DESIGN OF A BEAM-STEERABLE ANTENNA ARRAY FOR 5G APPLICATIONS USING A 3.7 GHZ BUTLER MATRIX

Abstract

Within this project, a passive 4x4 Butler matrix-fed microstrip patch antenna array at 3.7 GHz is presented, simulated, and integrated for fixed-beamforming applications in the 5G mid-band. A single rectangular patch element was initially designed for a return loss of less than -30 dB and a gain of 5.5 dBi. As per this, four-element subarrays were built and optimized to increase impedance matching (S11 ≈ –36 dB) with limited gain. Then, using microstrip techniques, the Butler matrix was designed and included crossovers, 45° phase shifters, and miniature hybrid couplers. Each of the components' electromagnetic simulations showed good performance: crossovers showed decent isolation (S41 < –30 dB) and very minor phase error; phase shifters delivered S11 ≈–40 dB with consistent 45° shifts; couplers showed –35 dB reflections, nearly ideal –3.4 dB insertion losses, and correct 90° quadrature. When integrated to the antenna subarrays, the assembled matrix maintained the necessary inter-port phase progression (≈–43° to –44°). Also, four distinct beam directions for respective input ports were verified through system integration simulations with an overall array gain of 11.7 dBi and efficiency of about 60%. So, the herein-proposed passive beamforming architecture is confirmed to be an energy-efficient and cost-effective solution to multi-beam 5G antenna systems.