Study on Cross-Coupled Substrate Integrated Evanescent-Mode Waveguide Filter

A direct-coupled and a cross-coupled substrate integrated evanescent-mode waveguide bandpass filter (BPF) are implemented with folded and ridge substrate integrated waveguide (FSIW/RSIW). The proposed BPFs have the advantages of high frequency selectivity, low loss, low cost, and easy integration. Compared with the conventional SIW cavity-coupled BPFs, the proposed cross-coupled BPF has much smaller size. The spurious suppression characteristics of both the direct-coupled and the cross-coupled evanescent-mode BPFs are also examined, and their superior performances are validated by the simulated and measured results, with good agreement obtained between them.