Compact Dual-Band Filters Using Single-Cavity SIW and Quarter-Wavelength Stripline Resonators

This letter proposes novel dual-band filters utilizing a universal hybrid structure that combines substrate-integrated waveguide (SIW) and quarter-wavelength stripline resonators (QWSLRs). By integrating a single-cavity SIW and different numbers of QWSLRs, two highly compact dual-band filters with large frequency ratios are presented. The dual-band response is achieved in the single-cavity SIW through the interaction of the fundamental mode and higher order modes of the SIW cavity, along with the fundamental modes of QWSLRs. Four metallic vias are introduced as perturbations to achieve more flexible responses. Two hybrid dual-band filters are fabricated for validation. These filters not only maintain the superiority of SIW but also achieve a size reduction exceeding 50% compared to conventional SIW filters of the same order.