High-Q, Tunable Microwave Superconducting Strip-Line Filters

The goal of this SBIR program is to develop a high Q (>10,000) tunable filter by using a cryogenic piezoelectric actuator to adjust the position of a split-ring stripline resonator made from high temperature superconductor. The critical technology in thiswork is the recent development of single crystal piezoelectric materials that have much larger field induced strains and piezoelectric properties than conventional PZT ceramics. In addition, single crystal piezoelectric have cryogenic propertiesequivalent to those of PZT ceramic at room temperature making single crystals, by far, the best cryogenic piezoelectric actuation technology in existence. High-strain, stacked crystal actuators will provide approximately 20% tunability with tuning speedsin the range of 1 to 10 us. Thus, combining single crystal piezoelectrics with superconducting filters will, for the first time, result in a viable high Q tunable filter.As demand for the communications frequency spectrum increases, there is a larger needfor high Q filters to achieve greater frequency discrimination. High temperature superconducting filters can fill this need but to minimize the number of filters and therefore reduce systems costs, the filters need to be tunable. Applications for high Qtunable filters would be any commercial or DOD communications system that requires a high degree of frequency discrimination, for example, increased portable phone usage, increased air traffic frequencies for aircraft safety and wireless data networkservices.