Characterization of EMI Sources from Reconstructed Current Distributions Based on Phase-Less Electric and Magnetic Near-Field Data

摘要

Localization of EMI sources can be a challenging task. The next step is often to identify the parameters of the EMI generating structure and find appropriate suppression. In this work, a method is presented to handle such problems by using only a phase-less scan of the electromagnetic near-field. Here, radiating conductor systems are investigated, like traces on a PCB. Using the electric and/or magnetic near-field distribution, the radiating current distribution can be reconstructed. In this paper an approach based on a known trace geometry and electric as well as magnetic field data is presented. When current distribution is known, critical EMI sources can be found. Furthermore, an approach is presented to design virtually a filter concept for a critical EMI source. For demonstration, based on measurement data, an exemplary conductor structure is investigated. It is pointed out that high currents and high local fields do not necessarily lead to a high far-field. For the exemplary conductor structure, critical sources are identified, and it is shown how the needed filter structures can be found.