Ultra-broadband 4×4 compact Butler matrix using multilayer directional couplers and phase shifters

The design of a novel ultra-wideband compact 4×4 Butler matrix operating between 3 and 10.6 GHz is presented. In this design, the multilayer topology is used to provide compact size. This matrix combines a compact ultra-wideband 3 dB multilayer microstrip directional coupler and a new 45° phase shifter. An innovative approach for realization of broad band 45° phase shifter using the same configuration of the coupler and a reference line as a phase correction network is presented. To examine the proposed approach, a Butler matrix was simulated, fabricated and measured. The measured and simulated results show a good agreement.