In this letter, a novel 2-D 180° filtering coupler based on all-resonator structures is proposed. The 2-D 180° filtering coupler, composed of four 1-D 180° filtering couplers, achieves phase shifts in two dimensions with an inherent bandpass filter function. The comprehensive design methodology and synthesis approach for the 2-D filtering coupler are presented. For experimental verification, an example of a 2-D 180° coupler with fourth-order filter response is devised, manufactured, and tested. Excellent alignment is achieved between the simulation and test outcomes, which indicates the correctness of the design method.
Shao et al. (Thu,) studied this question.