Teledyne LeCroy Eye Doctor II - Manual (Page 35)

Operator's Manual
If this is not what you want to see, use SDA II's Deskew control on its Ref. Clock Input dialog, to move the
eye horizontally. Do not change Eye Doctor II's Deskew (also shown on the DFE setup details page as
Clock Adjust) because the trained DFE taps are optimal at that Deskew setting.
This signal can be equalized with only the CTLE or the FFE. The following example shows the DFE disabled,
the CTLE is enabled, and the Data Path set to the CTLE Output so its effect can be observed.
Equalization by the CTLE:
Case 1, with CTLE equalization (at 50mV/div vertically).
The CTLE auto setup applies a DC gain of .667 (the default), and boosts high frequencies with a peak at
about half the bit rate, and then rolls off due to a second pole at the bit rate. This suppresses boosting
high frequency noise where there is little energy from the data signal. The CTLE does not have automatic
Training, it is very easy to adjust the Boost in auto mode until the eye looks good.
There are two other examples not pictured here; however, the following descriptions clearly explain the
logic:
l
Set Data Path to DFE In to From FFE, enabling only the FFE, and Training the FFE to equalize this
signal using only the FFE.
l
Set Data Path to DFE In to From CTLE (or From FFE), enabling only the CTLE and the DFE, setting
the CTLE to 2dB boost (its minimum) and Training the DFE so it supplies the rest of the equal-
ization.
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