Novel UWB multilayer Butler matrix

A 4x4 wideband multilayer Butler matrix has been designed using a bi-layer structure. In the proposed design, a combination of single and multilayer elliptic directional couplers is employed to widen the bandwidth and to avoid using any crossovers as conventional matrices. Simulated results show a good agreement and a bandwidth of about 2 GHz was achieved. Furthermore, the proposed matrix is connected to an antenna array to form a beamforming system, resulting in four orthogonal beams -45°, -15°, 15° and 45°. With these features, the proposed Butler matrix is suitable for wideband beamforming antenna array applications.