Overview of wideband Butler matrix in microstrip-slot technology for beamforming antenna applications

This paper describes the development of 4×4 wideband compact Butler matrix operating between 1.6 GHz and 2.4 GHz. In order to attain wideband characteristics, the matrix uses microstrip-slot technology, which involves two microstrip dielectric layers with a shared ground plane and a coupling slot. The multilayer beamforming network design is compact in size and avoids the use of crossovers, which makes it more advantageous than the conventional Butler matrix. To verify the performances of the beamformer, a four-antenna array is connected to the proposed 4×4 Butler matrix to shape a switched-beam system. Simulation results are presented and discussed.