How to rectify a data center switch that fails CE certification at a low cost?

For data center switches failing conducted emission CE tests, the priority order for low-cost rectification is as follows:

First, add a Y capacitor (1000pF-2200pF/400VAC capacitor in parallel with the power supply L/N to ground, cost <0.3 yuan, improving common-mode rejection by 6-10dB);

Second, add a ferrite bead clip, inserting the signal harness into a ferrite core such as PBZ3216E120Z0T (12Ω@100MHz) with 1-2 turns, cost <1.5 yuan;

Third, replace with a higher impedance common-mode inductor, such as upgrading from CMZ3225A-501T (500Ω) to CMZ4532A-101T (100Ω@100MHz, equivalent to higher inductance), cost difference 0.8 yuan;

Fourth, optimize PCB routing, cutting open the ground plane partition layer to add return vias at zero cost.

A measured low-cost solution (<5 yuan) can turn a 6dB excess margin into a positive margin.