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Optical Profilometers Using Adaptive Signal Processing

Sizes would be reduced, leading to development of hand-held profilometers. A method of adaptive signal processing has been proposed as the basis of a new generation of interferometric optical profilometers for measuring surfaces. Many current optical surface-measuring profilometers utilize white-light-interferometry and, because of optical and mechanical components essential to their operation, are comparable in size to desktop computers. In contrast, the proposed profilometers would be portable, hand-held units. Sizes could be thus reduced because the adaptive-signal-processing method would make it possible to substitute lower-power coherent light sources (e.g., laser diodes) for white light sources and would eliminate the need for most of the optical components of current white-light profilometers. Furthermore, whereas the height scanning ranges of current surface-measuring profilometers are of the order of millimeters, the adaptive-signal-processing method would make it possible to attain scanning ranges of the order of decimeters in the proposed profilometers.

Posted in: Briefs, Electronics & Computers

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T-Shaped Emitter Metal Structures for HBTs

Fabrication yields are increased. Metal emitter structures in a class of developmental InP-based high-speed heterojunction bipolar transistors (HBTs) have been redesigned to have Tshaped cross sections. More precisely, the modified cross sections can be characterized as having highly stylized T-shapes that are modified versions of prior trapezoidal shapes (see figure). T- cross- section metal features have been widely used in Schottky diodes and high electron- mobility transistors, but not in HBTs. As explained below, the purpose served by the present T- cross-sectional shapes is to increase fabrication yields beyond those achievable with the prior cross-sectional shapes.

Posted in: Briefs, TSP, Electronics & Computers

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Advanced Ka-Band Transceiver With Monopulse Tracking

This system would offer advantages over a conventional TWTA-based system. A proposed Ka-band transmitting/ receiving system would embody a unique combination of established and semi-proven design features. Although this system is intended primarily for telecommunication use aboard a spacecraft, its design could be adapted to terrestrial military and commercial radar systems. Systems like this one could be especially suitable as replacements for prior systems in which traveling-wave-tube amplifiers (TWTAs) are used in the final transmitter stages.

Posted in: Briefs, TSP, Electronics & Computers

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Improved Photon-Emission-Microscope System

An advanced photon-emission microscope is combined with the latest image-processing software. An improved photon-emission-microscope (PEM) instrumentation system has been developed for use in diagnosing failure conditions in semiconductor devices, including complex integrated circuits. This system is designed primarily to image areas that emit photons, at wavelengths from 400 to 1,100 nm, associated with device failures caused by leakage of electric current through SiO2 and other dielectric materials used in multilayer semiconductor structures. In addition, the system is sensitive enough to image areas that emit photons during normal operation. This system supplants a prior PEM system based on a photon-intensified, gated, charge-coupled-device (CCD) camera.

Posted in: Briefs, TSP, Electronics & Computers

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Repairing Chipped Silicide Coatings on Refractory Metal Substrates

Two methods have been demonstrated to be feasible. The space shuttle orbiter’s reaction control system (RCS) is a series of small thrusters that use hypergolic fuels to orient the orbiter in space. The RCS thrusters are constructed from a special niobium-based alloy — the C-103. This alloy retains excellent mechanical properties from cryogenic temperature all the way up to 2,500 °F (1,370 °C). Despite its excellent, high-temperature properties, C-103 is susceptible to rapid oxidation at elevated temperatures. Were the naked C-103 alloy exposed to the operational thruster environment, it would rapidly oxidize, at least losing all of its structural integrity, or, at worst, rapidly “burning.” Either failure would be catastrophic. To prevent this rapid oxidation during thruster firing, the RCS thrusters are coated with a silicide-based protective coating — the R512a. Over time, this protective coating becomes weathered and begins to develop chips. Launch Commit Criteria limit the diameter and depth of an acceptable pit; otherwise, the thruster must be removed from the orbiter — a very costly, time-consuming procedure. The authors have developed two methods to repair damaged R512a coatings on C-103.

Posted in: Briefs, TSP, Manufacturing & Prototyping

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Simplified Fabrication of Helical Copper Antennas

From concept to working prototype takes just a few hours. A simplified technique has been devised for fabricating helical antennas for use in experiments on radio-frequency generation and acceleration of plasmas. These antennas are typically made of copper (for electrical conductivity) and must have a specific helical shape and precise diameter.

Posted in: Briefs, TSP, Manufacturing & Prototyping

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Waveguide Power-Amplifier Module for 80 to 150 GHz

The amplifier can now be connected to other equipment more easily. A waveguide power-amplifier module capable of operating over the frequency range from 80 to 150 GHz has been constructed. The module comprises a previously reported power amplifier packaged in a waveguide housing that is compatible with WR-8 waveguides. (WR-8 is a standard waveguide size for the nominal frequency range from 90 to 140 GHz.) Because the amplifier in its unpackaged form was a single, fragile InP chip, it was necessary to use special probes to make electrical connections between the amplifier and test equipment in order to measure the power gain and other aspects of amplifier performance. In contrast, the waveguide poweramplifier module is robust and can be bolted to test equipment and to other electronic circuits with which the amplifier must be connected for normal operation. The amplifier in its unpackaged form was reported in “Power Amplifier With 9 to 13 dB of Gain from 65 to 146 GHz” (NPO-20880), NASA Tech Briefs, Vol. 25, No. 1 (January 2001), page 44.

Posted in: Briefs, TSP, Semiconductors & ICs

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