Adaptive Wireless Power Transfer Enabled IoT Sensor Nodes by a Polarization-Insensitive Scalable Planar Rectenna Module

Wireless power transfer (WPT) has emerged as a promising solution for recharging batteries in low-power Internet of Things (IoT) sensor nodes. However, implementing WPT-enabled sensor nodes poses a significant challenge due to the requirement of orientation-insensitive operation with a compact footprint and adaptive power requirements. To address these problems, this article proposes a novel compact polarization-insensitive rectenna module (RM) with scalable design feature to achieve adaptive RF power harvesting capabilities. The RM incorporates four sequentially rotated rectenna unit cells (RUCs) to achieve polarization insensitivity. Moreover, RUCs are conjugate matched with the rectifier circuit, and their dc outputs are connected in parallel to minimize insertion and combining losses, respectively. The RM offers wider coverage in the broadside direction, with a conversion efficiency of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${54}.{3}\%$ </tex-math></inline-formula> at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-{9}.{0123}$ </tex-math></inline-formula>-dBm input RF power. The proposed RM has four symmetric dc ports, enabling series and parallel dc combining of multiple RMs to achieve modular scalability. Thus, the polarization-insensitive RM is adaptable to a wide range of user requirements, making it a promising solution for low-power IoT sensor nodes.