A Novel Microstrip Triple Wideband Bandstop Filter Design by Using Adjacent Direct Coupled Dual-Mode Resonators

Abstract

In this article, a novel triple wideband bandstop filter design is proposed with two adjacent microstrip square loop resonators (MSLR) having different edge lengths. Degenerate modes of the square loop resonators are induced by using direct coupling mechanism. Perturbation and loading elements are located on resonators and used to control reflection zeros between the second and third bands. Even odd mode analysis of a single direct coupled dual-mode resonator is also extracted to elucidate the filter topology. The proposed resonator structure is designed by using a full-wave EM simulator and three different filter responses are obtained from the designed resonator structure. One of the filters is fabricated and, it is observed that measured results are compatible with simulated results.