RE: 8b/10b and EMI

["DOVE,DANIEL J (HP-Roseville,ex1)" <dan_dove@xxxxxx>]

Hi Ed,

>  From: Edward Chang [mailto:edward.chang@xxxxxxxxxxxxxxxx]
>  Tom, Rick and all:
>  
>  So far, in the real industry-wide installations, no one has 
>  the 8B/10B IDLE
>  EMI problem.  Furthermore, no one has proved that 8B/10B 
>  IDLE signals will
>  cause EMI problem for 10 GbE in an enclosed environment.
>  

Actually, I believe that there were some significant problems
getting 1000BASE-CX to meet FCC requirements and the first FC
optics also had trouble. Spreading the spectrum helps a lot.

I did some analysis for Gig E where I looked at the peak spectral
components of the IDLE sequence as opposed to a random stream and
the 1.25GHz component was substantially higher for IDLE than for
random data. I believe it was 6-8dB higher.

Regards,

Dan Dove

Regards,

Dan Dove