A Broadband $3\times4$ Butler Matrix and its Application in Multibeam Antenna Arrays

Abstract

A novel broadband three-input four-output ( $3 \times 4$ ) Butler matrix is proposed in this communication. The proposed Butler matrix achieves equal power division and −90°, 0°, and +90° phase differences between output signals in the 2–4 GHz frequency range. By using the $3 \times 4$ Butler matrix as a four-element antenna array feed network, a broadside beam and two symmetrical beams are realized over a wideband frequency range. The proposed Butler matrix has been verified by measurements of S-parameters and radiation patterns using the broadband four-element antenna array. The measurement results are in good agreement with the simulation results. In addition, the proposed $3 \times 4$ Butler matrix can be extended for use with antenna arrays with a higher number of beams.