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At least 721 records · Page 40

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NASA NTRS1979

Small signal amplifiers and converters for millimeter wave Satcom systems

This paper describes the current state of the art and the various design tradeoffs encompassing the variety of small signal active circuit 'building blocks' deployed in millimeter wave Satcom receivers and transmitters. Included in this catagory are such low noise receiver components as parametric and FET amplifiers and low loss mixer downconverters as well as low level transmitter driver components such as resistive and varactor upconverters. Current and projected state of the art performance data will be presented along with specific examples of operating hardware.

Okean, H. C.↗

NASA NTRS1980

The adapting of the crossed-field directional amplifier to the requirements of the SPS

Progress in adapting the crossed-field directional amplifier to the SPS is reviewed. Special emphasis is given to (1) recent developments in controlling the phase and amplitude of the microwave power output, (2) a received architecture for its placement in the subarray, and (3) recent developments in the critical pivotal areas of noise, potential cathode life, and efficiency.

Brown, W. C.↗

NASA NTRS1982

Amplified wind turbine apparatus

An invention related to the utilization of wind energy and increasing the effects thereof for power generation is described. Amplified wind turbine apparatus is disclosed wherein ambient inlet air is prerotated in a first air rotation chamber having a high pressure profile increasing the turbulence and Reynolds number thereof. A second rotation chamber adjacent and downstream of the turbine has a low pressure core profile whereby flow across the turbine is accelerated and thereafter exits the turbine apparatus through a draft anti-interference device. Interference with ambient winds at the outlet of the turbine apparatus is thus eliminated. Pivotable vanes controlled in response to prevailing wind direction admit air to the chambers and aid in imparting rotation. A central core may be utilized for creating the desired pressure profile in the chamber.

Hein, L. A.↗

NASA NTRS1983

Dye laser traveling wave amplifier

A flash lamp pumped dye laser suitable for use as an amplifier stage was developed. The desired output laser pulses are of nanosecond duration, tunable in center frequency, and of good optical quality. Its usefulness as a laser oscillator is emphasized, because it constitutes a compact, relatively efficient source of tunable dye laser light.

Davidson, F.↗

NASA NTRS1983

Resonant isolator for maser amplifier

An isolator is described for use in a low noise maser amplifier, which provides low loss across a wide bandwidth and which can be constructed at moderate cost. The isolator includes a train of garnet or ferrite elements extending along the length of a microwave channel parallel to the slow wave structure, with the elements being of staggered height, so that the thin elements which are resonant to the microwaves are separated by much thicker elements. The thick garnet or ferrite elements reduce the magnetic flux passing through the thin elements to permit altering of the shape of the thin elements so as to facilitate their fabrication and to provide better isolation with reduced loss, by increasing the thickness of the thin elements and decreasing their length and width.

Clauss, R. C.↗

NASA NTRS1983

A two-stage monolithic buffer amplifier for 20 GHz satellite communication

Design, fabrication, and test results of a two-stage GaAs monolithic buffer amplifier for 20 GHz satellite communication are described in this paper. A gain of 13 + or - 0.75 dB from 17.7 to 20.2 GHz was obtained from the 1.5 x 1.5 millimeter chip, which includes all necessary bias and dc blocking circuitry.

Petersen, W. C.↗

NASA NTRS1985

Improved RF Isolation Amplifier

Circuit has high reverse isolation and wide bandwidth. Wideband isolation amplifier has low intermodulation distortion and high reverse isolation. Circuit does not require selected or matched components or directional coupling device. Circuit used in applications requiring high reverse isolation such as receiver intermediate-frequency (IF) strips and frequency distribution systems. Also applicable in RF and video signaling.

Stevens, G. L.↗

NASA NTRS1984

A High-performance Hybrid RF Isolation Amplifier

A high-performance hybrid RF Isolation Amplifier (Iso-Amp) has been developed at JPL. The circuit exhibits a unique combination of RF characteristics at performance levels exceeding those of any commercially available device. Recent improvments in the design have resulted in significantly higher reverse isolation, a four-fold increase in bandwidth and improve reliability. These devices are very useful in RF and IF signal conditioners, instrumentation, and signal generation and distribution equipment. These Iso-Amps should find wide application in future DSN and R&D RF systems.

Stevens, G. L.↗

NASA NTRS1984

Thermal considerations in the use of solid state power amplifiers on the GOES spacecraft

The use of solid state power amplifiers (SSPA) in satellites has been quite prevalent in several frequency bands. This trend is evidenced by the use of SSPAs at Hughes in the UHF band (Leasat/Syncom IV), S band (GOES), C band (Telstar), and SHF band. The junction temperature of the transistor is the driving requirement which determines the lifetime of the transistor, SSPA, and the payload. This temperature is determined by the transistor characteristics, use of the device, and mounting temperature of the SSPA. The temperature of the spacecraft in the area of the SSPA can be controlled by active or passive means. The various factors and interrelationships used to calculate and control the temperatures of SSPAs are described. The thermal design and calculation of junction temperatures are exemplified with the Geostationary Operational Environmental Satellite spacecraft.

Mallette, L.↗

NASA NTRS1986

Molecular-Beam Chopper and Four-Channel Amplifier

Molecular-beam chopper phase controller and timing interface is subsystem of four-stage, differentially pumped, modulated molecular-beam/mass spectrometer. Subsystem maintains accurate phase control and timing for repetitive signal averaging over several hours of operation. Chopper phase controller/ timing interface and four-channel programable time-multiplexed amplifier provide substantial improvements in attainable signal-to-noise ratio, detection limit, and accuracy of molecular-beam/mass-spectrometer system.

Adams, B. R.↗

NASA NTRS1986

Electrometer Amplifier With Overload Protection

Circuit features low noise, input offset, and high linearity. Input preamplifier includes input-overload protection and nulling circuit to subtract dc offset from output. Prototype dc amplifier designed for use with ion detector has features desirable in general laboratory and field instrumentation.

Woeller, F. H.↗

NASA NTRS1986

Linearized traveling wave amplifier with hard limiter characteristics

A dynamic velocity taper is provided for a traveling wave tube with increased linearity to avoid intermodulation of signals being amplified. In a traveling wave tube, the slow wave structure is a helix including a sever. A dynamic velocity taper is provided by gradually reducing the spacing between the repeating elements of the slow wave structure which are the windings of the helix. The reduction which takes place coincides with the ouput point of helix. The spacing between the repeating elements of the slow wave structure is ideally at an exponential rate because the curve increases the point of maximum efficiency and power, at an exponential rate. A coupled cavity traveling wave tube having cavities is shown. The space between apertured discs is gradually reduced from 0.1% to 5% at an exponential rate. Output power (or efficiency) versus input power for a commercial tube is shown.

Kosmahl, H. G.↗

NASA NTRS1985

Nonlinear forcing of planetary scale waves by amplifying unstable baroclinic eddies generated in the troposphere

The present investigation is mainly concerned with isolating the effects of wave-wave coupling on the growth of planetary-scale baroclinic modes of zonal wavenumber 1-3. It is shown that a global distribution of amplifying intermediate-scale baroclinic modes can cause rapid growth of planetary-scale modes. The growth rates of the planetary modes are found to be comparable to the growth rates of the most unstable baroclinic modes during the first 5-10 days. Thereafter the planetary waves continue to grow (albeit at a slower rate and not necessarily monotonically), and do not exhibit a decay phase as pronounced as that which is characteristic of the intermediate-scale modes.

Young, R. E.↗

NASA NTRS1985

HEMT 60 GHz amplifier

A high electron mobility transistor (HEMT) amplifier has been fabricated which exhibits 7.5 dB gain at 61 GHz. This result was obtained with a quarter-micrometre gate-length depletion-mode HEMT. Reduction of source-gate resistance and gate length are primarily responsible for this performance. The letter describes the materials and device processing technology developed for fabricating these devices.

Berenz, J.↗

NASA NTRS1986

Analysis of the harmonic gyrotron traveling wave amplifier

A single nonlinear differential equation is derived for describing the spatial evolution of the wave field in a gyrotron amplifier on the cylindrical guide geometry. The equation is then used to determine the efficiencies and the optimized interaction lengths for gyrotron operated with TE sub N1 modes at the N-th cyclotron harmonic. The equation offers a significant advantage in simplifying numerical work in comparison with the brute force particle simulation approach. The efficiencies of the harmonic operations by using a hollow beam decrease quickly with increasing harmonic number, but are enhanced by using an axis-encircling beam instead.

Kuo, S. P.↗

NASA NTRS1987

Oscillator or Amplifier With Wide Frequency Range

Inductive and capacitive effects synthesized with feedback circuits. Oscillator/amplifier resistively tunable over wide frequency range. Feedback circuits containing operational amplifiers, resistors, and capacitors synthesize electrical effects of inductance and capacitance in parallel between input terminals. Synthetic inductance and capacitance, and, therefore, resonant frequency of input admittance, adjusted by changing potentiometer setting.

Kleinberg, L.↗

NASA NTRS1986

Progress in the development of integrating JFET amplifiers

A new approach to infrared detector readout has appeared with the development of integrating JFET amplifiers. This brief progress report includes results on the operation of commercially available devices at a temperature of 40 K, on their sensitivity and on an effort to develop a new JFET with properties optimized for cryogenic applications. Even with presently available devices it will be shown that for applications such as the Space Infrared Telescope Facility (SIRTF), the most strigent sensitivity requirements of noise currents as low as 1 electron/sec in less than 100 seconds of integration can be met.

Low, F. J.↗

NASA NTRS1987

Wind velocity measurement accuracy with highly stable 12 mJ/pulse high repetition rate CO2 laser master oscillator power amplifier

A coherent CO2 lidar operating in a master oscillator power amplifier configuration (MOPA) is described for both ground-based and airborne operation. Representative data taken from measurements against stationary targets in both the ground-based and airborne configurations are shown for the evaluation of the frequency stability of the system. Examples of data are also given which show the results of anomalous system operation. Overall results demonstrate that velocity measurements can be performed consistently to an accuracy of + or - 0.5 m/s and in some cases + or - 0.1 m/s.

Bilbro, James W.↗