vias for changing signal layers

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deba_fire

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Hi Everyone,

If signal changes layer it is a good practice to put vias near them where they change layers.But I am not able to understand what nets will these vias connect.In my case i have a 4-layer board,and some signals(high speed) are changing layers from top to bottom.I need to place vias close to them.But what these vias should connect to??Please someone help.
 

Have a look at this it may answer your question or point to other research:
**broken link removed**
 

you should connect those vias to GND in order to provide a close AC return for the signals.
 
So we should connect grounds on both sides of via...like ground filling on the top layer to the ground plane.
 

2nd Deba_fire, for high speed some GND vias next to the signal vias will provide a low inductance path for the signals.
Have a look at the diagram halfway down this link.
Via Inductance
 

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