Electromagnetic near-field focusing based on metasurfaces

Near-field electromagnetic focusing has become a hot research topic due to its high application value in wireless transmission, wireless sensing, biomedicine, and radio frequency identification. In this paper, anisotropic metasurfaces have been proposed to manipulate the phase of the electromagnetic (EM) wave for obtaining EM near-field focusing. Under orthogonal linearly polarized incidence, dual focus functions can be realized independently for polarization multiplexing on the metasurfaces. Meanwhile, Single focus and multi focus with different energy distributions and focal position is obtained by the proposed metasurfaces. By using the Vivaldi antenna as the feed source positioning at the focal of the metasurfaces, a lens antenna with high gain is obtained with circularly polarized far-field mode and broadband characteristics. Due to the unique advantages of metasurfaces in modulating the phase distribution of EM waves, the proposed method may pave a new way for EM focusing application.