Identifying Electromagnetic Noise-Source Impedance Using Hybrid of Measurement and Calculation Method

Identifying the noise impedance is a key step to improve the performance of an electromagnetic interference (EMI) filter. This paper proposes an impedance perturbation method to measure and calculate unknowns under a wide frequency range. Not only the differential mode/common mode (DM/CM) impedances but also the magnitude and the phase of impedances will be obtained at the same time. Moreover, the extraneous solution introduced by computation is checked. In addition, the profile of the perturbation infrastructure almost keeps the same under different cases, and it will limit the error of measurement under a very low level, which is also discussed in detail. Finally, the experimental results validate the methods very well.