Re: gEDA-dev: Numerical analysis of circuit boards

[Tomaz Solc <tomaz_dot_solc-at-NOSPAMtablix_dot_org>]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi

> What techniques are you using? Also, how do you validate your results?

I'm using a finite difference method.

So far I have only validated the results by trying some simple
geometries and comparing the values returned by my software with those
that can be analytically calculated. I'm also planning to make some
printed circuit boards with test patterns and compare the calculated
values with measurements.

> The times I've needed trace capacitance estimates I've used FastCap.
> However, instead of extracting PCB parameters and creating the FastCap
> finite element model, I only created FE models for those areas of interest
> in the PCB. This was useful for performing parametric analysis (like
> measuring the effect of parasitic capacitive coupling as a function of
> trace spacing between two nodes), but difficult to create new models. In
> addition, I never really could satisfactorily model the FR4 dielectric.

My program currently can't handle complex dielectrics. Support for
anisotropic materials would be quite simple to add, but I currently
wouldn't know how to handle lossy dielectrics.

> Another technique I've seen used is a simple parallel plate modeler. This
> is a first-order capacitance solver that extracts the copper geometry from
> a gerber (or whatever), and estimates capacitive coupling between nodes
> using the A/d formula. However this technique is not too accurate for
> geometric shapes with large aspect ratios (like traces!). Furthermore, the
> "second order" effects due to nearby nodes is very significant.

I'm currently loading the copper geometry from PNG files. I take a board
drawn in PCB, export it to postscript and convert postscript to PNG
images. Pin locations still must be entered by hand.

Best regards
Tomaz Solc
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.5 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQFE8codsAlAlRhL9q8RApmxAJ9b5HuZPcXnOah/Nrgg1pv4gTu6oQCfZMtf
p7wQn6CbSH/yUgta76XDYjc=
=jOaJ
-----END PGP SIGNATURE-----


_______________________________________________
geda-dev mailing list
geda-dev@moria.seul.org
http://www.seul.org/cgi-bin/mailman/listinfo/geda-dev