Space‐Time‐Modulated Metasurface Enabled High‐Performance Near‐Field Focusing with Enhanced Phase Modulation

Abstract Near‐field focusing (NFF) holds significant importance for applications such as communication, wireless power transfer, and sensing. Reconfigurable metasurfaces enable real‐time NFF, but current methods relying on 1‐bit or finite quantization limit performance and efficiency. Here, a space‐time‐modulated (STM) metasurface is proposed to overcome these limitations, enabling high‐quality NFF performance with low cost and reduced spatial requirements. By introducing a new phase term at harmonic frequencies ( f c + kf o ), where f c = 24.5 GHz is the carrier, and f o = 100 kHz is the modulation frequency and k is the harmonic order (k = ±1, ±2, ±3…). The STM method provides nearly continuous phase compensation at the +1 st harmonic, resulting in superior NFF performance compared to the fundamental frequency. Furthermore, as the number of meta‐atoms reduces, the STM metasurface maintains a stable focusing performance, whereas traditional 1‐bit transmission metasurface exhibits elevated sidelobe levels. Consequently, the STM approach provides enhanced NFF performance with fewer meta‐atoms, resulting in fewer active components, reduced hardware complexity, and smaller spatial footprints. An 8 × 8 prototype is fabricated and experimentally validated to assess its NFF characteristics. The findings of this research substantiate the proposed technology and lay the groundwork for future applications in compact, high‐performance imaging and detection systems.