Abstract：EMI filter plays an important role in restraining conducted EMI. Planar EMI filter has a decreased size and high reliability in high frequency performance compared to passive discrete EMI filter. However, the performance of EMI filter cannot be exactly expected using existing methods. Therefore, the method of scatter parameters is used to measure EMI filter performance in this paper. The relationship between scatter parameter and insertion gain of EMI filter is derived; the method to predict the insertion gain of filter under different impedance is proposed. The near field coupling model of the planar filter in high frequency is deduced. Based on the relationship of scattering parameters and impedance parameters relations, the method to extract the mutual inductance in the near field is proposed. A sample planar EMI filter is completed. The theoretical calculation and practical measurement under different impedance conditions of the insertion gain are completed. At the same time, the differential structure of the near field coupling model is deduced and the insertion gain in standard impedance conditions is calculated, and compared with the actual measurements. The feasibility of the theory is verified.
石磊磊, 王世山, 徐晨琛. 二端口网络散射参数理论及其在平面EMI滤波器测试中的应用[J]. 电工技术学报, 2013, 28(2): 78-85.
Shi Leilei, Wang Shishan, Xu Chenchen. Theory of Scatter Parameters of Two Port Network and Its Application in the Test of Planar EMI Filter. Transactions of China Electrotechnical Society, 2013, 28(2): 78-85.
2013, Vol. 28 
