Agilent Technologies J-BERT N4903, Руководство пользователя

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Understanding the Output Level Parameters
The following figure shows the parameters of a data or clock output
signal.
As shown in this figure, the signal output levels have the following
components:
•
V
hi
is the upper voltage level of the signal.
•
V
lo
is the lower voltage level of the signal.
• V
of
is the offset of the average voltage level from 0 V.
• V
ampt
is the amplitude of the signal.
When adjusting the output levels, it is important to understand the
concept of how the Serial BERT handles voltages.
Typically, during tests, when you adjust the amplitude, you want to keep
the offset constant. This keeps the ideal sampling point within the eye.
The Serial BERT handles this by keeping V
of
constant when V
ampt
is
changed.
On the other hand, you may want to adjust the output voltage level
without changing the amplitude. The Serial BERT handles this by
keeping V
ampt
constant when either V
of
, V
hi
, or V
lo
is changed.
The Serial BERT cannot generate a signal that has voltage levels out of
range. If you try to enter a value for one parameter that would put
another parameter out of limits, the Serial BERT rejects the change. This
could happen, for example, if V
lo
is already at the minimum, and you try
to lower either of V
hi
or V
of
, or increase V
ampt
.
Understanding Delay and Crossover
The Serial BERT provides the possibility of modifying the output data
signal by varying the signal's delay to the clock signal, and the signal's
crossover.
Setting up the Pattern Generator
3
Agilent J-BERT N4903 High-Performance Serial BERT 73
Changing the Amplitude
Changing the Output Levels
Voltage Level Restrictions