Evaluation of Radio Wave Exposure of the Human Head at Multiple Frequencies of Up to 6 GHz

Mobile communication devices have become widely used in various situations in our daily lives. Not only are our opportunities for exposure to radio waves increasing, but the exposure environment is also changing owing to developments in telecommunications technology. Conventional studies on radio wave exposure evaluation have focused on only a single frequency, and only a few studies have considered radio wave exposure at multiple frequencies, including the frequencies used in fifth-generation (5G) mobile communications. In this study, specific absorption rate (SAR) evaluations were conducted assuming the exposure of the human body to radio waves with multiple frequency components. To simulate the actual use of a smartphone, analytical models were created using a smartphone model as the electromagnetic wave source and a numerical human body model as the exposure target. In the case of multiple frequencies, SAR was calculated for each frequency component, and SARs were summed. In addition, by changing the power ratio of each frequency component to the total radiated power, the distribution of SAR and the shift in the peak spatial SAR<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ _{\text{10g}}$</tex-math></inline-formula> (psSAR<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ _{\text{10g}}$</tex-math></inline-formula>) were investigated. As a result, it was confirmed that the SAR distribution changes with the power ratio of each frequency component in the radio wave. In the case of radio waves with multiple frequency components, no specific power ratios were found to cause a significant increase in psSAR<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ _{\text{10g}}$</tex-math></inline-formula>.