Compact inline dual-band dual-mode BPF with a hybrid structure of single-layered SIW and CPW

Abstract

A compact inline dual-band dual-mode bandpass filter (BPF) using single-layered substrate integrated waveguide (SIW) is implemented by etching an H-shaped slot on the top surface of two adjacent rectangular cavities. The H-shaped slot consisted of two coplanar waveguide (CPW) resonators and two SIW cavities can achieve two adjustable transmission poles at the upper and lower passbands, respectively. Good lower stopband performance is inherited from SIW. Two transmission zeros can be generated by the cross coupling through the resonators which are not in resonance to obtain high isolation between passbands and sharp skirt. To validate the concept, a dual-band filter is designed and fabricated, and good agreements are obtained between measured and simulated results.