Optimizing three-phase three-layer coil array for omnidirectional wireless power transfer

Angular misalignment between transmitting and receiving coils leads to “dead spots”, i.e., no power is received for some receivers in electromagnetically coupled wireless power transfer (WPT) systems. Multi-layer multi-phase coil array is an alternative that can generate omnidirectional and homogeneous magnetic fields. In this work, the magnetic field from a coil array is calculated and explored for omnidirectional magnetic field characteristics. In order to improve the magnetic field at the “dead spots” in the receiving region, the worst-case power transfer efficiency is optimized, which is a different scheme from the conventional one. As an example, a WPT system for powering many fully implanted, distributed, and tiny neural recording implants under the restriction of 20-mm power transfer distance is optimized by this new scheme.