Electromagnetic Interference Source Positioning Algorithm Based On Near-Field Scanning

With the development of integrated circuit technique and packaging technique,IC tends to be more compact,and the internal structure of the package becomes more complicated,which makes the EMI problem more serious.Unknown interference positioning plays an significant part in EMI problem addressed and it is a hot topic in the industry.In recent years,due to the low cost and convenient operation,near-field scanning system has an great effect in EMI diagnosis.According to the actual requirements of industry,unknown interference positioning algorithm based on the near-field scanning system is proposed in this paper.The unknown interference positioning algorithm has been used for the production testing in company.The main points of this paper are as follows:1)Electromagnetic interference source positioning in open spaceNear-field-to-near-field transformation based on plane wave spectrum.According to plane wave spectrum,the electromagnetic field with phase is used for interference source positioning in the air or in the dielectric.Moreover,digital filters are used to reduce the influence of the truncation error on the electromagnetic imaging.The amplitude and phase of the electromagnetic field on a scanning plane above the DUT are used to reconstruct the field pattern around the DUT,which shows the location of the interference source.According to the testing results,the reconstructed fields are clearer and contain more detailed information.The advantages of this algorithm are time-saving,useful for wide bandwidth and of high accuracy.Phaseless near-field-to-near-field transformation based on differential evolution.On account that most commercial near-field scanning system can not measure the phase of the field accurately,the equivalent dipole model is used to reconstruct the phase through the amplitude of the field.Then the algorithm in a)is used for interference source positioning.This algorithm only needs the magnitude of the field and is more efficient and time-saving.2)Electromagnetic interference source positioning with shielding layer.On the basis of the 1),interference source positioning is further discussed when the interference source is inside the shielding layer.Electromagnetic interference source positioning based on wave inversion: the electromagnetic near-fields obtained by probes are used as the radiation sources.Then,the interference source position is obtained by wave inversion.Electromagnetic interference source positioning based on correlation coefficient: first,the near-fields of the interference source inside the shielding layer are obtained by probes outside the shielding layer.Then,the correlation coefficients between the near-fields of DUT and unknown interference source are calculated for interference source positioning.Electromagnetic interference source positioning based on DE algorithm: the first two algorithms mentioned need phase information of the near fields.Moreover,this algorithm is phaseless algorithm.The globally optimized DE algorithm is used to get the interference source localization by only amplitude information of the scanning field.