Two-Section Broadband Couplers with Wide-Range Phase Differences and Power-Dividing Ratios

A two-section broadband coupler with wide-range phase differences and power-dividing ratios is proposed. Closed-form design equations for the proposed couplers are derived. For verification, two couplers I and II operating at 2 GHz with phase difference of 45° and power-dividing ratio of 1, and phase difference of 60° and power-dividing ratio of 2, respectively, are fabricated and measured. For the coupler I (II), the measured 15-dB return loss and isolation bandwidth is 38.0% (51.5%). The measured bandwidths of the amplitude imbalance < 1 dB and the phase imbalance < 5° of the coupler I (II) are 29.5% (35.5%) and 29.0% (43.0%) with 15-dB return loss and isolation, respectively.