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NASA NTRS1987

Observation of millimeter-wave oscillations from resonant tunneling diodes and some theoretical considerations of ultimate frequency limits

Recent observations of oscillation frequencies up to 56 GHz in resonant tunneling structures are discussed in relation to calculations by several authors of the ultimate frequency limits of these devices. It is found that calculations relying on the Wentzel-Kramers-Brillouin (WKB) approximation give limits well below the observed oscillation frequencies. Two other techniques for calculating the upper frequency limit were found to give more reasonable results. One method employs the solution of the time-dependent Schroedinger equation obtained by Kundrotas and Dargys (1986); the other uses the energy width of the transmission function for electrons through the double-barrier structure. This last technique is believed to be the most accurate since it is based on general results for the lifetime of any resonant state. It gives frequency limits on the order of 1 THz for two recently fabricated structures. It appears that the primary limitation of the oscillation frequency for double-barrier resonant-tunneling diodes is imposed by intrinsic device circuit parameters and by the transit time of the depletion layer rather than by time delays encountered in the double-barrier region.

Sollner, T. C. L. G.↗

NASA NTRS1988

Millimeter-Wave Radiometer Imager

A 3-mm radiometer system with mechanically scanned antenna built for use on small aircraft or helicopter to produce near-real-time moderate-resolution images of ground. Main advantage of passive imaging sensor able to provide information through clouds, smoke, and dust when visual and infrared (IR) systems unusable. Used also for variety of remote-sensing applications such as measurements of surface moisture, snow cover, vegetation type and extent, mineral type and extent, surface temperature, and thermal inertia. Possible to map fires and volcanic lava flows through obscuring clouds and smoke.

Wilson, W. J.↗

NASA NTRS1988

Millimeter-wave diode-grid phase shifters

Monolithic diode grids have been fabricated on 2-cm square gallium-arsenide wafers with 1600 Schottky-barrier varactor diodes. Shorted diodes are detected with a liquid-crystal technique, and the bad diodes are removed with an ultrasonic probe. A small-aperture reflectometer that uses wavefront division interference was developed to measure the reflection coefficient of the grids. A phase shift of 70 deg with a 7-dB loss was obtained at 93 GHz when the bias on the diode grid was changed from -3 V to 1 V. A simple transmission-line grid model, together with the measured low-frequency parameters for the diodes, was shown to predict the measured performance over the entire capacitive bias range of the diodes, as well as over the complete reactive tuning range provided by a reflector behind the grid, and over a wide range of frequencies from 33 GHz to 141 GHz. This shows that the transmission-line model and the measured low-frequency diode parameters can be used to design an electronic beam-steering array and to predict its performance. An electronic beam-steering array made of a pair of grids using state-of-the-art diodes with 5-ohm series resistances would have a loss of 1.4 dB at 90 GHz.

Lam, Wayne W.↗

NASA NTRS1988

Microwave and millimeter-wave power generation in silicon carbide avalanche devices

Numerical simulations were performed to investigate the typical power-generating capabilities of SiC IMPATT diodes. Using available material parameters, SiC double-drift IMPATT diodes were simulated at 10, 35, 60, and 94 GHz, and the operating characteristics of these devices were compared to those of Si and GaAs devices. Compared to the Si and GaAs IMPATT performances in the pulsed mode, the SiC IMPATT performance was found to be far superior. The performance of SiC devices in the CW mode was also superior to that of GaAs devices, especially at lower frequencies. At a high frequency (94 GHz), the performance of the SiC device was found to be comparable to that of Si devices.

Mehdi, I.↗

NASA NTRS1988

Microwave and millimeter-wave resonant-tunneling devices

Resonant-tunneling devices in microelectronic component form, whose structure is the electron analog of a Fabry-Perot resonator, encompass oscillators, self-oscillating mixers, and harmonic multipliers. The negative differential resistance characteristic of these devices has been obtained at room temperature, and resonant-tunneling transistors capable of operation in the THz-frequency range appear to be feasible. Three-terminal resonant-tunneling device development is in its infancy, as is that of devices for digital applications.

Sollner, T. C. L. Gerhard↗

NASA NTRS1987

Microwave and millimeter-wave resonant tunneling diodes

Several demonstrated resonant tunneling devices including oscillators, mixers, multiplexers, and a variable negative resistance are discussed. Techniques of the millimeter/submillimeter regime are also discussed.

Sollner, T. C. L. Gerhard↗

NASA NTRS1989

External electro-optic probing of millimeter-wave integrated circuits

An external, noncontact electro-optic measurement system, designed to operate at the wafer level with conventional wafer probing equipment and without any special circuit preparation, has been developed. Measurements have demonstrated the system's ability to probe continuous and pulsed signals on microwave integrated circuits on arbitrary substrates with excellent spatial resolution. Experimental measurements on a variety of digital and analog circuits, including a GaAs selectively-doped heterostructure transistor prescaler, an NMOS silicon multiplexer, and a GaAs power amplifier MMIC are reported.

Whitaker, J. F.↗

NASA NTRS1989

Analytical and experimental procedures for determining propagation characteristics of millimeter-wave gallium arsenide microstrip lines

In this report, a thorough analytical procedure is developed for evaluating the frequency-dependent loss characteristics and effective permittivity of microstrip lines. The technique is based on the measured reflection coefficient of microstrip resonator pairs. Experimental data, including quality factor Q, effective relative permittivity, and fringing for 50-omega lines on gallium arsenide (GaAs) from 26.5 to 40.0 GHz are presented. The effects of an imperfect open circuit, coupling losses, and loading of the resonant frequency are considered. A cosine-tapered ridge-guide text fixture is described. It was found to be well suited to the device characterization.

Romanofsky, Robert R.↗

NASA NTRS1989

Microwave and millimeter-wave power generation in silicon carbide (SiC) IMPATT devices

There are two points that should be noted. First, in the thermal resistance calculations it is assumed that the device is operating at 773 K while the results of the room temperature simulations are used. This was done because there is not enough information to correctly predict the material parameters at 773 K. Since, in general, device performance degrades with increasing temperature, the cw results are perhaps a bit optimistic. Second, the electric field in these structures gets extremely high and there might be some possibility of tunneling. This was not incorporated into the simulation. Again, this could result in different device operating conditions.

Mehdi, I.↗

NASA NTRS1989

The tapered slot antenna - A new integrated element for millimeter-wave applications

Tapered slot antennas (TSAs) with a number of potential applications as single elements and focal-plane arrays are discussed. TSAs are fabricated with photolithographic techniques and integrated in either hybrid or MMIC circuits with receiver or transmitter components. They offer considerably narrower beams than other integrated antenna elements and have high aperture efficiency and packing density as array elements. Both the circuit and radiation properties of TSAs are reviewed. Topics covered include: antenna beamwidth, directivity, and gain of single-element TSAs; their beam shape and the effect of different taper shapes; and the input impedance and the effects of using thick dielectrics. These characteristics are also given for TSA arrays, as are the circuit properties of the array elements. Different array structures and their applications are also described.

Yngvesson, K. Sigfrid↗

NASA NTRS1989

W-band six-port network analyzer for two-port characterization of millimeter wave transistors

A W-band (75-100 GHz) six-port junction network analyzer was constructed from commercially available descrete waveguide components and was used for the direct two-port S-parameter measurement of active three-terminal devices. A comparison between the six-port and a down-converter-type frequency extender for a conventional network analyzer revealed the superior performance of the six-port. The application of the six-port to characterize a 0.1-micron gate-length HEMT at W-band is described, and representative results are presented.

Moeller, Karl J.↗

NASA NTRS1989

External electro-optic probing of millimeter-wave integrated circuits

Whitaker, J. F.↗

NASA NTRS1989

A millimeter-wave survey of CO emission in Seyfert galaxies

Emission in the 115 GHz 1-0 line of CO has been detected in 18 Seyfert galaxies in a sample of 43. The CO properties of 29 Seyferts in the Revised Shapley Ames Catalog (RSA) are compared with the CO properties of normal galaxies of the same Hubble type. These RSA type 2 Seyferts have an average ratio of CO-to-blue luminosity that is about twice as large as that of the normal galaxies, but the RSA type 1 Seyferts have normal CO luminosities. The RSA type 2 Seyfert galaxies have an unusually large average ratio of CO luminosity-to-H I mass compared to normal disk galaxies. The RSA type 2 Seyferts have an average far-IR luminosity that is about four times larger than a non-Seyfert comparison sample, while the RSA type 1 Seyferts are not significantly more luminous than the non-Seyferts. The result imply that the two classes of Seyferts are intrinsically different from one another and that one class cannot evolve into another in less than a few million years.

Heckman, T. M.↗

NASA NTRS1990

Millimeter-Wave Quantum-Well Frequency Multipliers

Double-barrier quantum-well GaAs diode achieved 0.61 percent efficiency as frequency tripler when operated at input frequency of 63.7 GHz, nearly one-tenth cutoff frequency of diode. Efficiency increased with drive level up to maximum input power available, 40 mW. Diodes studied for use in local-oscillator chains in microwave radiometers. Potential applications include spectrometers and radar.

Batelaan, Paul D.↗

NASA NTRS1990

Performance and modeling of superconducting ring resonators at millimeter-wave frequencies

Microstrip ring resonators operating at 35 GHz were fabricated from laser ablated YBCO thin films deposited on lanthanum aluminate substrates. They were measured over a range of temperatures and their performance compared to identical resonators made of evaporated gold. Below 60 Kelvin the superconducting strip performed better than the gold, reaching an unloaded Q approximately 1.5 times that of gold at 25 K. A shift in the resonant frequency follows the form predicted by the London equations. The Phenomenological Loss Equivalence Method is applied to the ring resonator and the theoretically calculated Q values are compared to the experimental results.

Bhasin, K. B.↗

NASA NTRS1989

Passive millimeter-wave imaging - A tool for remote sensing

This paper describes a program of airborne radiometric imaging at 90 GHz and 140 GHz. Using high sensitivity (below 1 K) and high angular resolution (0.5-1.0 degree), high quality images have been made. The following measurements are discussed: cloud and fog penetration at 90 GHz, discrimination between agricultural and urban areas, discrimination between different vegetation types, detection of vehicles on roads, detection and classification of airports and airplanes, ship detection and quantitative oil spill sensing. The application of information enhancement techniques with automatic and real time application aspects is also described, and results of applied techniques for contrast and contour enhancement are shown.

Suess, Helmut↗

NASA NTRS1989

Applications of ground-based radiometric observations of millimeter wave radiation

A three-channel transportable radiometer that operates at 20.6, 31.65, and 90.0 GHz has been developed. The design of the radiometer is described and the results of various experimental applications of the radiometer are presented. The experiments include a comparison of brightness temperature measurements at various frequencies with the water vapor absorption models of Waters (1976) and Lieve (1989). Measurements of absorption ratios for cloud attenuation are given and the radiometer measurements are compared with oxygen absorption calculated using the Rasenkranz (1988) model.

Westwater, E. R.↗

NASA NTRS1989

Millimeter-wave sensor image analysis

Images of an airborne, scanning, radiometer operating at a frequency of 98 GHz, have been analyzed. The mm-wave images were obtained in 1985/1986 using the JPL mm-wave imaging sensor. The goal of this study was to enhance the information content of these images and make their interpretation easier for human analysis. In this paper, a visual interpretative approach was used for information extraction from the images. This included application of nonlinear transform techniques for noise reduction and for color, contrast and edge enhancement. Results of the techniques on selected mm-wave images are presented.

Wilson, William J.↗