LeCroy DDA 7 Zi series, Руководство оператора

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WavePro 7Zi
337
WP700Zi-OM-E-RevA
Figure 5-11. Leveled DVD data, with cursors showing the approximate hysteresis requirements for Sliced
data.
The slicer produces waveforms that are exactly five divisions high. Each edge has two samples that are between
the high and low levels and are positioned 2.5 divisions apart such that the zero cross time of the sliced output
edge is the same as the zero cross time of the leveled data.
Extract CLK
It is usually not possible to get data and clock signals correctly aligned from an optical drive to visualize how the
data edges align with the clock; in some cases, the clock may not be available at all. This function produces a
clock waveform from the data by passing it through a software PLL. This output may be overlapped on the display
with Leveled or Sliced output on another trace; and it can be used for measurements of the clock frequency. If the
JTA option is present, a JitterTrack of Frequency of the extracted clock may give interesting insight into timing
variation in the input signal.
The only user-set parameter for clock extraction is the "PLL BW" setting on the "Equalizer and PLL” dialog. The
PLL Bandwidth is the unity gain intercept of the open-loop transfer function of the PLL. The closed loop -3 dB
frequency is approximately 1.274 time that. The loop filter meets the specification shown in Annex H of the DVD
Physical specifications (or Annex G of the DVD-R Physical specifications). For 1x DVD the PLL BW should be set
to 9 kHz. In that case the software PLL has this closed-loop response: