[SI-LIST] Re: problems encountered extracting radiation losses
- From: "Christian Schuster" <cschuste@xxxxxxxxxx>
- To: jan.vercammen.jv1@xxxxxxxxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Wed, 22 May 2002 13:41:24 -0400
Jan,
I know nothing about the LC code but maybe I have some useful suggestions
for you:
> The main issue is to reduce the reflection from the boundaries.
What makes you think that? You are right, of course, if you identify
imperfect ABCs as major source of errors in FDTD in general but are
you sure that it applies to your specific case? What about numerical
phase errors/discretization errors, i.e. have you tried different
cell spacings?
> Are there other approaches to gauge radiation loss possible besides
> the one technique above??
You could integrate the Poyniting vector over a surface enclosing
your antenna.
> -5- What is the optimal distance between (in cells) the structure under
> investigation and the boundary?? Currently I use about 10 cells, but a
> smaller value of 5 cells gives very similar results.
I'm not sure if the PML is for near fields as good as it is for radiation.
Have you checked with PMLs in 20, 50 cell distance?
> In Taflove's book there is mentioned a (faze) correction because of
> the 1/2 time step difference. But
> I suspect that this is a high frequency issue and not a low one (<
> 200-500MHz). Is this correct reasoning??
"High frequency" is not absolutely correct. The phase error factor
is proportional to exp(freq *time step size), so it depends ...
Hope this helps,
Christian Schuster
IBM
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