Magnetically tunable superconductor filters using yttrium iron garnet films

Magnetically tunable superconducting single-resonator filters using YIG films have been demonstrated experimentally. Tunability of 400 MHz at a center frequency of 6 GHz was achieved for a half wavelength microstrip comprising a YIG-YBCO-MgO composite structure. The reason why the quality factor of the filter is relatively low is possibly due to an increase of the magnetic linewidth /spl Delta/H at liquid nitrogen temperature. The theory on dispersion relation of the filter is also presented.