Showing papers on "Radio frequency published in 1978"

RF Connector assembly with provision for low frequency isolation and RFI reduction

Abstract: An RF coaxial connector assembly, having an inner and outer conductor, employs a washer-like capacitor fitted over the outer conductor for low frequency isolation and employs a transformer adapted for connection between a source of RF signals and the inner and outer conductors of the assembly for reducing the RF currents on the outer conductor. Reduction of the RF currents on the outer conductor is effective to reduce the radiation of RF energy from a coaxial cable coupling the connector assembly to the load.

Radio‐frequency plugging of a high density plasma

Abstract: Mirror end loss can be suppressed by applying an rf field at the mirror throat through low impedance coils. This method is verified to be effective for a high density plasma up to 1014 cm−3. Experimental results show that the rf field strength required for the plugging is dependent on the plasma density. The dependence differs according to the geometry of the coil. The mechanism of giving the density dependence is theoretically clarified for each coil. Particularly, it is shown that the electric field induced in the direction of the static magnetic field is intrinsic for the result of type‐III coil where its efficiency for rf plugging is insensitive to the plasma density.

Radio-frequency plugging of a high density plasma

Abstract: Mirror end loss can be suppressed by applying an RF field at the mirror throat through low impedance coils. This method is verified to be effective for a high density plasma up to 10 to the 14th power/cu cm. Experimental results show that the RF field strength required for the plugging is differently dependent on the plasma density according to the type of coil. The mechanism of giving the density dependence is theoretically clarified for each coil. The electric field induced in the direction of the static magnetic field is shown to be intrinsic for the density independent result of type 3 coil.

Energy deposition in simulated human operators of 800-MHz portable transmitters

Abstract: The measured values of energy deposited in simulated human tissue exposed for one minute in the immediate vicinity of 800 MHz portable radio transmitters are presented. The deposited RF energy was evaluated by temperature measurements. The portable radio used in the tests had a 6-W experimental transmitter operating at 840 MHz. Two different antennas were tested for energy deposition: a sleeve dipole and a resonant whip. The two antennas have given substantially different results indicating different field structures near the two radiators. The experiments with flat slabs have shown that the sleeve dipole deposits higher levels of power density than the resonant whip in the near field although the length of the latter radiator is about half the size of the former. The temperature profiles generated by both antennas inside the head of the simulated operator indicate the presence of a "hot spot" about 1 in below the surface of the temporal bone. This phenomenon was not detected previously at lower frequencies. The short antenna exposes the eye of the operator to more intense power deposition than the sleeve dipole. The temperature increases measured during the investigation are so small that no thermal damage to tissue should be caused by normal use of the portable radio.

High-Frequency Waveform Generation Using Optoelectronic Switching in Silicon

Abstract: Conversion of dc energy to RF pulses may be accomplished by fast optoelectronic switching in semiconductors. A particular device is described and demonstrated involving the simultaneous activation of an array of silicon switches by a laser pulse. The resultant traveling wave is a short RF pulse burst whose waveshape is determined by the static voltage profile established in the device. The possibility exists for generating megawatt-level pulses at frequencies extending into the higher microwave bands.

Radio propagation in urban areas

Abstract: This paper reviews earlier work on radio propagation in urban areas, including data, studies of multi-path fading, and empirical propagation models A model is described, for use with a digital computer, which provides a rapid means of calculating both the median attenuation and the location, or path-to-path, variaability

A versatile high frequency radio microcautery

Abstract: . The paper describes a radio frequency microcautery operating at 27 MHz. Unusually high power is used to achieve a high rate of temperature rise in the tissue in order to leave fluid transporting vessels unblocked, e.g. aphid stylets. The power is adjustable down to levels appropriate to normal radio cautery applications and a timer is provided for single pulse operation. A special-purpose thermionic valve is used to generate the power which is fed to a remote probe.

Apparatus for measuring electric and magnetic fields

Abstract: Measuring apparatus for providing a reading representing a magnetic field component or the electric field component of incident radio frequency electromagnetic radiation comprises a set of magnetic field sensors and a set of electric field sensors interchangeably connectable to a measuring device which has an indicator instrument and an optical output to which can be connected a repeater device by means of an optical fibre cable which thus does not exert a perturbing influence on the field being measured. The sensors are omnidirectional balanced devices in which the detector elements are constituted by suitably shaped metallic film deposits on dielectric substrates, and can be interchanged by a simple plug-in connection which also holds the sensor physically in position on the measuring device.

Monitoring the E.D.M. process by radio signals

Abstract: Experimental studies are described to show that high-frequency radio observations provide a simple way to monitor the E.D.M. process and to distinguish between the effective spark and arc discharges. The paper also describes how radio frequency emitted during machining could be used to optimize the E.D.M. process. It was found that radiation from the region of the gap between the electrode (tool) and the workpiece are significantly different when the following conditions occur: open voltage, sparking (effective machining), arcing and short circuit. However, a reliable technique was developed to monitor the rate of metal removal and machining efficiency during the E.D.M. process

Transmitter/receiver for single channel duplex communication system

Abstract: A transmitter receiver which can be used for a cordless telephone using radio communication. The receiver produces direct conversion from the radio frequency. Local oscillator frequency is modulated by an audio signal to be sent, the modulated signals being passed through a dual splitting and combining network. The splitting network has directional properties for duplex operation. The receiver processes the signals through a differential amplifier to cancel unwanted signals.

Radio frequency arraying method for receivers

Abstract: 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. 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 (REF. 2) 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 are 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.

Demodulating system for auxiliary channel in straight-through radio frequency repeater

Abstract: The present invention discloses an FM microwave radio frequency repeater using the straight-through system for relaying signals of a plurality of channels having different carrier frequencies, each of the channels including an auxiliary channel. The system according to the invention is characterized in that the auxiliary channel has the signals thereof demodulated through frequency discrimination of a difference frequency signal obtained by mixing together two received microwaves.

Radio and X-ray variability of the nucleus of Centaurus A (NGC 5128)

Abstract: Centaurus A was observed at radio frequencies of 10.7, 31.4, 85.2, and 89 GHz and at X-ray energies greater than 20 keV. The source exhibits significant variability in all the observed radio frequencies. The observed radio and X-ray intensities show some concurrent variations but do not track one another throughout the observations. A model of the source in which X-rays are produced by inverse Compton scattering of blackbody photons by relativistic electrons is proposed to explain these observations. The observed variations in the electromagnetic spectrum are consistent with adiabatic expansion of a trapped plasma in conjunction with turbulent accelerations of the relativistic electrons.

Interaction of electromagnetic and acoustic waves in a stochastic atmosphere

Abstract: In the Stanford radio acoustic sounding system (RASS) an electromagnetic signal is made to scatter from a moving acoustic pulse train. Under a Bragg-scatter condition maximum electromagnetic scattering occurs. The scattered radio signal contains temperature and wind information as a function of the acoustic-pulse position. In this investigation RASS performance is assessed in an atmosphere characterized by the presence of turbulence and mean atmospheric parameters. The only assumption made is that the electromagnetic wave is not affected by stochastic perturbations in the atmosphere. It is concluded that the received radio signal depends strongly on the intensity of turbulence for altitudes of the acoustic pulse greater than the coherence length of propagation. The effect of mean vertical wind and mean temperature on the strength of the received signal is also demonstrated to be insignificant. Mean horizontal winds, however, shift the focus of the reflected electromagnetic energy from its origin, resulting in a decrease in received signal level when a monostatic radio-frequency (RF) system is used. For a bistatic radar configuration with space-diversified receiving antennas, the shifting of the acoustic pulse makes possible the remote measurement of the horizontal wind component.

Circuit and method for reducing polarization crosstalk caused by rainfall

Abstract: A circuit for reducing the effects of polarization crosstalk occurring on a first RF signal due to a second RF signal, wherein the first and the second RF signals are two approximately orthogonally polarized RF signals having essentially the same frequency The circuit comprises a first antenna and a first signal path (including RF and IF sections) for the first RF signal and a second antenna and a second signal path (including RF and IF sections) for the second RF signals A first coupler diverts a portion of the signal on the second signal path into a first network comprising the series combination of a variable attenuator and a variable phase shifter A summing circuit sums both the signal on the first signal path and the signal output from the first network with the result that the undesired signal on the first signal path is reduced A logic circuit, responsive to the magnitude of one of the RF signals, controls the first network according to a predetermined relationship

Radio receiver for FSK signals

Abstract: A simple radio receiver for FSK signals as used in a paging system. RF signals from the aerial are mixed in two high gain mixers with local oscillator signals which are in quadrature and which are at the nominal center frequency of the input signal. The output from the mixers are low-pass filtered so as to extract the difference frequency. The low-pass filter bandwidth is equal to the sideband width of the RF signal. Baseband signals from the filters are now amplified in high gain limiting amplifier stages which deliver fully symmetrically limited outputs at logic level to a D-type flip-flop.

Low power radio-frequency and microwave effects on human electroencephalogram and behavior.

Abstract: In a pilot study of ten human subjects, temporary changes in brain waves and behavior were seen on exposure to power densities lower than 10(-12) W/cm2, which is substantially below typical urban levels. Frequencies included .1 to 960 MHz continuous and 8.5 to 9.6 GHz pulse-modulated waves. Since the relaxation frequency of protein-bound water is considered to fall between 100 and 1,000 MHz, absorptions and quantum effects may be the mechanistic basis for the electroencephalogram changes observed in most of the subjects produced by 10(-15) W/cm2 cw radio-frequency energy of between 130 and 960 MHz. Constructive and destructive interference patterns from standing waves within the skull possibly interact with the bioelectric generators in the brain, since electroencephalogram wave amplitudes and frequencies increased or decreased respectively at different radio wavelengths.

Fourier-transform nuclear gyromagnetic resonance spectrometer

Abstract: In a Fourier transform nuclear magnetic resonance spectrometer, as is known, a pulse modulated radio frequency is applied to a sample placed in a magnetic field, and a free induction decay signal resulting from the above application is Fourier transformed to obtain a nuclear magnetic resonance spectrum. In such a spectrometer, a material having a predetermined resonance peak, for example, tetramethylsilane is used as a reference sample, and the center frequency of the pulse modulated radio frequency is successively varied while maintaining a constant magnetic field intensity. The position of peak of tetramethylsilane in frequency spectra thus obtained is varied with the change of the center frequency. By measuring successively the signal strength of the peak, there can be obtained a frequency characteristic of a receiving system employed in the spectrometer, which is used to obtain correction coefficients of the receiving system. By multiplying a frequency spectrum of a sample to be analyzed by the correction coefficients, the frequency characteristic of the receiving system is corrected, and thus the signal strength of the frequency spectrum can be indicated with high accuracy.

Simple cell for the measurement of the radio frequency electrical properties of earth materials.

Abstract: The design of a simple cell for determining the radio frequency electrical properties of earth materials is described. Basically, the cell consists of a coaxial sample holder fitted with electric and magnetic field probes. When excited as a section of transmission line the induced probe voltages are related in a straightforward manner to the electrical properties of the sample. The device is intended for use with a vector voltmeter which permits the direct and simultaneous measurement of the relative amplitudes and phases of these probe voltages. The cell permits the accurate and rapid determination of the conductivity and dielectric constant of earth materials over the frequency range 1 MHz–1 GHz, without the tedious and time consuming procedures associated with the bridge and slotted line techniques commonly used in this frequency range.

Generation mechanism of proton cyclotron echoes due to pulsed radio frequency waves in space plasma

Abstract: Analyses of the proton cyclotron echoes observed on the Alouette 2 ionograms, in more than 800 examples, indicate that the echoes are produced in a range within ±25° width of the magnetic dipole latitude centered at the magnetic equator. The generation mechanism of these proton cyclotron echoes is clarified here as follows: (1) the transmitted RF pulse makes an electrostatic plasma wave that produces a fast electron stream in opposite directions with respect to the wave propagation direction during damping processes of the wave; (2) the RF pulse also produces a proton concentration surrounding the antenna due to negative excursion of the antenna potential; (3) the proton concentration produced is repeated each proton cyclotron period and makes a pseudo-wave of the electric field; and (4) the encounter of the electron stream with the pseudo-wave due to the proton concentration makes a plasma wave with frequency in the transmitted RF range. The place where the electron stream encounters the pseudo-wave should be located at a position relatively close to the satellite for the observation of the RF echoes.

Intrusion detection system

Abstract: An intrusion detection system utilizes a radio frequency radiative system whose near electromagnetic field is monitored by receiving devices which respond, in a measurable way, to any disturbance of the near electromagnetic field by physical intrusion.

RF Burst signal recirculation memory system having a diplexed feedback loop

Abstract: A radio frequency burst signal memory system is described which includes a feedback loop for recirculation of the received RF burst signal when a proper burst signal is detected. The output from an RF amplifier is split into separate frequency bands by a diplexer. When one of these bands is sensed at the input, only signals of the sensed frequency band are recirculated.

Transitions at the Rabi frequency in the AC Stark effect: a dressed-molecule description

Abstract: Studies are made of a system consisting of a molecule interacting with both an intense electromagnetic field resonant with a molecular transition frequency and a weak RF probe field at the Rabi frequency. An earlier study of this system (Freedhoff et al., ibid., vol.8, p.L209 (1975)) is extended to include the effects of photon cascades and of laser detuning. The method of calculation is the dressed-atom description and master-equation approach of Cohen-Tannoudji and Reynaud (1977). Unlike the earlier study, the present treatment produces quantitatively correct expressions for the emission and absorption spectra both in the visible and in the RF regions. More importantly, however, the predicted absorption intensity is greatly enhanced over that in the earlier study, and, for negative detuning of the laser, amplification of the RF signal is predicted.

Asymmetric versus Symmetric TEM Cells for EMI Measurements

Abstract: This paper d i s c u s s e s th e o p t io n o f d e s ig n in g a tr a n s v e r s e e le c tr o m a g n e t ic (TEM) tr a n sm is s io n c e l l w ith an o f f s e t septum a s a m u lt ip u rp o se chamber fo r perform ing e le c tr o m a g n e t ic in t e r f e r e n c e (EMI) measure­ m ents. The d e s ig n and e l e c t r i c a l performance charac ­ t e r i s t i c s o f such a c e l l are g iv e n and compared w ith a s im i la r s i z e d symmetric c e l l .

Trirotron: triode rotating beam radio frequency amplifier

Abstract: 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.

Method of making a radio frequency oscillator-modulator with ground metallization

Abstract: A radio frequency oscillator-modulator for use in a video game includes a folded metal shield box having a slot on one of its ends with which a similarly slotted printed circuit board containing the oscillator and modulator is mated. Circuitry of the oscillator and modulator provides for great linearity and low R.F. radiation. The slot arrangement provides for effective grounding of the ground metallization of the external portion of the printed circuit board which contains the radio frequency output terminal along with the various input terminals. This portion contains ground metallization which makes very effective electrical contact with the slot of the shield box thus again containing R.F. radiation.