Common Mode Filter Design to Reduce Radiation of PCIe3/4 Signal

摘要

Common mode filter constructed by ground plane voiding had been researched and verified in this paper. EMI test results shown radiation magnitude is reduced at target frequency with designed common mode filter. SSC (Spread Spectrum Clocking) is extensively used for PCIe signal to reduce radiation magnitude. While, SSC will not always be allowed in some PCIe3 configurations. Practicable design of common mode filter is essential to reduce radiation magnitude when system turns off SSC. This paper develops method to design common mode filter in PCB. This method had been verified by EMI test of actual system.