As simple as this phrase is, it’s one of my favorites from one of my favorite EMI engineers, Bruce Archambeault. It also touches on one of the most important things you can learn in PCB Design for Low EMI.
The term ground in Printed Circuit Boards is outdated and often misused, leading to confusion that makes understanding EMI and electromagnetic fields difficult.
The word ground says nothing about the current return path, potential reference for the signal, or impedance.
This is also why it’s easy to believe that GND nets work as some kind of sink for the current.
A better term I prefer to use is Return Reference Plane or, in short, RRP.
This term reminds me, when creating a PCB layout, of the three important functions this conductor must provide:
- Return: Provide the return path for current back to the source.
- Reference: Provide the reference potential to establish a voltage potential, which we call the signal.
- Plane: Provide the lowest impedance path possible for the return currents.
Once I switched from thinking of GND to RRP, my PC boards started delivering outstanding results in terms of EMI.
EMI is simple, not easy, but it’s certainly not black magic.
Learning from first principles allows us to build fundamental knowledge that helps us design even the most advanced projects.
I hope this helps,
Dario
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