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CHARACTERISTICS AND MEASUREMENTS OF MICROWAVE AND RADIOFREQUENCY RADIATION

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Bureau of Radiological Health, Food and Drug Administration

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The draft document describes characteristics of microwave and radiofrequency radiation and measurement methods for hazardous electromagnetic fields.

Plain English Summary

Summary written for general audiences

Microwaves and RF fields are almost totally reflected from metals, transmitted through plastics, ceramics, paper, or glass, and absorbed by most biological materials, particularly those with high water content. The document explains near-field and far-field regions, noting that the near field dominates when the distance is much smaller than the wavelength and that the far field begins where the ratio of electric to magnetic field approaches 377 ohms. It specifies measurement techniques for frequencies from 1 MHz to 100 GHz and distinguishes emission standards from exposure standards.

Why This Matters

It describes how antenna size affects the extent of the near field, with larger antennas extending the near-field region further into space. It emphasizes that reactive near-field components can couple into material and affect energy absorption even though they do not contribute to net energy flow.

Exposure Information

A logarithmic frequency spectrum from 10 Hz to 100 GHz showing where this study's 100 MHz to 10 GHz exposure sits relative to common EMF sources.Where This Frequency Sits on the EMF SpectrumELFVLFLF / MFHF / VHFUHFSHFmm10 Hz100 GHzThis study: 100 MHz to 10 GHzPower lines50/60 HzCell phones~1 GHzWiFi2.4 GHz5G mm28 GHzLogarithmic scale

Specific exposure levels were not quantified in this study.

Cite This Study
Bureau of Radiological Health, Food and Drug Administration (n.d.). CHARACTERISTICS AND MEASUREMENTS OF MICROWAVE AND RADIOFREQUENCY RADIATION.
Show BibTeX
@article{characteristics_and_measurements_of_microwave_and_radiofrequency_radiation_g5353,
  author = {Bureau of Radiological Health and Food and Drug Administration},
  title = {CHARACTERISTICS AND MEASUREMENTS OF MICROWAVE AND RADIOFREQUENCY RADIATION},
  year = {n.d.},
  
  
}
No DOI on file for this study.

Quick Questions About This Study

Microwaves are almost totally reflected from metals, transmitted through plastics, ceramics, paper, or glass, and absorbed by most biological materials, particularly those with high water content.
The standard specifies techniques and instrumentation for the frequency range of 1 MHz to 100 GHz.
The standard covers leakage fields, radiation fields, and reactive fields, and notes that multipath interference from reflections is nearly always present.
An emission standard specifies the maximum field intensity at a small distance from an emitting source, whereas an exposure standard specifies the maximum field intensity to which personnel should be exposed as a function of exposure duration.