Synthesis Design of Wideband High-Selectivity HTS Filter by Cascading Dual-Mode Resonators

A synthesis method for wideband filter design using dual-mode resonators is presented, which is helpful for the design of miniature high-order dual-mode filters. Using the frequency transformation for dual-mode resonators, the infinite frequency in lowpass prototype can be mapped to band-edge to create a quasi-transmission-zero, resulting in a new technique to improve filter selectivity. Dual-mode resonators are found to be either suitable for wideband filters or dual-band filters, depending on the relative positions of transmission zeros in the filter response. A demonstration filter composed of 11 dual-mode resonators is designed and fabricated for the first time, which surpasses a conventional 17-pole filter in both size and selectivity.