Keysight M8000 Series of BER Test Solutions User Guide 219
User Interface - M8020A Display Views 4
Jitter Setting in AWG(s)
The AWG integration into the M8070A software supports sinusoidal jitter,
random jitter and spread spectrum clocking (SSC).
Sinusoidal jitter and random jitter can be turned on and off per channel
while SSC can only be activated per module.
Periodic Jitter (Valid for PJ1, PJ2 and SSC)
When defining a sequence referencing a specific pattern it will
automatically be generated containing the specified jitter. For example in
case the given pattern has a duration of 1 µs for the selected baud rate
and the jitter period is 2 µs it would not be possible for this jitter to
correctly appear inside the pattern. To handle this a second iteration of the
pattern is appended giving the memory segment a total duration of 2 µs.
With this it is possible for the resulting waveform to contain the selected
jitter.
A side effect of this procedure is that the required sample memory for a
selected pattern changes depending on the selected jitter components.
In case the jitter cannot be mapped to the available memory while
adhering to the jitter accuracy defined in the data sheet a warning
message will be displayed to make the user aware of this shortcoming.
Measuring Periodic Jitter
When measuring periodic jitter on an oscilloscope it is important to note
that the jitter period will always be rounded in a way that the effective
pattern length (which may contain multiple iterations of the user defined
pattern) is a multiple of this jitter period.
Another thing to note is that for short pattern, high jitter frequency and the
case where the data rate is an integer multiple of the jitter frequency the
effective pattern can become maximally short. This will be observable by a
relatively fast start of waveform playback but can have an impact on the
measured jitter histogram.
For the above mentioned cases the number of distinct edge deviations
from their non-jittered positions can be limited which leads to a histogram
containing only a low number of lines.
To tweak the quality of the jitter histogram it is possible to use a larger
pattern e.g. by repeating the shorter pattern multiple times in the pattern
file or using an odd number for the jitter frequency.
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