High-Q, Tunable Microwave Superconducting Strip-Line Filters

The objective of the proposed Phase II SBIR program is to develop high Q, tunable microwave filters by using a cryogenic piezoelectric actuator to mechanically tune a high temperature superconducting resonator. This device will enable a broad range ofcivilian and military applications that require precise band selectivity over a broad frequency range. In Phase I of this project, a 25% tuning range was successfully demonstrated between 2 and 8 GHz by using a piezoelectric bending element to adjust thewidth of an air gap between a microstrip resonator and a dielectric or metal tuning plate. For Phase II high Q will be achieved with high temperature superconducting resonators requiring operation below 77K; temperatures at which conventionalpiezoelectrics exhibit poor performance. Instead, we will use relaxor ferroelectric single crystals such as Pb(Mg1/3Nb2/3)O3-PbTiO3, which exhibit over 10 times the strain of conventional ceramic materials at room temperature and exhibit a 5-foldimprovement at cryogenic temperatures. The Phase II program will be collaboration between TRS Technologies, Inc. and the Pennsylvania State University. The goal will be to develop a multipole bandpass filter at 1-3 GHz using half-wavelengthtransmission-line-resonator design, with 1% bandwidth, >25% tunability, and less than 1-dB insertion loss.