Design of Filtering Crossover and Diplexer on SIW Quadruple-Mode Resonators in a Single Cavity

This paper at first presents the proposal and design of a filtering crossover and diplexer with two second-order filtering channels on substrate integrated waveguide (SIW) quadruple-mode resonators (QMRs) and in single cavities. The proposed method has an interesting application in the overall size miniaturization design. The proposed resonator is yielded with four perturbed modes (TE103, TE104, TE201 and TE202) featuring distinct electric field distributions by inserting metal via-holes in the center of a rectangular SIW cavity. Next, a pair of resonances is applied to form a second-order filter channel while TE201 and TE202 modes are implemented to realize the other, thereby integrating the whole circuit in a single cavity. Besides, the transmission responses between the channels are isolated only by the perturbed via-holes. Slots are introduced in the metal surface to further increase each channel design flexibility. In this way, controllable frequencies and compact size have been well achieved. Two examples including a crossover and diplexer with two second-order filter channels are designed, fabricated, and measured to verify. Good agreement between simulation and measurement can be observed.