Comparison of Power Handling Capability of Double-strip Resonator Filters with Stripline Structure and Conventional Microstrip Line Filters

The power handling capability of a high temperature superconducting transmit filter with a double-strip resonator (DSR) was investigated by comparing the performances of such a filter with conventional microstrip-line (MSL) filter. The DSR structure consists of two coupled strips and the center pin of the SMA connector as feed line. The idea is to increase the effective film thickness to reduce the current concentration at the edges of the resonator compared with that of an MSL resonator. The two three-pole filters were designed using electromagnetic simulator. The center frequency and 3dB-bandwidth are a 5.0-GHz and a 100-MHz. The two filters were fabricated using YBa2Cu3Oy thin films on a CeO2-buffered r-Al2O3 substrate. The measured frequency responses of the filters were in reasonable agreement with the simulated ones. The measured power handling capability of the DSR filter was 3.5 dBm larger than that of the MSL filter.