STRIPLINE...

[Daniel Zimmerman]

Could someone please furnish me with the equations that are used to
calculate the impedance of a stripline transmission line, both with and
without solid dielectric? Thank you in advance.
-Dan
N3UMH

[Roy Lewallen]

A number of equations are used, of varying complexity, accuracy, and
range of dimensions over which they're accurate. One of the simpler ones
is:

Z0 = (60/sqrt(er)) * ln((4*b)/(0.67 * pi * w * (0.8 + t/w)))

where

er is the dielectric constant of the dielectric
b is spacing between the upper and lower ground planes
w is the width of the conductor
t is the thickness of the conductor

t, w, and b can be in any units but must all be in the same units.

It's assumed that the conductor is centered between the ground planes.

The equation is claimed to be accurate when w/(b-t)<0.35 and t/b<0.25.

This is from the Motorola MECL System Design Handbook. I've found the
microstrip equation in that book to be good in the vicinity of 50 ohms
and moderate er, but have never used the strip line equation quoted
above. The book shows measured results of a number of strip lines which
they say are very close to the equation's results, but all the
measuements are for er = 4.7, so I don't know the accuracy for air (er =
1).

Roy Lewallen, W7EL

[Woody White]

I have an old dos / basic program that does the stripline
calculations. You have to enter the board characteristics
and -either- the width or impedance (the other is the
calculated unknown). Interested?
73, Woody
----------------------------

Daniel Zimmerman wrote:
>
> Could someone please furnish me with the equations that are used to
> calculate the impedance of a stripline transmission line, both with and
> without solid dielectric? Thank you in advance.
> -Dan
> N3UMH

----------- de Woody, WB4QXE -----------

Ham Homebrew/ATV Circuits -*- Scanning Electron
Microscope Images

http://www.geocities.com/capecanaveral/3722

[David Snyder Hale]

> Daniel Zimmerman wrote:
>> Could someone please furnish me with the equations that are used to
>> calculate the impedance of a stripline transmission line, both with and
>> without solid dielectric? Thank you in advance.

The actual calculations are pretty complex and generally approximations
are used. I have some papers on this subject that I could photocopy and
mail them, or perhaps scan. (I'll make a followup post if I end up
scanning them.)

There was some stripline stuff in QST awhile back, and I ported some BASIC
code into C; you can get the ref's from my web page below...

best regards,

--
Dave * N3WTK (DM04xf) * http://isi9.mtwilson.edu * n3...@arrl.net