Sensitivity Analysis of Noise Source Impedance Measurements

The optimal design of electromagnetic interference (EMI) filters necessitates precise characterization of noise source impedance. While the insertion loss method theoretically enables accurate extraction of the magnitude and phase of noise source impedance by formulating a system of biquadratic equations for its real and imaginary components, inherent measurement inaccuracies during implementation often degrade extraction accuracy or lead to failure. To address this limitation, this paper proposes a series insertion loss method. First, analytical expressions for the exact magnitude and phase of the noise source impedance are derived. Subsequently, the applicability of the series insertion loss method is systematically analyzed, with particular emphasis on quantifying the impact of insertion loss measurement errors on impedance extraction accuracy. Critical requirements for improving extraction precision are identified, and the permissible range of insertion loss error to ensure solvability is mathematically established. Finally, comprehensive simulations validations confirm the efficacy and robustness of the proposed approach.