[SI-LIST] Re: Maximum frequency consideration for high-speed digital analysis of differential signals

0.35/Tr ---- 10% to 90%
0.22/Tr ---- 20% to 80%
 
Regards,
 
Cortex
________________________________

From: si-list-bounce@xxxxxxxxxxxxx ¥N²z Tom Dagostino
Sent: 2006/1/6 [¬P´Á¤­] ¤W¤È 10:03
To: rula.bakleh@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Maximum frequency consideration for high-speed digital 
analysis of differential signals



I'm not sure how you are computing your bandwidth.  If you have a 25 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 talk
about passing the 3rd or 5th harmonic of the clock.  In your case that 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 signal
speed is 5 Gbit/sec, operating frequency is 2.5 GHz, and fastest edge 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 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=1/trise), multiples/harmonics of the edge 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 0.35
or 0.5 of the edge rate, and yet others say multiples of the edge 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







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