Teledyne LeCroy QPHY-SAS3 - Manual (Page 21)

QPHY-SAS3 Software Option
Tx Group 2 Spread Spectrum Clocking Tests
There are 3 tests run in this group. The tests that are run are:
1. 5.2.1 - Tx SSC Modulation Frequency
2. 5.2.2 - Tx SSC Modulation Deviation and Balance
3. 5.2.3 - Tx SSC DFDT (Informative)
Each of these 3 tests is run when the DUT is using Center-spreading and Down-Spreading SSC. The
purpose of these tests is to verify the SSC Modulation Frequency, Modulation Deviation and Balance and
DFDT are within the specification limits. After the completion of each of the Spread Spectrum Clocking
tests the oscilloscope is in the following configuration:
Figure 11 - Oscilloscope Configuration after SSC Tests
Shown on this screen:
• F2 is the SSCTrack of the input. This signal is filtered by a 4 th
order Butterworth filter with a
200kHz cutoff as described by the specification.
• F3 is the SSCTrack of the input without the effects of the 4 th
order Butterworth filter used by F2.
• F4 is the Rate of Frequency Modulation (dF/dT). This is calculated by: slope = (f(t)–f(t–
0.27us))/0.27 us).
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