Dual-Mode Dielectric Waveguide Filters with Controllable Transmission Zeros

A novel dual-mode (DM) dielectric waveguide (DW) filter with controllable transmission zeros (TZs) is presented. The DM filter is based on a cascaded implementation, utilizing individual dual-mode DW cavities. The filter is practically realized by embedding three circular blind holes at different positions in the surface of a dielectric silver coated square cavity. By changing the relative position of the blind holes or rotating the direction of the proposed DW cavity, the filter’s TZs’ frequency locations can be flexibly adjusted. The zero points can be set in frequency at the low end of the passband, at the high end of the passband, or they can be generated at both the low and high ends of the passband in order to improve the selectivity of the filter. In this study, the two-cavity fourth-order filter is taken as an example, and the experimental results validate the feasibility of the presented theoretical design.