Quasi-Elliptic Triple-Stopband Filter Based On Six Cross-Coupled SIW Resonators

A new K-band triple-stopband filter in substrate integrated waveguide (SIW) technology is introduced. The filter consists of six rectangular cavities resonating in their fundamental TE101 mode. Main and cross couplings between resonators are used to design a filter with six transmission zeros, separating three stopbands and four passbands. A corresponding coupling matrix is presented. The initial filter covers an overall bandwidth of 4.50 GHz at center frequency of 19.50 GHz. The three stopbands are located at 17.6, 19.56, and 21.34 GHz with bandwidths of 0.92 GHz, 0.82 GHz, and 0.85 GHz, respectively. The two passbands located between the three stopbands have center frequencies of 18.70 and 20.56 GHz with corresponding bandwidths of 0.97 GHz and 0.88 GHz, respectively. The filter is prototyped and measured. Good agreement between simulated and measured results proves the reliability and robustness of the design method.