Inductive 3-coil wireless power transfer improved by T-type impedance matching for implanted biomedical IC

This paper applies the printed spiral coil (PSC) using T-type impedance matching in wireless power transfer (WPT) technology for analysis of biomedical implant devices. To reduce the loading effect in the implant devices, three-coil WPT systems are preferred rather than two-coil WPT systems. Two layers comprising of printed spiral resonator coils and load loops on each side of FR4 is designed and fabricated on the side of implantable devices. PSC for biomedical implant devices can be optimized by adjusting geometric parameters. The implanting coil occupies an area of 5×5 mm² fabricated on a FR4 board. The geometric parameters are investigated to find out PSC optimal values of the impedance matching for the load coil. The power transfer efficiency of the simulated and measured results are compared with for each case. After experiments, compared with other same type of WPT devices, the maximum power is transmitted to the load side to achieve the best efficiency. Finally, at distance of 5 mm, the measured three-coil architecture achieved more than maximum transmission efficiency increases of 83% compared to the equivalent two-coil system.