Electrically Tunable Superconducting Microstrip Line Band-Pass Filter for Mobile Applications

2 GHz band electrically tunable superconducting microstrip line band-pass filter was developed. The tunable filter used a thin interdigital electrode. The dielectric distribution of SrTiO 3 substrate included a calculated nonlinear effect of the electrode and ferroelectric material. As a result, the tunable microstrip line filter design with interdigital electrode enabled calculation by the finite element method and the moment method. The tunable filter with a measured unloaded Q factor of 9700 and a frequency shift of 1.25 MHz was obtained.