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Date: Wed, 31 Aug 2016 14:39:38 -0700
From: Larry Doolittle <ldoolitt AT recycle DOT lbl DOT gov>
To: "Evan Foss (evanfoss AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
Subject: Re: [geda-user] Microwave PCB layout simulation or How to eat all
 your processing power in 3 easy steps
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Evan -

On Wed, Aug 31, 2016 at 03:53:25PM -0400, Evan Foss (evanfoss AT gmail DOT com) [via geda-user AT delorie DOT com] wrote:
> On Wed, Aug 31, 2016 at 1:13 PM, Larry Doolittle <ldoolitt AT recycle DOT lbl DOT gov> wrote:
> > Connecting to reality can be hard.  So many assumptions about
> > e.g. materials parameters go into the calculations.  What's the
> > dielectric constant of soldermask?  How does the software deal with
> > outgoing radiation, even if the design goal isn't to build an antenna?
> > A realistic model can get very complicated very fast.  Complicated
> > 3D geometries push computational limits, leading to either long
> > run times or poor convergence, or both.
> 
> I know. The guys I am working with here are modelling the mechanics of
> the middle ear. Fundamentally it is an impedance matching transformer
> from air to fluid but there are all manner of bones in there and etc.
> 
> I thought soldermask issues were why most of the microwave and other
> RF hardware I have seen has no soldermask.

For the long lines, yes, depending on the designer, but eventually
those lines usually touch chips.  And high-speed serial lanes (with
the interesting frequency range now going up to 40 GHz) usually don't
have soldermask stripped off.

> I am writing to the openems maintainer to find out what the limits and
> etc are of openems.

Sounds good.

   - Larry