[SI-LIST] Re: FW: Copper interface cable proposal

  • From: david_instone@xxxxxxxxxxxxxx (David Instone)
  • To: Tegan.Campbell@xxxxxxxxxxx
  • Date: Wed, 29 Aug 2001 09:42:19 +0100

Hi Tegan,
    Well first off 4Ghz is not going to be enough! and in 6 - 12 months
time when we get 4G FC (FC-PI-2) it most definitely won't be enough. 
Forget also any thought of using differential probes or even plain
active probes they all have too much input capacitance.

    This leaves you with, to my mind, only 3 choices, the 11801, the
CSA803 and the CSA8000.   The csa803 is to all intents and purposes an
11801 that can take only 2 signal modules.  I think it costs less than
the 11801 and is the one I use.  The CSA8000 is simply the 'new
improved' 11801, personally the plug in modules seem to have the same
specs as the those for the 11801/803 so why pay more for them.

I don't think you'll go far wrong with the CSA803 with an SD24 sampling
and TDR head.  Team that with a pair (you'll be making differntial
measurements) of p6150 9GHz passive probes (includes x1 50 ohm and x 10
500ohm probes) and you won't go far wrong.  Only one bug and thats the
fact that you need to supply these scopes with an external trigger.  You
can use a power splitter but you'll need one in each arm to keep the
delays to the sampling head the same.  Or you could use a pair of SD20
loop through heads and take the output of one to the trigger.

No they can't do single shot.  They sample at a maximum rate of 200khz. 
Each sample requires one trigger event and you need 4096 samples for a
complete screen.

The 7404 requires only one initiating trigger event and will 'only' be
sampling at 10Gs/s (two channels), its single shot time resolution is
thus 100ps.  Thats only 5 samples per bit time at 2Gbd. That single shot
is not going to tell you much!



Tegan Campbell wrote:
> 
> Hi everybody,
> I'm new to the SI list(I'd like to thank Mike for telling me about it)
> and have a measurement question.  The gist of the following exchange is
> that I'm doing a 2Gb Fibre Channel design and need a scope to verify
> signal integrity.
> I was looking at the 4GHz Tek 7404, but I realize it will only be able
> to capture the fundamental 2G freq.  The first question is, Has anyone
> been able to look at a Fourier Transform out of the new SFP modules for
> Fibre Channel?  I'm wondering how closely they come to replicating an
> ideal square wave(energy at the fundamental, then have to worry about
> the odd harmonics).  If there is significant energy there, I won't be
> able to use the 7404.
> A scope Mike recommended is the Tek 11801.  The only thing I don't like
> about it is it's limited use for a high price(no single shot capability,
> unless I'm reading the data sheet wrong).
> Any experiences you have had with particular scopes in this freq range
> would also be appreciated.
> Also, please tell me if this is not a good question for this list.  I
> don't want to be "that guy".
> Thanks,
> Tegan Campbell
> Elec Eng
> Quantum Corp
> 
> -----Original Message-----
> From: Mike Jenkins [mailto:jenkins@xxxxxxxx]
> Sent: Wednesday, August 22, 2001 6:15 PM
> To: Tegan Campbell
> Subject: Re: Copper interface cable proposal
> 
> Mr. Campbell,
> 
> Sorry to be so late with a reply.  The scope I used is a
> Tektronix 11801B or 11801C with SD-24 sampling heads.  The
> scope body, I think, is about $25-30K, but the sampling heads
> are maybe $5K each (for two channels).  But please check the
> TEK catalog.
> 
> This is one of the scopes used typically for Fibre Channel
> applications.  Agilent also has appropriate scopes, but I
> don't know anything about them.
> 
> Lastly, I'm not sure what location/division you're in, but
> Quantum's division in Shrewsbury(?), Massachusetts was in the
> Fibre Channel business, but backed out a while ago.  They
> might have some good equipment just sitting around now.
> 
> Good luck,
> Mike
> 
> ps: If you want further opinions, you might try posting your
>     question to the signal integrity reflector
>     (si-list@xxxxxxxxxxxxx or subscribe with a note to
>     si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the
>     subject field)
> 
> >
> > Mr Jenkins,
> > I am in the beginnings of a fibre channel design and need a scope that
> > is capable of capturing signals in the 2Gbps range.  I saw the scope
> > traces in the paper you authored on the T11 site, and was wondering
> what
> > kind of scope you are using.  If it is not commercially
> > available(read:if it's over 100K) could you suggest a scope that would
> > do the job for 2Gb fibre?  I am currently leaning toward the 4GHz
> > Tek(the 7404 I believe).
> > Any hints or things to look out/look for would be appreciated.
> > Thank you for your time.
> > Tegan Campbell
> > Elec Eng
> > Quantum Corp
> > (720)406-5665
> 
> --
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>  Mike Jenkins               Phone: 408.433.7901            _____
>  LSI Logic Corp, ms/G715      Fax: 408.433.7495        LSI|LOGIC| (R)
>  1525 McCarthy Blvd.       mailto:Jenkins@xxxxxxxx        |     |
>  Milpitas, CA  95035         http://www.lsilogic.com      |_____|
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~pc
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-- 
Regards

Dave Instone. Compliance Engineer
 Storage Systems Development, MP24/22
 Xyratex, Langstone Rd., Havant, Hampshire, P09 1SA, UK.
Tel: +44 (0)23-92-496862 (direct line)
Fax: +44 (0)23-92-496014
http://www.xyratex.com  Tel: +44 (0)23-92-496000
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