Decoupling in a joint communication and sensing system with metasurface

The increasing demand for integrated communication and sensing has led to the development of Joint Communication and Sensing (JCAS) systems. However, strong self-interference (SI) between transmitting (TX) and receiving (RX) antennas remains a major obstacle, significantly degrading system performance in compact MIMO arrays. Traditional signal-processing-based cancellation methods face limitations in wideband scenarios due to high complexity and potential signal distortion. In this work, a novel metasurface-assisted decoupling structure is presented. The metasurface based on modified split-ring resonators (MSRRs) can suppress surface currents and reduce the coupling between TX and RX arrays. To further enhance isolation and reduce front-end self-interference in sensing-centric full-duplex JCAS, a multi-frequency null-space projection (NSP) beamforming algorithm is integrated with the antenna array design, forming a hardware-algorithm co-optimization framework. As proof of concept, a 2 × 2 patch antenna array incorporating the proposed metasurface operating in the 9-10 GHz band has been designed, fabricated, and characterized. The measurement results validate effectiveness. The findings suggest that the proposed decoupling approach offers a promising solution for enhancing electromagnetic isolation and overall system performance in next-generation JCAS applications such as intelligent transportation and indoor wireless sensing.