A Source Reconstruction Method for Unknown EMI Sources Inside a Shielding Enclosure Based on Magnitude-Only Near-Field Scanning

An effective source reconstruction method (SRM) to predict the noise coupling from an unknown electromagnetic interference (EMI) source inside a shielding enclosure is proposed in this work. On account of the difficulty and time-consuming in phase measurement of near-field, the magnitude-only near-field scanning is employed to obtain the near-field above EMI sources in free space, and the leakage near-field from the slots and/or holes of a shielding enclosure after the EMI source is inserted into the enclosure. The infinitesimal dipole is used as the equivalent source of the EMI source. The proposed method can generally be divided into three steps. First, the positions and initial moments of the equivalent dipoles of an unknown EMI source without any shielding enclosure are derived by using dynamic differential evolution (DDE) algorithm. Second, the obtained dipoles are thereafter placed into an arbitrarily shaped shielding enclosure, and the full-wave simulation is implemented to build the relationship between the dipoles and the measured leakage field from the slots/holes of the shielding enclosure. Third, the dipole moments are thereby optimized by using the DDE method again based on the magnitude-only leakage field. It is worth highlighting that only a relatively small region of near-field on the leakage plane is sufficient for obtaining an effective equivalent dipole model in the shielding enclosure. The results of numerical simulation and physical measurement have verified the effectiveness of the proposed SRM for modeling unknown EMI sources in a shielding enclosure.