Design of Butler Matrix Integrated with Antenna Array for Beam Forming

This paper presents a 4x4 Butler matrix as a beamforming network that is combined with a 4-elements linear aperture coupled antenna arrays to produce four narrow steerable beams. The designed array is aimed to obtain a operating frequency at 2350 MHz for LTE applications by using the Advance Design System (ADS) and CST Microwave Studio. The measurement result shows that the bandwidth for each port is more than 100 MHz. the isolation between ports in the range frequency 2.3 - 2.4 GHz is more than 20 dB. When port 1, 2, 3, or 4 is activated, the beamwidth of the array is 33.8 degrees, 39.8 degrees, 40.3 degrees and 35.6 degrees with the gain is about 6.11 dBi, 3.94 dBi, 4 dBi, and 6.05 dBi, respectively. The main beam of the array in azimuth direction is tilted to -20 degrees, 40 degrees, -40 degrees, and 20 degrees for respective input port.