X-band multi-layer phase gradient metasurface for high efficiency far field subwavelength imaging

The evanescent wave that can only exist on the surface of the objects is the main reason for diffraction limit, which limits the subwavelength details of the objects to the near field. This paper designs a multi-layer phase gradient metasurface with 10°/mm increment and 69% transmission efficiency in X-band. Evanescent wave can be converted into propagation wave and transmitted to the far field with the help of this metasurface. Through Fourier transform and spectrum analysis, two targets with 10mm subwavelength distance are successfully resolved and imaged around 10GHz.