[SI-LIST] Re: CPW

  • From: "Grossman, Brett" <brett.grossman@xxxxxxxxx>
  • To: <weirsp@xxxxxxxxxx>, <koul@xxxxxxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
  • Date: Thu, 9 Sep 2004 13:22:58 -0700

Vinod,

I concur with Steve's comment, a 2D solver will probably be sufficient.

Some other options: AppCAD is a free little application from Agilent
that should get you in the ballpark with your CPW calculations.  Also if
you have access to ADS, the Linecalc tool would also do.  Ansoft
Designer also has a transmission line calculator that would do this.  I
would assume most other simulation tools have some similar capability.

My experience with empirical solutions for CPW characteristics was based
on formulations in Wadell's Transmission Line Design Handbook.  As an
academic exercise, I implemented some approximations for the elliptic
integrals in Excel, which was very cumbersome. The results were in
general agreement with the tools I mention above, so this text may be an
alternate source of closed form expressions for you.

On a side note, one thing to be aware of (it may seem obvious, but has
bit me once).  Some methods/tools will ask for Er and calculate Eeff,
whereas others will assume you enter Eeff.  If you have a decent gap
width, and a high Er substrate then the difference will be significant
(up to about 2x in my experience).

-Brett

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of steve weir
Sent: Wednesday, August 25, 2004 3:21 PM
To: koul@xxxxxxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: CPW

Any decent 2D solver will give you a reliable answer.

Steve
At 03:57 AM 8/26/2004 +0530, Vinod Koul wrote:
>Hello SI experts,
>         Can any body help me in the synthesis of CPW.
>    I tried to calculate the CPW parametrs using the formulation given
>in RAINEE SIMONS: coplanar waveguide circuits, components and systems,
>wiley interscience. this is the only place which deals with synthesis
>of CPW. but has errors, i checked with the orignal ref and made
>corrections. well getting to point, there two sets of formulae are
>given 1st calclates slot width given all other things, and second
>central conductor width.
>But both these sets are not consistent with each other, like i tried
>to simulate both equations in MATLAB, and answers in both were not
>consistent with each other. For eg i calc, S=3D 272Micrometer for =
er=3D13,
>Z=3D50, w=3D100u, h=3D100u, now for second set, its giving w =3D 18u, =
for the
>same data as abive (s=3D 272u)!!!!
>can anyone help me out
>______________________________________________________
>Vinod Koul
>Graduate Student.
>Microwave Lab.
>Dept of ECE.
>IISc, Banglaore.
>
>Cell No +91 9886034503
>Lab +91 80 2293 2853
>________________________________________________________
>
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