[SI-LIST] Re: near and far end crosstalk in frequency domain

Dear Istvan

The following is my answer.
> Further questions:
> - what is the frequency where you see far-end crosstalk exzceeding near-end
> crosstalk?
300KHz-20MHz

> - what is the coupled length?
The coupling length is 6200mil

> - what was the isolation method you used?
I use transformer of 1:1 to isolate.

> 
> 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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