Investigation on radiated EMI noise identification for high speed digital PCB

In the paper, a new approach by using near-field probes is proposed to identify mechanism of radiated EMI noises, i.e. CM noise and DM noise, according to but only the internal relationship between radiated EM field and near-field wave impedance, but also the inner relationship between wave impedance and measurement distance. Then, radiated EMI noises decrease obviously after suppressed by using 3-m chamber measurement. The research shows that the proposed method is effective and valid.