Microwave applications of high-temperature superconductors

The major advance in the area of high temperature superconducting microwave devices has been in the incorporation of high performance devices (based on planar transmission line structures or shielded dielectric resonators) into microwave receiver systems with performances equivalent or better than those of conventional systems. These systems include reliable closed-cycle coolers that can allow access to the low temperatures required for efficient operation (<80K). Nonlinear effects at high powers have previously presented a drawback for these novel devices, but superconducting thin film disc resonators, operating in modes with radial current flow (in addition to compact, shielded dielectric resonators), do not suffer from the very high microwave edge current densities present in planar structures, and have demonstrated very encouraging microwave power handling capabilities.