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 crosscoupled 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.