Extraction of Electric and Magnetic Coupling for Coupled Symmetric Microstrip Resonator Bandpass Filter with Tunable Transmission Zero

Abstract

An effective approach is demonstrated for extracting the electric and magnetic coupling components from the coupling coefficient between two coupled symmetric microstrip resonators. It is found that the extraction provides an extra degree of freedom for circuit design. A transmission zero near passband can be created without any cross-coupling scheme but by properly selecting the parameters of the resonators. An equivalent circuit is derived for characterizing the extraction of the coupling and control of the zero. Two experimental filters are realized and measured to validate the approach.