Mobile and Portable Communications
Wireless Power Transfer
Javier Gozálvez

A group of researchers at the Korea Advanced Institute of Science and Technology (KAIST) has developed a wireless-power transfer (WPT) technology that allows mobile devices to be charged at any location and in any direction, even if the devices are away from the power source. With this technology, so long as mobile users stay in a designated area where the charging is available, the device will pick up power automatically, as needed. KAIST claims that the WPT system is capable of charging multiple mobile devices concurrently and with unprecedented freedom in any direction, even while holding the devices in midair or 0.5 m away from the power source, which is a transmitter. The solution uses high-frequency magnetic materials in a dipole coil structure to build a thin, flat transmitter system shaped into a rectangle with a size of 1 square meter.

Either 30 smartphones with a power capacity of 1 W each or five laptops with a capacity of 2.4 W each can be simultaneously and wirelessly charged at a 50-cm distance from the transmitter with six degrees of freedom [the degree of freedom represent mobile devices’ freedom of movement in three-dimensional (3-D) space], regardless of the devices’ three-axis positions and directions. This means that the devices can receive power all around the transmitter in 3-D space. The maximum power transfer efficiency for the laptops was 34%. The researchers said that fabricating the plane of the transmitter and receiver coils with the six-degree-of-freedom characteristic was a bottleneck of WPT for mobile applications. The research team used the dipole coil resonance system (DCRS) to induce magnetic fields. The DCRS is composed of two (transmitting and receiving) magnetic dipole coils placed in parallel, with each coil having a ferrite core and connected with a resonant capacitor.

Read the full article: "Advances in Wireless Power Transfer [Mobile Radio]", IEEE Vehicular Technology Magazine, Volume 10, Issue 4, December 2015.

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Mobile and Portable Communications
Wireless Power Transfer
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