Dual-Mode Substrate Integrated Waveguide Circular Cavity Filter Designed at Q-Band

This paper proposes a compact circular cavity for dual-mode substrate integrated waveguide (SIW) filter design. By adding a pair of symmetrical metallic via-holes perturbations, the coupling between a pair of orthogonal high order modes TM110 is induced. Transmission zeros can be obtained at upper side and lower side of the passband to enhance selectivity of the SIW filter. Therefore, flexible design and compact structure are available for the dual-mode SIW filter at Q-band. The experimental results show that the center frequency of the filter is 44.86 GHz with a 3-dB FBW of 10.5% and the minimum insertion loss in-band is about 1.8 dB.