Design of a new Ultra-wideband 4×4 Butler matrix for beamforming antenna applications

In this paper, a design of a new 4×4 ultra-wideband compact Butler matrix operating between 3 and 10.6 GHz is presented. In this design, two goals are set, the first is to obtain ultra-wideband performance, and this is done by using a new developed ultra-wideband directional coupler and a 45°-phase shifter. A multi-layer configuration of these two components is used to satisfy the second goal, which leads to avoid using any crossover and to design a compact Butler matrix. Simulated and measured results show a good agreement.