High temperature superconductor circuit components for cryogenic microwave systems

Recent progress in high temperature superconductor (HTS) technology has improved the prospects for a new generation of hybrid microwave systems based on passive HTS circuits and active semiconductor devices operating around 77 K. In this paper a review of the current state of passive HTS microwave circuits is given together with a critical appraisal of the problems facing circuit designers using this technology. The major factors to be resolved include the restrictions imposed by HTS film processing methods, the relatively low power-handling capability of HTS circuits and the rationale for moving to a liquid nitrogen cooled environment. These issues and the competition from other technologies are discussed with potential markets in mind