Bandpass Filters Based on Dual-Mode Slow Wave Substrate Integrated Waveguide Cavities
Zhixia Xu, Xiaonan Sun, Yulin Feng, Zhongbao Wang, Weiye Zhong, Shaojun Fang
Abstract
We propose compact bandpass filters (BPFs) based on a dual-mode slow wave (DMSW) substrate integrated waveguide (SIW) cavity, which consists of periodically arranged blind via holes. The ultracompact size ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 0.6\times \lambda _{g}^{2}$ </tex-math></inline-formula> ) and high unloaded quality factor (~465) bring advantages to BPFs. Two-pole BPFs based on a single DMSW SIW cavity are designed with a transmission zero (TZ) appearing in the lower or upper stopband. To realize more complex BPF topology, we design four-pole BPFs based on two traditional SIW cavities and one DMSW SIW cavity. It is the first time that the DMSW SIW cavity is used to implement compact higher order BPFs with the parallel-coupling topology. Results show that the proposed BPFs have competitive performance with significantly small size, which shows potential on microwave circuit designs.