Novel Dual-Mode Bandpass Filters Based on SIW Resonators under Different Boundaries

Two novel substrate integrated waveguide (SIW) resonators under different boundaries are proposed and analyzed. The closed-form solutions of the guided-mode field and the formulas for calculating the resonant frequencies of the SIW resonators under different boundaries are given. The coexistence mechanism of quasi-TEM (TE00) and TE mode was illustrated by the proposed equivalent principle. Two modes of each filter, TE100 (TEM mode) and TE102, TE001(TEM mode) and TE201, can be tuned independently by the perturbation slotlines. Finally, two dual-mode SIW bandpass filters utilizing the two SIW resonators are fabricated to demonstrate the proposed method. The measured results are in agreement with the simulated results.