Design of 3×3 Nolen Matrix With Integrated Filter Function

This letter proposes a novel approach for designing a 3×3 Nolen matrix with integrated filter function. The proposed Nolen matrix is realized by utilizing the combination of two 90° couplers, a compensation filter, and a 180° filtering coupler, providing phase increments of −90°, 30°, and 150° at the output ports. For experimental validation, a prototype 3×3 filtering Nolen matrix was devised, fabricated, and measured. The prototype operates at a center frequency of 2.4 GHz and exhibits second-order bandpass filtering characteristics. The measured results show close agreement with the simulated ones, thereby confirming both the validity of the design method and the practical feasibility of the proposed structure.