Space-Time-Coding Metasurfaces Enabling Programmable Range-Angle-Dependent Energy Auto-Scanning.

Dynamic regulation of electromagnetic energy distribution in space plays a pivotal role in fields like radar detection and wireless communications. However, the state-of-the-art solution based on antenna array requires transmit/receive (T/R) modules per radiating element, causing exponential cost scaling and high power consumption. While reconfigurable metasurfaces have been demonstrated to enable real-time beam scanning in prior works, they can only adjust beam direction and lack the ability to tune energy distribution across different distances. This paper presents a theory for space-time-coding metasurface (STCM) enabled spatiotemporal energy auto-scanning. By applying identical time-varying modulation signals with time delays to each column of the STCM, the reflected energy distribution can be made angle-range-time-dependent. Based on this principle, a novel positioning system is designed, enabling decoupled estimation of a target's angle and distance relative to the metasurface. For experimental validation, a 2-bit metasurface prototype is fabricated and tested. Experimental results align with theoretical analysis, confirming STCM's functional efficacy and deployment potential for applications in radar detection, wireless communications, and related fields.