-The interaction between wireless charging systems and the human body needs to be taken into account. Furthermore, a high power charging could lead to tissue heating and even irreversible tissue damage. In this paper, we propose an original approach to characterize the biological compatibility of the wireless charging system, from the transmitter coil to the human body: the influence of each element (Smartphone, coil orientation, human body, distance and charging power) on electromagnetic field is analyzed. The "specific absorption rate-SAR" estimations were carried out using a full environment model and a high resolution method. The electromagnetic level was measured and compared with simulation, showing a good agreement. The 10g averaged SAR values are then compared with maximum permissible levels of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the obtained results indicate that the inductive phone charging (from 100kHz to 200kHz) are within the safety limits.

Winding coils are key elements in the design and the implementation of an effective wireless power charging platform for wireless devices such as mobile phones, smart phones and tablet computers. Planar winding inductors are lowcost, ready to integrate with the electronics and fully compatible with a general printed circuit board (PCB) manufacturing process. This paper addresses the design and the simulation of the planar winding inductors in order to overcome some drawbacks of such structures concerning mainly the quality factor and the resistive/thermal losses.Index Terms -wireless power transfer, inductive antennas, charging platform, printed winding inductors.