Design of millimeter-wave dual-band filters based on ISGW resonant cavities

This paper presents a millimeter-wave dual-band filter based on an integrated substrate gap waveguide (ISGW) resonant cavity. The ISGW cavity is formed by removing part of the mushroom-shaped vias of the ISGW. The two resonant cavities are coupled by transverse coupling. The TE
101
and TE
201
modes are excited by the microstrip feeding which selecting suitable positions. Two metal perturbation vias are loaded in the cavities and used to modulate these two modes. The structure produces two transmission zeros and the transmission zero position can be adjusted by adjusting the coupling window size. The center frequencies of the filter are shown to be 22.22 GHz and 27.93 GHz, with fractional bandwidth of 7.5% and 5.6%, insertion losses of 0.55 dB and 0.75 dB, respectively.