High-Isolation Diplexer With High Frequency Selectivity Using Substrate Integrate Waveguide Dual-Mode Resonator

Two novel substrate integrated waveguide (SIW) high-isolation dual-mode diplexers based on electromagnetic perturbation technology have been presented in this paper. The capacitive perturbation and inductive perturbation have been introduced in the presented dual-mode diplexers. Furthermore, this perturbation can produce two transmission zeros in the real frequency axis, and those transmission zeros in the real frequency axis can improve the frequency selectivity of each channel of the diplexer and the isolation between two channels. Two different SIW dual-mode diplexers have been designed, fabricated, and measured. The measured insertion losses at each center frequency are 2.2 and 2.4 dB for the diplexer 1, 1.8, and 1.5 dB for the diplexer 2, with the fractional bandwidths of 1.95% and 2.08% for the diplexer 1 and 1.94% and 2.05% for the diplexer 2. The isolation is greater than 45 dB. Reasonable agreement between the simulated and measured results is achieved for the proposed dual-mode SIW diplexers.