Design of Two‐Dimensional 90° Filtering Couplers Based on Combined 90° and 180° Couplers

ABSTRACT This letter proposes a novel approach to design two‐dimensional (2‐D) 90° filtering coupler. Compared with the conventional 2‐D 90° coupler composed of four 90° couplers, this approach first introduces filtering characteristics by replacing two of the 90° couplers with 180° filtering couplers cascaded with a 90° phase shifter, and then uses a filtering crossover instead of the conventional crossover to further improve the selectivity of the filter. The comprehensive design methodology and synthesis approach for the 2‐D filtering coupler are presented. To validate the proposed concept, a 2‐D 90° filtering coupler was devised, fabricated, and tested. The measured data align closely with simulation results, thereby confirming the effectiveness of the proposed circuit design.