Microstrip bandstop filter using a dual-mode square loop resonator

Abstract

Dual-mode microstrip bandstop filter, which has an inductive or capacitive perturbation element located at one of its corners, with a 90°-bended ?/4 microstrip feeding line is proposed. The degenerate mode splitting of a conventional dual-mode square loop resonator and the coupling coefficient between these modes are investigated. The filter characteristic, is changed by the perturbation size. Finally, a novel dual-mode microstrip bandstop filter is designed and realized using degenerate modes of dual-mode microstrip square loop resonator. Two filters are designed, fabricated, and measured to demonstrate the validity of the proposed bandstop characteristic. © 2008 Wiley Periodicals, Inc.