Compact filter based on a hybrid structure of substrate integrated waveguide and coplanar waveguide

Abstract

This letter presents a compact bandpass filter using a hybrid structure of quarter-mode substrate integrated waveguide (QMSIW) and coplanar waveguide (CPW). The hybrid structure is realized by inserting a CPW resonator into the two side-coupled QMSIW resonators. The CPW structure not only works as a resonator but also introduces extra electric coupling between the two magnetically coupled QMSIW that generates additional transmission zero. Also, the CPW does not occupy additional circuit size which further reduces the whole circuit size of the filter. To validate the proposed concept, a prototype filter is fabricated and measured. Good agreement is achieved between simulation and measurement.