Interference‐free wireless power transfer system for biomedical implants using multi‐coil approach

Low‐frequency (1–20 MHz) inductive coupling is a leading technique to power biomedical implants wirelessly. Even though these are non‐radiating systems, the external and the implant coils can cause sufficient radiated electric field to exceed the federal standards for communication. A multi‐coil‐based wireless power transfer (WPT) technique is developed to selectively control the currents in the external and implant coils to reduce the radiated electric field. A four‐coil WPT system, which can achieve more than 37% reduction in the radiated electric field as compared with a two‐coil WPT system with the same dimensions and design constraints, is implemented and used to demonstrate the effectiveness of the proposed approach.