Compact Substrate-Integrated Waveguide Triplexer Based on a Common Triple-Mode Cavity

In this paper, a compact substrate-integrated waveguide (SIW) triplexer using a triple-mode cavity perturbed by centered cross-shaped metallized via-holes as a common resonator is synthesized, designed, and demonstrated for the first time, and the resonant characteristics of the perturbed triple-mode cavity are systematically analyzed. Besides, the frequencies and bandwidths of the three passbands can be flexibly controlled without extra matching circuit. Based on the multi-channel structure composed of a triple-mode and three single-mode cavities, a second-order prototype operating at 11, 12, and 13 GHz is synthesized, designed, fabricated, and tested. A compact circuit size of 2.07λg × 1.67λg and good performances have been achieved.