RE: [SI-LIST] : Coplanar Transmission Line

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From: WAUGH,RAY (HP-SanJose,ex1) (ray_waugh@agilent.com)
Date: Thu Feb 03 2000 - 15:33:42 PST


I doubt if losses in the metal are significant. In my experience (as a RF
and microwave circuit designer), losses in dielectric (particularly FR4)
dominate total losses in symmetrical stripline, microstrip and coplanar
waveguide. I would not worry much about skin effect when your dielectric is
so lossy.

I have found that CPW losses are generally about the same as those found in
a comparable microstrip. Keeping the potential on both CPW ground strips
exactly the same can be tricky, however.

Ray
------------------------------------------------------
      Raymond W. Waugh - WSD Diode Applications
      E-mail: ray_waugh@agilent.com

          USPS: Agilent Technologies
              Wireless Semiconductor Division
              39201 Cherry Street, MS NK20
              Newark, California 94560
------------------------------------------------------

-----Original Message-----
From: Zabinski, Patrick J. [mailto:zabinski.patrick@mayo.edu]
Sent: Thursday, February 03, 2000 12:49 PM
To: si-list@silab.eng.sun.com
Subject: RE: [SI-LIST] : Coplanar Transmission Line

Possibly.

If the CPW line width (and conductivity, roughness, etc.) is
the same as microstrip/stripline ***AND*** the CPW ground
traces are adequately wide, then the metal losses are
the same (within engineering tolerance anyway).

However, some compromise on the ground strip widths is generally
needed, which will incease the effective inductance and resistance
of the return path, which in turn increases the effective loss
of the line. There are rules of thumb to follow in terms of
how wide the grounds need to be to avoid this, but you won't
hear them from me.

Pat

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

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