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posted by janrinok on Monday August 03 2015, @02:21PM   Printer-friendly
from the charge! dept.

Now researchers from North Carolina State University and Carnegie Mellon University say they have hit upon a way to boost the efficiency of the energy transfer in that [wireless transfer] situation. They reported, in a paper published in the online edition of the journal IEEE Antennas and Wireless Propagation Letters, that by placing a magnetic resonance field enhancer (MRFE)—a loop of copper wire resonating at the same frequency as the AC current feeding the transmitter coil—between the transmitter and receiver coil, they could boost the transmission efficiency by at least 100 percent. "Our experimental results show double the efficiency using the MRFE in comparison to air alone," David Ricketts of NC State, said in a press release. The MRFE increases the strength of the magnetic field that reaches the receiver coil, resulting in an increase of the transmission efficiency.
...
For their experimental setup, the team used two coils of 4.25-centimeter- diameter copper wire with six turns for the transmitter and receiver coils. The coils were separated by 12.2 cm and the transmitter coil was powered with a 2.94-megahertz signal. They measured the transmission efficiency by placing a metamaterial between the transmitter and receiver coil and comparing it with a setup where a single, 12-cm-diameter copper-wire loop replaced the metamaterial. They found that the copper wire version improved the efficiency by a factor of almost two.

Does wireless charging solve any problems that an industry-adopted connector standard wouldn't?


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  • (Score: 1, Informative) by Anonymous Coward on Monday August 03 2015, @07:53PM

    by Anonymous Coward on Monday August 03 2015, @07:53PM (#217537)

    From the research paper (note: "MM" is using the metamaterial and "MR-FE" is a "resonant loop field enhancer"):

    . In Fig. 1(b), an isotropic MM (I-MM) disc is inserted equidistant
    between the source and receiver (optimal µmm = −1 − 0.1j
    from [3]) with a thickness of 0.25 m and a radius, RMM=0.34
    m (.091 m3). The dimensions were chosen to align with the
    maximum coupling enhancement found in previous work, [3],
    using an isotropic MM with the same permeability

    . . .

    Next, Fig. 1(c) shows the MR-FE structure inserted between
    the source and receiver coils. When driven at the resonant
    frequency, the MR-FE loop acts as a magnetic dipole that enhances
    the field between the source and receiver. The MR-FE
    is composed of a single coil of copper wire (σ = 5.998 × 107
    S/m, 2.04 mm cross-sectional diameter) with a radius of 0.25
    m, split at one location where a capacitor is placed in series
    with the coil to provide resonance at 10 MHz

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