A formula for human average whole-body SAR_wbunder diffuse fields exposure in the GHz region

Abstract

Abstract.A simple formula to determine the human average whole-body SAR (SAR wb ) under realistic propagation conditions is proposed in the GHz region, i.e., from 1.45 GHz to 5.8 GHz. The methodology is based on simulations of ellipsoidal human body models. Only the exposure (incident power densities) and the human mass are needed to apply the formula. Diffuse scattered illumination is addressed for the first time and the possible presence of a Line-Of-Sight (LOS) component is addressed as well. As validation, the formula is applied to calculate the average whole-body SAR wb in 3-D heterogeneous phantoms, i.e., the virtual family (34-year-old male, 26-year-old female, 11-year-old girl, and 6-year-old boy) and the results are compared with numerical ones -using the Finite-Difference Time-Domain (FDTD) method -at 3 GHz. For the LOS exposure, the average relative error varies from 28% to 12% (resp. 14% to 12%) for the vertical polarization (resp. horizontal polarization), depending on the heteregeneous phantom. Regarding the diffuse illumination, relative errors of -39.40%, -11.70%, 10.70%, and 10.60% are obtained for the 6-year-old boy, 11-year-old girl, 26-year-old female, and 34-year-old male, respectively. The proposed formula estimates well (especially for adults) the SAR wb induced by diffuse illumination in realistic conditions. In general, the correctness of the formula improves when the human mass increases. Keeping the uncertainties of the FDTD simulations in mind, the proposed formula might be important for the dosimetry community to assess rapidly and accurately the human absorption of electromagnetic radiation caused by diffuse fields in the GHz region. Finally, we show the applicability of the proposed formula to personal dosimetry for epidemiological research.

Radio-Frequency Electromagnetic Field Exposure of Western Honey Bees

“…The results in terms of P abs obtained for the honey bees in this study fall right in between those obtained in 11 for the smaller Australian Stingless Bee and the larger Desert Locust, which confirms again the dependency of P abs on phantom size. The same size-related effect was described for humans in 28,33,38 and comparable frequency trends were observed in humans that have larger full-body sizes at MHz frequencies 28,38 . It should be noted that this manuscript focused on exposure of individual insects in free space.…”

“…The larger Worker Bee 2 phantom has a larger diagonal, surface area, and volume. This leads to a higher absorption cross section 33 and higher P abs .…”

Comments on assessment of polarization dependence of body shadow effect on dosimetry measurements in 2.4GHz band

“…This propagation has several components: propagating modes around the human body, specular components, including the line‐of‐sight component between the source exposimeter, and reflections from the environment, and the diffuse multipath component (DMC). This DMC is the part of the incident power density that cannot be attributed to any incident angle [Bamba et al, ] (in contrast to the specular components).…”

“…Existing literature on the absorption of RF frequencies above >2 GHz is not conclusive on polarization dependence of the SAR wb . Some studies find a higher absorption for horizontally polarized (H‐polarized) incident plane waves [Hirata et al, ; Uusitupa et al, ; Bamba et al, ] at frequencies higher than 2 GHz. Others find only slightly higher absorption values for vertically polarized (V‐polarized) incident plane waves at frequencies higher than 2 GHz [Kühn et al, ; Bakker et al, ].…”

Fast Assessment of Rf Power Absorption in Indoor Environments by Room Electromagnetics Theory

“…Only Refs. (7,8) and Ref. (9) proposed a measurement method for indoor absorption and absorption cross section (ACS) in real environments, but this method is also time-consuming and expensive measurement equipment has to be used.…”