Re: [SI-LIST] : Coplanar Transmission Line

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From: Vinu Arumugham (vinu@cisco.com)
Date: Thu Feb 03 2000 - 12:11:54 PST


Will the skin loss not be higher in CPW than in microstrip/stripline?

Vinu

"Zabinski, Patrick J." wrote:

> Roy,
>
> Coplanar waveguide (CPW) is used quite frequently in RF/Microwave
> circuits to avoid multimode, decrease dielectric loss effects,
> and reduce discontinuities at bond wires/etc. However,
> we've had difficulty with PCB
> vendors being able to successfully obtain a desired
> impedance.
>
> >From what I can tell, the PCB folks have played around with
> microstrip/stripline enough that they have a sufficient
> pool of experience to know what to adjust to obtain the
> desired impedance (i.e., dielectric thickness or line
> width). In CPW, the dielectric thickness is not a
> first-order effect, which presents difficulty in processing.
> In other words, from a practical standpoint, CPW in
> PCB needs to be used with caution (at least until you've
> worked out the details with a vendor).
>
> If you can get the desired impedance, the electrical properties
> of CPW are generally better that microstrip and stripline (at
> the cost of reduced routing density).
>
> For specific papers that might help out, try these:
>
> TITLE Synthesis Formulas Simplify Coplanar-Waveguide Design
> AUTHOR T. Q. Deng, M. S. Leong, P. S. Kooi, and T. S. Yeo
> SOURCE Microwaves & RF
> DATE March, 1997
> PAGES 84-98
>
> TITLE Finite Width Coplanar Waveguide for Microwave and Millimeter-Wave
> Integrated Circuits
> AUTHOR G. E. Ponchak, S. Robertson, F. Brauchler, J. East, and L. P. B.
> Katchi
> SOURCE Proc of 1996 Int'l Symposium on Microelectronics
> LOC Minneapolis Convention Center, Minneapolis, MN
> DATE 8-10, October, 1996
> PAGES 517-521
>
> TITLE Microwave Planar Passive Circuits and Filters
> AUTHOR J. Helszajn
> DATE 1994
> PUBLISHER John Wiley & Sons, Ltd
> ISBN 0-471-94056-9
>
> In terms of more referenes, IEEE MTT (www.mtt.org) has a pile
> of papers in their journals on the topic, and their
> annual conference (http://www.ims2000.org/) generally
> has several very good papers each year.
>
> Pat
>
> > Dear SI Experts,
> >
> > Who out there has worked with coplanar (waveguide-like)
> > transmission lines as
> > opposed to stripline/microstripline?
> >
> > What can you tell me about it other than what I can find in
> > Collins or Bahl &
> > Bhartia?
> >
>
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