Compact Highly-Selective Bandpass Filter Based on Triple-Mode Ridge Substrate Integrated Waveguide Cavity

A compact highly-selective bandpass filter based on a novel triple-mode ridge substrate integrated waveguide (TMRSIW) cavity is proposed in this letter. The new TMRSIW cavity is realized by multiple capacitive-loaded patches (CLPs) with short circuit posts (SCPs), which can manipulate those three modes with controllable resonances and reduce their resonances. For the demonstration, a design example with a center frequency of 7 GHz and bandwidth (BW) of 160 MHz is fabricated and measured to verify the performance of the designed filter. The measured results agree well with the simulated ones. Compared with traditional triple-mode SIW filters, the size of the proposed TMRSIW filter can be reduced by 48.3%.