Design and Implementation of a Triple-Mode Planar Filter

A novel planar triple-mode resonator is proposed and implemented by placing an additional metallic via at the center of a circular dual-mode substrate integrated waveguide (SIW) cavity resonator. The resonant frequency of the dominant mode in the SIW cavity increases remarkably and become close to the resonant frequencies of the TM
₁₁₀
-similar mode. Three asymmetric bandpass filters utilizing this resonator are designed and fabricated. The measured results are in good agreement with the simulation results.