Investigation of Power Levels Related to Different EMF Exposure Metrics at 6 GHz

Abstract

Investigation of Power Levels Related to Different EMF Exposure Metrics at 6 GHz El Hajj W, Roman J, Yao Z, Paxman R, De Santis V. Investigation of Power Levels Related to Different EMF Exposure Metrics at 6 GHz. IEEE Access. 2023. doi: 10.1109/ACCESS.2023.3284690. Abstract New wireless technologies significantly utilize the spectrum around 6 GHz with some of them, like Wi-Fi®6E, using both the spectrum below and above 6 GHz. At these frequencies, the main challenge for electromagnetic field (EMF) exposure assessments is due to the exposure metric changing from specific absorption rate (SAR) to absorbed power density (APD). Moreover, due to current measurement limitations, the incident power density (IPD) rather than APD is used in practice. In this context, the maximum allowed output power to ensure exposure compliance is dependent on the metric used and can lead to a discontinuity below and above 6 GHz even for different channels of the same technology. This paper studies such a discontinuity at the transition frequency of 6 GHz using a dipole antenna and a Planar Inverted F Antenna (PIFA). The study was performed at several exposure distances by means of numerical simulations as well as experimental measurements. The assessment was based on the comparison between maximum power values obtained while remaining compliant to the SAR and IPD limits for the same exposure conditions. The results have shown that for a specific source there was a distance (between 5 and 10 mm) where the highest power reduction for compliance switched from SAR to IPD. The difference or discontinuity level varied between 2 and 6 dB depending on the exposure distance and the source. In summary, SAR is more restrictive at closer distances, while the IPD induces a higher back-off power with an increase in distance. ieeexplore-ieee-org.libproxy.berkeley.edu

AI evidence extraction

Main findings

Using numerical simulations and experimental measurements with a dipole antenna and a PIFA at several exposure distances, the study compared maximum power values compliant with SAR limits versus IPD limits under the same exposure conditions. A distance between 5 and 10 mm was identified where the highest compliance-related power reduction switched from being SAR-driven to IPD-driven. The discontinuity between SAR- and IPD-based maximum power levels varied by about 2–6 dB depending on distance and source; SAR was more restrictive at closer distances, while IPD required higher power back-off at larger distances.

Outcomes measured

• Comparison of compliance-related maximum allowed output power under SAR vs incident power density (IPD) limits at 6 GHz
• Discontinuity in maximum allowed output power across the SAR-to-APD/IPD metric transition around 6 GHz
• Distance dependence of which metric (SAR vs IPD) is more restrictive

Limitations

• Absorbed power density (APD) is discussed as the relevant metric above 6 GHz, but due to measurement limitations the study uses incident power density (IPD) in practice.
• Only two source/antenna types are explicitly studied (dipole and PIFA).
• Details on simulation/measurement setups and uncertainty are not provided in the abstract.

{
    "study_type": "engineering",
    "exposure": {
        "band": "RF",
        "source": "Wi-Fi 6E / wireless technology (6 GHz)",
        "frequency_mhz": 6000,
        "sar_wkg": null,
        "duration": null
    },
    "population": null,
    "sample_size": null,
    "outcomes": [
        "Comparison of compliance-related maximum allowed output power under SAR vs incident power density (IPD) limits at 6 GHz",
        "Discontinuity in maximum allowed output power across the SAR-to-APD/IPD metric transition around 6 GHz",
        "Distance dependence of which metric (SAR vs IPD) is more restrictive"
    ],
    "main_findings": "Using numerical simulations and experimental measurements with a dipole antenna and a PIFA at several exposure distances, the study compared maximum power values compliant with SAR limits versus IPD limits under the same exposure conditions. A distance between 5 and 10 mm was identified where the highest compliance-related power reduction switched from being SAR-driven to IPD-driven. The discontinuity between SAR- and IPD-based maximum power levels varied by about 2–6 dB depending on distance and source; SAR was more restrictive at closer distances, while IPD required higher power back-off at larger distances.",
    "effect_direction": "unclear",
    "limitations": [
        "Absorbed power density (APD) is discussed as the relevant metric above 6 GHz, but due to measurement limitations the study uses incident power density (IPD) in practice.",
        "Only two source/antenna types are explicitly studied (dipole and PIFA).",
        "Details on simulation/measurement setups and uncertainty are not provided in the abstract."
    ],
    "evidence_strength": "insufficient",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "6 GHz",
        "Wi-Fi 6E",
        "EMF exposure assessment",
        "specific absorption rate",
        "SAR",
        "absorbed power density",
        "APD",
        "incident power density",
        "IPD",
        "compliance",
        "dipole antenna",
        "PIFA",
        "numerical simulations",
        "experimental measurements"
    ],
    "suggested_hubs": []
}

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