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 > >>>>> > >>>>> > >>>>>------------------------------------------------------------------ > >>>>>To unsubscribe from si-list: > >>>>>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > >>>>> > >>>>>or to administer your membership from a web page, go to: > >>>>>//www.freelists.org/webpage/si-list > >>>>> > >>>>>For help: > >>>>>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > >>>>> > >>>>>List FAQ wiki page is located at: > >>>>> http://si-list.org/wiki/wiki.pl?Si-List_FAQ > >>>>> > >>>>>List technical documents are available at: > >>>>> http://www.si-list.org > >>>>> > >>>>>List archives are viewable at: > >>>>>//www.freelists.org/archives/si-list > >>>>>or at our remote archives: > >>>>>http://groups.yahoo.com/group/si-list/messages > >>>>>Old (prior to June 6, 2001) list archives are viewable at: > >>>>> http://www.qsl.net/wb6tpu > >>>>> > >>>>> > >>>>> > >>>>> > >>>------------------------------------------------------------------ > >>>To unsubscribe from si-list: > >>>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > >>> > >>>or to administer your membership from a web page, go to: > >>>//www.freelists.org/webpage/si-list > >>> > >>>For help: > >>>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > >>> > >>>List FAQ wiki page is located at: > >>> http://si-list.org/wiki/wiki.pl?Si-List_FAQ > >>> > >>>List technical documents are available at: > >>> http://www.si-list.org > >>> > >>>List archives are viewable at: > >>> //www.freelists.org/archives/si-list > >>>or at our remote archives: > >>> http://groups.yahoo.com/group/si-list/messages > >>>Old (prior to June 6, 2001) list archives are viewable at: > >>> http://www.qsl.net/wb6tpu > >>> > >>> > >>> > >>-- > >>Istvan Novak Sun Microsystems, Inc. > >>Istvan.Novak@xxxxxxx Workgroup Servers, BDT Group, > >>One Network Drive, Burlington, MA 01803 > >>Phone: (781) 442 0340 > >> > >> > >------------------------------------------------------------------ > >To unsubscribe from si-list: > >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > > >or to administer your membership from a web page, go to: > >//www.freelists.org/webpage/si-list > > > >For help: > >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > >List FAQ wiki page is located at: > > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > > > >List technical documents are available at: > > http://www.si-list.org > > > >List archives are viewable at: > > //www.freelists.org/archives/si-list > >or at our remote archives: > > http://groups.yahoo.com/group/si-list/messages > >Old (prior to June 6, 2001) list archives are viewable at: > > http://www.qsl.net/wb6tpu > > > > > > > > > > > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu