A Wideband Switched-Beam Antenna Array Fed by Compact Single-Layer Butler Matrix

This communication describes a wideband switched-beam antenna fed by a compact single-layer beamforming network. First, a novel hybrid coupler structure that can provide an arbitrary phase difference over a bandwidth larger than 58% is proposed with the theoretical analysis. Based on this compact coupler configuration, a wideband 4 ×4 Butler matrix is devised with the need for standalone phase shifters and crossovers eliminated. The proposed Butler matrix achieves the widest bandwidth among the single-layer structures up to present. Consequently, a wideband switched-beam antenna array is realized by utilizing the log-periodic endfire antenna elements with bowtie dipoles on the Butler matrix. For validation, a broadband switched-beam antenna array is designed, fabricated, and measured. A stable beamforming performance is ascertained with a gain variation smaller than ±1.66 dB over a bandwidth from 1.98 to 3.14 GHz.