High Selectivity Single Wideband and Quad-Band HTS Filters Using Novel Quad-Mode Resonators With Self-Coupled Structure

This paper presents improved quad-mode resonators based on the open/short-end load of center stub, which introduces self-coupled structure. Compared with traditional stub-loaded stepped impedance resonator (SLSIR), proposed can significantly reduce circuit size and further increase design freedom. First all, a comprehensive theoretical analysis is performed to infer resonant characteristics resonator. Then, two prototypes different loads were demonstrated verify feasibility method. First, prototype wideband high temperature superconducting (HTS) filter an FBW 89% proposed, whose frequency (CF) be flexibly controlled. Next, quad-band HTS using central stub centered at 1.20, 2.52, 3.51, 4.44 GHz 3-dB 4.8%, 3.96%, 3.97% 2.2%, respectively. The internal external coupling mechanisms are also carefully studied meet specified requirements. in this both have advantages compact size, ultra-low insertion loss steep suppressed skirts. In addition, measured results good agreement EM full-wave simulated results.