A Modular Composite Coding Strategy for Accurate and Continuous Beam Scanning in Full Space Based on Coding Metasurfaces

Abstract

With the rapid advancement of terahertz ( THz) imaging and high-speed communications, coding metasurfaces have attracted significant attention for THz wavefront manipulation. However, existing beam control methods mainly rely on mechanical motion or constrained coding strategies, limiting full-space beam coverage and precise scanning. To address this, a modular composite coding strategy is proposed, based on fractional-order scale factors (Mx and Ny) and composite code, with both Mx and Ny set to values greater than 0.5. Combined with the convolution and generalized superposition theorems, this strategy overcomes break through the discrete limitations of phase modulation, enabling continuous scanning of single and multiple beams across the entire space. As a proof of concept, a 2-bit coding metasurface based on Dirac semimetals (DSMs) is designed. By adjusting Mx and Ny through preset angles and integrating forward and reverse coding sequences, the beam directivity and accuracy at different angles θ and φ are verified. The simulation results show that the beam scanning achieves a smooth transition from 0° to 90° for θ and from 0° to 360° for φ, with angular errors below 0.5°. Furthermore, the introduction of the generalized superposition theorem ensures the scanning accuracy while realizing flexible switching between single-beam and multi-beam scanning modes, enhancing beam control versatility. This coding strategy significantly expands the beam manipulation capabilities of coding metasurfaces, opening new possibilities for applications in communication, sensing, and imaging.

Keywords: modular composite coding strategy, coding metasurface, beam scanning, beam scanning, full space, Dirac semimetals