Human exposure to pulsed fields in the frequency range from 6 to 100 GHz

The most recent safety guidelines define basic restrictions for electromagnetic field exposure at frequencies more than 6 GHz in terms of spatial‐ and time‐averaged transmitted power density inside the body. To enable easy‐to‐perform evaluations in situ, the reference levels for the incident power density were derived. In this study, we examined whether compliance with the reference levels always ensures compliance with basic restrictions. This was evaluated at several distances from different antennas (dipole, loop, slot, patch, and helix). Three power density definitions based on integration of the perpendicular real part of the Poynting vector, the real part of its three vector components, and its modulus were compared for averaging areas of λ2/16, 4 cm2 (below 30 GHz) and 1 cm2 (30 GHz). In the reactive near‐field (d < λ/(2π)), the transmitted power density can be underestimated if an antenna operates at the free space exposure limit. This underestimation may exceed 6 dB (4.0 times) and depends on the field source due to different coupling mechanisms. It is frequency‐dependent for fixed‐size averaging areas (4 and 1 cm2). At larger distances, transmission can be larger than the theoretical plane‐wave transmission coefficient due to backscattering between the body and field source. Using the modulus of the incident Poynting vector yields the smallest underestimation. © 2020 Bioelectromagnetics Society.

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“…These aspects are discussed, e.g. in Hashimoto et al [2017], Laakso et al [2017], Neufeld et al [2018], and Neufeld and Kuster [2018].…”

Section: Objectivesmentioning

confidence: 99%

Limitations of Incident Power Density as a Proxy for Induced Electromagnetic Fields

Christ

Samaras

Neufeld

et al. 2020

Bioelectromagnetics

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“…We study how the reflex time ref t varies with the beam spot area A while the power density dep P is maintained at a constant level. In case A (the case of no heat conduction), the analytical expression of ref t is given in (10). In expression (10), when the beam spot area A is fixed, the reflex time ref t is inversely proportional to the applied power density dep P .…”

Section: Time Until Withdrawal Reflex Vs Beam Spot Areamentioning

confidence: 99%

“…In case A (the case of no heat conduction), the analytical expression of ref t is given in (10). In expression (10), when the beam spot area A is fixed, the reflex time ref t is inversely proportional to the applied power density dep P . When dep P is fixed, as beam spot…”

Section: Time Until Withdrawal Reflex Vs Beam Spot Areamentioning

confidence: 99%

“…Let We assume that the time delay del t is an intrinsic property of the test subject, not affected by parameters of the electromagnetic beam, such as power density ( dep P ) or beam spot area (A). In case A (the case of no heat conduction), the true underlying reflex time ref t is given by (10). The observed reflex time obs t has the expression:…”

Section: Latency In Withdrawal Reflexmentioning

confidence: 99%

“…Far-field exposure of the human face to a linearly polarized plane wave at frequencies from 6 to 100 GHz and with exposure durations of 100 milliseconds to 10 seconds was modeled in [10]. The Maxwell equations were solved using a finite-difference time-domain solver.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A Concise Model and Analysis for Heat-Induced Withdrawal Reflex Caused by Millimeter Wave Radiation

Wang¹,

Burgei²,

Zhou³

2020

AJOR

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In this study, we consider the heat-induced withdrawal reflex caused by exposure to an electromagnetic beam. We propose a concise dose-response relation for predicting the occurrence of withdrawal reflex from a given spatial temperature profile. Our model is distilled from sub-step components in the ADT CHEETEH-E model developed at the Institute for Defense Analyses. Our model has only two parameters: the activation temperature of nociceptors and the critical threshold on the activated volume. When the spatial temperature profile is measurable, the two parameters can be determined from test data. We connect this dose-response relation to a temperature evolution model for electromagnetic heating. The resulting composite model governs the process from the electromagnetic beam deposited on the skin to the binary outcome of subject's reflex response. We carry out non-dimensionalization in the time evolution model. The temperature solution of the non-dimensional system is the product of the applied power density and a parameter-free function. The effects of physical parameters are contained in non-dimensional time and depth. Scaling the physical temperature distribution into a parameter-free function greatly simplifies the analytical solution, and helps to pinpoint the effects of beam spot area and applied power density. With this formulation, we study the theoretical behaviors of the system, including the time of reflex, effect of heat conduction, biological latency in observed reflex, energy consumption by the time of reflex, and the strategy of selecting test conditions in experiments for the purpose of inferring model parameters from test data.

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The influence of eyelashes on electric field distribution and absorbed power density in the cornea under millimeter‐wave exposure

Foroughimehr,

Vilagosh,

Yavari

et al. 2024

Bioelectromagnetics

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As millimeter wave (MMW) technology, particularly in fifth‐generation (5G) devices, gains prominence, there is a crucial need for comprehensive electromagnetic (EM) models of ocular tissues to understand and characterize EM exposure conditions accurately. This study employs numerical modeling to investigate the interaction between MMW and the cornea, aiming to characterize EM field distributions and absorption within an anatomically accurate eye model while considering the influence of eyelashes. Using the finite‐difference time‐domain (FDTD) method, we conduct simulations of EM radiation interactions from 20.0 to 100.0 GHz with a human eye model. Moreover, we analyze the temperature distribution increase within the eye model using a thermal sensor in XFdtd, employing a scheme based on the finite difference (FD) method. Our findings reveal a nonuniform distribution of the EM field, particularly intensified in corneal regions adjacent to eyelashes and eyelids. Despite similar EM field patterns, the presence or absence of eyelashes has minimal impact on temperature differences. However, the study highlights increased radiation absorption by the eyelid's epidermis at 100.0 GHz, reducing the rise in the cornea's temperature.

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Human exposure to pulsed fields in the frequency range from 6 to 100 GHz

Cited by 48 publications

References 40 publications

Limitations of Incident Power Density as a Proxy for Induced Electromagnetic Fields

Limitations of Incident Power Density as a Proxy for Induced Electromagnetic Fields

A Concise Model and Analysis for Heat-Induced Withdrawal Reflex Caused by Millimeter Wave Radiation

The influence of eyelashes on electric field distribution and absorbed power density in the cornea under millimeter‐wave exposure

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