EMI Bites: What Happens When Your Signal Crosses a Split Plane
EMI Bites: What Happens When Your Signal Crosses a Split Plane
In this simulation, a signal trace crosses a cut in the reference plane—and the result is clear:
The return current can’t follow, so the fields spread into the cavity between the two planes.
These spreading fields create unwanted radiation and signal integrity issues.
Why this matters:
- Split planes break the return path.
- The gap forms a cavity that radiates, especially at high frequencies.
- Signals can leak off the board, leading to EMC test failures.
Key Insight:
A broken return path creates a cavity antenna—avoid it.
Fix it:
- Don’t route signals across split planes.
- Keep return & reference planes continuous.
- Use return & reference vias if a transition is needed.
Dario
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