Re: gEDA-user: trace calculation[Scanned]

[daedalworks@xxxxxxxxxxx]

Vias also have problems with continuity of the ground plane.  There was a white paper a couple years ago that showed good results with four ground vias arranged around the signal via (I forget what they did for differential pairs).  Unfortunately, I don't have a copy any more.... :-(

 

> -------------- Original message -------------- 
> From: Dan McMahill <dan@xxxxxxxxxxxx> 
>
> > Robert Thorpe wrote: 
> > > Microvias in particular are thin and have significant inductive 
> > > reactance at high frequencies. Normal vias are not so bad. 
> > 
> > you can minimize the effect of a via by nominally matching it to the 
> > trace. In other words by varying the via diameter you have a handle on 
> > its impedance and there usually is an optimum value. Brian Wadell's 
> > book gives some details on this. 
> > 
> > -Dan 
> >