Novel HTS Double-Strip Resonator for High Power Application

The use of a double-strip resonator is proposed for improving the power handling capability of high-temperature superconductor transmit filter with stripline structure. A double-strip resonator reduces the current concentration at the edges of the resonator compared with that of a conventional single strip resonator due to the increase of the effective film thickness. A double-strip 2-pole filter with a 5.0-GHz center frequency and 100-MHz bandwidth and with an Al₂O₃ substrate was designed and fabricated. An electromagnetic simulator based on the moment method was used to design and investigate the filter. To suppress spurious resonance of odd mode near the pass band, we investigated the input/output structure. The maximum current densities at the edges of the resonator as a function of frequency were simulated. The results showed that the maximum current density in the filter was approximately 30% less than that of the conventional single-strip filter. The measured frequency response of the filter was in reasonable agreement with the simulated one.