Substrate integrated waveguide dual-passband filters with flexibly allocated center frequencies and bandwidths

A kind of substrate integrated waveguide (SIW) dual-band bandpass filters (DB-BPFs) with flexibly allocated center frequencies (CFs) and fractional bandwidths (FBWs) is presented based on TE₁₀₁ and TE₂₀₁ modes in SIW rectangular cavities. Emphasis is placed on filters design to simultaneously realize the external quality factors Q_e and coupling coefficients M_ij required for both passbands by determining proper offset positions and coupling dimensions of the feeding ports and coupling windows, respectively. Consequently, both the CFs and FBWs of the two passbands can be specified and allocated over wide ranges.