An ultra-wideband 4x4 CB-CPW Butler matrix has been designed using a two-layer structure. In the proposed design, a combination of a CB-CPW slot-coupled directional coupler and UWB crossover were employed to widen the bandwidth of the Butler matrix and reducing the number of crossovers. Simulated results show that a bandwidth of about 4 GHz was achieved. Furthermore, the proposed matrix has been used to form a beamforming system, resulting in four orthogonal beams at 5.8 GHz. With these features, the proposed Butler matrix is suitable for UWB-beamforming antenna-array applications.