Low-Power Consumption and Beam-Sustainable Reconfigurable Intelligent Surface for Fixed Wireless Communication at Millimeter-Wave 5G Band

This article presents a low-power consumption and beam-holding reconfigurable intelligent surface (RIS) for reliable millimeter-wave 5G fixed wireless communication. Conventional RIS designs require continuous power to maintain beamforming, with power consumption divided into two main parts: power drawn by the control board and power dissipated by unit cells. The strategies for reducing power consumption differ based on the adjustable components used. In this study, a liquid crystal (LC)-based RIS is employed to achieve low-power consumption, alongside a customized bias circuit that incorporates switches and capacitors. The proposed circuit operates using bias pulses, allowing charges to be stored in the capacitors, which in turn ensures beam sustainability. Prior research on LC-RIS reported the need for continuous power consumption and complex bias nodes to control the LC. Moreover, the proposed RIS, consisting of an N × N array, requires only 2N bias nodes for 2-D beamforming, unlike traditional RIS designs. This innovative biasing approach, referred to as an active-matrix scheme, enables a low-power, beam-sustainable RIS architecture and can be effectively applied to electrically large RIS arrays with 2-D beamforming capabilities.