Electromagnetic Signal Modulation by Chromatic Dispersion in Phase Gradient Metasurface

Chromatic dispersion in phase gradient metasurface and its impact on the scattered electromagnetic signals are studied in this paper. Due to its intrinsic material dispersion and special spatial arrangement of unit cells, phase gradient metasurfaces produce large chromatic dispersion for the scattering waves, resulting in anomalous reflection and refraction phenomena. Moreover, from the perspective of signal domain, the scattered waves no longer carry the whole information of the incident wave, especially for the wideband ones, because different frequencies are scattered into different directions due to the large chromatic dispersion. This progress is equivalent to a signal modulation in each scattering direction. Here we utilized a simple calculation method to achieve the direction-related spectral response characteristic for a given metasurface using 2D Fourier transform of the 2D phase pattern. Furthermore, a typical wideband radar signal was adopted to give a visualized display of the modulation effect. The simulated results showed that the scattered signals were greatly distorted, causing the correlation reduction and range deviation in radar detection. This work opens a new possibility for metasurface to manipulate the signal characteristic of electromagnetic waves and may prompt new applications in antennas, communication and radar systems