Single-Ended-to-Balanced Hybrid Coupler for In-Band Full-Duplex Transceivers

In this paper, a wideband single-ended-to-balanced hybrid coupler is proposed. The design is based on a transformer-based hybrid coupler, which has very high isolation between the sum and difference port. Multiple resonances are produced in the operating band to extend the bandwidth. Slotlines and microstrip-to-slotline transitions are used for converting the unbalanced signals to balanced ones. A prototype is modeled, simulated, fabricated and verified via experiment.