User guide

Output Timing Characteristics
The sampling point is swept automatically within a 1.5 clock period to generate a
"bathtub" curve. The resulting graph is centered around the optimum sampling
point of the port.
In addition, the results are available in a tabular view. If a clock signal is defined,
the software measures the data to clock alignment and displays the absolute delay.
Jitter Characteristics
The DUT Output Timing/Jitter measurement calculates the jitter histogram as the
absolute of the derivative of the measured bit error rate (jitter=d BER/dt).
The jitter histogram allows to separate and calculate the different components
making up the jitter:
• Random Jitter (RJ)
• Deterministic Jitter (DJ)
• Estimated Total Jitter (TJ)
The peak-to-peak, RMS, and mean values are displayed in the result table. They
can also be displayed graphically.
“Jitter Measurement Parameters” on page 260 describes how these components
are calculated.
A dedicated Gaussian marker allows to investigate the jitter graph in detail and to
measure the contribution of certain sections or jitter peaks to the overall results.
You can set several signal parameters, the values to be displayed and the output
format according to your needs.
Fast Total Jitter Measurement Characteristics
This measurement is an alternative to the standard jitter measurement. It can be
used to measure the total jitter at very low bit error ratios.
Whereas usual jitter measurements at a BER around 10
-12
can take days (due to
the huge number of bits that has to be compared for each measurement point), the
Fast Total Jitter measurement can, for example, determine the total jitter at a BER
of 10
-12
in less than 20 minutes (at a data rate of 10 Gbit/s).
For details refer to “Explanation of the Fast Total Jitter Measurement” on page
246.
6 Advanced Analysis
242 Agilent J-BERT N4903B High-Performance Serial BERT