RISCAM: A 576-Element 2-D Scalable Reconfigurable Intelligent Surface With Multibeam RF Camera at X-Band for ISAC

Reconfigurable intelligent surfaces (RISs) mitigate non-line-of-sight (NLOS) challenges but remain limited in 5G wireless systems due to poor scalability and the absence of integrated user localization needed for low-latency beam management and joint sensing–communication. Conventional AP-driven beam management adds significant delay and signaling overhead. This work introduces the first RIS with built-in user localization using a shared aperture integrating an RF camera forming 13 simultaneous beams. The 576-element (24x 24) surface forms reconfigurable beams scanning –50° to 50°, achieving ~36 dB directivity and ~3° beamwidth. Thirteen sensing subarrays (208 elements) enable dual-purpose sensing and reflection, realizing an RF camera with <2° RMSE localization accuracy. By combining multibeam sensing with reconfigurable reflection, the system can estimate the angle of arrival (AoA) and dynamically retro-reflect or steer wavefronts. Measurements validate precise AoA estimation, effective beam steering, and strong agreement with full-wave simulations for future 6G integrated sensing and communications (ISACs).