4×4 Broadband Butler Matrix and Its Application in Antenna Arrays

This paper introduces the design method of broadband 4×4 Butler matrix feeding network and applies it to broadband antenna array to realize broadband multi-beam antenna. The proposed Butler matrix switches to different forms of Butler matrices when operating in different frequency ranges to achieve broadband performance. The broadband 4×4 Butler matrix consists of three kinds of directional couplers: a conventional 3dB directional coupler, a broadband 3dB/90° directional coupler, and a three-section directional coupler. The antenna array is designed by stacking antenna patch and coupling between antennas. The Butler matrix feeding network and patch antenna array designed in this paper operate from 2 to 4 GHz. Four beams are obtained in one frequency octave operating frequency range (2 GHz-4 GHz), and the simulation result achieves the desired result.