Wideband Hybrid Coupler With Electrically Switchable Phase-Difference Performance

A wideband hybrid coupler with an adjustable output phase difference with equal power division is proposed. A compact, low-loss and low-cost reconfigurable transmission line with electrically switchable equivalent characteristic impedance and length is introduced and adopted in this design, which is based on a two-section quadrature hybrid structure. Additionally, only two bias points are needed in this hybrid coupler to operate six switches synchronously and provide three output phase differences; 90° and 90 ± a° (a ≤ 30° has been verified). Good matching, isolation, and equal power division are obtained under all phase-difference possibilities. Two examples of a = 15° and 30° are fabricated and measured for 2.4-GHz applications. Testing results demonstrate satisfying properties including the notably stable phase difference with an error less than ±6° over 30% frequency bandwidth. The presented hybrid couplers would be appropriate for Butler matrices to increase the number of possible beams, which will be more than the number of ports.