AbstractA high-isolation diplexer based on a dual-mode substrate integrated waveguide (SIW) resonator is proposed in this paper. Based on the theory of the dual-mode resonator, the miniaturized diplexers are designed by using the SIW dual-mode resonators. The superior isolation of the diplexers is obtained because the two operating modes of the dual-mode SIW resonators are not directly coupled and there is no interference with each other. In order to further improve the isolation of the circuit, the number of the order of the diplexer is added. Equivalent circuits are given to analyze and design the dual-mode high-isolation diplexers. Detailed analyses are given according to the equivalent circuits. The dual-mode third-order and fourth-order diplexers are designed and fabricated. The measured results agree well with the simulated ones. The total sizes of the fabricated third-order and fourth-order diplexers are 1.78λg × 2.64λg and 1.79λg × 3.63λg, respectively.
High-Q Substrate Integrated Waveguide Resonator Filter With Dielectric Loading