Multifocus Multinull Near-Field Transmitting Focused Metasurface

We propose a novel design of a near-field transmitting focused metasurface, which transforms a linearly polarized planar incident wave into a near-field focused beam with multiple foci and multiple nulls in this article. A generalized method of obtaining the metasurface field distribution on its aperture for specified near-field foci and nulls is first introduced. Then, a three-layer metasurface particle structure with close to full range reconfigurable amplitude and phase transmitting response for realizing the required field distribution is studied. By adjusting the arc length and the rotating angle of the middle-layer metasurface particle structure, a transmitting response with arbitrary amplitude and phase is achieved. Finally, a focused metasurface with two near-field foci and two near-field nulls is designed based on the proposed theory and metasurface particle structure. The designed metasurface is full-wave simulated, fabricated, and measured in the experiment. The experimental results agree well with the full-wave simulating results, showing that both the foci and nulls are well presented at the specified positions and the measured power of the near-field nulls is more than 26 dB below the power of the foci.