Evaluation of practical model of an on-board type common mode choke coil for 3D EMC simulation

A common mode choke coil (CMC) is mounted on the differential signal lines to suppress common mode noise propagating on differential signal lines. To evaluate the noise suppression effect of the CMC in the design phase of the equipments, 3D electromagnetic simulation considering the physical structure of the circuit, such as the pattern layout of the printed circuit board and inter connection, should be performed. In that simulation, the practical model of the CMC which can represent the performance of the real CMC with a simple simulation structure is required in order to simplify the total simulation model of the circuit. We have studied the practical model of an on-board type CMC for 3D EMC simulation. In this report, the common mode suppression effect of the CMC is calculated using the equivalent model with unbalanced structure of the differential signal lines. The calculated results are compared with the measurement results and the accuracy of the proposed practical model of CMC is verified.