A millimeter-wave bandpass filter and balun filter based on circular sector patch

A novel compact dual-mode bandpass filter is implemented based on the TE₁₀₂-TE₂₀₁ mode cavity for millimeter-wave systems. Two transmission zeros generated by the cross coupling between two modes are observed within the upper and lower stop bands of the filter for the improvement of frequency selectivity. Furthermore, a balanced-to-unbalanced conversion is combined within the patch element for function integration. For verification, a bandpass filter and balun filter are implemented, and the simulation and measurement results are presented.