Adjustable multilayer HTS filters

An adjustable multilayer high-temperature superconductor (HTS) bandpass filter has been fabricated. Taped comb-line filters with multilayer structures were designed, YBa₂Cu₃O_7-δ (YBCO) thin films deposited on LaAlO₃ were used to construct the packaged multilayer HTS filter. The electrical length of the resonators in the filter was smaller than a quarter-wave length. The frequency responses of the filter were measured at liquid nitrogen temperature 77 K. The insertion loss of the packaged filter was determined to be less than 0.5 dB. By mechanically adjusting the multilayer structure, the center frequencies of the filter changed from 1.78 to 1.92 GHz, and the variations of the bandwidth from 60 to 150 MHz were also obtained