User guide

Vertical Search Methods
You can specify that the jitter amplitude changes in linear steps from maximum to
minimum or vice versa. The step size is adjustable.
You can also specify that the jitter amplitude changes in logarithmic steps from
maximum to minimum or vice versa. Minimum and ratio are adjustable.
Alternatively, you can also specify one of two dynamic (binary) search methods.
Searching Down/Up
Both search directions, upwards and downwards, are supported. This helps to find
out whether the device exhibits some degree of hysteresis. The BER measured at
a specific jitter amplitude may be different if this amplitude is approached
downwards or upwards.
When you search in downward direction (from maximum to minimum), the test for
one frequency stops as soon as the measured BER falls below the target bit error
ratio.
The following figure shows an example of a logarithmic search downwards.
The maximum amplitude (indicated by the dotted blue line) is given by the capability
of the instrument.
Searching downwards is usually faster than searching upwards, because the
measurement of a single point is finished as soon as the BER is found to be above
the limit.
8 Jitter Tolerance Tests
436 Agilent J-BERT N4903B High-Performance Serial BERT
Searching downwards