Chapter 4 - Superconducting Microwave Device Properties and Applications

Abstract

The low microwave losses associated with high-temperature superconducting (HTS) thin films allow implementation of a variety of passive microwave devices with performance superior to similar components made with conventional, room-temperature materials. These HTS devices must, operate at cryogenic temperatures, typically 77 K, which imposes severe requirements on packaging in terms of size, weight, and power consumption, perhaps limiting the range of applications for this technology. In addition, developments in this area are tightly coupled with developments in cryocooler technology, their reliability and cost and to the development of an infrastructure suitable for the production of useful components at reasonably low cost. Microwave devices using thin films deposited on single-crystal substrates are generally configured in planar geometries following well-known microwave device practices such as microstrip, coplanar waveguide, and stripline. Both distributed and lumped-element microwave devices have been demonstrated, some being today in an advanced preproduction stage. The fundamental ideas behind HTS microwave devices will be reviewed in this chapter, followed by a discussion of the most promising devices demonstrated to date and their properties and potential. The point of view adopted here is that of practical system applications and situations in which the advantages of HTS devices over conventional approaches are apparent.