Exposure assessment for a wireless multi-phone charger

In this paper, we analyzed SAR and induced electric field inside of the Korean human model and flat phantoms exposed to a wireless multi-phone charger operating at 6.78 MHz, and also investigated correlation characteristics between SAR and spatially averaged magnetic field. For analysis, commercial simulators, XFDTD and HFSS were used. The simulated exposure levels were compared with the ICNIRP and Korean guidelines. The induced electric field was insignificant compared to SAR. The 1-g averaged SAR in the body, head and arm of the human model at 5 cm distance were 2.26 × 10^-2 W/kg, 3.59 × 10^-3 W/kg and 3.86 × 10^-3 W/kg for 1 W input power. The maximum allowed input power compared to the Korean SAR limit is about 70.29 W, 445.33 W and 413.98 W. For the nominal input power of 10 W, the exposure level of the charger is well within the exposure limit of the Korean guideline, which is stricter than ICNIRP guideline. Regarding correlation characteristics, almost perfect correlation was found between SAR and square of the spatially averaged magnetic field. This new finding can be applied to a measurement standard for certification of wireless charging devices.