A 45° Phase Shifter Integrated 4×4 Butler Matrix Without Crossover

This work proposes a design of a single band four input four output (4×4) butler matrix (BM) without a crossover, operated at 6.5 GHz. The proposed BM is structured with 3-dB quadrature couplers and 45° phase shifters. Hence, unlike the traditional BM, the proposed BM has a compact size of 1.5λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</inf>× 1.43λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</inf>. Moreover, it is easy to fabricate at a low cost because of its simple, compact, and single-layer design. The proposed BM provides ±45° and ±135° phase difference at the output ports based on input ports excitation. Impressive amplitude performance is obtained at 6.5 GHz with a maximum amplitude imbalance of ±1.28 dB. The proposed BM shows measured reflection loss and isolation better than −25 dB and −30 dB, respectively, which makes the design suitable for beamforming applications.