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

[john <johndp@xxxxxxxx>]

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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