[SI-LIST] Re: BER and Adaptive Equalization

  • From: tim stroud <tim.stroud@xxxxxxxxxx>
  • To: KKeskinen@xxxxxxxxxxxx
  • Date: Tue, 11 Sep 2001 08:52:38 -0400

Check out the book "Digital Communications"  by Lee and Messerschmidt
They have a good section on adaptive equalization.  Adaptive equalization
usually just falttens the spectral channel.  Transmission lines roll off with
a square root of frequency response, so the equalizers flatten the channel.
Recall that for distortionless transmission, you need a flat channel and linear
phase.
You need to check and see if the equalizer is also performing CDR or if it is
just straight equalization.  It seems to me that for it to lose edges, it would

almost have to be doing CDR as well.   can you explain your two cases a bit
more?


Hope that helps

Tim

Kai Keskinen wrote:

> Hello SI Folks:
>
> This question is in the general line of the 8b/10b trail.
>
> I know how BER can be calculated from the eye diagram for standard logic
> where the chip switches from high to low or vice versa at some given
> voltage.  Over a  given link, as the eye gets smaller, the BER goes up. How
> does one deal with adaptive equalizer chips? In our experience, in one case,
> we can have a totally closed eye at the receive pads and with the equalizer
> chip get an acceptable BER. In the next case, we also have a closed eye at
> the receive pads and we get a very high bit error rate. In both cases, the
> eye from the equalizer chip output looks good but it is losing transitions
> in the high BER case. I'm really interested in the behaviour of the chips in
> the presence of cross-talk and reflections for which the equalization
> doesn't work well. Does anyone know of any references to these topics or
> have any quantifiable data?
>
> Thanks,
>
> Kai Keskinen
> Signal Integrity Advisor
> C-MAC Engineering Inc.
> 425 Legget Drive
> Kanata, ON K2K 2W2
> kkeskinen@xxxxxxxxxxx
>
> ------------------------------------------------------------------
> 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 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
>

--
-------------------------------------------
Analog Devices              "Enjoy yourself -
7910 Triad Center Dr         it is later than you think"
Greensboro, NC
336-605-4317
tim.stroud@xxxxxxxxxx
-------------------------------------------



------------------------------------------------------------------
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 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
  

Other related posts: