FreeLists / si-list / [SI-LIST] Re: near and far end crosstalk in frequency domain

[Ed Sayre III <esayre3@xxxxxxxx>]

Zhangkun,
   Have you looked at the crosstalk in the time domain?  If not then you 
should also consider this.  Looking only in one domain is not the best way 
to isolate/debug an issue.  The near end or backward crosstalk, in the time 
domain, will give you insight as to where in the transmission line 
structure the coupling is occurring.  This uses the same techniques as 
determining the discontinuities base on the timing in TDR plot
    Have you tried to include a model your measurement setup in the 
simulations?  If you can replicate the setup, this will also give you 
insight into where the coupling is occurring.  You need to confirm all 
assumptions including signal returns and grounds.

Regards

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
               NORTH EAST SYSTEMS ASSOCIATES, INC
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                         "High Performance Engineering & Design"
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  Dr. Edward Sayre 3rd            e-mail: esayre3@xxxxxxxx
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At 09:18 PM 6/8/2004 +0800, Zhangkun wrote:
>Dear Istvan
>
>I am analyzing crosstalk at low frequency. The length of transmission line 
>is much less than the wave length.
>
> >From the tele-formular, it could be gotten that the polarity of 
> electrical coupling and magnetic coupling are same at the near end and 
> are adverse at the far end. Therefore, I think the farend crosstalk is 
> less than near end crosstalk in frequency domain. This is verified by 
> simulation in HSPICE, ANSOFT. I do not consider that in time domain, 
> which has been considered in a lot of books.
>
>By the way, this is still the topic about crosstalk between differential 
>pairs without reference plane. I have gotten good result about near end 
>crosstalk. But there is still some problem about the far end. I am sure my 
>measurement is right : )
>
>Best Regads
>
>Zhangkun
>2004.6.8
>----- Original Message -----
>From: "Istvan NOVAK" <istvan.novak@xxxxxxxxxxxxxxxx>
>To: <zhang_kun@xxxxxxxxxx>; "si-list" <si-list@xxxxxxxxxxxxx>
>Sent: Tuesday, June 08, 2004 8:11 PM
>Subject: Re: [SI-LIST] near and far end crosstalk in frequency domain
>
>
> > Dear Zhangkun,
> >
> > Unless you have a perfectly homogeious cross section of
> > material that carries the field, there is always a far-end
> > crosstalk component, even if you have perfect termination.
> > One major difference between near-end and far-end
> > crosstalk is that far-end crosstalk saturates at full coupling.
> > This means that beyond a certain frequency, the far-end
> > crosstalk response may be bigger than the near-end crosstalk
> > response.  'May be' refers to the fact that both near-end and
> > far-end crosstalk vary sinusoidally with frequency, but with
> > different periodicity: near-end crosstalk's periodicity depends
> > on the electrical length of coupled section, far-end crosstalk's
> > periodicity depends on the electrical length of coupled section
> > AND the strength of coupling.
> >
> > Regards,
> >
> > Istvan
> >
> >
> > ----- Original Message -----
> > From: "Zhangkun" <zhang_kun@xxxxxxxxxx>
> > To: "si-list" <si-list@xxxxxxxxxxxxx>
> > Sent: Monday, June 07, 2004 11:02 PM
> > Subject: [SI-LIST] near and far end crosstalk in frequency domain
> >
> >
> > > Dear all
> > > Now, we are analyzing the crosstalk between transmission line. There is
> > something interesting. The far end crosstalk is larger than the near end
> > crosstalk in frequency domain. Have anybody meet the similar problem?
> > >
> > > Best Regards
> > >
> > > Zhangkun
> > > 2004.6.8
> > >
> > >
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