A 24-GHz Beam-Steerable Multinode Wireless Power Transfer System With a Maximum DC Output of 5.7 dBm at 1-m Distance

This article presents the design methodology of millimeter-wave wireless power transfer (WPT) system and the implementation of a 24-GHz beam-steerable multinode WPT system. We first propose a new figure of merit (FoM) to evaluate the cost efficiency and spatial coverage of WPT system. Considering loss in a practical system, we establish a mathematical model to optimize FoM and draw design curves to get some insights into tradeoff among frequency, area cost, and power efficiency at the target distance. To demonstrate the utility of the design methodology, we implement a 24-GHz WPT system consisting of an 8\times 8 phased-array transmitter with 56-dBm effective isotropic radiated power (EIRP) and 5\times 5 high-gain angle-deflection planar rectennas with LED loads. The spacing between the transmitter (TX) and receivers (RXs) is 1 m and the aperture size of TX antenna array and high-gain receiving antenna is 6 cm \times 6 cm. Due to the beam-steering capability of TX, no calibration is required for the precise placement of individual rectennas. The measured results show that all LEDs can be lightened with maximum 5.7-dBm dc power and custom patterns can be displayed using such LED array by sequential beamforming of the TX.