Re: gEDA-user: trace calculation

[John Doty <jpd@xxxxxxxxxxxxx>]

On Jan 5, 2006, at 2:17 PM, Phil Taylor wrote:

> Or another way to consider this:  Isn't it possible to make a trace  
> that a
> certain frequency cannot pass through due to nothing other than its  
> length?

Nope. One of the simplest solutions to Maxwell's equations is a wave  
attached to an infinite straight conductor in an otherwise empty  
vacuum. Of course, in real life details get in the way: there's stuff  
in the neighborhood, the conductor has resistance, it isn't straight,  
etc. It's the nitty grittys of these details that are hard to  
calculate. It's even hard to automate, because the judgement needed  
to choose a suitable approximation is difficult to incorporate in a  
program.

I discovered long ago as a physics student that expertise in coupled  
transmission line problems carried over very well into quantum  
mechanics, especially at exam time, where the kinds of problems that  
could reasonably be solved with a pencil in an hour without a stack  
of reference books were often perfectly analogous to simple multimode  
transmission line problems. But most such problems aren't simple.

The folks who really first hit this problem head on were at the MIT  
"Radiation Lab", doing Radar R&D during WWII. If you read the Rad  
Lab's final report, the names you see are amazing: Dicke, Bethe,  
Schwinger, ...! Many of the future superstars of physics were working  
on *exactly* this stuff.

John Doty              Noqsi Aerospace, Ltd.
jpd@xxxxxxxxxxxxx