Over-Moded Cavity for Multiple-Electronic-Device Wireless Charging

This paper discusses a shielded over-moded conductive cavity for wirelessly powering multiple electronic devices simultaneously. The demonstrated cavity is designed for 10-GHz powering with a subwatt transmitter. A study of methods to increase power density uniformity within the cavity is presented, including mechanical stirring, conductive and absorptive object loading, and frequency modulation. It is found that very small frequency modulation of less than 0.1% is sufficient to provide a practical level of power uniformity. A device-under-charge (DUT) consisting of a rectenna, microcontroller, power management circuit, solid-state battery, and ISM-band wireless transceiver is used to validate the study by monitoring the battery charging at various locations within the cavity. The demonstrated shielded three-dimensional charging method is scalable in frequency, volume, power, and number of devices that can be charged.