Bernard D. Geller

Low-loss 360 degrees X-band analog phase shifter

A low-loss reflection-type analog phase shifter circuit is described, and experimental results are presented. The circuit incorporates several design features to produce nearly 360 degrees of phase shift at X-band while achieving an insertion loss of only 4.8 dB with +or-0.5 dB of variation over all phase states. These results improve upon previously reported X-band performance by demonstrating a large phase shift range together with low attenuation and low amplitude variation with phase state.<<ETX>>

A technique for the maintenance of FET power amplifier efficiency under backoff

An operational technique for FET power amplifiers which allows the maintenance of high efficiency as the amplifier is backed off from its rated output power level is described. Using this technique, an experimental single-state 1-W C-band amplifier, capable of 65% power-added efficiency at its rated output power, maintains a minimum efficiency of 55% for a 10-dB output backoff range. Comparable amplifiers operating under conventional Class B or Class A demonstrate efficiencies of about 18% and 4%, respectively. An analytic basis for the technique is given. Experimental results are also presented for a three-stage, 2-W C-band amplifier.<<ETX>>

Miniaturized multistage power amplifiers for the 10.95- to 12.75 GHz communications satellite band

The authors describe the design and performance of three prototype power amplifiers that use a combination of MMICs (monolithic microwave integrated circuits) and quasi-monolithic circuits. These amplifiers are intended for use in a satellite multibeam phased-array antenna. The amplifiers are designed to maximize DC-to-RF conversion efficiency and linearity while satisfying additional requirements for output power and minimum size. The four-stage, 30 dB gain modules deliver an output power of 2 W at 2 dB compression, with an efficiency of 25% and a two-tone, carrier-to-third-order intermodulation distortion level of 16 dB.<<ETX>>

MMIC: a key technology for future communications satellite antennas

The results of ongoing development programs in the area of advanced satellite antenna technology currently being pursued at COMSAT Laboratories, under the sponsorship of the World Systems Division of COMSAT Corporation, are described. These programs are exploiting the promise of monolithic microwave integrated circuits (MMICs) as they apply to active phased arrays. Performance data on two phased-array programs are presented. The first program involves the development of a 64-element array in which MMICs are used to optimize and reconfigure the radiation pattern performance. The array is capable of generating a single beam and accurately synthesizing a specified radiation performance. The second array program, building on knowledge gained in the first program, addresses the problems of generating multiple beams, as well as the effect of power amplifiers on multicarrier performance. MMICs are employed in the beam-forming matrix and in the distributed 2-W solid-state power amplifiers. This design is capable of forming four simultaneous, independently steerable beams while allowing for flexible power sharing among the beams.