Common-mode and differential-mode analysis of common-mode chokes

In this paper, three methods for the measuring common-mode and differential-mode S-parameters of common mode chokes are presented. The three methods involved: (1) ABCD chain matrix; (2) using hybrid couplers; and (3) modal decomposition. Each measurement method provides a specific level of accuracy. The modal decomposition method can work up to 10 GHz. Given a full characterization of a common mode choke, a passive equivalent circuit model can be synthesized that provides a fundamental understanding of the physical performance. SPICE equivalent circuit model of common mode chokes and the extraction of model parameters are provided.