[SI-LIST] Re: Why crosstalk calculation does not count into trace width?
- From: "Jian-X. Zheng" <jian@xxxxxxxxxx>
- To: <Ho.Jeff@xxxxxxxxxxxx>, <Allen_Wang@xxxxxxxxxxx>,<si-list@xxxxxxxxxxxxx>
- Date: Thu, 23 Oct 2003 13:44:15 -0700
Hi:
I think we can intuitively explain why there is more coupling between
narrower strips than wider strips in general.
Cross-Section of Two Wider Coupled Strips
======== ========
| |
average average
center center
Cross-section of Two Narrower Coupled Strips
==== ====
| |
average average
center center
We can think we can find an average center of the current flowing on a
trace. The average center should be slightly off the center and toward the
coupled edge. When the gap width is fixed, you can see the distance between
the average centers of the two narrower strips is smaller than that of the
two wider strips. Then, we should expect more coupling between the two
narrower strips.
Best regards,
----------------------------------------------------------------------------
------------
Jian-X. Zheng, Ph.D., Zeland Software, Inc., 48834 Kato Road, 103A, Fremont,
CA 94538
Tel: 510-623-7162, Fax: 510-623-7135, E-mail: jian@xxxxxxxxxx, Web:
www.zeland.com
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> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Ho, Jeff (¦ó¬F¾± IEC1)
> Sent: Wednesday, October 22, 2003 8:05 PM
> To: Allen_Wang@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Why crosstalk calculation does not count into
> trace width?
>
>
> Hi Allen,
> The trace width involve in the distance "D".
> Based on same configuration and just vary the trace width, I
> found trace width is relative to coupling effect.
> It shows high impedance traces(thinner) have more coupling influence.
> Attached file listed below for your reference.
>
> Regards,
>
> Jeff
>
> -----Original Message-----
> From: Allen_Wang@xxxxxxxxxxx [mailto:Allen_Wang@xxxxxxxxxxx]
> Sent: Wednesday, October 22, 2003 7:06 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Why crosstalk calculation does not count into trace
> width?
>
>
> Dear all:
>
> It's me again. Thanks Steve first to provide us good explanation of our =
> last question....
>
> We then come out another one that in crosstalk calculation, why the =
> trace width does not be counted in..
> For example, in Dr. Howard Johnson's first book page 192, there wrote:
> Crosstalk ~ K / (1 + (D/H)*(D/H)), where D: distance between two traces =
> center to center. H: height above the reference plane
>
> In real application, a pattern of 4.5/15 (trace width 4.5 and space 15) =
> will really have larger crosstalk than 5/15? (say the H is 4.1mil)
>
> Best regards!
>
> Allen Wang
> ASUSTeK Computer Inc.
> RD8- server centric division
> Manager
> Mobile: 886-935481831
> TEL: 886-2-28943447 ext:3102
> FAX: 886-2-28907689
>
>
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