User guide

• Optimizing the view of the results (see “How to Optimize the View of the
Results” on page 291)
• Using the color bar (see “How to Use the Color Bar” on page 292)
• Adding or changing colors (see “How to Add or Change Colors” on page 292)
• Changing the BER threshold (see “How to Change the BER Threshold” on page
293)
• Changing the BER range of a color (see “How to Change the BER Range of a
Color” on page 294)
How to Prepare the Eye Opening Measurement
To prepare an Eye Opening 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
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.
5
For the pattern generator setup you need to specify the logic levels and the bit
rate. Select ECL levels and a clock speed of 1250 MHz 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.
6
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.
7
Enable the pattern generator outputs by pressing the 0V (Disable) button.
8
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.
6 Advanced Analysis
290 Agilent J-BERT N4903B High-Performance Serial BERT