differencial impedance in broadside

[CptnChris]

Tom,
It has been a while since i rised my head from behind my keyboard, so you didnt hear too much about me lately...

I am working on signal at 1.25Ghz and have to route them in differencial (64 pairs). Until now the only problem is the room, but i live with it (he he !!).
But my real problem is that beside the "Polar" calculator, I cannot find a formula or a free calculator for DIFFERENCIAL impedance in BROADSIDE ..meaning one layer over the other...

Like this
i.e.:
---------
--
--
---------

If you have it, I would be very happy !! (i have the edge side calculator already)...

Thanks
Cptn Chris

[Tom]

Cptn Chris,

Rogers has a calculator that is free and does broadside differential pairs. They distribute it on a mini-cd rom. It runs in DOS mode and crashes a lot depending on what your doing.

But it's free. See the attached file.