Hi Hermann,
This topic came up a few times in the past and I dont think there is an
'official'
definition. In the old analog FM broadcasting world preemphasis meant
boosting
the high-frequency modulation contents at the transmit side and reduce it
correspondingly at the receive side. In the digital signaling world
they dont
seem to go hand in hand. The spectral contents is predistorted at the
transmitter
to boost it's high frequency content (and in this case Steve's
description fits well),
but usually the high-frequency contents is boosted again at the receiver
by the
CTLE circuit. So the source of confusion is that in the old days these
meant
complementary actions, one at the transmitter, the other at the
receiver. Today's
digital signaling boosts high-frequency contents at both ends and now the
differentiation is based on how we implement it: boosting lonely edges with
respect to the average versus reducing the average with respect to the
lonely edges.
Regards,
Istvan Novak
Oracle
On 5/11/2015 2:29 AM, Hermann Ruckerbauer wrote:
Hello,
I have heard serveral different explanations, but basically all mean the
same thing: Pre-destortion of the signal on the TX -Side (and in my
naming conventions Equalization means the equivalent on the RX side).
Sometimes I have heard De-Emphasis due to reduction of energy below the
nominal (as steve mentined), sometimes Pre-Emphasis for going above the
nominal, sometimes Pre for a Pre-Destortion before the channel.
In my "naming convention" I have a maximum energy available, and I can
only reduce this (so I'm not working with nominal, but with max.
engergy). Especially when talking about Pre-Curssor, Post-Cursor,
Boosting, Multibit Pre-Emphasis I prefer this explanation (similar to
what PCIe-Gen3 is doing).
But I have never seen any "official" explanation / description of this
names (and I would not know which consortium would define an official
naming).
I struggled with this also quite a while when working with this stuff,
and if somebody has a good explanation I'm really interested to learn
here too ..
Best Regards
Hermann
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Am 11.05.2015 um 04:55 schrieb steve weir:
It is the difference between increasing energy over the nominal, or------------------------------------------------------------------
decreasing energy below the nominal. In each case the effect is to
predistort the transmitted data pattern to complement the channel
distortion.
Steve.
On 5/10/2015 7:30 PM, mo han wrote:
Hi experts:
I am solving the sata ISI problem by using emphasis,but I am not very clear
about the differences between de-emphasis and pre-emphasis，could anyone
tell me?
Thanks!
Mo Han
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