Dual‐mode bandpass filters using triangular ring resonators with coupling stubs

A novel dual‐mode bandpass filter using a microstrip triangular ring resonator with coupling stubs has been designed and tested. The basic configuration of this novel dual‐mode filter is a triangular ring resonator. Quasi‐L‐shaped I/O arms used as coupling stubs for enhanced coupling are nonorthogonally and symmetrically separated on each corner of the triangular resonator, and a perturbation element is introduced within the resonator at a symmetrical location. The effects of the lengths of the coupling stubs and the width of the perturbation element are studied. New filters having narrower or wider bandwidth and transmission zeros are presented. The proposed filter responses are in good agreement with the simulations and experiments.