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THE NEAR FIELD OF DIPOLE AND HELICAL ANTENNAS

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Q. Balzano, O. Garay, K. Siwiak

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Current EMF safety standards near antennas may be overly restrictive by measuring stored energy instead of penetrating radiation.

Plain English Summary

Summary written for general audiences

This technical study measured electric field strength around dipole and helical antennas used in portable communication devices. Researchers found that near antennas, current safety standards based on electric field measurements are overly restrictive because they don't account for how electromagnetic energy actually penetrates human tissue. The study shows that reactive energy stored around antennas has high impedance and isn't all available for tissue penetration.

Why This Matters

This research exposes a fundamental flaw in how we measure EMF safety near portable devices. The science demonstrates that our current protection standards, which rely on electric field strength measurements, don't distinguish between energy that can actually penetrate your body and energy that simply exists around the antenna. Put simply, when you're close to your phone or wireless device, the safety criteria may be unnecessarily strict because they're measuring the wrong thing. What this means for you is that near-field exposure assessments using standard methods may overestimate actual biological risk. The reality is that reactive electromagnetic energy stored around antennas behaves differently than the radiating energy that travels away from devices, yet our safety standards treat them the same.

Finding

In the close proximity of sources the safety criteria are no longer valid because the value of |E|2 is not directly related to power flow, but, rather, to the level of electric energy stored around the radiator. This reactive energy, because of its high impedance, is not all available for penetration and deposition in human tissue. So, in the near field of radiators a Safety Standard based only on the value of |E| can be exceedingly restrictive, as shown by the measurements presented in the paper.

In their words

In the close proximity of sources the safety criteria are no longer valid because the value of |E|2 is not directly related to power flow, but, rather, to the level of electric energy stored around the radiator. This reactive energy, because of its high impedance, is not all available for penetration and deposition in human tissue. So, in the near field of radiators a Safety Standard based only on the value of |E| can be exceedingly restrictive, as shown by the measurements presented in the paper.

Figures from the Original Paper

Diagrams extracted from the original research document.

diagramPage 4 - AI-described figure: Figure 1 depicts an E-field probe with a coiled wire and a ruler for scale.
graphPage 5 - AI-described figure: Figure 2: E-field sensor data showing a decreasing trend over time.
diagramPage 6 - Fig. 3 Measurement System Block Diagram
diagramPage 7 - AI-described figure: Figure 4: Test Set-up showing a mechanical apparatus with various components and measurements.
diagramPage 8 - AI-described figure: Figure 5: Test Set-Up showing a mechanical setup with various components and measurements.
diagramPage 9 - Figure 6: E-Field Components Near Dipole and Helical Antennas
diagramPage 10 - AI-described figure: Figure 7: Dimensions of Helical Antennas showing two helix configurations with their respective dimensions and resonance frequencies.

Exposure Information

Specific exposure levels were not quantified in this study.

Cite This Study
Q. Balzano, O. Garay, K. Siwiak (n.d.). THE NEAR FIELD OF DIPOLE AND HELICAL ANTENNAS.
Show BibTeX
@article{the_near_field_of_dipole_and_helical_antennas_g4640,
  author = {Q. Balzano and O. Garay and K. Siwiak},
  title = {THE NEAR FIELD OF DIPOLE AND HELICAL ANTENNAS},
  year = {n.d.},
  
  
}
No DOI on file for this study.

Quick Questions About This Study

Near antennas, electric field strength doesn't correlate with power flow into tissue. Instead, it measures reactive energy stored around the antenna, which has high impedance and limited tissue penetration capability.
In far field exposure, electric field strength directly relates to power flow and potential hazard. In near field, it primarily reflects stored electromagnetic energy that doesn't all penetrate tissue.
Yes, these antenna types are commonly found in portable communication equipment like cell phones, radios, and wireless devices that people use in close proximity to their bodies.
Reactive electromagnetic energy has high impedance, meaning it resists current flow and isn't all available for penetration and energy deposition in human tissue compared to radiating energy.
No, the ANSI Radio Frequency Protection Guides are based on electric field measurements that work for far field but become overly restrictive in near field antenna environments.