In-circuit Noise Source Impedance Using Double Impedances Insert Loss Approach

Electromagnetic interference (EMI) filter as the most effective method to reduce the conducted EMI. In order to optimize EMI filter to provide effective insertion loss, it is necessary to understand the noise source and the load impedance. In this paper, a double impedance method is proposed to measure and calculate unknowns under interested frequency. First, the effects of noise source impedance on insertion loss are analyzed. Second, the configuration of the proposed method is presented. Finally, the feasibility and accuracy of the method are verified by simulation and experiment. Compared with the previous impedance extraction methods, the proposed approach can obtain the magnitude and the phase of impedances, and it requires no additional equipment.