A Broadband 3 x 4 Butler Matrix and Its Application in Multibeam Antenna Arrays

A novel broadband three-input four-output (3 x 4) Butler matrix is proposed in this communication. The proposed Butler matrix achieves equal power division and -90 degrees, 0 degrees, and +90 degrees phase differences between output signals in the 2-4 GHz frequency range. By using the 3 x 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 x 4 Butler matrix can be extended for use with antenna arrays with a higher number of beams.