Re : Impedance Software

Jim Tompkins ([email protected])
Wed, 31 Jul 1996 08:27:39 -0300

> Does anyone know where I can find an accurate, reliable software program,
> preferably PC-based, that calculates characteristic impedance for
> microstrip, embedded microstrip, stripline, and dual stripline traces on a
> PC board?
> jwf
> ----- End Included Message -----

We use a freeware DOS program called imped from HADCO. It calculates
Zo from geometry information. You can contact their tech centre in
Salem, NH for a copy.

We have found that HADCO can control impedance quite accurately.
We use their calculator to determine trace widths for the desired
impedance and then route with a slightly (0.001") wider track.
Then you specify to them that all X mil tracks on layer Y should be
Z Ohms. They will size the tracks as required to get your specified
impedance. They can easily size down; it's far more difficult to size up.

Not related to HADCO, just fairly satisified with their results.



Jim Tompkins, M.A.Sc., P.Eng.
Hardware Designer                Internet : [email protected]   
Applied Microelectronics Inc.    Voice    : (902) 421-1250 x252
1046 Barrington Street           Fax      : (902) 429-9983
Halifax, NS  CANADA B3H 2R1      WWW      :