Full-Space Four-Channel Independent Transmit and Receive In-Band Full-Duplex Antenna System With Enhanced Throughput

In this letter, a full-space four-channel in-band full-duplex (IBFD) antenna system is presented with independent transmit and receive beams. It employs a forward structurally multiplexed Fabry–Perot cavity transmitter, a backward folded transmitarray, and two reflectarrays for the four independent channels. The unit cell design adopts a cascaded multilayer metasurface scheme, which is developed to realize independent phase responses for transmission (Tx) and reflection (Rx), whereas the isolation between Tx and Rx is achieved through orthogonal circular polarizations. The proposed architecture therefore ensures four degrees of freedom in phase and two degrees of freedom in polarization. Experimental validation confirms high gain, low axial ratio, and channel isolation exceeding 35 dB across all operating modes. Enabling simultaneous co-frequency full-space transmission and reception, the antenna offers a theoretical fourfold throughput enhancement.