How to optimize EMC when multiple interfaces of an edge computing box are working simultaneously?

When multiple interfaces such as 4G, WiFi, Gigabit Ethernet, USB 3.0, and HDMI operate simultaneously in an edge computing box, internal crosstalk and total external radiation are typical challenges. Optimization strategies include:

1. Adding an independent common-mode filter to each high-speed interface (CMZ2012A-900T for Ethernet, CMZ2012A-900T for USB 3.0, and CMZ20212A-900T for HDMI). The common-mode Z impedance is 20212, the size is 2.0×2.1mm, and the 900T impedance is 90Ω. 100MHz is placed close to the connector layout.

2. Adding ESD protection to the RF front-end using ESDLC3V3D3B with a low capacitance of 0.8pF to avoid affecting sensitivity.

3. Using a star-shaped single-point grounding for power distribution and network to prevent digital noise from entering the RF circuit.

4. Physically isolating the antenna from the high-speed bus wiring (distance >30mm) and using a shielding cover.

Actual testing shows that after optimization, throughput increased by 30% when 4G and WiFi coexist, and the overall radiated emissions have a 6dB margin, achieving FCC certification.