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If you are still using two-layer PCBs without "Ground" planes for your awesome electronic design and you're planning to test for EMC, then this is for you.
At a fundamental level, something just doesn’t add up.
The reason is simple: it's in how the signal propagates in the PCB.
The "water flowing through pipes" analogy to describe how signals propagate in a PCB no longer works.
It fails to explain how electromagnetic fields actually travel through the dielectric medium (not the conductors), which is key to understanding signal propagation—especially in high-speed designs.
The EM fields we measure with EMC instruments are simply the fields that managed to escape the PCB structure we created.
These fields were supposed to stay inside the board as signals.
So, failing an EMC test—like radiated or conducted emissions—simply means that our design is not energy-efficient.
It leaks energy as signals outside the board, turning into interference and noise, instead of staying inside the board where it can do useful work like transferring information or power.
Moral of the story: design your PCB structures to contain the fields—not to broadcast noise—and EMC testing will feel much simpler.
-Dario
P.S. If you want to learn more about EMC/EMI design, I have full courses and guides where I show exactly how to do this, so you can eliminate EMI issues once and for all. Click here to learn more: