Joint time-frequency analysis on space-time-coding digital metasurfaces

Abstract Space-time and time-varying metastructures have attracted a lot of research interest in recent years. On the other hand, digital programmable metasurfaces also gained great attention owing to their powerful capabilities controlling electromagnetic (EM) fields waves real time, which is very suitable for implementing spatiotemporal modulations manner. Accordingly, space-time-coding (STC) recently been proposed realize advanced manipulations EM wavefronts information, allowing simultaneous control propagation directions space domain harmonic distributions frequency domain. However, instantaneous responses connection between time- frequency-domain characteristics not yet fully revealed. Here, we present joint time-frequency analysis method revisit STC metasurfaces, time-domain scattering patterns equivalent excitations are investigated analyze spatial-spectral modulated waves. This helps better explain basic working principle expected facilitate more applications wireless communications, radar, imaging, beamforming.