A dual-band 3-bit reconfigurable intelligent surface with independent control of phases

Reconfigurable Intelligent Surfaces (RISs) have received a great deal of attention from the wireless communication community due to their powerful ability to improve the wireless communication environment. Dual-band RIS enables aperture to share two bands, improving spectrum utilization in wireless communications and thus expanding communication capacity. However, most of the reported dual-band RISs cannot achieve independent controls of the dual-band phases, which greatly limits their practical application in wireless communications. In this paper, we propose a dual-band 3-bit RIS to achieve independent controls of the reflection phases in two frequency bands by designing two tunable structures without raising the profile. It also exhibits low sensitivity to incident angles between 0° and 50°. Thereafter, the beam steering ability of the proposed RIS is further investigated with experiments under normal and oblique incidences at two frequencies, which demonstrates the powerful potential of RISs to manipulate the electromagnetic wave propagation environment.