Showing papers on "Radio frequency published in 1969"

Wideband image terminated mixer

Abstract: Described is a wideband image terminated mixer of the type in which an input signal is split into two parts which are fed to separate mixers supplied with local oscillations from a single oscillator. After mixing, the resultant intermediate frequency signals at the outputs of the mixers are combined. The invention is characterized in that the image frequency signals returning from the mixers in the signal paths are summed at an image termination having a reactance such that the incident image frequency signals reflect back to the mixer where mixing with the local oscillator frequency converts at least portion of the image energy to the intermediate frequency. This reduces insertion losses and allows the image to be terminated over at least a 10 percent radio frequency bandwidth using a standard intermediate frequency such as 30 megahertz.

Effect of Radio-Frequency Fields on Mössbauer Spectra

Abstract: The effect of a radio-frequency field on M\"ossbauer spectra is reconsidered. Both the ground and the excited state of the source nuclei are simultaneously exposed to the rf magnetic field. As an example, the effect of the rf field on $^{57}\mathrm{Fe}$ nuclei in a source with magnetic splitting (detected by a single-line absorber) is discussed in detail for two experimental geometries. M\"ossbauer spectra taken at a constant velocity, but with varying radio frequency, show that the main features can be understood in terms of two-quantum processes (rf-induced transitions between the magnetic sublevels preceding or subsequent to the emission of a $\ensuremath{\gamma}$ quantum), as long as the rf amplitude is small compared to the static magnetic field at the nucleus.

Radio frequency absorber

Abstract: An absorber for radio frequency energy using incombustible materials to minimize adverse effects from the conversion of such energy to heat, including a fibrous mat of nonabsorbing material in which the absorbing material is distributed in such a manner that discontinuities in the index of refraction, meaning always the electrical index, in the path of the energy to be absorbed are minimized.

Phase correlation for an rf spectrometer employing an rf carrier modulated by a pseudorandom sequence

Abstract: The radio frequency spectrometer is disclosed employing a radio frequency transmitter which transmits a wide band of energy to the sample for simultaneously exciting radio frequency resonance of different spectral lines of the sample. The wide band transmitter energy is generated by a radio frequency carrier which is modulated by a pseudorandom binary sequence to produce the wide bandwidth for exciting the sample. The pseudorandom binary sequence is repetitive and the excited composite resonance signal is repetitively time scanned and sampled at a multiplicity of intervals during each scan. The sampled data derived from repetitive scans are digitized and sequentially stored and added in their respective channels of a storage unit to produce a time average for improving the signal noise ration. The pseudorandom binary sequence is synchronized with the time scan of the composite resonance signal to preserve the phase relation between successively sampled and stored data from successive scans, whereby either pure absorption or pure dispersion mode resonance data is obtained.

Correlation of Radio Noise and Quasi-Peak Measurements to Corona Pulse Randomness

Abstract: The quasi-peak readings of radio-noise meters have been generally accepted as an indication of the degree of nuisance to radio reception from ac and dc coronas. Simplified theoretical analyses were previously made to correlate the readings of radio- noise meters to some corona pulse characteristics.

Microwave Silicon Windows for High-Power Broad-Band Switching Applications

Abstract: Theoretical and experimental results obtained with a novel silicon window utilizing double-carrier injection to achieve high-power broad-band microwave switching are presented. The device consists of a wafer of high-resistivity silicon inserted across a waveguide with thin-line junction structures oriented orthogonal to the RF electric field. These line junctions provide hole-injecting contacts on one face and electron-injecting contacts on the other. With zero bias, the window appears as a thin low-loss dielectric slab, and the RF signal is transmitted. With forward bias, the window appears as a highly conductive slab due to the injected electron-hole plasma, and the RF signal is reflected. Calculations show that X-band windows 8 mils thick have a switching ratio of 0.5 to 15 dB if the resistivity change is from 300/spl Omega//spl dot/cm to 1/spl Omega//spl dot/cm. X-band windows have been fabricated having an insertion loss as low as 0.3 dB and a VSWR below 1.3 in the transmission state and an isolation as high as 18 dB (5 amperes at 1 volt) in the reflecting state. These characteristics are maintained across the complete waveguide band (8.2 to 12.4 GHz). Windows have been tested to 50-kW peak power without degradation in switching characteristics. The main advantages of the window over conventional p-i-n diodes are an order of magnitude or more increase in power handling (50 kW peak measured while 300 kW is predicted compared to 5 kW for a single p-i-n diode X-band high-power switch), full guide bandwidth operation (compared to 10 percent bandwidth for the conventional p-i-n), simpler bias circuitry (no reverse bias is required in the transmission state), and higher temperature operation (since no reverse voltage is needed).

Line shapes in the radio-frequency size effect of metals

Abstract: Thin metal plate surface impedance during excitation by HF electromagnetic field as function of magnetic field, calculating line shapes

Aerial drop telemetering sensor

Abstract: PRELIMINARY SEISMIC EXPLORATION AND EXPLORATION IN REMOTE ACCESS AREAS MAY BE CARRIED OUT WITH A LOW-COST, EXPENDABLE SEISMIC TELEMETERING UNIT CONTAINED IN A TWOPART AIR-DROPPABLE PROBE THAT INCLUDES AN UPPER SECTION (LIGHT MASS) DESIGNED TO REMAIN AT THE SURFACE AND A LOWER SECTION (HEAVE MASS) THAT IS BURIED TO A DEPTH DEPENDING UPON THE SOIL CONDITIONS. AS THE TWO-PART PROBE EMBEDS ITSELF IN AN EARTH-LIKE SURFACE, IT GENERATES UNDERGROUND SEISMIC WAVES, THEREBY ACTING AS ITS OWN SOURCE OF SEISMIC ENERGY. MANY PROBES MAY BE DROPPED IN AN EXPLORATION AREA IN ANY DESIRED SPREAD TO PRODUCE THE DESIRED SEISMIC DATA. THE IMPACT OF EACH PROBE GENERATES A NEW SET OF ENERGY WAVES THAT WILL BE PICKED UP BY ALL EARLIER DROPPED PROBES. BY APPROPRIATE CODING OF THE TRANSMITTED ENERGY, AN AIRBORNE COMPUTER WILL SEGREGATE THE SIGNALS FROM EACH PROBE TO PRODUCE SEISMIC DATA THAT MAY BE READ IN THE USUAL MANER. SEISMIC WAVES ARE DETECTED BY A SEISMIC SENSOR IN THE LOWER SECTION (SENSOR SECTION) WHICH GENERATES ELECTRICAL SINALS PROPORTIONAL TO TE TRAVELING WAVES. THESE ELECTRICAL SIGNALS ARE AMPLIFIED BY ONE OF MANY DIFFERENT AMPLIFICATION SYSTEMS, DEPENDING OF THE APPLICATION, AND CONVERTED INTO RADIO FREQUENCY SIGNALS IN A RADIO TRANSMITTER. AN ANTENNA IS MOUNTED TO EXTEND ABOVE THE EARTH''S SURFACE AS A COMMUNICATION LINK BETEEN THE RADIO TRANSMITTER AND A RADIO RECEIVER OPERATING AT A REMOTE LOCATION.

Radio frequency pulse generator using dc charging

Abstract: A radiofrequency generator employing a charging inductor connected to a source of direct current (DC) energy through a charging switch. The capacitor of a radiofrequency (RF) tank circuit cooperates with the charging inductor to achieve resonant charging of the RF tank circuit. A power switch is closed causing the charged tank circuit to oscillate at its natural resonant frequency through a series-connected load.

Radiological training device

Abstract: There is disclosed a training device for simulating the action of a nuclear radiation detector. A transmitter emits a singlefrequency RF signal in the VHF frequency range. The simulated detector is a radio receiver having a voltage-controlled multivibrator with an output to a meter and a headset. Thus, audible clicks are produced whose repetition rate varies inversely with the distance from the transmitter. The use of a VHF frequency results in the simulated field being distorted by reflection from surrounding terrain.

Polarization of Ionospherically Propagated HF Radio Waves with Applications to Radio Communication

Abstract: Sweep-frequency CW radio signals transmitted over 1300-km north-south and 1900-km east-west temperate-zone paths were received 24 hours per day for 21½ -day periods. Measurements of the incoming one-hop F-layer polarization, as a function of time-of-day and radio frequency, indicate that daytime rates of change of polarization rotation with frequency (at an instant of time) average 1 turn/MHz over the north-south path and 0.25 turn/MHz over the east-west path. These values are in good agreement with computer raytracing predictions of the rates of change of polarization rotation with frequency over similarly disposed paths. It was observed that nighttime polarization rotation rates are about 1 to 4 times as high as those measured during the day. It was also experimentally found that the rate of change of the incoming polarization with frequency first decreased and then increased with incoming radio frequency, the minimum rate occurring near 0.8 MOF0. Daytime rates of polarization rotation with time (at a given frequency) average 0.25 turn/min. The polarization rotation rates with time do not appear to vary either with path azimuth or transmitted radio frequency. Near-zero rates of polarization rotation with time occur for much of the nighttime period. Large fluctuations in the polarization variations occur with both time and frequency throughout the day. Polarization measurements made with signals that were reflected from a nonblanketing, nighttime sporadic E layer of about two hours duration indicate that, for this layer, circumstances other than polarization effects, probably multipath, determine much of the observed signal strength variations with frequency and time. The results suggest that for round-the-clock temperate zone propagation, when linearly polarized antennas are employed, a qualitative threshold for envelope distortion of broadband signals (due to variation in the incoming polarization with frequency) occurs when signal bandwidths exceed approximately 100 kHz for north-south paths and 400 kHz for east-west paths. The effects of such distortion may be reduced either by operating near 0.8 MOF0 or by the use of circularly polarized antennas.

Variable frequency generator combining outputs of two phase locked loops

Abstract: IN A PRECISION RADIO FREQUENCY SIGNAL GENERATOR, AN OUTPUT FROM A DIGITALLY CONTROLLED PHASE LOCKED FREQUENCY SYNTHESIZER LOOP IS MIXED WITH AN OUTPUT FROM A TUNABLE PHASE LOCKED VARIABLE FREQUENCY OSCILLATOR LOOP TO PROVIDE A RANGE OF ACCURATE FREQUENCY RF SIGNALS. THE SIGNAL GENERATOR IS PRO- VIDED WITH A DISPLAY WHEREIN THE FREQUENCY OF THE SIGNAL IS PRESENTED BY AN INDICATOR.

Receiver circuit assembly

Abstract: THE PRESENT INVENTION PERTAINS TO AN RF RECEIVER CIRCUIT ASSEMBLY AND MORE PARTICULARLY TO A RECEIVER OPERATIVELY ASSOCIATED WITH REMOTE CONTROLLED HEATING AND COOLING SYSTEMS HAVING FANS AND ADAPTED TO DEMODULATE A COMPLEX RF SIGNAL HAVING AN RF COMPONENT, A MIDRANGE AUTDIO FREQUENCY COMPONENT AND A LOW FREQUENCY COMPONENT AND INCLUDING ASSOCIATED OUTPUT CIRCUITS OPERATIVELY CONNECTED TO THE RECEIVER WHICH ARE RESPONSIVE TO THE LOW FREQUENCY COMPONENT TO SELECTIVELY ACTIVATE SAID HEATNG AND COOLING SYSTEMS AND THE FANS IN A PREDETERMINED MANNER. THE PRESENT INVENTION IS DIRECTED TO A RECEIVER AND ASSOCIATED OUTPUT CIRCUITS FOR ACTIVATING HEATING AND COOLING SYSTEMS AND FANS CONNECTED THEREWITH IN RESPONSE TO BE RECEPTION OF A SELECTED TRANSMISSION TO SAID RECEIVER.

Laser-Acoustic Signal Processing

Abstract: The variable delay and processing of RF and microwave signals is a current problem of considerable importance both for the many military applications in radar and electronic counter-measures and for the civilian applications in signal processing. The very low velocity of acoustic waves, as compared to the propagation velocity of electromagnetic signals, permits the fabrication of physically compact systems capable of storing and processing electromagnetic signals. Among the several suggestions for obtaining a continuously variable delay, the use of the laser-acoustic interaction has been shown to be among the most promising.

Standard field strength meter

Abstract: A hollow conductive sphere having a narrow insulated gap along an equator is suspended in a radio frequency electromagnetic field with the plane of the gap perpendicular to the electric field vector. The sphere halves are electrically connected together by a series resonant LC circuit disposed in the sphere. The resonant circuit is tuned to the frequency of the field. The field impinging on the sphere causes a current to flow across the equator of the sphere, via the resonant circuit. The field strength can accurately be related to the resonant current by an analysis of the scattering of the field by the sphere. To measure the current, the sphere contains a circuit for detecting the voltage developed across the inductance of the LC circuit and for energizing a miniature incandescent lamp when the detected voltage exceeds a threshold value. The light from the lamp is visible through a small diameter tube disposed through the sphere wall (the tube is a waveguide below cutoff for the impinging field). The sphere thus provides an optical indication when the field exceeds a threshold or standard field value. The sphere is calibrated by adjusting the threshold circuit to cause the lamp to light when the appropriate radio frequency current is passed through the resonant circuit. The calibration current is applied to the sphere by means of two hollow conductors of the same diameter as the sphere which are connected to the two sphere halves near the equator containing the insulated gap. The two hollow conductors form the inner conductor of a coaxial line. The calibration current applied to the coaxial line thus flows across the gap just as the induced current does when the sphere is in the field being tested.

Radio frequency noise during reentry

Abstract: In flight, measurements of the effective noise temperature of a reentry plasma are compared with computed data. The vehicle utilized for the experiment was the Trailblazer II. The measurements were made at a frequency of 2235 MHz and transmitted to the ground in real time by X -band telemetry. Noise temperatures in excess of 5000\deg K were recorded. The flight data also demonstrate the importance of antenna location and angle of attack in determining the performance of an RF system. Another result of the flight has been to point out the power of temperature measurements as a diagnostic tool for flow field studies.

Computer simulation of LSA oscillators with high doping to frequency ratios

Abstract: Computer simulations of twice oversized n-GaAs diodes with random doping fluctuations operated in a transmission line (multiresonant) circuit are presented. LSA operation in this multiresonant circuit, which provides an RF square wave voltage across the diode, has been obtained for n/f ratios as high as 1 × 106s/cm3.

Broadband radio frequency transmission line termination

Abstract: An electromagnetic energy termination device is provided with power absorbing means in a structure having plural reentrant electrical paths in series defined by concentric coaxial conductors within a substantially reduced mechanical configuration. Movement of a fluid dielectric medium within a fluidtight chamber is provided either in parallel or serially along the electrical paths to absorb high average and peak powers at ultrahigh radio frequencies over relatively wide bandwidths.

Overload compensation circuit for antenna tuning system

Abstract: As the RF signal supplied by an antenna to a varactor-tuned coupling circuit increases in magnitude, the impedance across an inductor in series with the varactor also increases due to the increased conductivity of an AGC-controlled field-effect transistor connected in the circuit of a secondary winding inductively coupled to the inductor. The system also is frequency sensitive, so that as the frequency of the RF signal applied across the inductor increases, the effective impedance also increases to compensate for increases of the reactance of the varactor diode at higher frequencies to maintain the RF signal level across the varactor diode at a level below that at which the diode rectifies the RF signals applied thereacross.

Amplitude modulated rf generator for quadrupole mass analyzer

Abstract: An improved radio frequency (RF) generator for use with a quadrupole mass analyzer is disclosed wherein a ramp of RF at constant frequency is provided by developing a difference signal between the output of the circuit and a control ramp input. The error signal is modulated by the desired frequency supplied from an oscillator and amplified by a push-pull arrangement. The amplified signal is applied to a series resonant tuned circuit which directly supplies the quadrupole rods.

Rf coaxial relay

Abstract: A radio frequency (RF) coaxial relay for connecting either of two coaxial terminals coupled, respectively, to a radio receiver and a radio transmitter, to a third coaxial terminal coupled to an antenna, includes a pair of magnetically actuated reed switches located within a cast nonmagnetic conductive housing. The reed contacts are capable of carrying high currents but are incapable of switching high currents, so that a sequencing circuit is provided so that the contacts of the reed switch coupled to the transmitter do not switch the transmitter when power is applied therefrom. In addition, the switch leaves of the reeds are copper-plated in order to cause the RF resistance of the reed switches to be low. 0This application is a continuationin-part of application, Ser. No. 722,319, now abandoned filed Oct. 31, 1968.

Device to detect motion

Abstract: A motion detector in which an oscillator-detector transmits a series of narrow bursts of radio frequency, electromagnetic energy, the period of which varies as a function of the radial motion of the object relative to the detector, and the varying pulse frequency provides information that an object is moving radially. Such a detector in which the varying pulse frequency of the oscillator-detector is converted to a varying D.C. voltage the magnitude of which varies at a rate determined by the rate of movement of the object, the varying voltage effecting energization of an alarm.

Damping Bunch Shape Oscillations in the Brookhaven AGS

Abstract: Bunch shape oscillations are present in the AGS both before and after the transition energy (?8 BeV) is reached. At transition, they can be excited by timing, phase and radial misadjustments, and beyond by rapid large radial position changes used for targeting or by rapid large (> 20%) targeting losses. They can also be excited before transition by misadjusting the low level RF control system. In addition, excitation before transition can occur when 2fs = 720 Hz, the magnet ripple frequency, or when 2fs = 360 Hz, the ripple frequency on the RF cavity tuning servo systems. An analysis of the RF phase control systems including second order effectsl indicates that it should damp these oscillations but at a rate~fs/s? except in the vicinity of transition. At 200 ms, E ? 6.5 BeV, ? ? 6.9, fs 200 Hz, and the damping rate is ? 0.46 s-1. Thus adequate inherent damping is present only early in the acceleration cycle. This, plus the fact that the sensitivity of the phase control electronics to bunch shape variations can at times produce antidamping, has led to the design and testing of various feedback damping systems to control these oscillations. An analysis of RF phase and amplitude feedback, using a peak detected signal, as applied to the RF control system, will be given. Operational results using both types of feedback will be described.

NAL Booster and Storage-Ring RF Systems

Abstract: The NAL booster - accelerator radio-frequency system design is described in detail. This rapid-cycling system is ferrite tuned from 30 MHz to 53 MHz. Each high-power module has an RF-output rating of 100 kW provided by a cascode amplifier which is a removable part of the cavity assembly. The low-level portion of the system corrects for both systematic and non-systematic tracking errors using a single set of wide-band beam sensors. In the design of a storage-ring RF system, the control of the beam-cavity interaction is a basic problem. This paper describes an arrange ment of TEM mode cavity, cascode power amplifier, beam pickup and feedback control loop to achieve a cavity-gap impedance of about 10 ohms over a frequency range from the synchrotron-oscillation frequency (a few Hz) to the higherharmonics of the bunch frequency. The design center radiofrequencyis 53.1 MHz.

Structures for Superconducting Electron Linacs and RF Separators

Abstract: Some basic principles underlying the design of structures suitable for superconducting electron linacs and RF separators are discussed. It is shown that the shunt impedance can be written as the product of two factors, one related to the shape of the individual cavities in the structure, and the other to the field flatness. Typical standing-wave structures are discussed, with emphasis on the ratio of peak-to-average field. The problem of field flatness is analysed using a coupled chain of resonant circuits. Results are given for the variation in field flatness with loss and detuning for the ?/2 and ? modes. Travelling wave resonators are also of interest, since they give the highest gradient for a given peak field. It is shown that such a resonator must be matched with great precision, or substantial power will flow in the reverse direction. Other factors which enter into the design of superconducting structures, such as coupling, thermal and mechanical stability, and beam break-up, are briefly considered.