Agilent Technologies J-BERT N4903B, User Manual, Page: 266 / 572

4 Use a shielded cable to connect the pattern generator's Data Out port and the
error detector's Data In port.
5 Switch to the
Pattern
panel and press
Pattern Select
. Select an appropriate
pattern for this test. We use a pure 2^23-1 PRBS segment.
6
For the pattern generator setup you need to specify the logic levels and the bit
rate. Select
ECL
levels and a clock speed of 1250MHz in this example. This
corresponds to a clock period of 0.8ns. See “Setting up the Pattern Generator
- Concepts ” on page 121 for more information.
7 Set up the error detector so that the input range and the termination matches
the pattern generator's levels:
– Select an
Input Range
from -2V to 0V
– Set the
Data Termination
to -2V
– Set the
Alignment BER Threshold
to 1E-6.
– Set the
Clock Setup
to
Clock Data Recovery
to get the error detector's
clock from the incoming data stream.
8
Enable the pattern generator outputs by pressing the
0V (Disable)
button.
9 Press
Sync Now
and then
Auto Align
to find the optimum sampling point. Check
that the synchronization and the alignment were successful. None of the error
indicators should show red.
The resulting BER should be zero.
How to Execute the Output Levels Measurement
To run the Output Levels measurement:
1
Switch to the
Analysis
panel and then press the
Output Levels
icon.
2 Press the
Properties
button to open the
Properties
dialog box.
3
On the
Parameters
tab, set the
Sample Threshold
parameters to suitable
values that fit to the expected signal levels, for example, -1.85V to -0.85V. Set
the
Resolution
to 10 mV.
6
Advanced Analysis
266 Agilent J-BERT N4903B High-Performance Serial BERT