Apple may bring wireless charging to the iPhone in a future iteration, but it likely won't use the same induction charging technology popularized by Palm's Touchstone charger. Instead, the company will likely implement more exotic near field magnetic resonance charging currently being championed by wireless power startup WiTricity.
Induction charging works by inducing a current in a coil of wire from one device to another. A charger device (Palm's Touchstone charger, for instance, or a mobile device "charging mat") contains a large coil of wire inside. When a current passes through the coil, it creates a small magnetic field around the coil. When a second coil—embedded in a mobile device like a smartphone—is brought into close proximity of the first coil's magnetic field, it induces a current to pass through the second coil.
This technique is the same one that is used to build power transformers—essentially, the charging coil and the device coil act as a transformer with an air core. The downside to this method is that power is transmitted wirelessly over very short distances. In effect, the device has to be in contact with the charging device to work. Also, power transmission isn't particularly efficient.
Near field magnetic resonance (NFMR), on the other hand, can work over much larger distances. The power source is a relatively low power magnetic resonator, which creates a stronger magnetic field than a typical induction charger. Devices then use a tunable resonant circuit that can "dial in" to the specific frequency of the power source. The tuned resonance increases efficiency, as high as 90 percent—while increasing the size of the usable resonant field.
(A side benefit of the technology is that magnetic fields are safe for living things compared to radiated energy.)
The technology was originally developed between 2005 and 2007 by a team led by MIT physics professor Marin Soljačić. WiTricity was founded in 2007 by Soljačić and others to commercialize the technology. Two years later, WiTricity CEO Eric Giler demonstrated the technology using a modified iPhone during the 2009 TED conference.
Wireless Electricity - WiTricity Showcase TED 2009MacRumors pointed out that a recent Wall Street Journal report about upcoming iPhone hardware revisions had briefly mentioned that Apple was exploring wireless charging. The site then drew a connection to an international patent application, filed by Apple and published in May of this year, titled "Wireless Power Utilization in a Local Computing Environment."
A magnetic resonance field around a computer (202) could power or charge a keyboard (204), mouse (206), and "portable media player" (208).Building on WiTricity's techniques and citing Soljačić's research, Apple's patent details the use of a desktop or laptop computer as a NFMR source, either with a built in resonator or alternately using a USB dongle. The computer could then power or recharge wireless devices, including keyboards, mice, and—you guessed it—mobile devices like iPhones and iPods. The devices would need to be within a meter of the computer to automatically couple and start receiving power. Furthermore, devices could "de-tune" themselves after fulling charging or entering an idle state to reduce power consumption.
Even if Apple is exploring wireless charging and made the effort to file a patent on one useful process for the tech, there's no guarantee that it will show up in a future iPhone anytime soon. Still, combined with iOS 5's upcoming WiFi syncing, wireless NFMR charging could eliminate the need to ever plug an iPhone into the wall or a computer ever again. That prospect leaves us hopeful that Apple will find a way to implement NFMR sooner rather than later.
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