[SI-LIST] Re: near and far end crosstalk in frequency domain
- From: Istvan Novak <Istvan.Novak@xxxxxxx>
- To: zhang_kun@xxxxxxxxxx
- Date: Tue, 08 Jun 2004 09:46:29 -0400
Dear Zhangkun,
Measuring far-end crosstalk with no reference plane is trickier than
near-end crosstalk. You may need higher isolation in the connecting
cables' braids. If you already have some means to break the ground
loop between the two VNA ports, look at it and try to improve on it
and repeat the measurement.
Regards,
Istvan
have to make
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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--
Istvan Novak Sun Microsystems, Inc.
Istvan.Novak@xxxxxxx Workgroup Servers, BDT Group,
One Network Drive, Burlington, MA 01803
Phone: (781) 442 0340
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