Brett corrected me. What I meant to say was 3X the highest fundamental frequency, which for a 10G links is 5 GHz. Scott McMorrow Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 (401) 284-1827 Business (401) 284-1840 Fax http://www.teraspeed.com Teraspeed® is the registered service mark of Teraspeed Consulting Group LLC Scott McMorrow wrote: >Just to throw something out there .... > >I contend that BW is not the most interesting specification to be >concerned about for serial links. BW only tells part of the story. The >other half is told by the phase response (or group delay). I generally >like to perform simulation and modeling at a minimum of 3X the Nyquist >frequency for the data stream, in order to accurately capture phase >information. For 10G NRZ links, that would require a 15 GHz bandwidth >in all modeling and simulation. > >regards, > >Scott > >Scott McMorrow >Teraspeed Consulting Group LLC >121 North River Drive >Narragansett, RI 02882 >(401) 284-1827 Business >(401) 284-1840 Fax > >http://www.teraspeed.com > >Teraspeed® is the registered service mark of >Teraspeed Consulting Group LLC > > > >Grossman, Brett wrote: > > > >>Wow, if I had a dime for every time this question came up... >> >>I had attended a seminar at DesignCon a few years back when I was >>struggling with this same question on the 40Gb/s interconnects we were >>designing. The instructor (Henri Merkelo) asked a question of the >>audience as to the necessary bandwidth for a 10Gb/s. From an audience >>of folks with collectively dozens of products already shipping in the >>10Gb/s space, there were plenty of different answers. Here is a >>sampling. >> >>1. BW=3D0.35/tr(10-90) >>2. BW=3D0.22/tr(20-80) >>3. f0=3D0.5*datarate, then BW=3D3*f0 >>4. or BW=3D5*f0 >>5. or BW=3D10*f0 (i.e. odd harmonics of the fundamental) >>6. f0=3D0.5*datarate or 1.0*datarate depending on the coding scheme (for >>example RZ vs. NRZ)=20 >>7. BW =3D datarate / 2*log2(number of encoded symbols) >>8. Enough bandwidth such that when passed through a brick-wall (or >>n-pole) filter the residual power spectral density of enough bits of a >>PRBS, is small enough. >> >>There are lots more, but I'll save the rest (along with the truth about >>the steroid abuse and wild parties of SI engineers) till I right my >>'tell all' book of the signal integrity world ;^) =20 >> >>In reality, I think you will be hard pressed to find a rule of thumb >>that satisfies all your needs. All those that have been mentioned by >>myself and others are a good start to help better understand the 'big >>knobs' in your system. The cost of trying these different approaches >>and evaluating the sensitivity of your system to the different choices >>can be pretty reasonable in a simulation environment. BTW, my response >>is intended to be very general and not specific to the Rocket I/O >>interface. For that interface some industry standard or customer >>reference designs may exist, but I am sorry that I haven't worked with >>it before. Maybe some of the Xilinx folks will have more input. >> >>My $0.02, >>-Brett >> >>-----Original Message----- >>From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] >>On Behalf Of art_porter@xxxxxxxxxxx >>Sent: Friday, January 06, 2006 8:18 AM >>To: Cortex.Chen@xxxxxxxxxxxx; tom@xxxxxxxxxxxxx; rula.bakleh@xxxxxxxxxx; >>si-list@xxxxxxxxxxxxx >>Subject: [SI-LIST] Re: Maximum frequency consideration for high-speed >>digital analysis of differential signals >> >>Well it all depends on the shape of the filter response. Is it =3D >>single-pole RC? 3rd-order Chebyshev? Gaussian? The ratios listed below = >>=3D >>are true for Gaussian but not necessarily for all responses. For =3D >>instance, for today's more brick-wall-like scope responses, the 10-90 = >>=3D >>numerator is closer to 0.42. =3D20 >> >>Art Porter >>Agilent=3D20 >> >>-----Original Message----- >>From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] >>=3D >>On Behalf Of Cortex.Chen@xxxxxxxxxxxx >>Sent: Thursday, January 05, 2006 7:26 PM >>To: tom@xxxxxxxxxxxxx; rula.bakleh@xxxxxxxxxx; si-list@xxxxxxxxxxxxx >>Subject: [SI-LIST] Re: Maximum frequency consideration for high-speed = >>=3D >>digital analysis of differential signals >> >>0.35/Tr ---- 10% to 90% >>0.22/Tr ---- 20% to 80% >>=3D20 >>Regards, >>=3D20 >>Cortex >>________________________________ >> >>From: si-list-bounce@xxxxxxxxxxxxx =3DA5N=3DB2z Tom Dagostino >>Sent: 2006/1/6 [=3DACP=3DB4=3DC1=3DA4=3DAD] =3DA4W=3DA4=3DC8 10:03 >>To: rula.bakleh@xxxxxxxxxx; si-list@xxxxxxxxxxxxx >>Subject: [SI-LIST] Re: Maximum frequency consideration for high-speed = >>=3D >>digital analysis of differential signals >> >> >> >>I'm not sure how you are computing your bandwidth. If you have a 25 =3D >>psec >>risetime (assuming 10-90%) your -3dB bandwidth is 0.35/25psec or 14 GHz. >> >>When analyzing bandwidth requirements for systems like this most people >>=3D >>talk >>about passing the 3rd or 5th harmonic of the clock. In your case that = >>=3D >>is >>7.5 or 12.5 GHz. Some analysis of your system requirements is in order. >> >>Tom Dagostino >>Teraspeed(R) Labs >>13610 SW Harness Lane >>Beaverton, OR 97008 >>503-430-1065 >>tom@xxxxxxxxxxxxx >>www.teraspeed.com >> >>Teraspeed Consulting Group LLC >>121 North River Drive >>Narragansett, RI 02882 >>401-284-1827 >> >>-----Original Message----- >>From: si-list-bounce@xxxxxxxxxxxxx >>[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of rula.bakleh@xxxxxxxxxx >>Sent: Thursday, January 05, 2006 2:19 PM >>To: si-list@xxxxxxxxxxxxx >>Subject: [SI-LIST] Maximum frequency consideration for high-speed >>digital analysis of differential signals >> >> >>Hi Everyone, >> >> >>I'm designing a differential signal for the Rocket I/O interface. My =3D >>signal >>speed is 5 Gbit/sec, operating frequency is 2.5 GHz, and fastest edge = >>=3D >>rate >>is 25 psec or 40 GHz. >> >> >> >>In regards to performing channel analysis, what is the highest frequency >>content to consider when designing this particular differential signal >>serial link? If I am measuring or simulating S parameters for various >>portions of this link what is the highest frequency of interest that I = >>=3D >>need >>to consider as a rule of thumb and why? >> >> >> >>Is it the operating frequency only, multiples/harmonics of the operating >>freq, edge rate frequency (f=3D3D1/trise), multiples/harmonics of the = >>edge >>=3D >>rate >>freq, or some fraction of the edge rate? I'm finding conflicting >>information: some people say that it's the full edge rate, others say = >>=3D >>0.35 >>or 0.5 of the edge rate, and yet others say multiples of the edge =3D >>frequency >>should be taken into account for analysis and design. I'm hoping that >>somebody could shed some light on this topic for me. >> >> >> >>Thank You, >> >>Rula Bakleh >> >> >> >> >> >> >> >>------------------------------------------------------------------ >>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: =3D20 >> //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 >>=3D20 >> >> >> >>------------------------------------------------------------------ >>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: =3D20 >> //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 >>=3D20 >> >>------------------------------------------------------------------ >>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: =20 >> //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 >>=20 >>------------------------------------------------------------------ >>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 > > > > ------------------------------------------------------------------ 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