How do gaps in the edge computing box structure affect shielding effectiveness?

Gaps in the metal casing of the edge computing box can create slotted antennas. When the gap length is greater than λ/20, radiation leakage is significant and shielding effectiveness decreases. At 1GHz, λ=300mm, λ/20=15mm. If the gap length is 20mm, the shielding effectiveness is less than 10dB, while a continuous conductive design can achieve 40dB. Improvement methods:

1. Add conductive springs or conductive foam with a compression of 30% at the joint between the upper and lower covers, with a contact resistance of <20mΩ. Recommended: Conductive cloth padding from Etymotic.

2. The screw spacing should be less than λ/20. For example, at 1GHz, the screw spacing should be <15mm.

3. Replace the ventilation holes with waveguide windows. Hexagonal honeycomb holes with a side length of <3mm can achieve a shielding effectiveness of 60dB.

4. Apply an optically transparent conductive film to the window opening of the display screen.

The light transmittance is 85%, and the surface resistance is <1Ω/□. After actual measurement and optimization, the shielding effectiveness of the edge box at 1GHz has increased from 12dB to 38dB, with a 6dB margin in radiated emissions.