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

[Zhangkun <zhang_kun@xxxxxxxxxx>]

Dear Istvan

How to improve it? I really doubt the far end measurement, too. Why the far end 
need more strict isolation?

Best Regards

Zhangkun
2004.6.8
----- Original Message ----- 
From: "Istvan Novak" <Istvan.Novak@xxxxxxx>
To: <zhang_kun@xxxxxxxxxx>
Cc: "Istvan NOVAK" <istvan.novak@xxxxxxxxxxxxxxxx>; "si-list" 
<si-list@xxxxxxxxxxxxx>
Sent: Tuesday, June 08, 2004 9:46 PM
Subject: Re: [SI-LIST] Re: near and far end crosstalk in frequency domain


> 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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