A Lumped-Element Circuit Model of Ferrite Chokes

An RLC model of ferrite chokes for suppressing common-mode (CM) currents is presented. The equivalent lumped-element circuit parameters are obtained from the frequency-dependent input impedance of a ferrite choke on a wire above the ground plane. This input impedance can be either measured (using vector network analyzer or impedance analyzer), or numerically modeled based on the known ferrite material properties (permittivity and permeability). An example of using both numerical modeling and measurements is provided. Results show good agreement at comparatively low frequencies (below 200 MHz). The upper frequency limit for the proposed equivalent lumped-circuit model is discussed