Flexible beamforming using transmission-type coding metasurface

Abstract

The emergence and rapid development of metasurfaces have paved the way towards arbitrarily manipulating electromagnetic (EM) waves through amplitude and phase control. However, most real time manipulations were realized in reflection-type metasurfaces depending on phase control. Shaping transmitted fields with metasurface dynamically is still lacking to date. Herein, we propose a strategy combining active transmission amplitude control with phase coding to achieve excellent ability of tailoring the transmitted field patterns dynamically in microwave regime. The metasurface consists of a binary phase coding part on the bottom and an amplitude control part with loaded PIN diodes on the top. When biasing the diodes with variable voltage, active transmission amplitude control is obtained for specific phase coding units without affecting the others. Through phase coding and active amplitude control, manipulating the radiated EM waves on two degrees of freedom is realized. Dynamic beamforming on two coding schemes with this method is exhibited to the demonstrate the manipulation mechanism. The experiment results show good agreements with the theoretical predictions and numerical simulations, hence confirm the proposed concept. In addition, the elaborately designed bias network makes the metasurface polarization-insensitive. This work adds a convenient and feasible way for dynamic EM manipulation and can found new applications, such as reconfigurable beam emitter for adaptive communication and radar systems.