Inductive Power Transfer Link at 13.56 MHz for Leadless Cardiac Pacemakers

Abstract

Inductive power links are most viable for the long-term powering of cardiac pacemakers. Designing an inductive power link without surpassing the specific absorption rate (SAR) for modern leadless cardiac pacemakers (LCPs) remains a challenging task because of its size and implantation depth. The inductive power link employed in the conventional works is either designed at a high frequency or based on the size, shape, weight, and implantation depth of conventional cardiac pacemakers. Here, a 3-coil inductive power transfer link with a circular transmitter coil and solenoidal receiver coil is designed at 13.56 MHz to provide uninterrupted power to the modern LCPs. Considering the food and drug administration approved term for implant size of modern LCP, the receiver coil is designed with 6 mm diameter and 6.5 mm length. The performance of the link has been verified through simulations and measurements under perfect alignment, lateral and/or angular misalignments, and distance variation between the coils. At a 50 mm horizontal distance between transmitter and receiver coils, the transmission coefficient is −30.9 dB. The maximum simulated average SAR at heterogeneous phantom is 0.30 W/kg, which is lower than the limit set by the Federal Communications Commission for radiation threshold exposure. Experiments conducted on pork’s heart verified the reliability of the simulated results. At a 50 mm distance between the coils, the measured transmission coefficient is −34 dB, and at an input power of 1 W, the power delivered to the load is 0.7 mW.

Keywords

• leadless cardiac pacemaker
• 3-coil inductive power transfer link
• solenoidal receiver
• transmission coefficient
• specific absorption rate