Wireless Power Transfer with Multi-Layer Planar Spiral Coils as Secondary Coils

As the sizes of implantable medical devices such as implantable cardioverter defibrillators, deep brain stimulators, and retinal implants shrink; powering these devices become more challenging. Wireless power transfer (WPT) enables the use of rechargeable and thus smaller batteries, however it also requires additional space for the receiving coil. Depending on the location of the implant in the body, device area or volume can be more constrained. In this paper, we investigate multi-layer planar spiral coils via simulations. We study the impact of number of turns on the quality factor for multi-layer coils including coils with different number of turns in each layer (hybrid coils) and we offer recommendations on the approximate number of turns for having high Q values.