Influence of Multi-stage Choke Coupling on Insertion Loss and Optimization Design

Mutual inductance in multistage filter will cause uncontrolled noise coupling from multiple chokes, so filter components between the two magnetic components will be bypassed to a certain extent. This will lead to weaken insertion loss (IL) value of filter circuit much less than what expected, that is detrimental to pass Conducted Emission (CE) and Radiation Emission (RE) tests, so it's important to analyze it and prepare the remediation. In order to study the influence of mutual inductance between multi-stage chokes on the insertion loss of filter circuit, this paper establishes the model of multi-stage chokes by electromagnetic simulation software, analyzes different installation methods by simulation, calculates the influence law of mutual inductance between chokes on the insertion loss of filter circuit, and proposes the optimization scheme. The simulation results show that the change of common mode choke spacing has the greatest influence on the insertion loss, which can reach 3dB. While the change of angle has the least influence, and the horizontal installation of two-stage choke has the least influence on the insertion loss. After optimization design, this effect can be reduced to 2 dB.