Broadband 4x4 Butler Matrix with Tunable Phase Shifters Group

A broadband 4x4 Butler matrix with cascaded tunable shifters, capable of providing 16 switchable differential phases, is proposed in this paper. First, a single layer broadband 4x4 Butler matrix is designed. By using the broadband 3-dB hybrid coupler and broadband 45 degrees/0 degrees shifter, a Butler matrix with phase imbalance of +/- 3 degrees can be obtained from 2.3 GHz to 2.5 GHz (+/- 5 degrees from 2.12 GHz to 2.57). Then a tunable shifters group is designed to produce 0 degrees, +/- 22.5 degrees, 45 degrees phase shifts. By combining the broadband Butler matrix with the tunable phase shifters group, a 4x4 Butler matrix which can produce 16 differential phases is designed and simulated for demonstration.