User guide

• You can switch between linear and logarithmic scales.
• Graphical markers and the zoom function assist you when you are analyzing
the graph visually.
• The numerical results include bit error rate, total power, and noise power. They
provide also frequency and power information about the dominant peaks in the
spectrum.
• Absolute and relative power values are available. Relative values can be
normalized to the total jitter power or the power of a selected tone (frequency
bin).
• Pass/fail limits can be set for the bit error rate, total power and noise power,
and the allowed jitter power in user-defined frequency regions.
Periodic Jitter and Bit Error Information
When the incoming signal is sampled at the transition point, periodic jitter
manifests itself in the bit error record. An example may be helpful to understand
the phenomenon.
Let us assume we expect and correctly receive a simple 0, 1, 0, 1, 0, ... pulse signal.
If we would sample this signal one clock period earlier (-1 UI), we would see a bit
error rate (BER) of 1.0. This is the maximum BER for this pattern.
Let us also assume, this signal is overlaid by a periodic jitter source with sinusoidal
characteristics.
Now we sample the incoming signal at the transition point (-0.5 UI from the
optimum sampling point).
The result is illustrated in the figure below.
6 Advanced Analysis
346 Agilent J-BERT N4903B High-Performance Serial BERT