Application of source reconstruction techniques and NF-FF transformations to estimate the EMI regulation compliance of a power electronic circuit

One of the requirements that power electronics circuits may satisfy are conducted and radiated noise specifications. While the first one is well covered in the literature, the later is not. Regulations on radiated emissions impose limits on noise levels measured three or ten meters far away from the electronic equipment. These measurements are usually made in anechoic chambers, which are a very expensive resource. Also, the measurement procedure is not a plug-and-play feature, but a carefully protocol of measurement is required. Once the electronic circuit has been tested, and in case the regulation has not been met, the designer usually doesn´t know the source of the problem. Then a ´cut-and-try´ procedure is commonly used to reduce emissions, and in such process the designer´s experience plays a major role. A new radiated noise measurement technique is proposed in this paper with two objectives: to simplify the measurement procedure and to provide more information about the noise sources. The main idea is to scan the electromagnetic field at two arbitrary but known distances from the electronic circuit. From these measurements, the source reconstruction technique (SRT) allows the identification of noise sources on the surface of the circuit and the estimation of field levels at any distance, so that regulation compliance can be evaluated.