A Miniaturized Bandpass Filter Based on a Quarter-Mode Comb Substrate Integrated Waveguide

An X-band bandpass filter based on quarter-mode comb substrate integrated waveguide (QMCSIW) is proposed in this paper. In order to reduce the size and realize the miniaturization for the substrate integrated waveguide (SIW) filter, the comb substrate integrated waveguide (CSIW) and quarter-mode substrate integrated waveguide (QMSIW) are effectively combined together. At the same time, the capacitive loading is added to the resonator so that the resonant frequency can be reduced while its volume can be kept unchanged. Simulation results show that the filter has a bandwidth of 7.46−10.18 GHz with a center frequency of 9.0 GHz, and its size has been reduced by 71.97% relative to the full-mode SIW.