Triple‐mode dual‐band bandpass filter based on cross‐shaped substrate integrated waveguide

Abstract

A novel dual-band bandpass filter based on substrate integrated waveguide (SIW) which is realised with mode distribution of the special cross-shaped structure is presented in this Letter. In the cross-shaped SIW, there are six symmetrically stimulated resonant modes in the first eight higher order resonant modes that are perturbed to achieve dual-band responses, and each passband contains triple-mode. By introducing 45° rotated cross via-holes at the centre position of the structure, the two lower symmetrical resonant modes are closer to the unaffected asymmetrical higher resonant mode in both passbands. Compared with existing multimode multi-band filters which are achieved by coupling or cascading mechanism, the presented filter design based on single cross-shaped SIW is simple and easy for implementation. A prototype dual-band filter operating at 8.23 and 11.48 GHz with 3 dB fractional bandwidths of 7.1 and 12.1% is designed and fabricated. Measured and simulated results are presented to validate the predicted performances of the proposed filter.