Design for EMC from the first schematic
Most EMC failures are decided long before the test lab. A few habits at schematic and layout stage save weeks of re-spins.
Pre-compliance failures rarely come from one big mistake. They come from many small decisions — a long return path here, an unfiltered cable there — that add up. The cheapest time to fix them is before the first board is ordered.
Start with the return current
Every signal current comes back to its source. At high frequency it returns directly underneath the trace on the nearest reference plane. Keep that plane solid: no splits under fast signals, and stitch planes with vias wherever a signal changes layers.
Treat every cable as an antenna
- Filter signals where they leave the board, not where they are generated.
- Place connectors along one edge so cable common-mode currents share a reference.
- Leave footprints for common-mode chokes and series resistors even if you fit 0 Ω first.
Slow down what does not need to be fast
Edge rate, not clock frequency, sets the emission spectrum. Series termination, reduced GPIO drive strength and spread-spectrum clocking on MCUs that support it are free wins.
Plan for the lab
Add test points for a near-field probe, keep a ground stud near the I/O connectors, and make sure firmware has a mode that exercises the worst-case radios and interfaces continuously. It turns a day of guessing in the chamber into an hour of measurements.
Talk to the IDEAS team about your hardware or firmware.
