Size-Reduced Highly Selective Bandpass Filters Based on Dual-Mode Slow-Wave Patch Resonators

A novel dual mode slow-wave patch resonators (SWPRs) are proposed based on capacitive-load patches arrays (CLPAs) with short circuit posts in this brief. Owing to CLPAs and cross slots, size of patch can be reduced significantly. Using SWPR’ s TM100 and TM010, two types of bandpass filters (BPFs) with size-reduced and highly-selective are realized. Moreover, different cascading methods of dual-mode SWPRs for high-pole filters’ design by stepped impedance folded coupling line (SIFCL) are analyzed and compared to maintain high selectivity. For the demonstration, two four-pole quasi-elliptic BPFs are designed, fabricated, and measured to verify the performance and design method of the proposed dual-mode SWPR filters. Compared with traditional patch filters, size of the proposed filters can be reduced by 55% and 42%.