Highly‐selective pseudoelliptic filters based on dual‐mode substrate integrated waveguide resonators

A non‐degenerate dual‐mode resonator derived from circular substrate integrated waveguide is proposed, and two pseudoelliptic bandpass filters with non‐resonant mode based on the dual‐mode resonators are presented. Two resonant modes (higher order modes) are employed to degenerate a passband, while a non‐resonant mode (fundamental mode) is designed to provide a direct input‐to‐output coupling. Owning to an additional path provided by non‐resonant mode, the filters have good selectivity and very compact size. The presented simulation and measurement results are in good agreement.