Re: transmission line z

On Sun, 8 Jun 2025 22:20:58 +0200, Leo Baumann <ib@leobaumann.de>
wrote:

Am 08.06.2025 um 21:29 schrieb john larkin:

air
__________________ copper
.........................................fr4
__________________ copper
 
air

>
The formulars are for 2 symmetrically lines in picture 4.20.1-3 on the
2nd page of the *.pdf
>
... have fun ...

What impedance is being calculated? Top line against dotted one below?

It occurred to me that if I drive my top and bottom lines out of
phase, which I will, there will be an equipotential plane midway
through the board. So I could sneak a ground plane in there and
nothing would change. With the ground plane, it becomes two
microstrips, and there are lots of microstrip solvers.

There would still be some fringing errors, like in your fig 4.20,
which doesn't assign a symbol to the board width.