Study on impedance extraction methods applied in conductive EMI source modeling

Two-current probes method and S-parameter method are studied comparatively for conductive EMI noise source modelling in this paper. Firstly, the basic theory of the two-current probes method and S-parameter method are introduced for noise source impedance extraction. Secondly, Z_X and Z_setup are important intermediate results in the two methods, therefore their extractions are analyzed respectively. Moreover, the single probe method is proposed to obtain better accuracy, stability and low-cost. The experimental results show that due to the parasitic effect, the lengths of short wire in two-current probes method have negative effects on Z_setup extraction. And the direct measurement method in S-parameter method is superior in Z_setup extraction. The inaccuracies of the two-current probes method and S-parameter method for Z_X amplitude extraction reach to 4% and 1.5%, and S-parameter method has a comparatively better performance on both Z_X amplitude and phase extraction.