[SI-LIST] Re: Serpentine/Spiral Lines (was Re: Trace Bends)
- From: Alex McPheeters <amcpheeters@xxxxxxxx>
- To: cpad@xxxxxxxxx,"SI-List Discussion Group" <si-list@xxxxxxxxxxxxx>
- Date: Wed, 01 May 2002 14:21:22 -0400
Many "general interest" references to trace bend can be found in Dr. Howard
Johnson's "HSD Design - A Handbook Of Black Magic" from which a clear
illustration of bends and skew effect was excerpted for Dr. Johnsons column
in the April 18 edition of EDN (www.ednmag.com). It would behoove any
younger engineer or engineer without experience in the layout area to take
a look. The verdict: corner style is less critical to skew than line spacing.
Alex McPheeters
www.acdi.com
>
>This is slightly off-topic of trace bends but one of the main reasons some
>of us worry about trace bend is they are chiefly used to create time
>delays. This method is known as "serpentining."
>
>There was a paper presented at the 16th Annual Applied Computational
>Electromagetics symposium presented at the Naval Postgraduate School in
>Monterey, CA from March 20-24, 2000.
>
>"FDTD Analysis of Conventional and Novel Delay Lines" by Omar M. Ramahi (he
>is the co-author of a great little handbook: "EMI/EMC Computational
>Modeling Handbook") Try him at Omar.Ramahi@xxxxxxxxxx but I've no clue if
>that email address is still viable...I have my doubts! :|
>
>Basically, the paper talks about delay lines and minimizing crosstalk while
>maintaining the same spacing and density of the serpentined line. The
>conclusion is to use a spiral method of delay line. This is difficult to
>describe without a picture, unfortunately.
>
>Being an EMI Engineer, I wonder about the EMI radiation from such a
>structure as a whole rather than just the many 90-degree bends present!
>
>Two references were sited:
>
>R-B. Wu and F-L. Chao, Laddering wave in serpentine delay line, IEEE Trans.
>Components, Packaging and Manufacturing Tech., Part B: Advanced Packaging
>vol. 18, no. 4, pp. 644-650, Nov. 1995.
>
>R-B. Wu and F-L. Chao, Flat spiral delay line design with minimum crosstalk
>penalty, IEEE Trans. Components, Packaging and Manufacturing Tech., Part B:
>Advanced Packaging vol. 19, no. 2, pp. 397-402, May 1996.
>
>Thanks----->Chris
>
>
>>As a follow-up to this subject, there was a paper
>>presented at the Denver EMC symposium
>>(1998 I believe) which stated a *lowering* of
>>emissions from serpentine construction of traces.
>>Can't remember who presented it nor what
>>speed of signals were involved.
>>
>>Regards, Doug McKean
>
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Alex McPheeters
Vice President, Business Development
American Computer Development Inc.
Office - (301) 620-0900
Fax - (301) 620-9099
Cell - (301) 305-3051
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