The investigation of specific absorption rate measurement system for intelligent connected vehicles and its uncertainty analysis

Radiation from wireless communication devices inside intelligent connected vehicles has been an expeditious growth of concern regarding possible adverse effects on human health. Due to the significant differences in the working scenarios compared to traditional mobile products, the traditional measuring systems of specific absorption rate (SAR) are not applicable to in-vehicle scenarios. This paper has developed a SAR measurement system and a SAR measurement method, which are suitable for in-vehicle scenarios. Since the measurement hardware and methods are significantly different from traditional systems, it is necessary to assess the measurement uncertainty for the new measurement system. Due to the significant influence of tissue fluid on the SAR, this paper focuses on analyzing the relationship between tissue fluid and SAR. Based on the validated electromagnetic simulation model, linear and quadratic fitting models reflecting the relationship between tissue fluid properties and SAR are established. Then, the uncertainty propagation was realized using both the Guide to the Expression of Uncertainty in Measurement and MCM (Monte Carlo Method) through these models. The results of uncertainty analysis were analyzed in combination with the fitting error. The results of the analyses show that the fitting error of the quadratic measurement model is smaller because there is no simple linear relationship between the tissue fluid properties and the SAR values, and thus, it is more reasonable to use the MCM method to evaluate the uncertainty.