Hi Karl,

 

What simulator are you using?  I'd like to look into what parameters they are using.  While I agree that the return plane can make a difference at very high speeds, at what point can make a significant difference?  If the speed of the signal is under 1GHz (I'm still searching for what speed would be the low end cut off) or more, what is the actual effect on the signal?  Sometime this can be compensated for through software if it is known.

 

The reason I ask is I have had some conversations lately around "what changes the actual circuit" when previously "standard" fabrication adjustments are made.  What determines a change that should NOT be made (teardrops, unused pad removal, copper theiving, minimum finished copper thickness, etc) for efficiency or cost savings and when is it ok to allow these when they weren't there before.  Should we be putting this information into a document that accompanies the fabrication drawing or adding specific parameters into the notes?

 

Thanks,

Cherie