Special Coverage

Technique Provides Security for Multi-Robot Systems
Bringing New Vision to Laser Material Processing Systems
NASA Tests Lasers’ Ability to Transmit Data from Space
Converting from Hydraulic Cylinders to Electric Actuators
Automating Optimization and Design Tasks Across Disciplines
Vibration Tables Shake Up Aerospace and Car Testing
Supercomputer Cooling System Uses Refrigerant to Replace Water
Computer Chips Calculate and Store in an Integrated Unit
Electron-to-Photon Communication for Quantum Computing

Customizable Digital Receivers for Radar

These receivers are unusually compact and versatile.

Compact, highly customizable digital receivers are being developed for the system described in “Radar Interferometer for Topographic Mapping of Glaciers and Ice Sheets” (NPO-43962), NASA Tech Briefs, Vol. 31, No. 7 (August 2007), page 72. In the original intended application, there is a requirement for 16 such receivers, each dedicated to, and mounted directly on, one antenna element in a 16-element array. The receivers are required to operate in unison, sampling radar returns received by the antenna elements in a digital beam-forming (DBF) mode. The design of these receivers could also be adapted to commercial radar systems. At the time of reporting the information for this article, there were no commercially available digital receivers capable of satisfying all of the operational requirements and compact enough to be mounted directly on the antenna elements.

Posted in: Briefs, Electronics & Computers, Antennas, Cartography, Radar, Weather and climate
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A Data Type for Efficient Representation of Other Data Types

Some obstacles to programming of parallel computers are removed.

A self-organizing, monomorphic data type denoted a sequence has been conceived to address certain concerns (summarized below) that arise in programming parallel computers. [“Sequence” as used here should not be confused with “sequence” as the word is commonly understood or with “sequence” as used elsewhere to denote another, polymorphic data type that is also relevant to computer programming.] A sequence in the present sense can be regarded abstractly as a vector, set, bag, queue, or other construct. A sequence is defined in terms of the behavior of the operators that can be applied to it without any foreknowledge of the underpinnings of its representation or particular implementation.

Posted in: Briefs, Information Sciences, Architecture, Data management
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Lower-Dark-Current, Higher-Blue-Response CMOS Imagers

Semiconductor junctions are relocated away from Si/SiO2 interfaces.

Several improved designs for complementary metal oxide/semiconductor (CMOS) integrated- circuit image detectors have been developed, primarily to reduce dark currents (leakage currents) and secondarily to increase responses to blue light and increase signal- handling capacities, relative to those of prior CMOS imagers. The main conclusion that can be drawn from a study of the causes of dark currents in prior CMOS imagers is that dark currents could be reduced by relocating p/n junctions away from Si/SiO2 interfaces. In addition to reflecting this conclusion, the improved designs include several other features to counteract dark-current mechanisms and enhance performance.

Posted in: Briefs, Semiconductors & ICs, Imaging and visualization, Integrated circuits, Semiconductor devices, Performance upgrades
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Broadband Microstrip-to-Coplanar Strip Double-Y Balun

This balun is compact, broadband, and can be fabricated easily.

A new version of the double-Y balun, transitioning from an unbalanced microstrip to a balanced coplanar strip (CPS) line, has been designed to feed a complementary spiral antenna with an input impedance of 100 Ω. Various versions of the double-Y balun have been investigated in previous literature for use with balanced mixers and pulsed antennas. Of the previous versions, the double-Y balun transitioning from a coplanar waveguide (CPW) to CPS was found to exhibit the widest bandwidth of operation while having little metal content (attractive for use in ground-penetrating radar applications). However, the double-Y balun transitioning from a CPW to CPS requires coplanar waveguide bridges at the junction; the inductive behavior of the bridges, in addition to CPW parasitic resonances, degrades the passband performance of the balun.

Posted in: Briefs, TSP, Electronics & Computers, Antennas, Electronic equipment
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A Topographical Lidar System for Terrain-Relative Navigation

Demand for memory is reduced by digitizing over a limited altitude range.

An imaging lidar system is being developed for use in navigation, relative to the local terrain. This technology will potentially be used for future spacecraft landing on the Moon. Systems like this one could also be used on Earth for diverse purposes, including mapping terrain, navigating aircraft with respect to terrain and military applications. The system has been field-tested aboard a helicopter in the Mojave Desert.

Posted in: Briefs, TSP, Electronics & Computers, Cartography, Lidar, Navigation and guidance systems, Terrain, Entry, descent, and landing, Spacecraft
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Electronic Switch Arrays for Managing Microbattery Arrays

Array circuitry is dynamically configured to optimize performance and disconnect defective elements.

Integrated circuits have been invented for managing the charging and discharging of such advanced miniature energy-storage devices as planar arrays of microscopic energy- storage elements [typically, microscopic electrochemical cells (microbatteries) or microcapacitors]. The architecture of these circuits enables implementation of the following energy- management options:

Dynamic configuration of the elements of an array into a series or parallel combination of banks (subarrays), each array comprising a series or parallel combination of elements; Direct addressing of individual banks for charging and/or discharging; and Disconnection of defective elements and corresponding reconfiguration of the rest of the array to utilize the remaining functional elements to obtain the desired voltage and current performance.
Posted in: Briefs, TSP, Electronics & Computers, Downsizing, Architecture, Batteries, Capacitors, Integrated circuits
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Programmable Low-Voltage Circuit Breaker and Tester

This system could also detect some faults before turning on power.

An instrumentation system that would comprise a remotely controllable and programmable low- voltage circuit breaker plus several electric- circuit-testing subsystems has been conceived, originally for use aboard a spacecraft during all phases of operation from pre-launch testing through launch, ascent, orbit, descent, and landing. The system could also be adapted to similar use aboard aircraft. In comparison with remotely controllable circuit breakers heretofore commercially available, this system would be smaller, less massive, and capable of performing more functions, as needed for aerospace applications.

Posted in: Briefs, Electronics & Computers, Architecture, Electrical systems, Switches, Performance upgrades, Fixed-wing aircraft, Spacecraft
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Fabricating Large-Area Sheets of Single-Layer Graphene by CVD

Such sheets are components for high-speed digital and RF electronics for defense and commercial communications.

This innovation consists of a set of methodologies for preparing large area (>1 cm2) domains of single-atomic-layer graphite, also called graphene, in single (two-dimensional) crystal form. To fabricate a single graphene layer using chemical vapor deposition (CVD), the process begins with an atomically flat surface of an appropriate substrate and an appropriate precursor molecule containing carbon atoms attached to substituent atoms or groups. These molecules will be brought into contact with the substrate surface by being flowed over, or sprayed onto, the substrate, under CVD conditions of low pressure and elevated temperature. Upon contact with the surface, the precursor molecules will decompose. The substituent groups detach from the carbon atoms and form gas-phase species, leaving the unfunctionalized carbon atoms attached to the substrate surface. These carbon atoms will diffuse upon this surface and encounter and bond to other carbon atoms. If conditions are chosen carefully, the surface carbon atoms will arrange to form the lowest energy single-layer structure available, which is the graphene lattice that is sought.

Posted in: Briefs, TSP, Manufacturing & Prototyping, Fabrication, Graphite, Nanotechnology
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Heat Transfer Analysis for Optimizing Solar Cell Casting Equipment

Finite element analysis was used to develop a miniature furnace to cast the solar cell wafers.

Solar Power Industries’ (SPI) current annual production capacity for processing polycrystalline silicon feedstock into completed solar cells has grown to 40 megawatts, with plans to increase capacity to 250 megawatts over the next several years. SPI’s solar cell manufacturing process consists of three main steps:

 

Ingot and Wafer Production—High-quality silicon feedstock (containing specific quantities of dopants such as boron in order to alter electrical properties) is melted and solidified inside a directional solidification furnace to cast polycrystalline silicon ingots. The ingots are cut into rectangular blocks with a square cross-section, and then the blocks are sawed into thin multicrystalline wafers. Cell Production — The wafers are etched to remove surface damage caused by sawing. The wafers are then processed in a series of steps to produce photovoltaic cells. Module Assembly — Individual cells are connected by soldering to flat wires. Strings of cells are then joined to parallel connector wires and laminated to produce a solar module.
Posted in: Briefs, Manufacturing & Prototyping, Solar energy, Heat transfer, Suppliers, Casting, Production
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Support for Diagnosis of Custom Computer Hardware

The Coldfire SDN Diagnostics software is a flexible means of exercising, testing, and debugging custom computer hardware. The software is a set of routines that, collectively, serve as a common software interface through which one can gain access to various parts of the hardware under test and/or cause the hardware to perform various functions. The routines can be used to construct tests to exercise, and verify the operation of, various processors and hardware interfaces. More specifically, the software can be used to gain access to memory, to execute timer delays, to configure interrupts, and configure processor cache, floating-point, and direct-memory-access units.

Posted in: Briefs, Electronics & Computers, Computer software and hardware, Diagnostics, Test procedures
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