Design and Implementation of a 2.4-GHz Fully Integrated Butler Matrix for Smart Antenna System

Abstract

This work proposes and analyzes a low-cost fixed microstrip beamforming system based on a uniform linear array with four rectangular patch antennas controlled by a Butler matrix that operates in the 2.4 GHz ISM band. A 4×4 Butler matrix consisting of four hybrid quadrature directional couplers, two crossovers, and two 45° phase shifters was designed and implemented to control the beam direction of the entire system. Similarly, a comparative study is performed between two different antenna arrays, the first consisting of a conventional linear antenna array and the second antenna array consisting of four patch antennas loaded with metamaterial structures on the ground plane. Finally, the electrical performance of both smart beamforming systems was evaluated, and their potential application as a wireless power transmitter was evaluated. Four beams with distinct orientations were created in each situation. The smart antenna based on a conventional array has a higher gain, while the smart antenna based on metamaterial structures has a higher HPBW.