A Compact Single-Bit Dual-Pol Unit Cell Design for mmWave Reconfigurable Intelligent Surfaces

Except for the sub-6GHz bands, 5G and future generations of wireless communications rely on millimeter wave (mmWave) frequencies to achieve higher data rates, extend broadband internet to a larger portion of the population, and potentially achieve new promising applications and services that combine the synergy or sensing and communications. However, the effort to achieve practical coverage of mmWave signals stumbles on the unfavorable propagation characteristics of higher frequency EM waves. Mmwaves cover much shorter distances than the sub-6GHz signals due to absorption and/or strong scattering from most materials in a typical communication channel. As such, it is very common for the user equipment (UE) to receive unacceptably low signal-to-noise (SNR) signals or experience no coverage at all. Densifying the base station (BS) network is an approach that will improve signal coverage, this comes at a substantial capital expenditure due to the costs associated with the hardware, installation, and maintenance of such complicated systems. Alternatively, using active repeaters or passive reconfigurable intelligent surfaces (RISs) are potential solutions to the mmWave coverage challenges.