Narrow passband high-temperature superconducting filters of highly compact sizes for personal communication service applications

A novel highly compact high-temperature superconducting filter based on spiral lumped elements was demonstrated for personal communication system applications. The filter consists of eight-pole microstrip resonators enclosed in a substrate 0.5 * 5 * 32 mm. The filter was designed to have a bandwidth of 17 MHz and a center frequency of 1760 MHz. A low insertion loss of 0.4 dB in the passband with an out-of-band rejection loss of about -70 dB was observed at 65 K. Measured characteristics of the filter showed good agreement with simulated responses.