Hi John,

I opened my mouth too soon... I missed the part that is was coplanar.

I would suggest contacting the fab house you are going to use.  Most
reputable fab houses have engineering staff that do the calculations and
will provide the data to you. The calculators only give you part of the
equation anyway especially on a 2 layer card.

Does the reference signal have to be coplanar?  I wouldn't think it wouldn't
give much of a reference.

Regards,
Brent



-----Original Message-----
From: John Parsons [mailto:[log in to unmask]]
Sent: Thursday, November 20, 2003 11:48 AM
To: TechNet E-Mail Forum.; Alcorn, Brent
Subject: RE: [TN] Co-planar Impedance Calculations


Brent,

Yes, from what I understand this is correct but that is my problem, I don't
have a calculator to model this design to verify the parameters.  I could do
as Jason has suggested and just build to "spec" but I don't know if a
complete material spec has been provided.  I am enquiring as to this.  I
would however still like to understand the design, especially when the
designer has come to us to help him understand and verify the design.

Thanks to all for the input - keep it coming.

John

> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Alcorn, Brent
> Sent: November 20, 2003 8:36 AM
> To: [log in to unmask]
> Subject: Re: [TN] Co-planar Impedance Calculations
>
>
> Perhaps the "other" trace is the reference?  Although ideally,I
> believe, you would want the reference to be about 2x the width of the
> signal trace. Perhaps the design dictates that each signal has its own
> reference??
>
> Just my 2cents or 1.4 CDN.
> Brent

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