacent the antenna.

Hybrid ring having improved bandwidth characteristic

Abstract: A hybrid ring useful in the microwave and millimeter wave regions as a mixer for producing an IF output signal in response to applied LO and RF input signals. The ring is designed to exhibit a narrow bandwidth at the LO signal port and a moderately broad bandwidth at the RF signal port.

Radio frequency laser pumping system

Abstract: An improved laser power supply is disclosed. The invention is designed to provide the high electric field required for starting a laser in addition to the capability of automatically readjusting after laser action is initiated to provide an optimum impedance match for high efficiency energy transfer. The invention includes variable means for matching the impedance of a laser cavity with a source of RF energy. In addition, means are provided for sensing a change in the impedance of the laser cavity. The sensed change is then utilized to vary the impedance of the matching elements to provide and maintain an optimal coupling between the laser cavity and the RF source.

A Phase Sensitive Laser Probe for Pulsed SAW Measurements

Abstract: [ 1 l ] R. C. Peach, “ A general approach to the electrostatic problem of [ 121 W. R. Smith, “Basics of the S.A.W. interdigital transducer,” Wave Electron., vol. 2, pp. 25-63, July 1976. [ 131 W. J. Tanski, “Surface acoustic wave resonators on quartz,” ZEEE Trans. Sonics Ultrason., vol. SU-26, no. 2, p. 93, Mar. 1979. [ 14) R. C. Rosenfeld, T. T. O’Shea, and S. H. Arneson, “Turning quartz SAW resonators by opening shorted reflectors,” in Proc. 3ls tAnn. Symp. Frequency Contr., p. 231, 1977. [l51 C. Dunrowicz, F. Sandy, and T. Parker, “Reflections of surface waves from periodic discontinuities,” in I 9 76 Ultrason. Symp. Proc., p. 386, IEEE Cat. no. 76 CH1120-55U.