[SI-LIST] Re: Cross talk and Trace length
- From: bala <balaseven@xxxxxxxxx>
- To: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Wed, 17 Aug 2011 23:34:59 +0530
Whats fext and next.its tx and rx xtalk?cross+talk=what?
On Aug 17, 2011 11:25 PM, "Fred Balistreri" <fred@xxxxxxxxxxxxx> wrote:
> This is true in theory for matched impedance lines. In practice forward
> crosstalk can get larger if the lines are not matched due to reflections
> which add to the problem.
> I've seen the terminology where it's called far end xtk. Far end xtk can
get
> large enough to cause issues especially for microstrips. Striplines less
> so.
>
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On
> Behalf Of Doug Brooks
> Sent: Wednesday, August 17, 2011 10:25 AM
> To: rajesh kumar; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Cross talk and Trace length
>
>
> 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
>>
>>
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>
> Check out our resources at http://www.ultracad.com
>
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