Use of Additional Patch Conductor to Realize HTS Dual-mode Filter with Double-strip Resonator

We propose a novel transmit high-temperature-superconducting (HTS) dual-mode double-strip octagonal patch resonator filter with an additional patch conductor working as a perturbation. The dual-mode double-strip resonator consists of two stacked octagonal patch resonators and an additional patch conductor which is placed between the resonators to provide coupling between the orthogonal resonating modes. This reduces the current concentration at the perturbation compared with that of conventional dual- mode filter with stub perturbation. The bandwidth is adjusted by changing the size of the additional patch conductor. A 2-pole HTS dual-mode double-strip octagonal resonator filter using an additional patch conductor with a 5.0 GHz center frequency and 100 MHz bandwidth was designed using an electromagnetic simulator based on the moment method. The filter was fabricated using YBa2CuO7 thin films on r-Al2O3 substrates. The filter is evaluated by experiment and simulation with good agreement.