J. J. Kuek, K. T. Chandrasekaran, M. F. Karim, Nasimuddin and A. Alphones, "A compact Butler matrix for wireless power transfer to aid electromagnetic energy harvesting for sensors," 2017 IEEE Asia Pacific Microwave Conference (APMC), Kuala Lumpar, 2017, pp. 334-336. doi: 10.1109/APMC.2017.8251447
In this work, a novel compact 4×4 butler matrix is proposed for power transfer to aid electromagnetic energy
harvesting for sensors. The butler matrix is designed to operate at 2.4 GHz. The butler matrix is composed of miniaturized couplers and a crossover. The coupler achieves a miniaturization of 14% and the crossover size is reduced by 17.5% when compared to a conventional crossover. An array of patch antenna is designed
along with the butler matrix and the beam scanning capability of over 1000 is validated by simulation and measurement results.