A Model Independent Scheme of Adaptive Focusing for Wireless Powering to In-Body Shifting Medical Device

A novel method for wireless power transfer (WPT) in complex multipath propagation environments of human body, based on the reversal pretest and the principle of reciprocity, has been proposed in this paper to adaptively enhance the intensity of the field on the surface of implanted antenna. As a model-independent scheme, this method makes all the field components focus adaptively on a given position in unknown inhomogeneous media which can be very complicated, random, and even time varying. The principle and the steps of the adaptive focus (AF) WPT are described first. The design of the implanted antenna conformal with a capsule inside the tissue and the multiple antennas out of the body is then given to build a principled prototype for the AF-WPT. Both the numerical simulation and the experimental measurement for the AF-WPT model with the operation frequency in Industrial Scientific Medical Band have been given to show the validation of this method. It has been shown from the simulation and experimental results that in comparison with the other methods, the field focusing scheme increases 6 dB higher intensity of the field at the position of the capsule antenna while keeping the level of the received power more stable with the continuous shifting of the implanted antenna.