Unlike conventional systems in which two identical resonant loops are employed, a pair of novel planar loops is developed for wireless power transfer. The proposed transmitting and receiving coils have different distances between turns while the wire length is the same. The effect of mutual inductance on transfer efficiency is analyzed. The mutual inductance of the proposed loops is more uniform than the conventional one, which is helpful for suppressing frequency splitting at closer transfer distance. Moreover, the power transfer performance is enhanced at longer distance. Additionally, an experimental prototype is fabricated to verify the distance insensitive characteristic of the proposed system.
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