Design of Wideband Rat-Race Hybrid Using Combined Slot-Coupled Balun and Power Divider

A wideband rat-race hybrid is proposed in this paper. Out-of-phase Marchand balun and in-phase power divider is combined to realize hybrid response with bandwidth enhanced using slot-coupled resonators. A prototype hybrid centered at 3 GHz is fabricated to validate the design. Measured and simulated results are in good agreement, demonstrating that the proposed rat-race hybrid has fractional bandwidth of 64% and 45.2% at ∑- and Δ-port with low insertion loss and imbalance.