Scalable adaptive wireless powering of multiple electronic devices in an over-moded cavity

This paper presents a method for wireless powering of multiple electronic devices placed in an over-moded 2.2-GHz shielded microwave cavity using watt-level high-efficiency sources. Two transmitters based on a 77% efficient pHEMT PA to feed the cavity incoherently via strategically placed microstrip probes. The field patterns inside the cavity result from multiple excited modes ensuring a relatively uniform power density. Narrowband frequency modulation of the sources further improves uniformity. Each electronic device contains a rectenna, power management circuitry, and a rechargeable battery. A microcontroller performs power management and the available battery power is monitored using a low-power 900-MHz transceiver and communicated through a separate monopole probe and displayed external to the cavity. The approach is scalable in terms of power level, field profile, number of devices and overall size. Applications include personal electronics, powering of toys and powering of products in storage crates.