Multi-coil approach to mitigate the design limitations for wireless power transfer in biomedical implants

A popular technique for wireless power transfer, particularly in biomedical implants, is inductive coupling. One of the first applications of this technique in the biomedical field was to supply power to an artificial heart. Since then, it has commonly been used in implantable devices. For short-range wireless power transfer systems, working on inductive coupling, power transfer efficiency, voltage gain and data bandwidth are generally key performance parameters that need to be optimized to design an efficient system. These parameters are strong functions of the quality factor (Q) of the magnetic coils and the coupling between the external and implant coils. Traditionally, two coils are employed in power/data transfer systems: however, due to the moderate Q-factor of the coils and low coupling between the coils, these inductive coupled power/data transfer systems have generally limited power transfer efficiency (<; 40 %) and limited data bandwidth (<; 10% of carrier frequency). Performance variation during the operation of the device is one of the main challenges for a two-coil based system. Two-coil based Wireless Power Transfer (WPT) systems suffer from instable link performance due to variation caused by the change in operating distance, coil misalignment, device operation mode, and change in driver resistance.