Published on: Oct 18, 2012
SAR Reduction Technique by the High Impedance Surface using the Artificial Magnetic Conductor
My presentation at the 34th Annual Meeting of the Bioelectromagnetics Society in Brisbane, Australia was a reduction technique for the specific absorption rate of the RF-EMF according to the wireless devices (e.g. the tablet PC, wireless phone, etc.). The artificial magnetic conductor (AMC) is designed in order to analyzing and reducing the specific absorption rate (SAR) to be applied to 2.4 GHz WLAN or Wifi.
The reflector consists of the periodically arrayed AMC structure. When the dipole antenna applies to the PEC reflector and the AMC reflector, the PEC reflector has the best reflection characteristic at a shorter distance. Precisely the wavelength of 2.4 GHz is 125 mm, then the distance, which has the best reflection characteristics is 31.25 mm at the PEC reflector and 12.5 mm at the AMC reflector, respectively.
In this case, the radiation patterns show 3 dB increase. When the AMC reflector is applied to the tablet PC with the 2.4 GHz antenna for WLAN (or Wifi), the specific absorption rates (SAR) is dramatically decreased or shielded by the structures. For this theory, we have simulated the specific absorption rate of the human phantom with the AMC reflector having the size of 84 mm × 126 mm in the tablet PC by the computer simulation tools(SEMCAD-X). At that time, the tablet PC is separated about 20 cm from the phantom. As the results of the SAR analysis, in the absence of the reflector, the averaged peak SAR is 0.125 W/kg. However, in the use of the reflector, the averaged peak SAR is 0.002 W/kg. This results show a 98.4 % decrease of the SAR by using the proposed AMC reflector. The electromagnetic field from the radiation source does not affect to the human body when the AMC reflector applied to the commercial products.