[SI-LIST] Re: CPW r.o.t?
- From: "Raymond W. Waugh" <ray_waugh@xxxxxxxxxxx>
- To: "Scott McMorrow" <scott@xxxxxxxxxxxxxxxx>
- Date: Fri, 24 Aug 2001 07:44:51 -0700
That depends upon the length of the transmission line. I've found that CPWG
has about the same loss per unit length as microstrip (for a given board
thickness).
Ray
-----Original Message-----
From: Scott McMorrow <scott@xxxxxxxxxxxxxxxx>
To: ray_waugh@xxxxxxxxxxx <ray_waugh@xxxxxxxxxxx>
Date: Friday, August 24, 2001 12:14 AM
Subject: Re: [SI-LIST] Re: CPW r.o.t?
Ray,
What do you measure for S12?
scott
"Raymond W. Waugh" wrote:
> 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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--
Scott McMorrow
Principal Engineer
SiQual, Signal Quality Engineering
18735 SW Boones Ferry Road
Tualatin, OR 97062-3090
(503) 885-1231
http://www.siqual.com
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