Designing of Miniaturized 4 × 4 Butler Matrix Using Coupled Line Coupler and Schiffman Phase Shifter

A novel and miniaturized 4 × 4 butler matrix (BM) is proposed in this work. This proposed butler matrix is designed with four 3 dB quadrature (90°) forward wave coupled line coupler (FWCC) and two 45° Schiffman phase shifter. This BM is designed at center frequency of 2.4 GHz using FR4 substrate. The crossover of this BM has been replaced with a 0 dB FWCC. The performances of all couplers have been improved with the help of defected ground structures (DGS). Two C-shape and one I-shape DGSs are etched at the ground plane of each coupler, and two C-shape and one dumbbell shape DGSs are etched at the ground plane of 0 dB crossover which enhance the performance of the BM. This proposed BM provides a maximum bandwidth of 120 MHz at each port and occupies a total area of 0.677 λ 0 (84.74 mm) × 0.612 λ 0 (76.56 mm).