Metasurface Design on Low-Emissivity Glass via a Physically Constrained Search Method

Low-emissivity (Low-E) glass, crucial for thermal insulation, significantly attenuates wireless signals, hindering 5G communication. Metasurface technology offers a solution, but the existing designs often neglect the etching ratio constraint and lack physical interpretability. In this work, we propose a physically constrained search method that incorporates prior knowledge of the capacitive equivalent circuit to guide the design of metasurfaces on Low-E glass. First, the equivalent circuit type of the metasurface is determined as a capacitive structure through transmission line model analysis. Then, a random walk-based search is conducted within the solution space of topological patterns corresponding to capacitive structures, ensuring etching ratio constraints and maintaining structural continuity. Using this method, we design a metasurface pattern optimized for 5G communication, which demonstrates over 30 dB improvement in signal transmission compared with full-coating Low-E glass. A fabricated 300 mm × 300 mm prototype, etched with a ratio of 19.5%, demonstrates a minimum transmission loss of 2.509 dB across the 24–30 GHz band with a 3 dB bandwidth of 4.28 GHz, fully covering the 5G n258 band (24.25–27.5 GHz). Additionally, the prototype maintains a transmission coefficient reduction of no more than 3 dB under oblique incidence angles from 0° to 50°, enabling robust 5G connectivity.