[SI-LIST] Re: De-emphasis in 3GIO

Colleagues:

That is not strictly correct.  What de-emphasis does is lower the 
low-frequency spectral content to "flatten-out" the spectrum.  It is what 
one does in "passive equalization".  It is also possible to provide 
selective high frequency boost to accomplish the same thing, but one has to 
be careful not to over-drive the high frequencies and cause the envelope 
high-low eye limits to be exceeded.  It all looks like control systems but 
for non-linear electronics and at a lot higher frequencies!!!

ed
PS: Don't forget DesignCon East  June 23, 24 in the Boston area! Great time 
to come to New England - bring the family.
=======
At 02:05 PM 2/21/2003 -0600, Christopher_Brewster@xxxxxxxx wrote:

>Gabriel
>
>As I understand it, and somebody correct me if I am wrong, de-emphasis is
>just another term for the same concept as pre-emphasis.  In most SERDES
>designs, it is called pre-emphasis, however, most communications guys use
>the term de-emphasis due to the fact that the DC gain is, "de-emphasized."
>Technically, it means the same thing.
>
>-Chris Brewster
>
>-----Original Message-----
>From: Fuentes, Gabriel [mailto:g.fuentes@xxxxxxxxx]
>Sent: Tuesday, February 18, 2003 10:04 AM
>To: [SI-LIST]
>Subject: [SI-LIST] De-emphasis in 3GIO
>
>
>
>Hi all.
>  I am looking for a document describing the de-emphasis technic used  in the
>3GIO physical layer. I need to understand how does it works,  how it helps
>to reduce ISI, etc.
>  I understand the Tx pre-emphasis in RS-485 communications, but I have not
>   been able to deduce de de-emphasis in PCI-E
>
>Gabriel
>
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