A new balanced dual-band SIW bandpass filter with high common-mode suppression

A new balanced dual-band bandpass filter (BPF) utilizing substrate integrated waveguide (SIW) technology is proposed in this paper. By wisely arranging TE102-mode SIW cavities on the symmetrical plane, the presented balanced BPF can realize selective differential-mode (DM) transmission and quite high common-mode (CM) suppression. In addition, by adopting the extracted-pole mechanisms simultaneously, two controllable finite transmission zeros can be achieved, ensuring flexible dual passbands. The desired DM response can be easily analyzed and obtained by the equivalent 2-port circuit model. A prototype balanced BPF operating at 9.40 and 9.98 GHz has been realized to validate the proposed concept and theory. It exhibits more than 55.1 dB of maximum CM rejection within the DM passbands. Both theoretical and simulated results are provided with good agreement.