Showing papers by "Teruo Onishi published in 2021"

Quantitative Comparison of Power Densities Related to Electromagnetic Near-Field Exposures With Safety Guidelines From 6 to 100 GHz

Abstract: This paper presents a quantitative analysis of the differences between the various definitions of spatially averaged power densities ( $sIPD_{s}$ ) for localized exposure to electromagnetic near-fields at frequencies from 6 to 100 GHz. The spatially averaged modulus of the complex Poynting vector ( $sIPD_{mod}$ ) and spatially averaged norm of the real part of the complex Poynting vector ( $sIPD_{norm}$ ) were compared using numerical approaches, where their relationships with the spatially averaged absorbed power density ( sAPD ) and the local peak temperature elevation on skin tissue were analyzed. Our results demonstrated that outside the typical boundary of the reactive near-field, i.e., $> \lambda $ /( $2\pi$ ), which is used as a rough guide of the applicable condition for reference levels in the RF safety guidelines, but at most 10 mm from the radiation source, the maximum difference between $sIPD_{norm}$ and $sIPD_{mod}$ is smaller than 0.7 dB from 6 to 100 GHz. For the appropriate conditions recommended in the RF safety guidelines, the differences between the ratios of sAPD to $sIPD_{s}$ and those for the plane-wave normal incidence, are at most 1.4 dB and 0.9 dB for $sIPD_{norm}$ and $sIPD_{mod}$ , respectively. Under the same condition, the ratios of the temperature rise to $sIPD_{s}$ for the relatively small antennas (total dimension less than $2\lambda$ ) do not significantly exceed that for the plane-wave normal incidence, which means that the expected maximum temperature rise is lower than the temperature rise that is derived from the operational health effect threshold in terms of the temperature rise divided with the reduction factors employed in the RF safety guidelines. The above results provide suggestive evidence that the effect of the definition of $sIPD_{s}$ on the human exposure characteristics is not significant compared with those of the other factors, i.e., the antenna type (size), frequency, distance from the source, and averaging area.

Radiofrequency Exposure Levels from Mobile Phone Base Stations in Outdoor Environments and an Underground Shopping Mall in Japan.

Abstract: Recent progress in wireless technologies has made human exposure to electromagnetic fields (EMFs) increasingly complex. The situation can increase public concerns related to possible health effects due to EMF exposure. Monitoring EMF exposure levels and characterizing them are indispensable for risk communications of human exposure to EMFs. From this background, a project on the acquisition, accumulation, and applications of EMF exposure monitoring data in Japan was started in 2019. One of the objectives of this project is to obtain a comprehensive picture of EMF exposure in actual daily lives. In 2019 and 2020, we measured the electric field (E-field) strength from mainly mobile phone base stations in the same areas as those in measurements conducted in 2006 and 2007 by the Ministry of Internal Affairs and Communications (MIC), Japan, and compared the data to investigate the time-course of the EMF environment. The number of measured points was 100 (10 × 10 grids) in an area of 1 km × 1 km in two urban and two suburban areas, and that in an underground shopping mall was 158. This large-scale study is the first in Japan. As a result, we found that the measured E-field strengths tended to be higher in 2019 and 2020 than those in 2006 and 2007, especially in the mall. However, the median ratios to the Japanese radio wave protection guideline values for urban areas and malls are lower than -40 dB.

Incident Power Density Assessment of Smart Surfaces for Exposure Compliance

Abstract: This paper presents preliminary research on the compliance assessment of smart surfaces, which are one of the most promising technologies for 5G higher frequency band (NR2) applications. Two different approximate approaches are provided and compared with the reference approach, which is based on full-wave simulation, in terms of assessment accuracy and efficiency to verify their availability and capability quantitatively. Both the two approximate approaches can significantly reduce the assessment time while providing acceptable assessment accuracy.