Modeling and Experimental Validation of a Capacitive Link for Wireless Power Transfer to Biomedical Implants

Abstract

This brief reports on the modeling and experimental validation of a capacitive link as an emerging strategy for wireless power transfer to biomedical implants. The capacitive link comprises two pairs of coated parallel plates that are placed at a distance of L apart, with a tissue layer acting as the dielectric material. A series-resonant structure is then formed by placing two inductors in series with the capacitive link. A comprehensive circuit model is proposed that accounts for the L-dependent, parasitic, cross-coupled, and longitudinal resistive elements contributed by the tissue between the two pairs. The series-resonant capacitive link is also realized with 400-mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> capacitive pads on printed-circuit boards that are coated with a 1-μm-thick layer of Parylene-N, aligned around a 5-mm-thick tissue layer, and placed in series with two 100-μH inductors, resulting in resonance frequencies of ~115 and 127 kHz. At an operation frequency of 120 kHz and over a wide range of load resistance from 10 Ω to 100 kΩ, the effect of L on the power delivered to the load and power transfer efficiency parameters of the link is measured from 2 cm to ∞ and shown to be in very good agreement with simulation results from the related circuit model.