Rahayu, Y., J. R. M. Simanihuruk, and Yuyu Wahyu. “A Compact Design of 4×4 Butler Matrix With Four Linear Array Antenna at 38 GHz”. International Journal of Electrical, Energy and Power System Engineering, Vol. 5, no. 3, Nov. 2022, pp. 80-85, doi:10.31258/ijeepse.5.3.80-85.