Re: [SI-LIST] : CPW and CPS

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From: Scott McMorrow ([email protected])
Date: Fri Jan 19 2001 - 11:15:50 PST


You are right. Most of the data is in the Microwave literature.
All of the microwave simulators will handle the analysis of
these structures and there are some free (or relatively inexpensive)
planar 2D field solvers or calculators which will also handle these
structures. (polar cits25, HP APPCAD, Ansoft Serenade ....)

Rambus is an example of the use of CPW, where the area between
traces is flooded with ground copper.

I've not looked at CPS to determine if there are any manufacturing
advantages, but with CPW there are some distinct tolerance
advantages. As long as the traces are kept wide, impedance
tolerance is generally better for a coplanar structure than for
a microstrip structure. This trend probably holds true for
CPS structures, also.

CPW is a very good construction for high speed signals, analog
signals and differential pairs when you have the room.



Scott McMorrow
Principal Engineer
SiQual, Signal Quality Engineering
18735 SW Boones Ferry Road
Tualatin, OR  97062-3090
(503) 885-1231

Chris Padilla wrote:

> Scott, > > In my young career as an EMI engineer, I have never seen anyone use CPW or > CPS. These waveguides seem mostly reserved for and used by the microwave > community. Is there any good common literature out there on the web > somewhere regarding these seemingly little used waveguides? We have tons > and tons of stuff on microstrips and striplines (and the slight variations > of those) but I don't see much on the CPW or CPS. CPS = coplanar striplines > > ----->Chris > > >Aubrey, > >*<snip>* > >Another solution which works quite well is to use CPW or > >grounded CPW construction for diff pairs on outer layers. > > > > > >regards, > > > >scott

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