Near-field magnetic resonance is a highly localized -- traveling a few millimeters to a few feet before transfer efficiency drops off rapidly as the source and receiver are separated by more than a coil diameter. "Likewise, it is not possible to strongly couple coils of drastically different sizes," Disney said.
Disney Research used far-field electromagnetic waves to generate uniform field patterns in a metallic chamber, which can create near-field standing waves for strong coupling to small receivers.
"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."
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