EMI/EMC Academy ~30 min Interactive

Cables, Connectors & Grounding

Cables are the receiving antenna. Common-mode chokes, 360° bonds and ferrites — the mirror image of the emissions fixes.

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Since cables deliver the RF as common-mode current, a common-mode choke at the connector is the front-line fix — it presents high impedance to the incoming CM current while passing the wanted differential signal. This is the exact mirror of the emissions fix in the Pre-Compliance chokes module.

Learning objectives. Use CM chokes, 360° shield bonds and ferrites to cut RF ingress; and filter at the connector.

Bond cable shields 360° to chassis at entry (a pigtail's inductance lets RF straight in), add connector-area filtering, and use ferrites/CM chokes sized so their impedance peak covers the susceptible band you found in Module 4. A snap-on ferrite is a quick bench confirmation.

Bidirectional fixes. A CM choke + 360° bond that lowers radiated emissions also blocks incoming RF — one change, two benefits.

Ground strategy. Keep RF common-mode current in the dirty entry zone and bonded to chassis, away from sensitive references.

Common mistakes: relying on an unbonded/pigtailed shield; placing the choke after the RF has already coupled into the board; or filtering the signal but leaving the cable shield floating.

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