RE: [SI-LIST] : Matched Length Traces

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From: Ray Anderson ([email protected])
Date: Fri Nov 10 2000 - 09:57:50 PST

There has been quite a bit of interesting conversation on the
list recently concerning "meander" or "serpentine" delay lines.

A recently published technical report by Sun Microsystems Laboratories
(Sun Labs) entitled "Measurements and Modeling of Delay Lines on Printed
Circuit Boards" is available for public download at the following URL:

Here is the abstract describing the report:

Traces on printed circuit boards (PCBs) are often turned into meandering
lines to introduce an additional delay. This technical report explores the
electrical parasitics involved in that practice by reporting measurements of
traces fabricated on a test board. Traces that meander have shorter
propagation delays than expected due to coupling between segments.
Calculations of the time delay reduction are presented and a model is

If such topics interest you, feel free to download the report.

-Ray Anderson
Sun Microsystems

> From: "Loyer, Jeff W" <[email protected]>
> To: "'Andrew W. Riley III'" <[email protected]>
> Cc: SI LIST <[email protected]>
> Subject: RE: [SI-LIST] : Matched Length Traces
> Date: Fri, 10 Nov 2000 08:07:04 -0800
> Andrew,
> I recently had an opportunity to study "meanders" (serpentines) when we had
> a small board come back with flight time variations which couldn't be
> attributed to differences in trace length (traces were matched within 5mils;
> flight times varied as much as 50pS). Here's what I came up with...
> ____________________________________________________________________________
> Here's a quick note on my initial conclusions about "meanders" and their
> effect on flight times. It's not intended to be a comprehensive analysis,
> but is a quick synopsis of what I've learned in the short time I've
> investigated the phenomena.
> Special thanks to those who responded to my e-mail question, especially the
> pointers towards IEEE papers about the subject. The specific papers I found
> most useful were:

   ..... much interesting and relevant stuff deleted.........

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