Teledyne LeCroy QPHY-ENET - Manual (Page 43)

QPHY-ENET Software Option
QPHY-ENET Operator’s Manual Rev G
43
100Base-TX Duty cycle distortion
The duty cycle distortion measurement determines the timing error on four consecutive transitions of the
transmitter signal, consisting of consecutive positive and negative pulses. This MLT-3 code is generated by a
10101010
sequence. Duty cycle distortion is measured as the maximum deviation from the nominal 16 ns
spacing between all of the transitions at their 50% amplitudes.
1. Apply power to the Device Under Test. An MLT-3 signal trace should be displayed on the oscilloscope
screen at this point.
2. Set the Device Under Test to transmit a 1010... pattern.
3. Touch the 100Base-TX button under “Select Standard.”
4. Select Duty Cycle Distortion in the “Select Test” field.
5. Check Differential Data on 2 Channels.
6. Enter C2 in the Source for + Data field and C3 in the Source for - Data field.
7. Touch the Set Up and Start Test button to begin testing.
8. P1 indicates the duty cycle distortion and the number of passing sweeps (acquisitions) out of the total.
9. The Average Result checkbox, when checked, averages measurements over the number of sweeps
(acquisitions) specified in the Avg Weight field.
Figure 32. 100Base-TX duty cycle distortion