Design of 4×4 Butler matrix for beam-forming antenna in phased array networks

In this paper, Design and simulation of 4×4 Butler matrix in 2.45 GHz is proposed. This network is utilized to feed of phased array antenna in order to create patterns in proper direction of space. The Butler matrix is designed on FR4 substrate by 125×113×0.5 mm dimensions. To enhancing the bandwidth, improved microstrip passive elements such as directional branch-line hybrid coupler, cross over and Schiffman phase shifter are used. In the proposed design, isolation of 20-25dB at the central frequency is achieved, and outputs phase differences are coinciding to Butler matrix theory. The resulting bandwidth of ±10º phase response is more than 10% in the central frequency.