This letter focuses on improvements in the performance of flat-wire coils for wireless power transfer in smartphones based on the Qi interface standard. At high frequencies, alternating-current copper losses increase due to the proximity and skin effects. A low-permeability magnetic composite with low hysteresis loss was applied to a coil to reduce coil losses. A parametric analysis was used to obtain the optimum composition of the magnetic coating. Power transmission experiments on a coated coil designed for minimum loss showed that the steady-state temperature was lower than that of an uncoated coil. The coated-coil resistance was lower at high frequencies, where resistance due to skin and proximity effects are significant. When misaligned with respect to a charging pad's transmit coil, the coated coil had a smaller decrease in efficiency compared to an uncoated coil.

中文翻译：

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用于无线电力传输的具有磁性复合材料的扁平线线圈的改进性能

这封信重点介绍了基于 Qi 接口标准的用于智能手机无线电力传输的扁平线线圈的性能改进。在高频下，由于邻近效应和趋肤效应，交流铜损耗会增加。将具有低磁滞损耗的低磁导率磁性复合材料应用于线圈以减少线圈损耗。参数分析用于获得磁性涂层的最佳组成。在设计为最小损耗的涂层线圈上进行的功率传输实验表明，稳态温度低于未涂层线圈的稳态温度。涂层线圈电阻在高频时较低，其中由于趋肤效应和邻近效应引起的电阻很显着。当与充电板的发射线圈未对准时，