Distance Conversion Factors for In Situ H-Field Emissions Tests

This article derives and validates a set of distance conversion factors for the magnetic field emissions limits in the frequency range from 9 kHz to 30 MHz, which are intended to be proposed for their inclusion in new electromagnetic compatibility standards. Simulation models based on loop-type electromagnetic field sources are employed to evaluate, using the method of moments, the changes in the amplitude of the H-field components along the measurement axes. An algorithm is developed to extract the H-field strengths normalized to the reference distance and then, through methods for optimal detection of changepoints, such a normalized curve is fitted to a piece-wise linear function that becomes the generalized distance conversion factor, presented in the form of simplified equations. The fitness of the model is checked through experiments carried out in representative locations, showing a very good agreement between measurement and simulations. The adequacy of the conversion factors and the problem around the equipment under test are also analyzed.