A Miniaturized SIW Triplexer Based on a Triple-Mode Resonator with Slot Perturbation

A miniaturized substrate integrated waveguide (SIW) triplexer with a common triple-mode resonator has been proposed in this paper. The common triple-mode resonator is perturbed by centered cross-shaped slots etched on the top surface of a square SIW cavity. By investigation of surface current distributions on the slot perturbed triple-mode square cavity, the first and second higher-order spurious resonant frequencies can be respectively controlled by each slot, and the fundamental mode frequency is not affected. Meanwhile, the triple-mode resonator has merit of compact size due to slot perturbation. Besides, bandwidths of the three filter channels can be flexibly controlled without extra matching network. Based on systematic analysis of resonant characteristic of the perturbed triple-mode SIW resonator, a triplexer with second-order Chebyshev frequency response at each channel is synthesized and designed. Furthermore, a compact circuit occupation of only approximately 1.79λg × 1.19λg has been obtained. The synthesized, simulated and measured results show a good agreement.