Gregory's Server@funkylab yeah the book advises building a ground "bridge" directly underneath high speed traces that cross over. they have high frequency return currents that take the path of least inductance (directly underneath) and if you have a ground cut underneath then the loop area increases, and you start radiating...
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 @MarkAtMicrochip @funkylab you can sorta cheat a bit with high slew rate signals if they have a very long period and if you quasipeak during the EMI scan, but yeah usually high slew rate signals are a problem. |
@tubetime @funkylab I think you’re right. Just remember that “low frequency” that does cross the ground plane better have very slow rise/fall times. I could not find the >1GHz EMI that was radiating from my board. Long story short, it was a 32kHz oscillator with a 800fs rise/fall time. In the oscillator manufacturers defense, the datasheet only had a maximum rise time spec. But who would have thought the edges would be that sharp!