Yasutoshi Yoshioka

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.

Performing in-situ radiated emissions measurements, that is, in locations different from a standard test site, can be a challenging task because of the high electromagnetic noise levels in the ambient. A harsh electromagnetic environment characterizes such sites, and it usually results in difficulties when discerning between emissions from the equipment under test and electromagnetic fields generated by surrounding devices. Moreover, communications signals from broadcasting services are generally significantly higher than the standard emission limits making it even harder to determine compliance. In this paper, we present different techniques leveraging the advantages of time-domain measurement systems to provide effective and practical solutions to mitigate ambient noise’s effect on radiated electromagnetic interference measurements. First, the test method used is described, and pragmatic considerations are given to ensure reliable and repeatable measurements. Multi-channel time-domain measurement systems are introduced as the fundamental tool for the proposed strategies. Subsequently, different study cases are evaluated with real test examples, highlighting several criteria intended to reduce the impact of ambient noise on the actual emissions measures produced by the equipment under test. Finally, a real application of those strategies for measuring a photovoltaic system is described. Overall, the methods employed and the main advantages of using full-time domain FFT-based receivers are reviewed. In addition, the possibility of incorporating this paper’s outcomes into forthcoming electromagnetic standards about in-situ radiated emission measurements is also debated.