Intrinsic limits on the Q and intermodulation of low power high temperature superconducting microstrip resonators

Cuprate superconducting thin films are being used to make compact low power microwave devices. In recent years, with improved materials and designs, there has been a steady improvement in device performance, notably an increase in resonator Q and a decrease in the nonlinear intermodulation. It is important to understand how much improvement can be expected. Here we discuss the intrinsic limiting behavior that one might achieve with a perfect film, review the present status, and discuss what the limiting behavior implies for high temperature superconducting filters. Our analysis indicates that increases in unloaded Q to similar to 10(6) and decreases in intermodulation by a factor of similar to 10(4), compared with today's values, might be achieved. (C) 1998 American Institute of Physics. [S0021-8979(98)06322-1].