Time-varying digital coding of induced-magnetism Huygens’ metasurfaces for flexible and continuous control of harmonics

Time-varying digital coding metasurfaces have garnered significant attention due to their ability to achieve flexible and continuous control over harmonics through the flexible design of coding sequences. These metasurfaces have important applications in wireless communications, radar detection, and biomonitoring. However, the majority of existing time-varying digital coding metasurfaces are reflective in design, leading to an inevitable masking effect at the location of the feed source. Therefore, there is an urgent need to explore the design of transmissive time-varying digital coding metasurfaces that enable flexible and continuous control of harmonics. In this study, we propose a transmissive time-varying digital coding metasurface based on the induced-magnetism Huygens’ principle. We conduct a detailed study of the phase modulation theory for flexible and continuous control of harmonics in the time-varying digital coding induced-magnetism Huygens’ metasurface. By precisely modulating the transmission phase difference of this metasurface and introducing time-delay gradients in each column of metasurface units, we achieve flexible and continuous control over harmonics successfully. Our study presents a solution for the design of transmissive time-varying digital coding metasurfaces, enabling flexible and continuous control over harmonics and expanding the application potential of time-varying metasurfaces.