[SI-LIST] Re: CPW r.o.t?
- From: "Raymond W. Waugh" <ray_waugh@xxxxxxxxxxx>
- To: <scott@xxxxxxxxxxxxxxxx>, <brett.grossman@xxxxxxxxx>
- Date: Thu, 23 Aug 2001 21:51:18 -0700
I have used our AppCAD calculator for CPW and CPWG (coplanar waveguide over
a ground plane) with great success to 6 GHz. I also use Dan Swanson's MWTLC
(microwave transmission line calculator, a DOS design program) -- it is
equally as accurate as I define accurate.
I define accurate as being able to make a line, put two cheap E.F. Johnson
connectors on the ends, and get 25dB return loss to 6 GHz.
Ray
Raymond Waugh
Agilent Technologies, Communications Components Division
-----Original Message-----
From: Scott McMorrow <scott@xxxxxxxxxxxxxxxx>
To: brett.grossman@xxxxxxxxx <brett.grossman@xxxxxxxxx>
Cc: si-list@xxxxxxxxxxxxx <si-list@xxxxxxxxxxxxx>
Date: Thursday, August 23, 2001 6:58 PM
Subject: [SI-LIST] Re: CPW r.o.t?
Brett,
Agilent AppCAD, which is a free download, has a CPW calculator.
We have used AppCAD to get close to the correct CPW structure
and then Ansoft 2D to converge on a more exact solution.
You can use HFSS to design them, but getting a good co-planar
launch is a bit of a pain. We ended up using HFSS to perform a final
verification of the design.
This process worked for a 10GHz package design.
regards,
scott
--
Scott McMorrow
Principal Engineer
SiQual, Signal Quality Engineering
18735 SW Boones Ferry Road
Tualatin, OR 97062-3090
(503) 885-1231
http://www.siqual.com
"Grossman, Brett" wrote:
> Anyone out there have a decent rule of thumb or closed form equation for
> approximating characteristic impedance of a CPW structure?
>
> Preferably something that doesn't involve me opening up my head and
shaking
> my brain to try and remember what an elliptic integral of the first kind
is
> (no Bessel or Henckel functions either please). I have found a few of
these
> types in the literature but am really only looking for a sanity check at
> this point.
>
> My application is on silicon geometries. I designed some characterization
> structures that are off being fabbed and at the 11th hour threw on some
> additional coplanar structures. Now I did what I could to throw them into
> HFSS and optimize till I got a close match to a real 50 Ohm source, but I
> don't have infinite trust in my HFSS'ing with large aspect ratios nor
> infinite experience in designing CPW's.
>
> Any pointer would be appreciated.
>
> Best regards,
>
> -Brett
>
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