Showing papers on "Radio frequency published in 1986"

Ion Bombardment Secondaty Electron Maintenance of Steady RF Discharge

Abstract: The results of both theoretical and experimental study of a steady E-type RF discharge, in which ionization is controlled by fast electrons generated in RF sheaths near the electrodes (y regime), are presented. It is shown that the transition of an RF discharge into the ? regime is of a threshold nature and is accompanied by a sharp increase in plasma density and a decrease in electron temperature. The suggested theoretical model of an RF discharge in the ? regime satisfactorily describes experiments carried out in a wide range of frequencies, RF voltages, and gas pressures.

CMOS RF circuits for data communications applications

Abstract: The author describes the recent development of two analog CMOS circuits operating at RF frequencies with applications to data communications. One is a four-quadrant analog multiplier which exhibits a 100-MHz bandwidth with a measured linearity error of 0.7% for X and Y inputs of 0.6 and 0.8 V, respectively. The other is a 90/spl deg/ phase shifter which maintains the grain and phase errors of less than 0.5 dB and 3/spl deg/, respectively, for a signal within 40-60-MHz frequency range.

Power line communication system

Abstract: A low-level, low-power radio frequency (RF) communications system designed to operate as a point-to-point power line communications sytem (PLC) utilizing frequencies from 50 to 600 MegaHertz (MHz) superimposed onto the AC power signal in a building.

Multiple tuning NMR probe

Abstract: A multiple tuning NMR probe includes a radio frequency (RF) probe tuned by means of a circuit which creates a multiple pole circuit response in the probe, each of the poles being sufficiently separated from each other as to cause resonance of the probe at distinct frequencies. When tuning for nuclei with resonances substantially apart, this function may be accomplished using a parallel capacitor-inductor (L-C) trap with an impedance matching network. When tuning for nuclei with substantially closely spaced resonances, a tank circuit is used which has a single resonance which is split into two resonances by strongly coupling it to another tank circuit in resonance with the sample coil tank circuit.

Electro-optical beamforming network for phased array antennas

Abstract: A fiber optic device 50 designed to steer the radiation beam of a phased-array antenna 10 has been demonstrated. A radio frequency (RF) signal is generated via photomixing at the output of a single-mode fiber optic interferometer. The phase of the electrical signal is shifted over several cycles in direct proportion to a voltage applied to an optical modulator 34, 60. The modulator consists of a Pockels-type optical phase modulator located in one arm of the heterodyne interferometer. Rapid changes in RF phase are feasible. A miniature low-voltage version of the device 50, 72, based upon integrated optics, has been devised.

Radio frequency energy sensitized compositions and method for sensitizing compositions to radio frequency energy

Abstract: A composition of enhanced radio frequency sensitivity and a method for providing enhanced radio frequency sensitivity to a composition in which a substance suitable for enhancement of radio frequency sensitivity is admixed with a radio frequency sensitizing amount of an inorganic radio frequency sensitizer treated essentially to remove absorbed water and/or other volatiles with the radio frequency sensitizer chosen from among zinc oxide (American Process), bentonite clay, and crystalline or amorphous alkali or alkaline earth metal aluminosilicate. A process for molding using these compositions and the molded product. The composition, method for enhancing radio frequency sensitivity, process for molding and molded product with a polymeric substance, particularly ultra high molecular weight polyethylene, as the substance suitable for enhancement of radio frequency sensitivity.

Improved multiple site communication system

Abstract: Disclosed is a communication system of the type adapted to communicate a message substantially simultaneously between a plurality of fixed location sites having respective radio coverage areas. The system has an arrangement comprising first and second radio frequency transceiver means located at respective first and second sites. The first radio frequency transceiver means is designed for operating on a first set of frequencies. The second radio frequency transceiver means is designed for operating on a respective different set of frequencies than the first set of frequencies. The second radio frequency transceiver means has means for receiving and converting the first set of frequencies to the respective different set of frequencies.

Microprocessor controlled tuning system

Abstract: A tuning system receives signals from a radio frequency source and supplies an intermediate frequency signal to a signal detector under the control of a microprocessor The microprocessor reads a channel selector and produces a control voltage which is used to tune the system to the selected channel The intermediate frequency signal is connected to the microprocessor and a direct measure of the actual IF signal frequency is used by the processor to continuously adjust the tuner to compensate for drifting of the RF signal In a preferred embodiment, the IF signal increments a counter in the microprocessor for a predetermined period of time to provide a direct measure of the actual IF signal frequency

Mooring location system

Abstract: A buoy for marine vessels that is responsive to a transmitted RF signal of a set frequency consisting of an RF receiver disposed within the buoy and tuned to a set frequency of the transmitted RF signal and an antenna coupled to the input of the RF receiver. A switching circuit is coupled to the RF receiver, and a lamp is disposed on the buoy so that when the RF receiver receives a signal at the set frequency, it will operate said switching circuit and turn on said lamp. The buoy may be a pick-up buoy having an elongated stem on the top of the buoy, and containing the antenna. The lamp can also be mounted on the end of the antenna. A sound source coupled to the output of the switching circuit can sound an audible signal in response to the transmitted RF signal.

Radio frequency filter having a temperature compensated ceramic resonator

Abstract: An RF filter (100) includes a ceramic resonator (116) sandwiched between first and second compensating discs (114 and 120) for temperature compensation, low loss mounting and heat sinking of the ceramic resonator (116). Good thermal contact between the ceramic resonator (116) and discs (114 and 120) is produced by a compressive force applied by copper plates (112 and 128) and copper can (124). The resonant frequency of the RF filter is tuned by means of a copper-plated tuning shaft (104) and ceramic tuning slug (118) which are positioned by brass bushing (134) in copper pipe (130 and 132). Input and output signals are coupled to the RF filter via respective probes (122).

RF Nonlinear Device Characterization Yields Improved Modeling Accuracy

Abstract: A new method for measuring the nonlinear characteristics of microwave GaAs field-effect transistors (FETs) has been developed and evaluated. The technique, which involves RF rather than DC FET measurement, has yielded significant improvement in circuit compression point and harmonic content modeling accuracy.

Method of and apparatus for radio-frequency generation in resonator tank circuits excited by sequential pulses of alternately opposite polarity

Abstract: A method of and apparatus for exciting harmonic generation of radio frequency in a tank resonant circuit by bipolar spaced, half-cycle pulses, wherein the period of the tank resonant frequency oscillations is 1/N the period between successive pulses of similar polarity, where N is an odd integer greater than unity.

A model of radio frequency planar discharges

Abstract: A simple model, using an asymmetrical double probe theory, is presented to describe a rf planar glow discharge. It reasonably agrees with available experimental results for a capacitively coupled excitation electrode and frequencies of about 100 kHz.

High-Power Modulated Intense Relativistic Electron Sources with Applications to RF Generation and Controlled Thermonuclear Fusion

Abstract: Recent advances in the physics and technology of the modulated intense relativistic electron beams (IREB's) are reviewed in this paper. Bunched dense electron beams can be used to construct high-power RF sources, which may critically affect future progress in fusion technology. In this paper a system is described in which electrical energy can be converted from a single pulse of relatively long duration into a series of subpulses of short duration (nanosecond and subnanosecond) and of high power (~1010 W). This electrical system consists of an IREB propagating through passive structures. The mutual interaction between the electron beam and one passive structure modifies the IREB so that power compression and beam modulation occur. When the modified IREB interacts with the next passive structure, the kinetic energy of the electrons is converted into electrical energy or RF energy. The beam current modulation depends on the injected IREB and the structure parameters. A 100-percent modulation of the current has been achieved. A single-beam source may be used for exciting radiation in a frequency range of 60 MHz to 10 GHz. In the frequency range of 60-750 MHz a modulated beam with power ~1010 W has already been achieved. IREB modulation at a frequency of ~3 GHz was performed and RF energy was extracted from the bunched beam with power output of 5 × 108 W.

RF frequency spectrum analyzer subsystem

Abstract: A spectrum analyzer subsystem for analyzing the frequency content of an RF signal including an optical source means responsive to an RF signal for generating a plurality of intensity modulated optical signals and a filter means responsive to each one of the intensity modulated optical signals for providing a plurality of output optical signals each corresponding to a respective one of the intensity modulated optical signals. Each output optical signal corresponds in intensity to the frequency content of an RF signal within a different predetermined frequency bandwidth. Detector means, which is responsive to each output optical signal converts each output optical signal into a corresponding electrical signal.

Moisture and density determination

Abstract: Apparatus and methods for producing a signal or signals related to the moisture content of a substance using impedance, radio frequency loss or dielectric loss techniques are disclosed. Apparatus and methods for producing a signal or signals related to the density and/or thickness of a substance using backscattered gamma-rays are described. Apparatus and methods using a combination of a.c. impedance, radio frequency or dielectric loss and backscattered gamma-ray techniques for producing signals related to the moisture content, density and/or thickness of a substance are also described. Means and methods for determining the moisture content, density and/or thickness of the substance from the signal or signals are disclosed. The apparatus and methods are particularly applicable to determining the moisture content, density and/or thickness of coal and coke.

Propagation of radio signals inside buildings at 150, 450 and 850 MHz

Abstract: A comprehensive study designed to characterize the propagation of radio frequency signals inside buildings is presented. Propagation curves at 150, 450 and 850 MHz are generated for a large office building in Ft. Lauderdale, Florida. The measurement apparatus is computer driven, to enable rapid integration of a large number of samples from a test location. The representation of the signals in the time domain provides for a good characterization of multipath fading for the different frequency bands. The number of samples needed for repeatable and accurate power averaging, are determined empirically. The vast amount of data is used to document the attenuation due to office walls and building floors. Probability distributions and standard deviations for the three frequency bands are also presented.

Electrosurgical apparatus having a safety circuit

Abstract: An electrosurgical device having a generator for producing a radio frequency current. The device senses an RF current leakage and thereby reduces the output of the RF generator so as to limit the amount of RF leakage to levels below a predetermined value.

Low distortion RF switching circuit without DC bias

Abstract: During a transmit cycle portion, a radio frequency transmitter (C) continuously generates an AC biasing signal and selectively generates a radio frequency signal. The AC biasing signal gates a first switch (10) and a second switch (32) such that the radio frequency signals from the transmitter are conducted to a magnetic resonance probe (E) but are blocked from being conducted to a receiver (F). A first filter (20) prevents the bias signals from being applied to the probe. The second switch includes a pair of crossed diodes (34, 36) which are gated conductive by the AC bias signal. A filter (72) passes the radio frequency signals but not the bias signals to ground to prevent the radio frequency signals from reaching the receiver. A filter (80) allows the bias signals to be applied across a load (88) such that the transmitter sees the load at the bias signal frequency. Another filter (40) prevents the bias signal from reaching the transmitter. An additional switch (50) provides further isolation between the receiver and the transmitter during the transmit cycle portion. During the receive cycle portion, radio frequency signals received by the probe pass through the filters (20,40) directly to the receiver but are blocked by switch (10) from passing to the transmitter.

Dual-mode AFC circuit for an SSB radio transceiver

Abstract: An automatic frequency control (AFC) circuit is disclosed for use in an SSB radio transceiver having the capability of transmitting and receiving SSB and FM data signals over any one of a number of communication channels having equal bandwidths. The dual-mode AFC circuit includes AFC circuitry which is capable of tracking the frequency of either: (a) a first radio frequency (RF) carrier having voice signals modulated via a signal sideband amplitude modulation within a first channel bandwidth by locking to the reduced pilot carrier transmitter with the SSB signals; or of (b) a second RF carrier having high speed data signals modulated by narrowband frequency modulation within the designated channel bandwidth. The AFC circuit also includes control circuitry to memorize the AFC control voltage during the time the mobile is transmitting, and to assist the acquisition of the FM data carrier by varying the AFC sweep rate on the signalling channel.

QD MRI RE coil using non-homogeneous and non-uniform RF field distribution

Abstract: A pair of co-located RF surface coils extend axially and part-circumferentially about a volume to be imaged. Because surface coils are employed, the RF field distribution will be non-symmetric, non-homogeneous and non-uniform within the volume. Nevertheless, if the two coils are rotationally offset by the proper amount (and possibly including capactive isolation coupling therebetween), the coils produce a pair of RF signals to/from the volume which are in quadrature phase thus providing signal-to-noise ratio improvements due to: (a) the fact that quadrature detection techniques are employed and (b) the fact that only a portion of the cross-sectional volume is effectively addressed by the surface coils (i.e., due to their non-symmetric, non-homogeneous and non-uniform field distribution).

Programmable radio frequency communications device capable of programming a similar device

Abstract: A computer controlled radio communications device (e.g. a radio) having functional characteristics such as operating frequencies (i.e. a "personality") determined, at least in part, by characteristic-defining stored digital data and having the ability to automatically transmit/receive such characteristic/defining stored digital data to/from a similar computer-controlled radio communications device so as to provide another device having similar functional characteristics (i.e. a "cloned" device). A special unidirectional data transfer wiring harness is preferably used in conjunction with externally accessible plug connectors on each device to temporarily effect the requisite interconnection between the devices during such a personality "cloning" process.

Double probe model of radio frequency capacitively coupled planar discharges

Abstract: A simple model, using a quasi‐stationary, asymmetric, double probe theory, is presented to describe radio frequency planar glow discharge with a capacitively coupled excitation electrode. It reasonably agrees with available experimental results at frequencies lower than the ionic plasma frequency.

Radar-optical transponding system

Abstract: An airport landing system includes an airborne transmitter and receiver for transmitting RF energy at a first frequency and receiving RF energy at a second frequency. A stationary RF energy focusing means for focusing received RF energy. At least four receive/transmit modules and at least one RF source module. The RF source module for amplitude modulating and amplifying the received RF energy for retransmission by the receive/transmit modules. The receive/transmit modules having RF energy collector horns physically arranged with at least two vertically disposed horns and two horizontally disposed horns for transmitting at least four relatively high gain powered beams whose patterns cross over at their half power points with the crossover point defining the approach path.

Principles of a resonant cavity optical modulator.

Abstract: We describe the principles of a resonant cavity optical modulator capable of modulation frequencies in the 10-GHz range. The dispersive properties of waveguides are used to achieve phase matching of the optical and rf waves, which differ in velocity by a factor of 3 in bulk electrooptic materials. The difference in propagation velocities also allows us to form a rectangular cavity with two opposite sides open through which the optical beam may be easily passed. A modulator employing this design is thus both efficient in its use of rf power and is easily optically aligned.