Broadband Measurement Methodology for Specific Absorption Rates Above 300 MHz

Specific absorption rate (SAR) is an indicator of biological effects on human tissue caused by exposure to microwave radiation. An electric field probe scanning method has been traditionally used for SAR evaluation. However, since the electric field probe exhibits strong frequency dependence, it is difficult to evaluate SAR continuously in the broadband. In addition, preparing a physically different SAR measurement methodology from the electric field probe is an important task for validating measurement standards or regulations. Therefore, the authors developed a thermal SAR measurement method using optical fiber thermal sensors. In the present paper, we present a thermal SAR evaluation methodology that can be used in the broadband from 300 MHz to 6 GHz, which is frequently used by mobile devices. It was confirmed for the first time that SAR showed the peak with this continuous broadband measurement around 1.8 GHz. In addition, as a comparison measurement result with the electric field probe system and the proposed system, the mean value of each measured datum showed a deflection of approximately 10% to 20% in the whole frequency range.