Hi ,
I have a doubt, i studied one article related to ethernet routing . In that they have mentioned, while using 4 layer board, choose the 4th layer has ground plane. But in my scenario First layer and fourth layer is signal layer and second layer is ground plane. If i am using 2 layer is ground plane means what should i do???
currently what i have done except that area of the differential pair routing to ethernet connection. I have poured the copper in power plane and ground plane. whether it is right
You might want to link to that article.
To my knowledge one would normally use one of the inner layers as ground as this allows for uninterrupted copper pour.
It makes little difference. What matters is that at least one layer is a good solid plane. External planes do improve near field RF shielding a little, but make modification impossible.
Having read that bottom paragraph on p5 it sounds more like that the copper pour in that area is optional for EMI purposes and if one wants/needs to do it, he has to put the GND layer further away from the signal wires, ie layer 4. In other words, the ground pour on layer 2 should have cutout-no-fill-zone in the area they describe, as otherwise you’ll wind up with some nasty effects.
The drawing a page earlier depicts your layer buildup with GND on the inside anyway:
If this isn’t mission critical and you’re not going to sell those boards in products that need to confirm to some EMI rules and can/will be checked I wouldn’t sweat about it. If that’s not the case - well, then you have to do a lot of catching up to do and find a way to measure what effects this or that has anyway and this forum might be out of it’s league for the topic, unless there is someone around that would know what to do and can help you
