Automated SAR measurements for compliance testing of cellular telephones

Determination of peak 1-g SAR is required for all new personal wireless devices to ensure that it complies with the RF safety guidelines approved by U.S. Federal Communications Commission (FCC). We have developed an automated SAR measurement setup which uses a 3D stepper motor system to move the Narda Model 8021 implantable E-field probe to determine the SAR distributions inside a homogenous human phantom. The E-field probe was calibrated against FDTD using a slab phantom and was checked to have good isotropy (+/- 0.23dB) and a wide dynamic range (10 mW/kg to 10W/kg) both at AMPS (840 MHz) and PCS (1900 MHz) frequencies. The system was validated using a sphere model and has been used for SAR testing of several commercial telephones with different operating frequencies and antenna structures, the agreement between the measurements and FDTD calculations of 1-g SARs is excellent and generally within +/- 25%.