Design of High Efficiency Planar Spiral Coil for Implantable Wireless Power Transfer Systems

This paper proposes a five-coil array united structure for implantable wireless power transfer system. The coil structure comprises a radiating coil and a driving coil. The driving coil drives radiating coil to radiate power. Both coils resonate at 13.56 MHz. It can generate almost uniform magnetic distribution which would improve the dislocation tolerance of the wireless power transfer system. At 13.56 MHz, the S parameter is used to calculate the system efficiency. The five-coil array united structure is fabricated on planar printed circuit board. The structure is compact and suitable for implants. According to the experimental results, the system efficiency can reach as high as 54.7% when coils align (transfer distance from 10 mm to 20 mm) and keep almost unchanged with a dislocation from 5 mm to 10 mm (transfer distance is 10 mm). And almost all efficiency values are above 50%. Efficient and stable power transmission is realized.