A Broadband 3 dB Directional Coupler With Ultra-Low Amplitude Imbalance

This paper presents a broadband 3 dB directional coupler based on a multi-branch hybrid waveguide. By placing a two-stage stepped waveguide-height discontinuity in the middle of the coupler symmetrically, a controllable ripple is introduced to achieve better overall amplitude imbalance. The simulation results show that over the most of the operating frequency bands from 385 GHz to 481 GHz, the amplitude imbalance is less than 0.037dB. The return loss of the operating frequency band is less than −17 dB and the phase imbalance is better than ± 1.85°.