Time-modulated 1-bit amplitude-coded metasurface for space-frequency beam shaping.

Two-dimensional (2D) space-encoded metamaterials enable the progressive development of a multitude of functionalities for controlling electromagnetic (EM) waves. Recently, time-modulated phase-coded metasurfaces have been introduced into 2D metamaterials, allowing for EM wave manipulation across both spatial and frequency domains. This approach is naturally suited to microwave frequency range where the compact phase controlling elements, such as diodes and varactors are readily available. However, as future generation communication systems target frequencies above 100 GHz with a much higher speed and more densification, enhanced solutions utilizing the novel concepts will be inevitable because the metasurface integration with the common active elements is challenging. Here, we propose the space-time 1-bit amplitude-coded metasurfaces instead of phase-coded one to support the complex functionality for the intelligent control of the environment in wireless communication systems. The solution is implemented using graphene-based meta-atom, where 1-bit amplitude-coding is reconfigurable via bias voltage. To validate the effectiveness of this approach for beam shaping, we demonstrate beam steering with low sidelobe patterns by achieving the desired effective amplitude and phase distributions. This proposed method is anticipated to broaden the applications of digital coding metasurfaces, particularly in THz wireless communication systems.