User`s guide

Agilent X-Series Signal Generators User’s Guide 301
BERT (Option UN7)
Bit Error Rate Tester–Option UN7
Special Pattern Ignore Function
The special pattern ignore function is especially useful when performing BERT analysis on radios
that generate consecutive 0’s or 1’s data for traffic channels when they fail to detect the Unique
Word or lose synchronization. If 160 or more consecutive incoming data bits are either 1’s or 0’s, and
the
Spcl Pattern Ignore Off On softkey is set to On, then all of the consecutive 0’s or 1’s are ignored. Select
either 0’s or 1’s as the data to ignore by using the
Spcl Pattern 0’s 1’s softkey. The following figure shows
an example of the special pattern ignore function.
Figure 11-11 Pattern Ignore Function Example
The 160 or more ignored bits can be anywhere in the PN sequence. The signal generator ignores
these bits as error, but they are counted in the PN sequence bit count.
Pass/Fail Judgement
There are two pass/fail judgement update modes: cycle end and fail hold. With cycle end selected,
either pass or fail judgement is made for the results of each measurement cycle. With fail hold
selected, the fail judgement is retained whenever a failure occurs during one loop of BERT repeat
measurements. Fail hold mode allows you to determine when a failure occurs at least once during an
entire cycle of measurements.
Repeat Measurements
When the Cycle Count softkey is set to more than 1, the synchronization performed before the start of
each measurement is only executed the first time; then it keeps track of the clock signal and the
PRBS generation for the incoming data. This function can reduce the total time for BERT
measurements. Also, once synchronization is established, it is retained even if the BERT measurement
result degrades. You may wish to adjust the signal level to find a specific BERT value. However, once
synchronization is lost in a repeat sequence, it will not be restored until the initiation of a new
sequence. The following figure shows an example of the repeat measurements.