Superconducting miniature microstrip resonators, operating at X band, have been constructed using vacuum-deposited lead on low-loss sintered alumina substrate. Unloaded Q's as high as 200 000 and 500 000 have been measured at 14.3 GHz at 4.2 and 1.8 K, respectively.

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This paper describes the develonment of an efficient, compact ampllfler with a gain of 20 dB and an output of 2 W in J Band. An overall efflciency of greater than 10% was achieved using GaAs Read IMPATT diodes with Schottky barrier contacts in a three stage reflection amplifier. The severe gain compression that usually occurs with IMPATT amplifiers can present a considerable problem in that owing to the presence of a small-signal oscillation, there will be an output signal in the absence of an input signal. It is shown that by operating the IMPATT diode at a constant voltage and by appropriate selection of the Schottky barrier metal, the diode bias current will increase with increasing rf signal

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