Tech Briefs

Design Study of a C-Band Crestatron

Total Efficiencies of the designed crestatron and a comparable complex-gain-optimized TWT as functions of frequency were predicted by computational simulation.A design study of a crestatron that would operate in the frequency range from 3 to 6 GHz (which overlaps with the C band) has been performed. The basic crestatron concept was developed during the 1950s. The present interest in crestatrons is spurred by the prospect of realizing compact, efficient, high-power, high-gain microwave transmitters in which crestatrons would be combined with low-noise, solid-state drivers into microwave power modules (MPMs). Such transmitters and MPMs could be attractive for applications in which there are severe constraints on volume and weight.

Posted in: Briefs, Electronics & Computers

Protection Schemes for Advanced Shipboard Electrical Systems

A research program has made progress toward the development of schemes for protection against faults in next-generation DC zonal shipboard electrical systems (DC SESs) and for configuration management in these systems to enable surviving parts of the systems to continue to distribute electric power to critical loads. Computational simulations of a representative prototype DC SES have shown that these schemes could afford protection at a system level (in contradistinction to a local level), thereby imparting, to the DC SES, an intended capability for self-healing.

Posted in: Briefs, Electronics & Computers, Architecture, Electrical systems, Reliability, Marine vehicles and equipment

DC Power Converter for 200°C Containing SiC Transistors

A DC-to-DC power converter, nominally rated for a power of 180 W, an input potential of 28 V, an output potential of 270 V, and a maximum operating temperature of 200°C has been designed, built, and tested. This power converter serves as a prototype for further development of power converters required to be capable of operating in high-temperature environments in diverse settings, including automobile, aircraft, and spacecraft engines, and oil and gas wells.

Posted in: Briefs, Electronics & Computers, Capacitors, Transistors, Product development

Simulation of a Flywheel Energy-Storage System

A computational model has been developed to simulate the operation of a laboratory flywheel energy-storage system that is a subsystem of the Flywheel Attitude Control, Energy Transmission, and Storage (FACETS) system located at Kirtland Air Force Base in New Mexico. The FACETS, which includes three advanced flywheel energy-storage units and an apparatus denoted the Agile Multi- Purpose Satellite Simulator (AMPSS), is used to demonstrate conceptual spacecraft operations involving integral combinations of attitude-control maneuvers and energy-storage operations. The flywheel units include high-hoop-strength carbon composite rotors that turn on magnetic bearings. The flywheels have a maximum rated angular speed of 40,000 rpm, making it possible to store as much a 1 kW·hr of energy in each unit. An air bearing supports the entire AMPSS test article allowing three-axis rotation with minimal damping. In addition to the flywheel units, the system includes DC-to-DC power converters and a three-phase rectifier.

Posted in: Briefs, Information Technology, Computer simulation, Energy storage systems, Flywheels, Spacecraft

A Comparison of SiC-Based Devices for Use as Power Switches

A report details a survey of the state of technological development and commercial availability of SiC-based electronic devices that has been performed to evaluate the suitability of such devices as power switches in present and future applications in which high reliability and/or capability for high-temperature operation are or will be required. Examples of such applications include high-temperature motor drives, switch modules, and DC-to- DC power converters, and DC-to-AC power inverters. The survey consisted primarily of a comparative study of the relative advantages and disadvantages of SiCbased vertical-junction field-effect transistors (VJFETs) and SiC-based metal oxide/semiconductor field-effect transistors (MOSFETs). Other devices, including conventional Si-based MOSFETs and SiCbased bipolar junction transistors (BJTs) were considered, but only in passing, because it was assumed, at the beginning of the study, that the superiority of SiCbased VJFETs and SiC-based MOSFETs over other devices for power-switching applications had already been established.

Posted in: Briefs, Electronics & Computers, Switches, Transistors, Technical reference

Advances in Organic-Based Electronic Devices

A program of research has addressed multiple topics in the field of electronic and optoelectronic devices based on polymers and other organic substances, with special attention to memory devices and solar photovoltaic cells. The accomplishments of this research are summarized as follows:

Posted in: Briefs, Electronics & Computers, Electronic equipment, Research and development, Polymers

AlxInyGa1-x-yN Ultraviolet Light-Emitting Triodes

Light-emitting triodes (LETs) have been the focus of a program of research with a goal of increasing the quantum efficiencies of ultraviolet-lightemitting devices implemented in the AlxInyGa1-x-yN (0 ≤ x+y ≤ 1) material system. Heretofore, AlxInyGa1-x-yN-based light-emitting diodes (LEDs) have exhibited "efficiency droop" — decreasing quantum efficiency with increasing injection current. LETs can be used as means of studying and overcoming efficiency droop.

Posted in: Briefs, Electronics & Computers, Light emitting diodes (LEDs), Performance upgrades