Two-Layer Planar-Circuit Filters Based on the Cul-de-Sac Coupling Matrix Under Consideration of Cross-Coupling Suppression

Planar-circuit filters based on the Cul-de-Sac coupling matrix is proposed by using open-loop microstrip resonators. The filter is constituted by the two dielectric layers having a coupling apertures. The resonators and the input or output port are arranged so that the cross coupling become small as much as possible. Effectiveness of the proposed filter is investigated numerically and experimentally.