Design of a millimeter-wave dual-band bandpass filter using SIW dual-mode cavities

A millimeter-wave dual-band bandpass filter using substrate integrated waveguide (SIW) dual-mode cavities is proposed in this paper. The proposed filter consists of three SIW cavities, and each cavity can provide two resonant modes, the TE
₂₀₁
mode and TE
₁₀₂
mode, as well as a transmission zero. The resonant frequencies of TE
₂₀₁
and TE
₁₀₂
modes can be adjusted by the length and width of the SIW cavity, respectively. And the transmission zero can be adjusted by the location of the coupling window between the SIW cavity and the positions of the input and output ports. An example dual-band bandpass filter is designed, and the center frequencies of the two passbands are 26.73GHz and 31.52GHz, respectively. The 3dB-passbands are 26.24-27.21GHz (3.6%) and 31.2-31.84GHz (2%), respectively, with maximum insertion loss of 0.48dB and 0.67dB, respectively, and return loss larger than 12dB in both pass-bands.