User guide

• Optimizing the View of the Results. (See “How to Optimize the View of the
Results” on page 311 ).
How to Prepare the Fast Eye Mask Measurement
To prepare a Fast Eye Mask measurement to test a shielded cable:
1
Disable the pattern generator outputs by pressing the 0V (Disable) button in
the PG Setup -> Data Output screen.
2
Use a shielded cable to connect the pattern generator's Data Out port and the
error detector's Data In port.
3
Terminate all non-connected pattern generator output ports with 50 Ω.
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 example a pure 2^15-1 PRBS, for both the pattern generator and
the error detector.
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 800ps. 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 bit error rate should be zero.
How to Execute the Fast Eye Mask Measurement
To run the Fast Eye Mask measurement:
1
Switch to the Analysis panel and then press the Fast Eye Measurement icon.
2
Press the Start button to execute the measurement.
6 Advanced Analysis
310 Agilent J-BERT N4903B High-Performance Serial BERT