The majority of existing wireless power solutions are capable of 2-D surface charging of one or two devices but are not well suited to deliver power efficiently to large numbers of devices placed throughout a large 3-D volume of space. In this paper, we propose an unexplored type of wireless power transfer system based on electromagnetic cavity resonance. Here, we use the natural electromagnetic modes of hollow metallic structures to produce uniform magnetic fields which can simultaneously power multiple small receiver coils contained almost anywhere inside. An analytical model is derived that predicts the coupling coefficient and power transfer efficiency from the cavity resonator to a small coil. These predictions are verified against simulated results with a coefficient of determination of 0.9943. By using two resonant modes, we demonstrate that a 3-in diameter receiver can be powered in nearly any location in a 140 cubic foot test chamber, at greater than 50% efficiency. Additionally, we show that ten receivers can be powered simultaneously and that this system is capable of recharging consumer electronics such as a cell phone.
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