Near-field-to-near-field Transformation Algorithm For Electromagnetic Interference Diagnosis

The fast development of 5G communication,artificial intelligence,automatic drive and high performance computing,promotes the electronic devices' increasing working frequency and integration level,resulting in that the electromagnetic environment is more and more complicated,and the electromagnetic interference is more and more severe.In recent years,near-field scanning technology has become a new tool for electromagnetic interference diagnosis,which was widely used in antenna engineering field and then applied to electromagnetic compatibility field.According to the actual requirements of industry and the electromagnetic algorithm problems which restrict electromagnetic interference diagnosis,this paper is based on the plane wave spectrum theory,studies the near-field-to-near-field transformation algorithm in the deep reactive near field of radiators,and aims to solve problems of existing near-field scanning algorithms,such as low scanning efficiency and disability of locating electronic devices' internal electromagnetic sources.The main work of this paper is as follows.Firstly,the electromagnetic near-field scanning platform is established,including scanning without phase by using a spectrum analyzer and scanning with phase by using a vector network analyzer,and a scanning control software is developed.In addition,a magnetic probe is designed,whose equivalent circuit and calibration method are analyzed.Secondly,a near-field-to-near-field transformation algorithm for single substrate is proposed to solve the low efficiency problem of near-field scanning technology,that only one plane can be scanned at a time.By using the plane wave spectrum expansion of the probe output,the conventional spectrum domain probe calibration method is extended,and the field distributions on multi-planes are obtained through a single-plane scanning.The proposed algorithm is validated with both numerical and experimental examples.In comparison with the conventional spectrum domain probe calibration method,the proposed algorithm does well especially in determining the fields below the probe's scanning-plane.This is deterministically useful for accurately identifying the potential radiation sources during the electromagnetic interference diagnosis,and this algorithm is applied to an enterprise cooperation project practically.Thirdly,a near-field-to-near-field transformation algorithm for multiple substrates is proposed as the further extension of the near-field-to-near-field transformation algorithm for single substrate.By scanning the external field of an electronic device,its internal field can be predicted,and the location of the unknown radiation source inside the electronic device can be determined.Simulation and measurement show that correlation coefficients between the predicted internal field of electronic devices and the reference are larger than 0.9,which proves the good accuracy of the proposed algorithm.Conventional antenna near-field scanning is usually in the radiating near-field,in which the propagating wave contributing to the far-field is mainly paid attention to,and evanescent wave is neglected.Because the scanning plane is close to the radiator for electromagnetic interference diagnosis,this paper stresses to study the scanned field in the deep reactive near-field region,and develop the near-field-to-near-field transformation algorithm for the evanescent wave,which is applied to analyze devices' interference.The proposed near-field-to-near-field transformation algorithm in this paper can be combined with the existing antenna near-field scanning's near-field-to-far-field transformation algorithm,which has the potential to form a complete near-field and far-field transformation theory.