[SI-LIST] Re: near and far end crosstalk in frequency domain
- From: "Istvan NOVAK" <istvan.novak@xxxxxxxxxxxxxxxx>
- To: <zhang_kun@xxxxxxxxxx>, <johndp@xxxxxxxx>
- Date: Tue, 8 Jun 2004 20:37:47 -0400
Dear Zhangkun,
Further questions:
- what is the frequency where you see far-end crosstalk exzceeding near-end
crosstalk?
- what is the coupled length?
- what was the isolation method you used?
Regards,
Istvan
----- Original Message -----
From: "Zhangkun" <zhang_kun@xxxxxxxxxx>
To: <johndp@xxxxxxxx>
Cc: "si-list" <si-list@xxxxxxxxxxxxx>
Sent: Tuesday, June 08, 2004 7:44 PM
Subject: [SI-LIST] Re: near and far end crosstalk in frequency domain
> Dear Istvan and John
>
> I have made some attempt. The diagram is below
>
> Port1==================Port3
> Port2==================Port4
>
> When I measure near end crosstalk coefficient, I use terminal of 50Ohm to
terminate Port3 and Port4. When I meausre far end crosstalk coefficient, I
use terminal of 50Ohm to terminal Port2 and Port3. I found that using
isolation or not do not seriously affect the measurement result.
>
> Best Regards
>
> Zhangkun
> 2004.6.9
> ----- Original Message -----
> From: "john" <johndp@xxxxxxxx>
> To: <zhang_kun@xxxxxxxxxx>
> Cc: "si-list" <si-list@xxxxxxxxxxxxx>
> Sent: Wednesday, June 09, 2004 5:28 AM
> Subject: Re: [SI-LIST] Re: near and far end crosstalk in frequency domain
>
>
> > Zhangkun
> >
> > Improvements can be made by increasing the impedance of the braids, this
> > can be accomplished by
> > adding ferrites to the cables.
> >
> > Regards
> >
> > John
> >
> >
> > Zhangkun wrote:
> >
> > >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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> >
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