Space-time-coding digital metasurfaces

TLDR

Digital coding metasurfaces enable real‑time, programmable control of electromagnetic waves, yet existing designs encode only spatial information and ignore the temporal dimension. This work introduces a general theory of space‑time modulated digital coding metasurfaces that simultaneously steers propagation direction and shapes harmonic power distribution. The authors demonstrate the concept with harmonic beam steering, beam shaping, and scattering‑signature control, implementing a prototype driven by an FPGA that optimizes the space‑time coding sequence. Numerical and experimental results confirm the approach’s effectiveness and suggest applications in wireless communications, cognitive radar, adaptive beamforming, and holographic imaging.

Abstract

Abstract The recently proposed digital coding metasurfaces make it possible to control electromagnetic (EM) waves in real time, and allow the implementation of many different functionalities in a programmable way. However, current configurations are only space-encoded, and do not exploit the temporal dimension. Here, we propose a general theory of space-time modulated digital coding metasurfaces to obtain simultaneous manipulations of EM waves in both space and frequency domains, i.e., to control the propagation direction and harmonic power distribution simultaneously. As proof-of-principle application examples, we consider harmonic beam steering, beam shaping, and scattering-signature control. For validation, we realize a prototype controlled by a field-programmable gate array, which implements the harmonic beam steering via an optimized space-time coding sequence. Numerical and experimental results, in good agreement, demonstrate good performance of the proposed approach, with potential applications to diverse fields such as wireless communications, cognitive radars, adaptive beamforming, holographic imaging.