Tech Briefs

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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Manufacture of Sparse-Spectrum Optical Microresonators

Multiple units having the same spectral parameters could be produced. An alternative design for dielectric optical microresonators and a relatively simple process to fabricate them have been proposed. The proposed microresonators would exploit the same basic physical phenomena as those of microtorus optical resonators and of the microsphere optical resonators described in several prior NASA Tech Briefs articles. The resonances in such devices are associated with the propagation of electromagnetic waves along circumferential.paths in “whispering-gallery” modes. The main advantage afforded by the proposal is that the design and the fabrication process are expected to be amenable to production of multiple microresonators having reproducible spectral parameters — including, most notably, high values of the resonance quality factor (Q) and reproducible resonance frequencies.

Posted in: Briefs, TSP, Physical Sciences

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Exact Tuning of High-Q Optical Microresonators by Use of UV

Resonance frequencies can be shifted permanently by controlled amounts. In one of several alternative approaches to the design and fabrication of a "whispering-gallery" optical microresonator of high resonance quality (high Q), the index of refraction of the resonator material and, hence, the resonance frequencies (which depend on the index of refraction) are tailored by use of ultraviolet (UV) light. The principles of operation of optical microresonators, and other approaches to the design and fabrication of optical microresonators, have been described in prior NASA Tech Briefs articles, including the two immediately preceding this one.

Posted in: Briefs, TSP, Physical Sciences

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