Search NASA⌕ Search

SEARCH · Search NASA

Results for “GHz”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

High-power generation in IMPATT devices in the 100-200-GHz range

A silicon double-drift IMPATT diode with high uniform doping levels was simulated. Simulation results show that it is possible for silicon IMPATT diodes to generate extremely high pulsed output power for frequencies above 100 GHz under high current-density operation. The highest output power matched to a 1-ohm load resistance obtained at 150 GHz is 37.7 W, with a dc current density of 200 kA/sq cm, although the calculated power conversion efficiency is low. It is also shown that the low-power conversion efficiency limits the diode's continuous wave power operation.

Chen, Chien-Chung↗
NASA NTRS1991

Submicron gate InP power MISFET's with improved output power density at 18 and 20 GHz

The microwave characteristics are presented at 18 and 20 GHz of submicron gate indium phosphide (InP) metal-insulator-semiconductor field-effect transistors (MISFETs) for high output power density applications. InP power MISFET's were fabricated and the output power density was investigated as a function of drain-source spacing. The best output power density and gain were obtained for drain-source spacing of 3 micron. The output power density is 2.7 times greater than was previously measured for InP MISFET's at 18 and 20 GHz, and the power-added efficiency also increased.

Biedenbender, Michael D.↗
NASA NTRS1991

On the use of passive microwaves at 37 GHz

Recently a number of studies have been presented on the use of the 37 GHz channels of the Scanning Multichannel Microwave Radiometer (SMMR) on board the Nimbus 7 satellite, and on the synergisms between the SNMMR and the AVHRR (Advanced Very High Resolution Radiometer). The approaches are interesting but raise a number of questions on the validity of the interpretation of the results. A study to analyze the Microwave Polarization Difference Temperature (MPDT) in terms of sensitivity to surface and atmospheric parameters is presented. For this a radiative transfer model is used so as to depict the shortcomings of this index. Another approach, using lower frequencies is described and compared to the 37 GHz MPDT.

Kerr, Yann H.↗
NASA NTRS1990

Future mobile satellite communication concepts at 20/30 GHz

The outline of a design of a system using ultra small earth stations (picoterminals) for data traffic at 20/30 GHz is discussed. The picoterminals would be battery powered, have an RF transmitter power of 0.5 W, use a 10 cm square patch antenna, and have a receiver G/T of about -8 dB/K. Spread spectrum modulation would be required (due to interference consideration) to allow a telex type data link (less than 200 bit/s data rate) from the picoterminal to the hub station of the network and about 40 kbit/s on the outbound patch. An Olympus type transponder at 20/30 GHz could maintain several thousand simultaneous picoterminal circuits. The possibility of demonstrating a picoterminal network with voice traffic using Olympus is discussed together with fully mobile systems based on this concept.

Barton, S. K.↗
NASA NTRS1991

Retrieval of total precipitable water over high latitude regions using radiometric measurements near 90 and 183 GHz

The functional dependence of brightness temperature, at frequencies near 183 and 90 GHz, on total precipitable water in the range less than 0.5 g/cm is examined by means of radiative transfer calculations of a number of observed temperature and relative humidity profiles over both ocean and land surfaces. A wide range of land and sea surface reflectivities is assumed in the calculations. Both sensitivity and precision of total precipitable water estimates are derived from these calculations. The estimated values in the Southern Hemisphere showed a gradual decrease toward the polar region, as expected. Radiative transfer calculations were made with a number of radiosonde data sets for a wide range of surface reflectivity and temperature. The calculated results are used to estimate total precipitable water from the airborne radiometric measurements over Alaska. Reflectivities at both 92 and 193 GHz are found to be mostly in the range of 0.2-0.4. High reflectivity is attributed to scattering by the snow particles on the ground.

Wang, J. R.↗
NASA NTRS1992

Effect of an applied magnetic field on the performance of a SIS receiver near 300 GHz

A superconductor-insulator-superconductor (SIS) receiver has been successfully constructed and tested for operation at 265 - 280 GHz using 1 micron/sq area Nb-AlO(x)-Nb tunnel junctions fabricated at Stony Brook. The best performance to date is a double sideband (DSB) receiver noise temperature of 129 K at 278 GHz. It is found that suppression of the Josephson pair currents with a magnetic field is essential for good performance and a stable dc bias point. Fields as high as 280 gauss have been used with no degradation of mixing performance. The improvement in the intermediate frequency output stability with progressively increasing magnetic fields is illustrated.

Mallison, W. H.↗
NASA NTRS1992

A low-noise 492 GHz SIS waveguide receiver

The design and performance are described of an SIS waveguide receiver which provides low noise performance from 375 to 510 GHz. At its design frequency of 492 GHz the receiver has a double-sideband noise temperature of about 172 K. By using embedded magnetic-field concentrators Josephson pair tunneling is effectively suppressed. Techniques for improving receiver performance are discussed.

Walker, C. K.↗
NASA NTRS1992

Enhancement of Thomson scatter by charged aerosols in the polar mesosphere - Measurements with a 1.29-GHz radar

The summer polar mesosphere was observed with the Sondrestrom 1.29-GHz radar with a new high-resolution data acquisition mode. On one occasion, a spatially narrow enhancement in the backscattered power was seen near an altitude of 88 km. Possible explanations are discussed and it is proposed that this layer may be the first example of polar mesosphere summer echoes detected above 1 GHz. Specifically, suggested that these echoes are enhanced Thomson scatter from a layer of charged aerosols, and speculate on the size and charge state.

Cho, John Y. N.↗
NASA NTRS1992

Theoretical and experimental development of 10 and 35 GHz rectennas

A 35 GHz rectenna has been developed with 39 percent conversion efficiency. The rectenna uses a microstrip dipole antenna and a commercially available mixer diode. Over 60 percent conversion efficiency was demonstrated using this diode at 10 GHz. A theoretical analysis was derived to predict the performance of the rectenna. The analysis is a useful tool for device and circuit design. The theoretical and experimental results should have many applications in microwave power transmission and detection.

Yoo, Tae-Whan↗
NASA NTRS1992

Nb/Al-Al2O3/Nb junctions with inductive tuning elements for a very low noise 205-250 GHz heterodyne receiver

The superconductor-insulator-superconductor (SIS) junction is the most sensitive nonlinear element for millimeter-wave heterodyne detection. An Nb/Al-Al203/Nb junction fabrication process has been developed which allows the use of planar tuning circuits integrated with the junctions. These tuning elements permit the use of junctions with relatively large areas and small current densities with excellent results. Recent measurements have yielded a double sideband receiver noise temperature less than 50 K from 205 to 240 GHz and 44 K at 230 GHz. This Nb/Al-Al203/Nb trilayer technology is also being extended to the fabrication of sub-square-micron area planar junctions for submillimeter-wavelengths.

Lichtenberger, Arthur W.↗
NASA NTRS1992

A 380 GHz SIS receiver using Nb/AlO(x)/Nb junctions for a radioastronomical balloon-borne experiment: PRONAOS

The superheterodyne detection technique used for the spectrometer instrument of the PRONAOS project will provide a very high spectral resolution (delta nu/nu = 10(exp -6)). The most critical components are those located at the front-end of the receiver: their contribution dominates the total noise of the receiver. Therefore, it is important to perform accurate studies for specific components, such as mixers and multipliers working in the submillimeter wave range. Difficulties in generating enough local oscillator (LO) power at high frequencies make SIS mixers very desirable for operation above 300 GHz. The low LO power requirements and the low noise temperature of these mixers are the primary reason for building an SIS receiver. This paper reports the successful fabrication of small (less than or equal to 1 sq micron) Nb/Al-O(x)/Nb junctions and arrays with excellent I-V characteristics and very good reliability, resulting in a low noise receiver performance measured in the 368/380 GHz frequency range.

Febvre, P.↗
NASA NTRS1992

A low-noise 492 GHz SIS waveguide receiver

We discuss the design and performance of an SIS waveguide receiver which provides low noise performance from 375 to 510 GHz. At its design frequency of 492 GHz, the receiver has a double sideband noise temperature of approx. 172 K. By using embedded magnetic field concentrators, we are able to effectively suppress Josephson pair tunneling. Techniques for improving receiver performance are discussed.

Walker, C. K.↗
NASA NTRS1992

Progress in integrated-circuit horn antennas for receiver applications. Part 2: A 90 GHz quasi-integrated horn antenna receiver

A receiver belonging to the family of integrated planar receivers has been developed at 90 GHz. It consists of a planar Schottky-diode placed at the feed of a dipole-probe suspended inside an integrated horn antenna. The measured planar mixer single-sideband conversion loss at 91.2 GHz (LO) with a 200 MHz IF frequency is 8.3dB plus or minus 0.3dB. The low cost of fabrication and simplicity of this design makes it ideal for millimeter and submillimeter-wave receivers.

Ali-Ahmad, Walid Y.↗
NASA NTRS1993

Measurements of the cosmic microwave background temperature at 1.47 GHz

We have used a radio-frequency-gain total-power radiometer to measure the intensity of the cosmic microwave background (CMB) at a frequency of 1.47 GHz (20.4 cm wavelength) from White Mountain, California in 1988 September and from the South Pole in 1989 December. The CMB thermodynamic temperature, T(CMB), is 2.27 +/- 0.25 K (68 percent confidence limit) measured from White Mountain and 2.26 +/- 0.20 K from the South Pole site. The combined result is 2.26 +/- 0.19 K. The correction for Galactic emission has been derived from scaled low-frequency maps and constitutes the main source of error. The atmospheric signal is extrapolated from our zenith scan measurements at higher frequencies. These results are consistent with our previous measurement at 1.41 GHz and about 2.5 sigma from the 2.74 +/- 0.01 K global average CMB temperature.

Bensadoun, M.↗
NASA NTRS1993

A 250 GHz planar low noise Schottky receiver

A planar quasi-optical Schottky receiver based on the quasi-integrated horn antenna has been developed and tested over the 230-280 GHz bandwidth. The receiver consists of a planar GaAs Schottky diode placed at the feed of a dipole-probe suspended on a thin dielectric membrane in an etched-pyramidal horn cavity. The diode has a 1.21 micron anode diameter and a low parasitic capacitance due to the use of an etched surface channel. The antenna-mixer results in a measured DSB conversion loss and noise temperature at 258 GHz of 7.2 dB +/- 0.5 dB and 1310 K +/- 70 K, respectively, at room temperature. The design is compatible with SIS mixers, and the low cost of fabrication and simplicity makes it ideal for submillimeter-wave imaging arrays requiring a 10-20 percent bandwidth.

Ali-Ahmad, Walid Y.↗
NASA NTRS1993

A 10-GHz amplifier using an epitaxial lift-off pseudomorphic HEMT device

A process to integrate epitaxial lift-off devices and microstrip circuits has been demonstrated using a pseudomorphic HEMT on an alumina substrate. The circuit was a 10 GHz amplifier with the interconnection between the device and the microstrip circuit being made with photolithographically patterned metal. The measured and modeled response correlated extremely well with a maximum gain of 6.8 dB and a return loss of -14 dB at 10.4 GHz.

Young, Paul G.↗
NASA NTRS1994

Monolithic Three-Stage 32-GHz Power Amplifier

Monolithic three-stage 32-GHz power amplifier compact and offers state-of-the-art performance. Operates at frequencies around 32 GHz. Designed for use aboard communication satellite and is also suitable for terrestrial applications in which moderate power and high efficiency needed.

Saunier, Paul↗
NASA NTRS1993

Insertion loss and noise-temperature contribution of high-temperature superconducting bandpass filters centered at 2.3 and 8.45 GHz

Two superconducting Tl-Ca-Cu-Ba-O bandpass filters were fabricated for JPL by Superconductor Technologies Incorporated, Santa Barbara, California. The filters were designed to operate at 2.3 GHz (S-band) with a 0.5-dB bandwidth of 60 MHz and at 8.45 GHz (X-band) with a 0.5-dB bandwidth of 150 MHz. The structure selected for both filters incorporates half-wavelength thin-film resonators in a stripline configuration. The S-band filter uses an edge-coupled interdigital design and the X-band filter uses an end-coupled design. The insertion loss and the noise-temperature contribution were measured at 12 K for both filters.

Prater, J. L.↗