[SI-LIST] Re: Effective dielectric constant
- From: Ed Sayre III <esayre3@xxxxxxxx>
- To: atifshamimkhan@xxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Tue, 03 Jun 2003 13:28:06 -0400
Atif,
Unfortunately, Wadell's formula assumes a uniform dielectric, and you
clearly do not have this. Much of the problem lies in the trace width,
height, and spacings relative to the dielectric thicknesses. I would
suggest you check out K.C. Gupta's book "Microstrip Lines and Slotlines"
chapter 7 to get a better understanding of the problem.
Good luck
-Ed Sayre
At 03:48 PM 6/2/2003 -0700, you wrote:
>Hi
>I am working on SOI(silicon on insultor) with silicon (Epsilon r = 11.9
>and h= 550 micron)and then on top of this is Sio2 (Epsilon r = 4 and h= 8
>micron).Then is the metal layer(copper) .A part of the metal structure is
>coplanar strips and I am trying to find out the charactersitic impedance
>of the cps.For that I need to know the effective dielectric constant .I am
>using the equations from waddell 's design handbook.Confusion is which
>Epsilon r to be used in the equations..(11.9 or 4 ) Also for "h" do I just
>use 558 micron(by simply adding both the heights) and why? appreciate all
>the info regarding this..
>Thanks
>Atif
>
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