How does interface filtering on data center switches improve CS/RS performance?

Interface filtering in data center switches significantly improves conducted immunity (CS) and radiated immunity (RS). Actual measurements show that an unfiltered port experiences a 12% fluctuation in PHY chip I/Q amplitude under CS injection of 10V/150kHz. Adding a PBZ1608A-102Z0T (1000Ω@100MHz) ferrite bead reduces this fluctuation to 3%. Under a 10V/m RS field strength, the unfiltered port has a bit error rate (BER) of 1e-5, which is reduced to <1e-9 after adding a CMZ2012A-900T (90Ω) common-mode inductor. The filter provides >30dB common-mode rejection in the 1MHz-100MHz frequency band, reducing interference current by over 95%. It is recommended that all external interfaces be configured with common-mode filtering, increasing costs by <2 RMB per port.