Re: gEDA-user: Trace impedance calculations in PCB

[Steven Michalske <smichalske@xxxxxxxxx>]

On Feb 12, 2009, at 10:27 AM, Stuart Brorson wrote:

>> Are there any plans to add trace impedance calculations to PCB?  If
>> not, is there an argument against it or just that no one has time and
>> interest?  What alternatives do people use?
>
> As Joe pointed out too, PCB doesn't not know about the metal layer
> separation distance, nor does it know the dielectric constant of your
> insulating material.  Therefore, it cannot do impedance calcs.
>
> I am not aware of any PCB layout programs which provide you impediance
> calcs.  However, Microwave Office might, since it targets this type of
> application -- I've just never used it.
>
> If you know your trace geometry and dielectric coefficient, you can
> use Dan McMahill's program wcalc to analyze impedances:
>
> http://wcalc.sourceforge.net/
>
> HTH,
>
> Stuart
>

I think integration of this is a great idea,  as others has mentioned  
two things are needed.

1.  stack-up information:
	- one needs to know what each layer of the board is like.
2. a simulator
	- i would tend to want to write one that could plug in many of the  
types of simulators out there, many mentioned in this thread.


i know that for our work we have specifications on boards that states  
that impedances are controlled for specific trace types, and we have  
test layouts for verification on the panels.

so the tool i see has two modes

- give me the impedance of my layout
- tell me what traces to place.

Steve

>
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