Broadband 4x4 Butler Matrix Using Wideband 90° hybrid Couplers and Crossovers for Beamforming Networks

The design and simulation of a wideband four-port steerable beamforming networks using a 4x4 Butler matrix for the 2.4 GHz applications is presented. The aim of this work is to develop an antenna array feeding network based on Butler matrix with a large bandwidth in order to cover the IEEE 802.11b/g/n band. In order to achieve wideband features, the matrix uses two-section branch-line couplers and four-section branch-line crossovers instead of the standard ones. The proposed circuit exhibits a high isolation and wideband 4x4 Butler matrix designed and simulated by using a single-layer FR4 substrate, which covers the frequency band ranging from 2.1 GHz to 2.75 GHz. The return losses and the isolation are better than 28 dB and 30 dB, respectively, with its good performance is more suitable for IEEE 802.11b/g/n and ISM applications.