Monte Carlo Simulation of Clothed Skin Exposure to Electromagnetic Field With Oblique Incidence Angles at 60 GHz

Abstract

Monte Carlo Simulation of Clothed Skin Exposure to Electromagnetic Field With Oblique Incidence Angles at 60 GHz Li Kun, Sasaki Kensuke. Monte Carlo Simulation of Clothed Skin Exposure to Electromagnetic Field With Oblique Incidence Angles at 60 GHz. Frontiers in Public Health. Vol. 10. 2022. doi: 10.3389/fpubh.2022.795414. Abstract This study presents an investigation of clothed human skin exposure to obliquely incident electromagnetic waves at 60 GHz. We clarified the combined impacts of the cloth material, incidence angle, and polarization on the assessment of transmittance and absorbed power density (APD) at the skin surface. A Monte Carlo simulation was conducted considering the thickness variation of the cloth material and skin tissue. For the case of transverse magnetic™ wave exposure, the transmittance increases with increasing incident angle up to the maximum transmittance angle in the range from 60 to 80°, which is known as the Brewster effects, regardless of textile materials and air gap between cloth and skin. The air gap results in a periodic fluctuation of the APD, where the variation is almost within 1 dB when the incident power density is constant and the incident angle is smaller than 40°. Our results also show that as the air gap increases to 2.5 mm, i.e., half-wavelength at 60 GHz in the air, the APD within the skin surface covered by typical cloth materials increases up to 40% compared with that of bare skin. Although the use of several cloth materials may increase the transmittance and APD in oblique incidence scenarios, all the results of the APD do not exceed the basic restriction for local exposure, demonstrating that the current guidelines for human exposure to electromagnetic fields are appropriate for preventing the excessive exposure at 60 GHz considering the impacts of oblique incidence angles and cloth materials. Open access paper: frontiersin.org

AI evidence extraction

Main findings

Monte Carlo simulations of obliquely incident 60 GHz waves indicated that for transverse magnetic wave exposure, transmittance increased with incident angle up to a maximum transmittance angle (60–80°; Brewster effects) regardless of textile materials and air gap. Increasing the air gap to 2.5 mm increased APD at the clothed skin surface by up to 40% compared with bare skin, but simulated APD values did not exceed the basic restriction for local exposure, and the authors conclude current guidelines are appropriate for preventing excessive exposure at 60 GHz under the modeled conditions.

Outcomes measured

• Transmittance through cloth to skin at 60 GHz
• Absorbed power density (APD) at skin surface
• Effects of incidence angle, polarization, cloth material, and air gap on APD/transmittance
• Comparison of APD to basic restriction for local exposure (guidelines compliance)

Limitations

• Simulation study (Monte Carlo); no human measurements reported
• Specific frequency (60 GHz) and modeled scenarios (cloth materials, air gaps, incidence angles, polarization) may limit generalizability

Suggested hubs

• who-icnirp (0.6)
  Abstract explicitly discusses compliance with basic restriction for local exposure and concludes current guidelines are appropriate at 60 GHz.
• 5g-policy (0.45)
  Study evaluates 60 GHz (mmWave) exposure metrics relevant to mmWave communications and guideline considerations.

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    "outcomes": [
        "Transmittance through cloth to skin at 60 GHz",
        "Absorbed power density (APD) at skin surface",
        "Effects of incidence angle, polarization, cloth material, and air gap on APD/transmittance",
        "Comparison of APD to basic restriction for local exposure (guidelines compliance)"
    ],
    "main_findings": "Monte Carlo simulations of obliquely incident 60 GHz waves indicated that for transverse magnetic wave exposure, transmittance increased with incident angle up to a maximum transmittance angle (60–80°; Brewster effects) regardless of textile materials and air gap. Increasing the air gap to 2.5 mm increased APD at the clothed skin surface by up to 40% compared with bare skin, but simulated APD values did not exceed the basic restriction for local exposure, and the authors conclude current guidelines are appropriate for preventing excessive exposure at 60 GHz under the modeled conditions.",
    "effect_direction": "mixed",
    "limitations": [
        "Simulation study (Monte Carlo); no human measurements reported",
        "Specific frequency (60 GHz) and modeled scenarios (cloth materials, air gaps, incidence angles, polarization) may limit generalizability"
    ],
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    "peer_reviewed_likely": "yes",
    "keywords": [
        "60 GHz",
        "millimeter wave",
        "oblique incidence",
        "clothed skin",
        "textile material",
        "air gap",
        "polarization",
        "transmittance",
        "absorbed power density",
        "Monte Carlo simulation",
        "Brewster effects",
        "exposure guidelines"
    ],
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