[SI-LIST] Re: Cross talk and Trace length
- From: Doug Brooks <dbrooks9@xxxxxxxxxxxxxxx>
- To: rajesh kumar <msrajesheee@xxxxxxxxx>,si-list@xxxxxxxxxxxxx
- Date: Wed, 17 Aug 2011 10:24:59 -0700
Actually, it depends on whether you are talking about forward or
backward crosstalk.
Backward crosstalk: The backward crosstalk pulse WIDTH increases with
coupled length. But the backward crosstalk AMPLITUDE increases with
coupled length UP TO THE CRITICAL LENGTH, at which point the
amplitude stops increasing and peaks out. The peak amplitude is a
function of coupling, which (among other things) is related to the
rise time and to the spacing. The critical length is similar to the
one we use in transmission line analysis --- when the propagation
time along the coupled length is one-half the rise time.
Forward crosstalk: The pulse WIDTH of the forward crosstalk signal is
related to rise time. The AMPLITUDE of the forward crosstalk signal
is related to the coupling, which is related to the rise time, the
separation, and the coupled length. For practical purposes, for PCB
design, traces in a stripline environment exhibit no forward
crosstalk. Microstrip traces can exhibit forward crosstalk, but the
coupled regions have to be relatively long. In general, forward
crosstalk is not often a problem on PCBs. It might be, however, on
multiconductor cabling.
These things can be easily simulated with Hyperlynx. I have done show
and shown the results of the simulations in an article
<http://www.ultracad.com/mentor/mentor%20crosstalk%20part%202.pdf>Crosstalk
Part 2; Simulating Crosstalk Effects available on our web site at
http://www.ultracad.com
Doug Brooks
UltraCAD Design, Inc
At 12:19 AM 8/17/2011, rajesh kumar wrote:
>Hello SI Gurus,
> Please share your thoughts on the relationship between cross
>talk and trace length. In general i consider that the spacing between trace
>is the main factor that influences cross talk. Still now i assume that 4X
>spacing between traces (X is a trace width) is a good way to avoid cross
>talk irrespective of the length of trace. Please share your views on this.
>
>Thanks,
>Rajesh
>
>
>------------------------------------------------------------------
>To unsubscribe from si-list:
>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
>or to administer your membership from a web page, go to:
>//www.freelists.org/webpage/si-list
>
>For help:
>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>
>List technical documents are available at:
> http://www.si-list.net
>
>List archives are viewable at:
> //www.freelists.org/archives/si-list
>
>Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>
Check out our resources at http://www.ultracad.com
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List technical documents are available at:
http://www.si-list.net
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
