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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.

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At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Flip-flop resolving time test circuit

Integrated circuit (IC) flip-flop resolving time parameters are measured by wafer probing, without need of dicing or bonding, throught the incorporation of test structures on an IC together with the flip-flop to be measured. Several delays that are fabricated as part of the test circuit, including a voltage-controlled delay with a resolution of a few picosecs, are calibrated as part of the test procedure by integrating them into, and out of, the delay path of a ring oscillator. Each of the delay values is calculated by subtracting the period of the ring oscillator with the delay omitted from the period with the delay included. The delay measurement technique is sufficiently general for other applications. The technique is illustrated for the case of the flip-flop parameters of a 5-micron feature size NMOS circuit.

Rosenberger, F.↗
NASA NTRS1990

GaAIAs Traveling-Wave Electro-optical Modulators

Microwave signals modulate optical signals in unit integrable with GaAs and GaAIAs devices. Experimental GaAIAs electro-optical modulators designed and built for operation at wavelength of 0.82 micrometers. Easily integrable with GaAs monolithic microwave integrated circuits. Integrated optical and microwave waveguides in electro-optical materials constitute traveling-wave electro-optical modulator in configuration of Mach-Zehnder interferometer. Because characteristic impedance of waveguide 50 ohms - standard value - no impedance-matching network required.

Bhasin, Kul B.↗
NASA NTRS1994

JTEC Panel report on microelectromechanical systems in Japan

This report summarizes recent activities in the development of microelectromechanical systems (MEMS) in Japan. For the purposes of this study, 'MEMS' means batch-fabricated miniature devices that convert physical parameters to or from electrical signals and that depend on mechanical structures or parameters in important ways for their operation. The report covers advanced materials and process technology; sensors and sensing microstructures; microactuators and actuation mechanisms; sensor-circuit integration and system partitioning; advanced packaging, microassembly, and testing technologies; and MEMS design techniques, applications, and infrastructure. The panel found that Japanese industry is emphasizing approaches to MEMS that are similar to those taken by U.S. industry (i.e., approaches based on silicon integrated-circuit technology); these efforts are comparable in their level of development to those in the United States. However, the ten-year, $250 million, MITI-sponsored program in micromachines emphasizes the miniaturization of more traditional (nonlithographic) machining processes, an area in which there is no comparable U.S. effort. Packaging technology and applications for batch-fabricated MEMS devices is considered a major challenge in both countries. The panel concluded that these and other issues will require global leadership and international cooperation to realize the benefits of MEMS in a timely way.

Wise, Kensall D.↗
NASA NTRS1997

Root-Raised Cosine Filter Implementation That Uses Canonical Signed Digits for High-Speed Digital Filter Applications

NASA Lewis Research Center's Space Communications Division has been investigating high-speed digital filters that can operate at a higher speed than those in current use for a digital modulator and demodulator (modem). Using the Canonical Signed Digits (CSD) number representation for filter coefficients is a very effective way to increase the filter's speed while reducing complexity in the digital filter hardware design. This approach is a good alternative to using an expensive parallel-processing design technique or custom, application-specific integrated circuits. Such integrated circuits may not be suitable for applications that require filter speeds faster than what application-specific integrated circuits digital signal processors can offer for a dedicated channel. When a communication channel is a dedicated, multiplication process--a costly, time-consuming process--it can be greatly simplified by a replacement of the filter coefficients with CSD numbers. A computer code written with the MATLAB software package runs the program and generates CSD-represented filter coefficients that are based on minimizing minimum mean square errors. Also, the Alta Group of Cadence's Signal Processing Workstation is used to simulate and analyze the CSD filter responses. The impulse response of the root-raised cosine filter that is used as a base model is defined. From this filter, a set of coefficients is sampled and stored in a file. For the all coefficients, the optimal CSD number for each coefficient is searched on the basis of the minimum-mean-square-errors criterion. Because the distribution of CSD numbers is not uniform, quantization errors tend to be bigger for coefficients greater than 1/2. To offset errors that occur in a region of coefficients between 1/2 to 1 and to better represent fractions with CSD numbers, an extra nonzero digit is allowed for any coefficients exceeding 1/2. This will greatly improve frequency response as well as intersymbol interference at the receiver. The frequency response of a set of collected CSD-represented filter coefficients was compared with the same filter that was conventionally implemented. Analyses show CSD-implemented filters perform as well as conventional filters. Comparison of eye diagrams and bit-error-rate curves between CSD filters and traditionally implemented filters are almost indistinguishable. However, filter complexity was reduced from almost 3.5 to 1 for CSD filters. Complete computer simulation results are available. In the near future, work will focus on building actual working digital filter hardware in a field programmable gate array (FPGA).

Kim, Heechul↗
NASA NTRS1999

Silica Integrated Optical Circuits Based on Glass Photosensitivity

Integrated optical circuits play a major rule in the new photonics technology both in communication and sensing due to their small size and compatibility with integrated circuits. Currently integrated optical circuits (IOCs) are fabricated using similar manufacturing to those used in the semiconductor industry. In this study we are considering a new technique to fabricate IOCs which does not require layers of photolithography, depositing and etching. This method is based on the photosensitivity of germanosilicate glasses. Waveguides and other IOC devises can be patterned in these glasses by exposing them using UV lasers. This exposure by UV light changes the index of refraction of the germanosilicate glass. This technique enjoys both the simplicity and flexibility of design and fabrication with also the potential of being fast and low cost.

Abushagur, Mustafa A. G.↗
NASA NTRS1990

Fiber optic gyroscope using an eight-component LiNbO3 integrated optic circuit

A LiNbO3 integrated optic circuit (IOC) containing eight optical functions has been successfully incorporated into an interferometric fiber optic gyroscope. The IOC has the minimum configuration optical functions (a phase modulator, a polarizer, and two beam splitters) and Jet Propulsion Laboratory's novel beat detection circuit (a phase modulator, two optical taps, and a beam splitter) which provides a means of directly reading angular position and rotation rate. The optical subsystem consisting of the fiber-pigtailed IOC and a sensing coil of 945 meters of polarization-maintaining fiber has a loss of 18.7dB, which includes 9dB due to the architecture and unpolarized source. A random walk coefficient was measured using an edge-emitting LED as the source.

Minford, W. J.↗
NASA NTRS1985

Accelerators for critical experiments involving single-particle upset in solid-state microcircuits

Charged-particle interactions in microelectronic circuit chips (integrated circuits) present a particularly insidious problem for solid-state electronic systems due to the generation of soft errors or single-particle event upset (SEU) by either cosmic rays or other radiation sources. Particle accelerators are used to provide both light and heavy ions in order to assess the propensity of integrated circuit chips for SEU. Critical aspects of this assessment involve the ability to analytically model SEU for the prediction of error rates in known radiation environments. In order to accurately model SEU, the measurement and prediction of energy deposition in the form of an electron-hole plasma generated along an ion track is of paramount importance. This requires the use of accelerators which allow for ease in both energy control (change of energy) and change of ion species. This and other aspects of ion-beam control and diagnostics (e.g., uniformity and flux) are of critical concern for the experimental verification of theoretical SEU models.

Zoutendyk, J. A.↗
NASA NTRS1983

Advanced 3-V semiconductor technology assessment

Components required for extensions of currently planned space communications systems are discussed for large antennas, crosslink systems, single sideband systems, Aerostat systems, and digital signal processing. Systems using advanced modulation concepts and new concepts in communications satellites are included. The current status and trends in materials technology are examined with emphasis on bulk growth of semi-insulating GaAs and InP, epitaxial growth, and ion implantation. Microwave solid state discrete active devices, multigigabit rate GaAs digital integrated circuits, microwave integrated circuits, and the exploratory development of GaInAs devices, heterojunction devices, and quasi-ballistic devices is considered. Competing technologies such as RF power generation, filter structures, and microwave circuit fabrication are discussed. The fundamental limits of semiconductor devices and problems in implementation are explored.

Nowogrodzki, M.↗
NASA NTRS1971

Catheter transducer and circuit

Simple integrated circuit located at transducer, enables use of single coaxial cable for both input and output connections. Circuit is sensitive to changes in RC time constant, has much improved sensitivity characteristics, and is unaffected by changes in cable capacitance effects.

Harrison, D. R.↗