[SI-LIST] Re: Estimating Crosstalk
- From: Doug Brooks <dbrooks9@xxxxxxxxxxxxxxx>
- To: Mark Filipov <markfilipov81@xxxxxxxxx>,si-list@xxxxxxxxxxxxx
- Date: Mon, 05 Dec 2011 09:24:56 -0800
In studies I have done (see especially
<http://www.ultracad.com/mentor/crosstalk_coupling.pdf>Crosstalk
Coupling: Single-ended vs. Differential on our website,
www.ultracad.com) This formula (1/(1+(d/h)^2)) works pretty well
for Microstrip. It is a worst-case formula for stripline, depending
on conditions. This is shown with Hyperlynx simulations in the article.
There is a freeware calculator, also on our website, that is based on
this formula (taken from Howard Johnson's first book and an interview
with him.)
Doug Brooks
At 07:39 AM 12/5/2011, Mark Filipov wrote:
>In many books dealing with SI & PCB's, (Brooks, Johnson&Graham, Khandpur,
>..) there is a simple equation for estimating crosstalk.
>
>
>Crosstalk between two traces separated by distance D, and which both are at
>distance, H, from their reference plane is proportional to
>
>
>
>K / (1 + (D/H)^2 ), where K < 1. Usually, I have seen that K is set equal
>to 1.
>
>
>In book "Grounds for Grounding" recently published by IEEE Press (Joffe &
>Sang Lock), on page 835 (which can be seen online in Google Books), there
>is stated "... Assuming a trace width of 10 mils placed above the return
>plane with separation, h, of 10 mils, the crosstalk between the traces
>(where the traces are separated by 40 mils) will have an upper bound of
>1/(1+(d/h)^2) = 1/(1+4^2) = 0.06 = -25 dB "...
>
>How well does this equation agree with empirical data? Is it an upper bound
>for estimating crosstalk?
>Does this equation give only the amount of coupling between the traces,
>since crosstalk is also data pattern dependent?
>How does this equation relate for estimating crosstalk between differential
>pair traces, separated by distance D?
>
>I have seen an similar expression K/(1+(D/H)^2)), when estimating how far
>the return current will spread underneath the traces, so I guess this
>formula is derived on basis of that??
>
>BR /Mark
>
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