Performance characterization of variable width square coils for inductive link wireless power transfer

Supplying power to electronic medical implants (EMI) by inductive coupling has always been appreciated for its biocompatibility and its ability to transmit sufficient power to the implants. Although this method was introduced a long time ago, several challenges remain. The major challenge is the sensitivity of the link to coupling and quality factor variations which are strongly dependent on the separation distance and lateral displacements between receiving and issuing coils. In this context and in order to increase the coils' quality factor and to improve the system robustness to coupling factor variations, a new variable width square coil models are proposed and compared with conventional inductive link structures. Walking through experimental validations, this paper shows that employing variable width single layer coil, the quality factor and inductance of the coils are enhanced by 3.4 % and 8.2 % respectively in comparison with standard uniform with coil. Lateral misalignment robustness investigations confirms that, compared with single layer coils, an inductive link composed of double layer square coils is 120 % and 45% less sensitive to lateral misalignments according respectively to x and y axis.