Engineering topics

Frerking, Margaret A.

Publications and source records attributed to Frerking, Margaret A..

32 records · Page 2

NASA NTRS1992

Quantum-well diode frequency multipliers - Varistor case

Local oscillators for heterodyne receivers at submillimeter wavelengths are typically made using a fundamental source followed by a harmonic frequency multiplier. An investigation of the required circuit embedding conditions for a possible new harmonic generator, the quantum-well resonant-tunneling diode, is summarized. A low-frequency multiplier has been tested that employs the resistive nonlinearity of the device as opposed to the reactive nonlinearity. The results show good agreement between practice and theory.

Batelaan, Paul D.↗

NASA NTRS1992

Anomalous capacitance of quantum well double-barrier diodes

The S-parameters of several different quantum well double barrier diodes have been measured. A technique has been developed for measuring whisker contacted diodes with an HP 8510B automatic network analyzer. Special coaxial mounts using K-connectors were designed to enable measurements up to 20 GHz. The voltage-dependent conductance and capacitance were derived from the measured reflection coefficient of each device. The C/V characteristics were observed to exhibit an anomalous increase at voltages corresponding to the negative differential resistance region (NDR). These are the first reported S-parameter measurements in the negative differential resistance region of quantum well double barrier diodes. A theory is presented that explains, in part, the observed results.

Boric, Olga↗

NASA NTRS1992

Current saturation in submillimeter wave varactors

In semiconductor devices the speed of electrons cannot exceed certain limits. This phenomenon will affect varactor multipliers as well as other high frequency devices where the RF current through the active part of the device is primarily displacement current. Hence, 'saturation' of the varactor output power is expected at some point. This phenomenon is discussed in some detail and shown to severely deteriorate the multiplier performance at higher frequencies. Single barrier varactors should have an advantage over GaAs Schottky diode varactors because they can be fabricated on InAs and stacked in a series array, allowing for lower current densities and higher power handling.

Kollberg, Erik L.↗

NASA NTRS1992

Modeling of planar varactor frequency multiplier devices with blocking barriers

Models for optimization of planar frequency triplers with symmetrical C-V curves are presented. Role and limitation of various blocking barriers (oxide, Mott, heterojunction) are discussed. Devices with undoped drift regions (BIN) have moderate efficiency but a broad range of power operation, whereas devices with doped drift regions (BNN) have high efficiency in a narrow power window. In particular, an upper power limit of the BNN is caused by electron velocity saturation. Implementations in SiO2/Si and AlAs/GaAs and means for increasing the power of BNN structures are considered.

Lieneweg, Udo↗

NASA NTRS1992

A new fabrication technique for back-to-back varactor diodes

A new varactor diode process has been developed in which much of the processing is done from the back of an extremely thin semiconductor wafer laminated to a low-dielectric substrate. Back-to-back BNN diodes were fabricated with this technique; excellent DC and low-frequency capacitance measurements were obtained. Advantages of the new technique relative to other techniques include greatly reduced frontside wafer damage from exposure to process chemicals, improved capability to integrate devices (e.g. for antenna patterns, transmission lines, or wafer-scale grids), and higher line yield. BNN diodes fabricated with this technique exhibit approximately the expected capacitance-voltage characteristics while showing leakage currents under 10 mA at voltages three times that needed to deplete the varactor. This leakage is many orders of magnitude better than comparable Schottky diodes.

Smith, R. Peter↗

NASA NTRS1992

A 200 GHz tripler using single barrier varactor

The GaAs Schottky varactor diode is the nonlinear device most commonly used for submillimeter wave harmonic generation. Output power adequate to serve as a local oscillator source for SIS tunnel junctions has been demonstrated with whisker-contacted GaAs Schottky varactor multipliers in waveguide mounts up to about 800 GHz. In this paper, we present results for a tripler to 200 GHz using a new multiplier device, the single barrier varactor (SBV). This new varactor has a potential advantages such as stronger nonlinearities or special symmetry, which make it attractive for submillimeter wave frequency multiplication. The performance of a tripler using a SBV over a output frequency range from 186 to 207 GHz has been measured in a crossed waveguide mount. The theoretical performance of the device has been calculated using large signal analysis. A comparison of theoretical and measured results and a discussion of various losses in the mount and the varactor have also been presented.

Choudhury, Debabani↗

NASA NTRS1991

Theoretical performance of novel multipliers at millimeter and submillimeter wavelengths

A theoretical comparison of various low and high order multipliers for 200 GHz and 1 THz has been carried out. Novel diodes including single barrier varactors, barrier-intrinsic-n(+)diodes and high electron mobility varactors are shown to have excellent theoretical performance, comparable or better than the conventional Schottky varactors for single and double diode frequency multipliers at millimeter and submillimeter wavelengths, whereas quantum well diodes, since they suffer from high resistive losses, are shown to be less attractive. In comparison to the conventional Schottky varactor, these new diodes have some potential advantages in their characteristics such as a stronger nonlinearity or a special symmetry. For future optimization some general comments on these advantages as well as other factors affecting multiplication are given.

Tolmunen, Timo J.↗

NASA NTRS1991

Quasi-Optical Millimeter-Wavelength Resonator

Quasi-optical reflection cavity serves as prototype resonator for oscillators at millimeter and submillimeter wavelengths. Exploits diffraction and reflection effects to achieve high Q. Useful mainly at wavelengths too short for conventional waveguide techniques but too long for optical techniques.

Frerking, Margaret A.↗

NASA NTRS1990

Development of components for submillimeter wave heterodyne radiometers at JPL

Components for the key elements of submillimeter wave heterodyne receivers are described. The devices and components are inherently space qualifiable having low power and mass needs and exhibiting robustness. Nb and NbN superconductor insulator superconductor (SIS) tunnel junctions are selected for the nonlinear mixing element because of their robustness. NbN exhibits a large superconducting bandgap, allowing operation in excess of 1500 GHz. Both waveguide mounts, for the lower frequencies and planar antenna mixer mounts for the higher frequency range, are used. Quasi-optical components are used for frequency multiplexing and combining.

Frerking, Margaret A.↗

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 NTRS1989

The abundances of atomic carbon and carbon monoxide compared with visual extinction in the Ophiuchus molecular cloud complex

Emission from the 492 GHz lines of C I have been observed toward six positions in the Ophiuchus molecular cloud complex for which accurate visual extinctions are available. The column density of C I increases with A(V) to greater than 2 x 10 to the 17th/sq cm at 100 mag, the column-averaged fractional abundance reaches a peak of about 2.2 x 10 to the -5th for A(V) in the range 4-11 mag and the column-averaged abundance ratio of C I to CO decreases with A(V) from about 1 at 2 mag to greater that about 0.03 at 100 mag. These results imply that, while C I is not the primary reservoir of gaseous carbon even at cloud edges, its fractional abundance remains high for at least 10 mag into the cloud and may be significant at even greater depths.

Frerking, Margaret A.↗

NASA NTRS1989

Experimental results of a high Q quasioptical reflection cavity

A quasi-optical reflection cavity intended to be used as the resonant load of a submillimeter wavelength oscillator has been designed, constructed, and tested. The resonator consists of three elements in cascade: a high Q, high finesse folded Fabry-Perot resonator, a lower Q, low finesse Fabry-Perot resonator, and a Littrow mounted diffraction grating. The resonator exhibits a Q of 6600 and 2.5 dB of loss at 63 GHz. The design can be scaled to 1 THz, where waveguide structures become impractical, to serve as the resonator for high frequency quantum well resonant tunneling device oscillators.

Lee, Karen A.↗

NASA NTRS1988

A dual-frequency 183/380 GHz receiver for airborne applications

A complete dual-frequency cryogenic heterodyne receiver operating at 183 and 380 GHz is described. The cooled mixers are whisker-contacted GaAs Schottky diodes mounted in reduced-height fundamental-mode waveguide. The local oscillators are Gunn-oscillator-driven multipliers using GaAs varactor diodes as the harmonic generators. Quasi-optical techniques are used extensively for coupling the remote and local oscillator signals into the mixers. The overall system double side-band (DSB) noise temperature is 320 K for the 183-GHz receiver and 650 K for the 380 GHz receiver.

Batelaan, Paul D.↗

NASA NTRS1987

The structure and dynamics of Bok globule B335

Results are reported from mm-wave observations CO isotopes and other molecules in the Bok globule B335 (Lynd L663). The data cover the C-12O, C-13O, C-18O, and H-12CO(+) J = 1 yields of 0 rotational transition. Spectral data were also obtained for the preceding molecules and C-17O, H-13CO(+) and DCO(+). The data were used to calculate quantitative density and mass relationships and distributions, determine the rotational parameters, and characterize the force balance within the cloud for inclusion in a spherically averaged cloud model. A nonspherical cloud model which considers magnetic fields is presented. B335 has a dense core within a moderately dense cylindrically shaped envelope, which in turn is surrounded by a more diffuse elliptical envelope. The object is 250 pc from the earth.

Frerking, Margaret A.↗