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

[Zhangkun <zhang_kun@xxxxxxxxxx>]

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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