A new HTS microwave filter using dual-mode multi-zigzag microstrip loop resonators

A new HTS planar microwave filter using dual-mode multi-zigzag square loop resonators is developed. A method for the accurate calculation of the coupling coefficient between two degenerate modes in a resonator is presented. The results of the full wave analysis of the 4-pole filters have shown that the filter has high performance, selectivity, and substantial size reduction. A 4-pole HTS bandpass filter with the bandwidth 1.36% at a central frequency 1.39 GHz is designed and fabricated and measured at 77 K. The agreement between theoretical and experiment results is good.