Anisotropic impedance holographic metasurface for near-field imaging

In this paper, the concept of anisotropic impedance holographic metasurface is proposed and validated by realizing holographic imaging with multipoint focusing techniques in near-field areas at the radio frequency domain. Combining the microwave holographic leaky-wave theory and near-field focusing principle, the mapped geometrical patterns can be constructed based on the correspondence between meta-atom structural parameters and equivalent scalar impedances in this modulated metasurface. Different from conventional space-wave modulated holographic imaging metasurfaces, this surface-wave-based holographic metasurface fed by monopole antenna embedded back on metal ground enables elimination of the misalignment error between the air feeding and space-wave-based metasurface and increase of the integration performance, which characterizes ultra-low profile, low cost, and easy integration. The core innovation of this paper is to use the classical anisotropic equivalent surface impedance method to achieve the near-field imaging effect for the first time. Based on this emerging technique, a surface-wave meta-hologram is designed and verified through simulations and experimental measurements, which offers a promising choice for microwave imaging, information processing, and holographic data storage.