TUNABLE AND ADAPTIVE BANDPASS FILTER USING A NONLINEAR DIELECTRIC THIN-FILM OF SRTIO3

We have prepared an electrically tunable and adaptive 3-pole half-wave bandpass coplanar waveguide filter incorporating a 1.2-mu m-thick par aelectric SrTiO3 bottom layer and a 0.4-mu m-thick superconducting YBa 2Cu3O7-x top electrode layer on a LaAlO3 substrate. By applying a sepa rate bias voltage on each pole and also on each coupling capacitance o f the device at 4 and 76 K, the filter response is not only fine tuned to achieve symmetric and optimized filter characteristics with less t han 2% bandwidth centered around 2.5 GHz, but also broadband tuned to shift the passband by more than 15%. (C) 1996 American Institute of Ph ysics.