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Date:	Fri, 23 Oct 2015 22:52:07 +0200
From:	"Nicklas Karlsson (nicklas DOT karlsson17 AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
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Subject:	Re: [geda-user] Board DRC
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> >> There should be exactly one short at the star ground point. If
> >> algorithm calculate their lines meet at the edge end point have to
> >> checked in some way.
> > 
> > Or if a particular bit of copper could be tagged as "star point" or
> > something, the algorithm could know that it should be the edge of
> > multiple nets, and verify it.
> > 
> > I'm just thinking, our DRC isn't designed to handle these types of
> > problems, but a new DRC might, and give us other benefits too.
> > 
> 
> I spent the morning in a video meeting reviewing a complicated layout from a geda-gaf->Allegro flow. The issues were far beyond the things discussed in this (thoroughly mutated) thread. We have segmented grounds, but not star connections. Star connections only work well if you can neglect inductive coupling. And then there ware other things: I was able to say at one point “Don’t worry about crosstalk between signals X and Y: they crosstalk so badly in the sensor that any conceivable crosstalk on the board will be negligible.”
> 
> So, it’s complicated. I found myself wishing for a tool that would show concentrations of AC magnetic field. As far as I know, Allegro can’t handle these issues: humans have to pay attention.
> 
> I don’t think a tool that works from the top down can ever do this stuff well. You need a bottom-up model of a circuit board to even start to think about how to analyze how your layout really works. Pcb has no such foundation, which is the root of the frustration it causes for a reductionist like me.
> 
> John Doty              Noqsi Aerospace, Ltd.
> http://www.noqsi.com/
> jpd AT noqsi DOT com

To do this kind of electromagnetic calculation the file format or internal storage in pcb is probably the smallest problem. To show concentrations of AC magnetic field current need be known in each segment. Once current and shapes are known it I guess it will be possible to make calculations. Capacitance and inductance between nets would probably be more realistic and maybe not practical impossible?

Trace impedance calculation however are probably more realistic, thes kind of calculations are available on the net http://www.eeweb.com/toolbox/microstrip-impedance together with equations.

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