Teledyne LeCroy Eye Doctor II - Manual (Page 12)

Eye Doctor II Software
Emphasis Implementation
Emphasis is implemented as a tapped delay line filter, with 2 taps for auto-add and 8-taps for auto-
remove. For more information on how the filter is computed.
EyeDoctor II's Emphasis feature incorporates algorithms to automatically determine tap values for use in
a tapped delay line filter. The filter is equivalent to Feed Forward Equalization (FFE), (without user-select-
able precursor taps), and is mathematically described as follows:
Where:
n
y
in
(t) is the initial waveform
n
y
out
(t) is the transformed waveform
n
N is the number of taps, which is either 2 or 8
n
k is the tap index, ranging from 0 to N
n
C
k
are the coefficients, or tap values
n
T is the time delay for each of the delay elements (nominally 1/bitrate)
Take care to have the nominal bitrate set correctly. The bitrate is configure in the .
Auto Add Emphasis
Auto Add Emphasis automatically determines the appropriate tap values for your input signal when the
amount of emphasis to add is specified using the Gain box. It implements a 2-tap FFE filter that boosts
the amplitude of transitional bits in your input signal by the amount Gain specified.
Either pre-emphasis or de-emphasis can be automatically added. Use this feature when wanting to add
pre-emphasis or de-emphasis to an signal that is not emphasized in order to emulate the behavior of a
transmitter that nominally includes emphasis.
The image below shows SDAIII-CompleteLinQ performing simultaneous multi-lane analysis to illustrate
the effect of adding pre-emphasis and de-emphasis. Three lanes are being analyzed, with each lane con-
taining a simulated 5Gbps NRZ pattern configured on F1 using the JitSim function.
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