Abstract
Recently, international exposure guidelines/standards for human protection from electromagnetic fields were revised. For frequencies between 6–300 GHz, the permissible incident power density is defined as the reference level, which is derived from a new metric “absorbed/epithelial power density” based on thermal modeling. However, only a few groups computed the power density and the resultant temperature rise at frequencies greater than 6 GHz, where their exposure conditions were different. This study presents the first intercomparison study of the incident power density and the resultant temperature rise in a human body exposed to different frequency sources ranging from 10 to 90 GHz. This intercomparison aims to clarify the main causes of numerical calculation errors in dosimetry analyses through objective comparison of computation results from six organizations using their numerical methods with various body and antenna models. The intercomparison results indicate that the maximum relative standard deviation (RSD) of peak spatially averaged incident power densities for dipole and dipole array antennas is less than 22.1% and 6.3%, respectively. The maximum RSD of the heating factor, which is defined as the ratio of the peak temperature elevation at the skin surface to the peak spatially averaged incident power density in free space, for dipole and dipole array antennas is less than 43.2% and 41.2%, respectively. The deviations in the heating factors caused by different body models and dielectric/thermal parameters are within 33.1% and 19.6% at 10 and 30 GHz, respectively, when the antenna-to-skin model distance is greater than 5 mm. Under this condition (>5 mm), the deviation in the heating factors caused by different antenna models at 30 GHz does not exceed 26.3%. The fair agreement among the intercomparison results demonstrates that numerical calculation errors of dosimetry analyses caused by the definition of spatially averaged incident power density are marginal.
Highlights
Permissible external exposure reference levels or internal basic restrictions have been prescribed in international exposure guidelines and standards, which are established by the International Commission on Non-Ionizing Radiation
International standards of products for compliance assessment have been established by International Electrotechnical Commission (IEC) TC106 and IEEE International Committee on Electromagnetic Safety (ICES) TC34 based on the exposure guidelines and standards
Comparison of Peak Spatial-Average Incident Power Density Figures 4 and 5 show the intercomparison results of peak spatial-average PD (psPD) as a function of the antenna-to-skin separation distance d exposed to the single dipole and the 4 × 4 dipole array antenna for the exposure scenarios in Table I, respectively, at a frequency from 10 to 90 GHz
Summary
Compliance assessment of electromagnetic field (EMF) emitted from wireless devices is one of the essential procedures to protect humans from excessive EMF exposure. With the progress in the development of product standards for compliance assessment, the importance of a more precise and unambiguous definition of the spatial average of IPD based on the correlation of that with temperature elevation became obvious in facilitating practical evaluation procedures One aspect of this definition is related to the IPD quantity averaged over the prescribed surface area, which can be calculated using two methods:. Some recent studies have investigated these two IPD definitions by [19]−[26], including oblique incidence for near-field [27][28] and plane-wave exposure conditions [29]−[32] In this emerging frequency range, a limited number of groups computed the power density and temperature rise in the human body models for EMF exposure above 6 GHz. The cause of numerical computation errors has not been objectively investigated by comparing different numerical methods and models. The antenna models for numerical simulations, the simplified human body models, and the thermal parameters are described in Sections II-B, II-C, and II-D, respectively
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