How to rectify excessive EMC interference from the HDMI interface of an edge computing box?

The edge computing box's HDMI interface transmits high-speed TMDS signals at rates up to 3.4Gbps, resulting in radiated emissions exceeding the standard frequency band, typically between 1-3GHz. Remedial measures include:

1. Adding a surface-mount common-mode filter CMZ20212A-900T to the HDMI connector. This filter is named CM common-mode Z, with an impedance of 20212, dimensions of 2.0×2.1mm, and a 900T impedance of 90Ω. This device is optimized for HDMI with a common-mode rejection ratio >20dB for the 1-3GHz range.

2. Adding a PBZ1608E600Z0T ferrite bead and a 10μF capacitor to the HDMI 5V power supply to filter power supply noise.

3. Ensuring the HDMI socket's metal casing maintains 360° contact with the chassis ground via conductive springs, with an impedance <10mΩ.

4. Strictly controlling the TMDS differential pair on the PCB to 100Ω impedance and incorporating ground planes with a hole spacing <λ/20.

5. Using high-quality finished shielded HDMI cables with the ferrite core close to the device end.

After these remediations, the edge computing box's HDMI interface radiated emissions meet the EN55032 Class B limit with a margin of 3.2dB.