Assessment of incident power density in different shapes of averaging area for radio-frequency exposure above 6 GHz

2022 · Mixed · Low evidence

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MixedLow evidencePaper 678

Study snapshot

Publicationmanual · 2022

Study typeengineering

Reported directionMixed

Evidence ratingLow

Abstract

Assessment of incident power density in different shapes of averaging area for radio-frequency exposure above 6 GHz Morimoto R, Hirata A. Assessment of incident power density in different shapes of averaging area for radio- frequency exposure above 6 GHz. Phys Med Biol. 2022;67(21):10.1088/1361-6560/ac994d. Published 2022 Oct 31. doi:10.1088/1361-6560/ac994d. Abstract Objective.The International Commission on Non-Ionizing Radiation Protection guidelines and IEEE C95.1-2019 standard for human protection from local electromagnetic field exposure above 6 GHz state that absorbed (or epithelial) power density (APD) and incident power density (IPD), averaged over a square area, are internal and external physical quantities, respectively, that set the exposure limit. Per exposure standards, the measurement procedure and evaluation of the IPD have been established in technical standards, where a circular averaging area is recommended only for non-planar surfaces in IEC/IEEE 63195-1 and -2. In this study, the effects of two averaging shapes on the APD and IPD are evaluated computationally to provide new insights from the viewpoint of exposure standards. Approach. The relation between the APD, IPD, and the steady-state temperature rise (heating factor) in rectangular and human models for exposure to a single dipole, dipole arrays, and the Gaussian beams is investigated computationally with finite-difference method. Main results. The maximum differences in the heating factor of the APD and IPD for square and circular averaging areas were 4.1% and 4.4% for the antenna-model distance >5 mm, respectively. These differences appear when the beam pattern on the model surface has an elliptical shape. For an antenna-model distance ≤5 mm and at frequencies ≤15 GHz, the heating factors for square averaging areas were not always conservative to those for circular ones (-7.8% for IPD), where only the antenna feed point are visible before beam formation. Significance. The heating factors of the APD and IPD for a circular averaging area are conservative for near-field exposure of canonical sources for frequencies up to 300 GHz, except for a beam with a significant major-to- minor axis ratio and an angle of 30°-60° to a square averaging area. This tendency would help bridge the gap between exposure and product standards. Open access paper: iopscience.iop.org

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AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typeengineering

Effect directionmixed

PopulationNot supplied

Sample sizeNot supplied

ExposuremmWave

Evidence strengthLowConfidence: 74% · Peer reviewed: yes

Main findings

Computational finite-difference evaluations found maximum differences in heating factor between square and circular averaging areas of 4.1% (APD) and 4.4% (IPD) for antenna-model distance >5 mm, particularly when the surface beam pattern was elliptical. For antenna-model distance ≤5 mm and frequencies ≤15 GHz, square averaging was not always conservative relative to circular averaging (reported -7.8% for IPD).

Outcomes measured

incident power density (IPD) averaging (square vs circular area)
absorbed/epithelial power density (APD) averaging (square vs circular area)
steady-state temperature rise / heating factor

Limitations

Computational study using rectangular and human models; no empirical measurements described in abstract
Results evaluated for specific canonical sources (single dipole, dipole arrays, Gaussian beams) and specific geometries/conditions

View raw extracted JSON

{
  "study_type": "engineering",
  "exposure": {
    "band": "mmWave",
    "source": null,
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "incident power density (IPD) averaging (square vs circular area)",
    "absorbed/epithelial power density (APD) averaging (square vs circular area)",
    "steady-state temperature rise / heating factor"
  ],
  "main_findings": "Computational finite-difference evaluations found maximum differences in heating factor between square and circular averaging areas of 4.1% (APD) and 4.4% (IPD) for antenna-model distance >5 mm, particularly when the surface beam pattern was elliptical. For antenna-model distance ≤5 mm and frequencies ≤15 GHz, square averaging was not always conservative relative to circular averaging (reported -7.8% for IPD).",
  "effect_direction": "mixed",
  "limitations": [
    "Computational study using rectangular and human models; no empirical measurements described in abstract",
    "Results evaluated for specific canonical sources (single dipole, dipole arrays, Gaussian beams) and specific geometries/conditions"
  ],
  "evidence_strength": "low",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "incident power density",
    "absorbed power density",
    "epithelial power density",
    "averaging area",
    "square averaging",
    "circular averaging",
    "near-field exposure",
    "above 6 GHz",
    "IEEE C95.1-2019",
    "ICNIRP guidelines",
    "IEC/IEEE 63195",
    "finite-difference method",
    "Gaussian beams",
    "dipole arrays"
  ],
  "suggested_hubs": [
    {
      "slug": "who-icnirp",
      "weight": 0.78,
      "reason": "Abstract explicitly discusses ICNIRP guidelines and IEEE/IEC exposure standards for >6 GHz power density averaging."
    },
    {
      "slug": "5g-policy",
      "weight": 0.55,
      "reason": "Focus on RF exposure assessment above 6 GHz (relevant to mmWave exposure limits and compliance methods)."
    }
  ]
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1088/1361-6560/ac994d
PubMed: Not supplied

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