Impact of noise in the characterization of magnetic field radiated emissions

This article reports the statistical analysis of an experimental procedure to monitor magnetic flux density (MFD) emissions on board of rolling stock. Measurements are operated in the time-domain and are aimed to track possibly modulated sinusoidal components of MFD emissions. The impact of additive internal noise (generated by the measurement equipment) as well as external noise (due to nonsinusoidal sources) is investigated. Since the final goal is safety assessment, the transformations experienced by the experimental data are analyzed and the statistics of a safety parameter (reported in the ICNIRP guidelines) is derived in closed form. Specifically, the expected value and variance of such a parameter are obtained analytically. Results´ validity is checked on test signals with known statistical properties, by a repeated-run analysis.