A High-Isolation Sub-6 GHz In-Band Full-Duplex Communication System

In 5G networks, the sub-6 GHz band offers broader user coverage and more reliable connections compared to its millimeter-wave counterpart. The increasing spectrum congestion in sub-6 GHz has driven research into the in-band full-duplex (IBFD) communication. This work explores the design principles of a high-isolation IBFD transceiver prototype for future 5G-Advanced networks. The designed IBFD transceiver employs a high-isolation spiral antenna design, which offers high spatial isolation while avoiding the complicated radio frequency self-interference cancellation. Prototype test results demonstrate that the provided spatial isolation is over 70 dB, and the overall self-interference cancellation performance exceeds 120 dB combined with nonlinear digital self-interference cancellation.