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 x 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.

Automated summary

The communication presents a wideband switched-beam antenna design utilizing a novel hybrid coupler structure and compact Butler matrix, achieving the widest bandwidth without the need for standalone phase shifters and crossovers. The antenna array fabricated using this design method demonstrates stable beamforming performance with a gain variation smaller than 1.66 dB in the 2 to 3 GHz frequency range.