Triple-Band Triple-Mode Compact Multilayer SIW Bandpass Filter

In this paper, a novel multiple-band filter based on double-layer SIW rectangular cavities is proposed achieving a three-order three-passband response. The triple-mode characteristics of the SIW cavities, namely TE101, TE201, TE301 modes, are used to generate three passbands. Different from the conventional multi-band filter, this design utilizes a vertical structure. The filter with central frequencies operated at 11.7 GHz, 14.44 GHz, 18.48 GHz is then designed and fabricated for validation, which shows a compact size with controllable transmission zeros. The filter size is 20.3 mm $\times 20.2$ mm, while the minimum insertion loss for the tree passbands is -1.14 dB, -1.12 dB, and -1.37 dB, respectively. The proposed triple-band filter demonstrates the merits of compact structure and low insertion loss with good selectivity.