Enhanced Bandwidth Compact Hybrid Rat-Race Coupler for 5G Dual Band Applications

A compact hybrid rat-race coupler with dual-band behavior at 2.4 GHz, respectively at 5.2 GHz is presented. The transmission lines used for the design consist of three impedance inverter symmetrical unit cells with complementary behavior. The implementation with real lumped elements shows a very good agreement between the ideal case and the real one. The simulations for the real implementation of the return and isolation losses are around 40 dB, while the insertion and coupling losses are around 3.5 dB at both frequencies. The phase difference at the output ports shows an imbalance of ±1o from the ideal case.