GROUNDED: Your PCB, EMC/EMI, and SI Nuggets

“Routing signal traces over a gap only messes you up at high frequencies.”

That’s what a lot of engineers think, and it’s an easy mistake to make.

But here’s the reality: it’s a problem way sooner than you’d expect.

Check this simulation with #Simbeor software, first at 10 kHz, then at 1 GHz.

Guess what?

When the signal crosses a gap, its return current takes a detour, forming a much bigger loop.

That might not sound like a big deal,

except radiated emissions from differential mode current

scale directly with the size of that current loop.

And that’s where things get messy.

So, it’s not just a “high-speed” thing.

We need to be smart about PCB layout at all frequencies.

This is actually one of the sneaky reasons designs fail radiated emissions tests during EMC certification.

In this sim, the culprit was a bad stackup choice,

specifically, a gap in the return path forcing that bigger loop.

Here’s the good news:

by understanding electromagnetic field propagation (not electrons),

you can spot these issues early, and dodge those pricey EMC test failures.

-Dario

P.S. Want to catch EMC/EMI problems before they bite?

Grab my new EMI Control Guide here below: