[SI-LIST] Re: looking for (differential) crosstalk calculator onthe web
- From: Scott McMorrow <scott@xxxxxxxxxxxxxxxx>
- To: doug@xxxxxxxxxx
- Date: Sat, 04 May 2002 10:29:16 -0700
Doug,
You are correct. There will be forward crosstalk, but it is generally
low compared to the
reverse crosstalk. In this case, the reverse crosstalk will reflect off
the source impedance
and dominate at the receiver.
regards,
scott
Doug Brooks wrote:
> For a stripline environment, forward crosstalk is not an issue. I have done
>several simulations in the 5 to 10 foot range (using HyperLynx) and forward
>crosstalk simply isn't there (in a stripline environment). (it certainly is
>there in a microstrip environment.)
>
>Backwards crosstalk reaches a maximum amplitude very quickly. Its amplitude
>does not increase with length of line (at least in the 5 foot range)
>although-- of course -- backwards crosstalk pulse width does increase with
>length.
>
>Therefore, your concern over long length is probably unfounded.
>
>Doug Brooks
>UltraCAD
>
>
>
>
>
>At 04:26 AM 5/3/2002 +0000, you wrote:
>
>I would appreciate if anyone could let me know if there is a free
>crosstalk calculator available somewhere on the web. I know of the
>one on www.ultracad.com[1], and on www.bay-technology.com[2]. However, I am
>not sure if they are appropriate for electrically long lines.
>
>I have many differential pairs about 5'-6" long, offset and embeded
>between two planes, side-by-side traces in each pair, Zo= 100 Ohm,
>carrying 100 ps edge-times, Zsource about 20 Ohm, Zload=100 Ohm
>(differential only), and due to the PCB constrains I must place the
>traces and the pairs relatively close together (the chip vendor
>recommends 0.2" between the pairs, I can maybe have 0.05"). The
>requirement is -50 dB of max crosstalk between the pairs. I could use
>a single-ended crosstalk calculator and get the differential
>crosstalk from the matrix of single ended crosstalks between the
>traces, but unless I know that the calculation takes into account the
>electricaly long lenghth of the line I am not confident in the
>results.
>
>Eventually I will get Hyperlynx, but that will be too late for this
>particular problem that I have now. Until then, I'd appreciate if
>anyone can tell me if there is some freebie that may help.
>
>Thak you, Neven Pischl
>
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--
Scott McMorrow
Principal Engineer
SiQual Interconnect Engineering
18735 SW Boones Ferry Road
Tualatin, OR 97062-3090
(503) 239-4400
http://www.siqual.com
--
Scott McMorrow
Principal Engineer
SiQual Interconnect Engineering
18735 SW Boones Ferry Road
Tualatin, OR 97062-3090
(503) 239-4400
http://www.siqual.com
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