EMI Bites: Poor Layer Stackup = Antennas You Didn't Plan For
When routing signals across multiple layers, think about layer coupling.
Let’s walk through a typical issue:
A signal (or power) layer not referencing the return and reference plane (RRP), but another signal layer or another power plane.
Why this causes problems:
- Incomplete or broken reference planes break the return current path, causing signal distortion.
- Field spreading occurs when return paths are unclear, increasing crosstalk and emissions.
- Segmented copper pours create areas that act as antennas.
- These unintended antennas pick up or radiate high-frequency noise, hurting your EMI performance.
Key Insight:
Every signal layer needs a proper, continuous return reference plane.
Poor stitching or segmented plane design turns copper into antennas.
How to fix it:
- Pair every signal (and power) layer with an adjacent solid return reference plane (RRP).
- Avoid partial planes—cover the full area beneath signal traces.
- Treat every copper pour as a potential radiator unless it's well connected.
To electromagnetic enlightenment,
- Dario
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