UIR-Loaded Dual-Mode SIW Filter with Compact Size and Controllable Transmission Zeros

A novel high performance filter architecture by loading a uniform impedance resonator (UIR) to a dual-mode substrate integrated waveguide (SIW) filter is proposed in this paper. The filter is composed of an SIW cavity, a UIR, and a perturbation metallic via, generating a three-pole passband by combining the UIR and dual-mode resonances. Two transmission zeros (TZs) can be created at the lower stopband by the nonresonant mode (TE101), which provides a direct source-to-load bypass coupling. The TZs are controllable by changing the bypass coupling magnitude. Moreover, an extra TZ is generated at the upper stopband because of the UIR. By changing the position of the perturbation via, the two TZs created by the bypass coupling could be moved to the two sides (left & right) of the passband. A second filter is then proposed and presented with enhanced the selectivity on the upper stopband. Both of the two filters are fabricated and measured, showing consistent filtering responses compared with simulations.