RISCAM: A 576-Element 2D Scalable Reconfigurable Intelligent Surface with Multi-Beam RF Camera at X-band for ISAC

Reconfigurable intelligent surfaces (RISs) mitigate non-line-of-sight challenges but remain limited in 5G 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 that integrates an RF camera forming 13 simultaneous beams. The 576-element (24 × 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 multi-beam 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 (ISAC).