Cross-Coupled Bandpass Filter Based on Circular Substrate Integrated Waveguide Resonator

Abstract

In this paper, circular substrate integrated waveguide (CSIW) filters are presented. Π-shape slots etched along the electric walls of the CSIW on the upper layer are proposed firstly, which enhance the magnetic coupling parameters between two CSIW cavities. Meanwhile, S-shape slots as the electric coupling structure are firstly used on CSIW filters. With both magnetic and electric coupling, the third-order and fourth-order cross-coupled bandpass filters based on circular substrate integrated waveguide resonator (CSIWR) are designed, which possess one transmission zero (TZ) and two transmission zeros, respectively. Measured results of these filters with a high selectivity agree well with simulated ones.