A Wideband Differentially Fed Multi-beam Antenna Array

A differential Butler matrix is presented in this paper using a new type of wideband unbalanced-to-balanced power dividers. The differential Butler matrix has the merit of high levels of common-mode signal suppression. A differential array with four elements is also designed, fabricated and tested. By feeding the differential array with the differential Butler matrix, two beams are produced in the E-plane radiation pattern. The differentially fed array achieves very low cross-polarization level due to the excellent common-mode suppression from the Butler matrix. The design approach is verified experimentally, and the measured result agrees well with the predicted one, demonstrating the application potential for the presented differential beam-forming networks.