Microwave applications of superconducting electronics

Since the discovery of the high-transition-temperature (Tc) superconductive oxide materials, there has been very substantial progress in the understanding and control of these materials in thin film form. Although the initial projections of rapid and pervasive applicability of the high Tc materials in the market place have not been met, the sensibly reproducible synthesis of high-quality thin films on substrate wafers of up to 50.8 mm diameter has generated a wide variety of preprototype microwave components, some of which are already edging into the market place. The current state of the microwave properties of low Tc and high Tc thin film materials will be reviewed and selected examples of preprototype devices drawn from low Tc and high Tc technology will be described. These components include transmission lines, filters, mixers and amplifiers for microwave signals, and information processing circuits for wideband analogue and high-speed digital waveforms. Speculation is offered on the long-term applications of superconducting electronics. Despite the substantial progress in materials, much more is required. The technology which must be developed in order to deliver practical superconducting circuits will be highlighted.