Abstract: A multimedia communication system having a plurality of mobile, fixed location, and portable terrestrial communication terminals. The system links terrestrial communication terminals together through a network of non-geostationary satellites. The satellites communicate with a communication protocol similar to terrestrial communication protocols to reduce protocol conversion. The source and destination addressing uses static terrestrial cells for the uplink and the downlink. The terminal data stream is segmented into communication packets at the terrestrial gateway based on the uplink satellite's determination of system parameters. A control satellite dynamically balances up-links and down-links in the terrestrial areas with over-lapping satellite coverage.

Abstract: A method and apparatus measure the accuracy of and optically calibrate a scan mirror. Both the method and apparatus may operate over a wide range of environmental conditions. The environmental conditions may include variations in pressure from a vacuum to several atmospheres. Similarly, large variations in temperature may be accommodated. The apparatus includes a laser source, a plurality of facet mirrors and a detector. The laser source projects a beam onto a reflective surface of a rotatable scan mirror, which directs the beam to each of the plurality of facet mirrors. Each facet mirror is positioned at a known angle. Each facet mirror in turn reflects the beam from the reflective surface of the scan mirror substantially back onto itself (autocollimation). The angle detector then receives the reflected beam and measures a value related to a return angle of the beam.

Abstract: A reflector for an antenna includes a plurality of reflector elements, each having a transmission line and an aperture at a distal end of the transmission line. Each transmission line having a length which varies in accordance with the position of each aperture relative to the antenna. The varying length of transmission creates a time delay that phases re-radiated waves.

Abstract: The present invention provides a switching power supply which operates at a high efficiency over a wide operating load range. When the output power is below a first power level, the first power converter stage operates in a hard-switching mode and the second power converter stage is off. When the output power is greater than the first power level and less than a second power level, the first power converter stage operates in a soft-switching mode and the second power converter stage is off. When an output power is greater than the second power level, the first power converter stage operates in a soft-switching mode and the second power converter stage operates in a soft-switching mode.