Presentation Information
[B-1B-39]Investigation of a Compact Butler Matrix for 28 GHz Band
◎Tatsunori Okimura1, Yasutaka Murakami1 (1. The University of Electro-Communications)
Keywords:
Butler matrix,5G,Microstrip Line
In the 28 GHz band, high-gain antennas and beamforming techniques are important because the propagation loss is large. In this study, a compact Butler matrix structure operating as a power combiner is investigated for the 28 GHz band. A conventional 4×4 Butler matrix consists of 3 dB hybrid couplers, crossovers, and phase shifters, and it can divide an input signal into four output signals with specific phase differences. In contrast, the proposed structure is used as a power combiner by feeding four input ports with specific phase differences and combining the power into one output port. Therefore, the final-stage crossover can be removed. As a result, the circuit length is reduced from 24.7 mm to 17.6 mm, corresponding to approximately 29 % size reduction. The S-parameters and combining characteristics were analyzed around 28 GHz. The results show that the proposed structure can concentrate the input power into one selected output port, while unwanted output power at the other ports is sufficiently suppressed. These results indicate that the compact Butler matrix is effective as a power-combining circuit for 28 GHz band applications.