Energy harvesting and wireless power transfer in a unified system for wearable devices

This paper presents a device concept that allows us to utilize the coils of an electromagnetic vibration-based energy harvester as a receiver for a magnetic resonant coupled wireless power transfer system (WPTS), with focus on low-power wearable applications. The parasitic capacitances of the coils along with their inductances form a single equivalent receiver coil configured in parallel. This self-resonance characteristic relaxes the requirement of adding an additional capacitor and still retains the system inherent simplicity. Measurements with an arbitrarily chosen load resistance of $R_{L}\,= 100 \Omega$ demonstrate a generated power of $\sim 397.4 \mu W$ at a distance between the transmitter and receiver of 2 cm at a root mean square applied $\mathbf{B}$ – field of $200 \mu T$, approximately.