Eye, Mask and Eyeline Mode Measurement Tutorials
Making Eye Diagram Measurements
Measuring duty cycle distortion
Duty cycle distortion is a measurement of the time separation of the rising
and falling edge of the eye at the center threshold level. The default
center value is 50%, and can be changed in the
4
Dene meas
5
menu. Narrow
horizontal histograms are computed at the center threshold level to determine
the mean location of the rising and falling edge at that level. The time
dierence between the falling and rising edge can be expressed in absolute
time:
D
C
D
time
=
j
T
r
ise
center
0
T
f
al
l
center
j
The time
dierence between
the falling
and
rising
edge
,
expressed
as
a
percentage of
the bit
period:
D
CD
per
cent
=
j
T
r
ise
center
0
T
f
al
l
center
j
bit
per
iod
Figure 5-8. Duty cycle distortion measurement.
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