Do high-speed cables in data center switches exacerbate radiation (RE)?

Data center switch high-speed cables (DAC/SFP+) do not actively radiate as passive transmission lines, but as antennas, they can export and radiate common-mode noise from inside the chassis. Actual measurements show that using a 3-meter DAC cable results in 8-15 dB higher radiated field strength in the 30MHz-200MHz frequency band compared to using optical modules. Suppression measures include: adding a CMZ2012A-900T common-mode inductor (90Ω@100MHz) to the cable port to suppress common-mode current; 360° grounding of the cable shield with a grounding impedance <5mΩ; and using a double-shielded cable structure. Case study: A certain model's 1.25GHz clock harmonics exceeded the limit through the DAC cable; adding a ferrite bead reduced the harmonics by 11 dB, passing the Class B limit.