Dynamic radiation steering with transmission-type coding metasurface

In this paper, we integrate continuous transmission amplitude modulation and phase coding into a metasurface, and dynamic transmitted electromagnetic field manipulation is realized in microwave regime. The active metasurface is obtained by placing a PIN diodes loaded amplitude modulation metasurface on a binary phase coding metasurface whose coding matrix is optimized by genetic algorithm. Changing the bias voltage applied on the diodes, the transmission amplitude of the phase coding units covered by amplitude modulation units can be tuned continuously while other coding units are not affected, leading to the fact that the transmitted field pattern of the metasurface varies from strongly directional transmission to diffusion-like radiation. By this means, two degrees of freedom of dynamic amplitude modulation and predesigned phase coding are achieved to control the electromagnetic waves. Additionally, a bias network is designed to ensure the polarization-stability of the metasurface. The proposed concept is predicted by analytical model, and verified by numerical simulations and experiment. This design with low profile and diverse functionalities can yield potential applications ranging from radio frequency energy harvesting to wireless communication systems.