Compact Wideband HTS Filter With Multiple TZs Using Integrated Shorted-Stub and Slot SSPPs

In this letter, a novel spoof surface plasmon polaritons (SSPPs) unit is proposed by embedding slot into the shorted stub. Based on the newly SSPPs structure, a compact wideband high-temperature superconducting (HTS) filter with fully controllable passband is designed. The upper and lower cutoff frequencies of the filter can be independently adjusted by the heights of shorted stubs and slots. Also, due to the etched slots, the signal interference can be introduced by adding an additional microstrip line. Then, multiple transmission zeros (TZs) are therefore produced and enhance the passband selectivity. Finally, a low-loss filter operating at 1.1–1.6 GHz is designed and fabricated on MgO wafer with deposited YBCO thin films. The measured results agree well with the simulations, validating the proposed SSPPs structure and design method.