Keysight M8000 Series of BER Test Solutions User Guide 491
Working with Measurements 8
The sampling point- the amplitude decision threshold and the time at
which the bits are measured – is scanned across the eye pattern over the
time period while monitoring the BER. The bathtub curve can also be used
to separate random from the deterministic jitter.
The slope of the bathtub curve is the measure of the random jitter,
whereas the slope offset positions on the time axis are set by deterministic
jitter. Total jitter is quantified by noting points where BER reduces to at
both the eye edges and subtracting this interval from the bit period.
Calculated Results
The calculated results for the Output Timing measurement are displayed
in the tabular format. It includes the following elements:
• Location: Location or Location/Group against which the data
acquisition is performed.
• Show Graphics: Displays the measurement graph in the measurement
output window.
• Optimal Sample Delay: Sample delay coordinate of the center of a
bounding box around the BER threshold contour line.
• Phase Margin: Period of time where the bit error rate is lower than the
BER threshold.
• Total Jitter Peak-to-Peak: Peak-to-peak value for total jitter.
Calculated as the pulse period (unit interval) minus the Phase Margin.
BER
DJ
DJ
RJ
BERT scan
(bathtub curve)
Time
A = Period; B = Eye opening @ BER 10
A - B = Total Jitter
0.5
10
-12
-12
RJ
B
A
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