A Broadband 4×4 Butler Matrix with Tunable Phase Shifters Group

A broadband 4×4 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° /0° shifter, a Butler matrix with phase imbalance of ±3° can be obtained from 2.3 GHz to 2.5 GHz (±5° from 2.12 GHz to 2.57). Then a tunable shifters group is designed to produce 0°, ±22.5°, 45° phase shifts. By combining the broadband Butler matrix with the tunable phase shifters group, a 4×4 Butler matrix which can produce 16 differential phases is designed and simulated for demonstration.