Synthesis Design of SIW Multiband Bandpass Filters Based on Dual-Mode Resonances and Split-Type Dual- and Triple-Band Responses

A synthesis design method for substrate-integrated waveguide (SIW) multiband bandpass filters (BPFs) with flexible frequency and bandwidth allocations is presented by incorporating SIW dual-mode resonances with split-type dual- and triple-band symmetrical frequency responses. By different combinations of the split-type dual- or triple-band responses for two virtual wide passbands dominated by TE101 and TE201 modes in SIW rectangular cavities, SIW tri-/ quad-/quint-/sext-band BPFs with improved band assignments can all theoretically be implemented. In addition, by introducing our previously proposed dual-mode coupling controlling technique, the bandwidths of the two virtual wide passbands can also be allocated flexibly. Three experimental prototypes, including a quad-band BPF based on four dual-mode SIW cavities, a quad-band and quint-band BPFs based on two dual-mode SIW cavities coupled with multiple single-mode ones, are synthesized, designed, fabricated, and tested to demonstrate and validate the collaborative design concept.