Large Power Division Ratio Branch-Line Coupler With Differential Through and Differential to Single-Ended Coupling

This article presents a large power division ratio (PDR) branch-line coupler. The proposed coupler can realize the differential signal pass-through from the balanced-to-balanced ports and the single-ended signal coupling from the balanced to unbalanced ports. The authors demonstrate the proposed coupler using a microstrip circuit prototype with a PDR of 10 dB.