Near field radiofrequency metrology and occupational exposure assessment: In situ measurements and accuracy analysis

Reactive and radiative near-fields are important to be measured in connection with occupational human exposure. Both electric (E) and magnetic (H) field components need to be evaluated in this case and they are to be compared against the occupational safety limits. The need for a proper device and a correct procedure for these measurements are crucial. Present work focused on exposure assessment very near to HF and VHF radiofrequency sources (portable and vehicular) by using a personal exposimeter enabled with both E- and H-field sensors. Uncertainty analysis is considered in order to improve reliability; for present situation, even if the expanded measurement uncertainty is ±0.8 dB in calibration conditions, the accuracy is worse in realistic cases. On this background, our results show that the exposure level decreases very fast with distance from the source in the reactive and radiative near-field, and even in medium-power emission conditions (50W), for distances exceeding 1m (in HF band), the occupational exposure is safe. Non-shielded cables inside vehicles may also pose exposure problems, but only in the very near distance, i.e. not further than 20-30cm.