Design of Compact and High-Power HTS Double-Strip Dual-Mode Patch Resonator Filter for Transmit Filter Applications

We presented a compact and high-power dual-mode high-temperature superconducting filter with double-strip resonator (DSR) for transmit filter applications. The DSR structure reduces not only the current concentration at the edges of the resonator compared with that of a conventional microstrip resonator due to the increase of the effective film thickness but also the coupling between resonators. Thus, the DSR structure contributed not only to enhance the power handing capability of the filter but also to the size reduction of the dual-mode filter. An electromagnetic simulator based on the moment method was used to design and investigate the filter. A double-strip four-pole dual-mode square patch filter with a 5.0-GHz center frequency and 100-MHz (2%) bandwidth was designed. A compact (25 mm × 25 mm) filter was fabricated using YBa₂Cu₃O_y thin film on an Al₂O₃ substrate. The measured frequency response of the filter was in reasonable agreement with the simulated one. Power-handling capability of the filter was more than 41.7 W (46.2 dB·m) at 70 K.