Balanced triple‐mode substrate integrated waveguide bandpass filter

This Letter proposes a novel balanced triple‐mode substrate integrated waveguide (SIW) bandpass filter for the first time. The new triple‐mode resonator is realised by a square‐shaped SIW cavity with a capacitive loading patch. The resonance of higher‐order mode TE 301 can be controlled and shifted to that of modes TE 102 and TE 201 . High‐performance common mode suppression, controllable bandwidth, compact size and quasi‐elliptic differential mode response can be achieved. For demonstration, a balanced triple‐mode SIW filter is designed, fabricated and measured.