Design and Implementation of Wireless Charging Antenna Array Using Highly Isolated Coils for Expanding Spatial Freedom

In this paper, we propose a two-dimensional (2D) wireless power transfer (WPT) system using highly isolated coils for expanding spatial freedom. The proposed transmitting coil is arrayed with highly isolated coils comprised three different coils with a 2D structure. The proposed 2D WPT system can transmit the power to the receiving coil regardless of lateral and angular misalignments of receiving coil through all directions magnetic fields generated by isolated coils. For the performance verification, the power transfer efficiency (PTE) under the lateral and angular misalignments in the operating area is measured and is compared with the conventional WPT system, highly isolated WPT system, and proposed 2D WPT system implemented on the 2D plane. The proposed 2D WPT system is matched at 6.78 MHz and achieves approximately 50% or more PTE regardless of all lateral and angular misalignments when the receiving coil is set to $200\times 200\mathrm{m}\mathrm{m}^{2}$ and the PTE is measured in the operating area of $300\times 300\times 100\mathrm{m}\mathrm{m}^{3}$.