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为了有效降低电子设备产生的传导电磁干扰噪声,需要设计合适的电磁干扰滤波器,而噪声抑制效果与噪声源阻抗的精度有关。插入损耗法和电流探头法等传统方法虽能初步得到噪声源阻抗,但测试电路耦合电容和测试过程中存在的近似及约束条件会严重影响测试结果,亦无法得到噪声源阻抗的幅值和相位。针对上述问题,该文提出了基于双阻抗校准和麦夸尔特法的噪声源阻抗提取方法,分别利用2个电流探头和2个标准阻抗获取被测噪声源阻抗的幅值和相位,再利用麦夸尔特算法提取全频段(9kHz~30MHz)噪声源阻抗的频率特性,并确定其电阻、电容和电感参数。实验结果表明,采用文中方法能够较大提高噪声源阻抗的提取精度,从而为EMI滤波器的设计提供理论依据。
In order to effectively reduce the conducted electromagnetic interference noise generated by the electronic device, an appropriate electromagnetic interference filter needs to be designed, and the noise suppression effect is related to the accuracy of the noise source impedance. Traditional methods such as insertion loss method and current probe method can obtain the noise source impedance initially. However, the coupling capacitance of the test circuit and the approximation and constraints existing in the test process will seriously affect the test results and the amplitude and phase of the noise source impedance can not be obtained . In view of the above problems, this paper proposes a noise source impedance extraction method based on the two-impedance calibration and the Michart method. Two current probes and two standard impedances are used respectively to obtain the amplitude and phase of the impedance of the noise source under test. Macquarie’s algorithm extracts the frequency characteristics of the noise source impedance in the full band (9kHz ~ 30MHz) and determines its resistance, capacitance, and inductance parameters. The experimental results show that using the proposed method can greatly improve the extraction accuracy of the noise source impedance, and thus provide a theoretical basis for the design of the EMI filter.