Loosely Coupled Wireless Charging of Footwear-based Sensor System

This paper presents a wireless charging system that can power up footwear-based sensors. Loosely coupled magnetic resonant technique was applied to achieve a 20 mm-long charging distance relative to the conventional Qi charging, which requires close proximity and precise alignment. Transmitting and receiving resonators are modeled and simulated with a full-wave solver, ANSYS HFSS. Simulation results match measured results with respect to coupling coefficient (k). The resonator coupling efficiency (RCE) for the loosely coupled wireless charging system over a 20 mm gap is 65%, which seems feasible for a small battery-operated sensor system.