At 01:21 AM 1/25/96 -0700, you wrote:
>does anyone have any data concerning 50 ohm transmission lines
>starting on the first layer and using vias to transport it to an inner layer.
>I have looked at the IPC specs concerning microstrip etc.  good info.
>unfortunately it just doesn't mention anything about how to get a 
>impedance controlled line from one layer to the next.  I know that 
>someone out there has done the numbers or knows where to go to
>get them.  Please let me know 
>
>thanks in advance.
>
>


Step 1. Define the geometries necessary to meet your impedance requirements
on each layer you want to use. 

Step 2. Then, don't worry about the via.

UltraCAD, with a supporting grant from the Washington Technology
Center, did a detailed study of the effects of vias on PCB traces.
A copy of the results are available from our ftp site

     ftp.eskimo.com/u/u/ultra/notes
        download file   t009.exe

This is a self-extracting print file in Laserjet II format. If
you do not have access to a Laserjet II emulation printer, e-mail
us for a copy by snail mail.

Also, you can download the file from our web site at
     http://www.eskimo.com/~ultra/homepage.htm

Doug Brooks
President, UltraCAD Design Inc.