An In-Band Co-Circularly Polarized Full-Duplex Antenna With Scattering Manipulation

This letter presents a novel in-band co-circularly polarized full-duplex antenna with scattering manipulation to achieve simultaneous transmitting, receiving, and scattering on the same aperture. By leveraging nonreciprocal phase shifters and six-port balanced cancellers, the proposed design achieves enhanced isolation among the scattering, receiving, and transmitting paths, thereby enabling independent control over their respective performance. In the scattering path, this structure not only facilitates signal amplitude amplification but also enables precise control over the direction of the reflective signal through the phase gradient method. Consequently, this design significantly contributes to an improved radar crosssection (RCS) by providing retro-reflection characteristics with high-angle selectivity. In addition, the structure can effectively mitigate leakage from the transmitting path to the receiving path, resulting in increased isolation between the transmitter and receiver. To validate the improvements offered by the proposed design, a 1 x 6 array centered at 5.5 GHz is subjected to both simulation and fabrication. Experimental measurements confirm that the proposed structure achieves interport isolation exceeding 30 dB within the operating band. Notably, the maximum normalized RCS is approximately 3 dB under the -30 degrees retroreflective angle.