Basic operating characteristics of wireless power transfer system for small portable devices

Recent research in wireless power transfer using resonant inductive coupling has made a significant progress and reached very high efficiency (usually above 85 %) at large distances. This paper offers a methodology for the basic analysis and prediction of efficiency of the wireless power transfer system for small portable devices. It also gives an overview of operating characteristics of the system for different positions of transmitting and receiving elements. All presented theoretical presumptions are consequently verified by detailed measurement.