Discussion on Spatial and Time Averaging Restrictions Within the Electromagnetic Exposure Safety Framework in the Frequency Range Above 6 GHz for Pulsed and Localized Exposures

Abstract

Overview

This study examines the efficacy of current and newly proposed safety guidelines for human exposure to millimeter-wave frequencies, specifically focusing on local temperature increases in the skin which could lead to tissue damage.

Findings

• The study highlights that the application of limits for pulsed fields can lead to significant temperature rises of up to 10°C for short pulses at frequencies between 6 and 30 GHz.
• It is demonstrated that a reduced proposed averaging area of 4 cm2 does not prevent high-temperature increases in cases of narrow beam exposure.
• With a realistic Gaussian beam profile of 1 mm radius, the temperature increase can be about 10 times higher than the 0.4°C increase producing the same averaged power density in a plane wave scenario.
• For pulsed narrow beams, the new guideline values for time and spatial-averaged power density may lead to extreme temperature increases.

Conclusion

The results indicate that the current and proposed exposure limits may not adequately prevent excessive heating in cases of pulsed and localized radiation, suggesting that pulse-duration-dependent limits and a consideration of narrow-beam exposures are essential for setting safe electromagnetic exposure standards.