GROUNDED: EMC/EMI & PCB Design Nuggets

One of the biggest game-changers for me in EMI control is visualizing the EM fields as signals propagate.

Too often, we focus only on the signal path and treat the return path as an afterthought, just to close the current loop at the end of the design.

In reality, the loop is closed as the signal travels (yes, displacement current in the dielectric magically closes it!), so any gaps or breaks in the return path—like splits in the reference plane—can mess with your signals, causing crosstalk or turning cables into antennas.

How bad? It depends on frequency (high-speed signals are pickier!), but it’s always better to know it’s coming.

I like to think of the PCB as a set of channels for guiding EM fields exactly where I want them.

It’s not just about copper traces but building these channels with the stackup—signal layers paired with solid return planes and tight dielectric spacing.

A well-designed stackup keeps fields contained, cutting down on noise and emissions.

Hope this helps you design with EMI in mind!

-Dario

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