Resonant Cavity Wireless Power Transfer

We introduce quasistatic cavity resonance (QSCR); which can be used to create near-field standing waves that fill the interior of the resonant structure with uniform magnetic fields, allowing for strong coupling to small receivers contained within. This is accomplished by stimulating the resonant electromagnetic mode of a specially designed, enclosed metallic structure such that induced currents flowing through the walls, ceiling and floor are channeled through discrete capacitors. These oscillating currents in turn generate magnetic fields that permeate the interior of the structure, thus enabling wireless power transfer to receivers contained within, while simultaneously isolating the potentially harmful electric fields in capacitors. This high Q-factor structure efficiently stores electromagnetic energy, and the discrete capacitors allow the resonant frequency to be lowered to a point where the cavity enters the deep sub-wavelength regime, effectively separating the magnetic field from the electric field.

The conceptual diagram of a QSCR depicts a generic rectangular cavity with a central pole that incorporates the capacitors. The magnetic fields are highly uniform and decay at a rate of less than 1/ρ towards the walls, making it possible to strongly couple to coil receivers 1000s of times smaller than the size of the QSCR. Furthermore, deep sub-wavelength operation results in a magnetic field to electric field ratio that is on average 100 times greater than in free space, allowing for a substantially higher level of power to be safely transferred.

Our experimental demonstration shows that a 16ft x 16ft (1,920 cubic feet) QSCR room can deliver power to small coil receivers in nearly any position with 40% to 95% efficiency. Ultimately, QCSR based wireless power offers a method for eliminating the wires and batteries that have limited many innovative solutions in the industrial, medical, and consumer electronic spaces while providing an unprecedented amount of spatial charging freedom.

Wireless Resonant Energy Link (WREL)

This project explores the use of magnetically coupled resonators to safely deliver 10s-100s of watts of power wirelessly to receivers. Our key contribution is the development of adaptive tuning techniques that enable near constant power transfer efficiency, as a function of varying transmitter-to-receiver range and orientation as well as changes in the loads power consumption.