A new approach to conductive electromagnetic interference (EMI) noise source modeling, i. e. the source internal impedance extraction, is presented. First, the impedance magnitude is achieved through an exciting probe and a detecting probe, or through calculations based on insertion loss measurement results when inserting a series high-value known impedance or a shunt low-value known impedance in the circuit. Then the impedance phase is extracted by the Hiibert transform (HT) of the logarithm of the obtained impedance magnitude. Performance studies show that the estimated phase error can increase greatly at a zero frequency in the Hilbert transform because of the existence of a singular point, and this effect can be eliminated by introducing a zero-point when the noise source does not include a series-connected capacitive component. It is also found that when the frequency is higher than 150 kHz, the estimated phase error is not sensitive to the inductive source but sensitive to the capacitive source. Finally, under the conditions of the same measurement accuracies for impedance magnitude, the accuracy of complex impedance based on the HT can be improved about 10 times when compared with the accuracy of estimated parameters based on the impedance magnitude fitting method (IMFM).%提出一种传导噪声源建模即内阻抗提取新方法.该方法首先通过激励和检测探头测得阻抗模,或通过串联已知高阻抗、并联已知低阻抗的插损测量,计算得到阻抗模.然后利用得到的阻抗模的对数进行Hilbert变换(HT)提取阻抗相位.对该方法的性能研究表明,Hilbert变换在零频率处存在的奇异点会引起该处相位估计误差骤增,对不含串联电容的情况可引入零点以消除该影响;当频率高于150 kHz时,估计误差对感性噪声源的变化不敏感,而对容性噪声源的变化敏感;同样阻抗模测量精度下,基于HT获取复阻抗比基于阻抗模拟合的参数估计精度提高近10倍.
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