Anritsu BERTWave MP2100B, Operation Manual, Page: 175 / 382

6.3 Setting Conditions for Error Detection
6-15
6
Measuring Bit Error
An example is shown in Figure 6.3-7. There is just one bit different
between data addresses 0x000000 to 0x00007F and addresses 0x000080
to 0x0000FF.
When Frame Position is set to 1 at this programmable pattern, the 8
bytes of data from address 0x000000 to 0x000007 are used to detect
pattern synchronization.
The matches for these data bytes are between received bit string
addresses 0x000000 and 0x000007, and addresses 0x000080 and
0x000087. There is no bit error in the former but there is one bit error at
bit 1024 in the latter. In this case, the bit error rate is 9.77 x 10
–4
.
When the bit error rate (Sync Threshold) used to evaluate pattern
synchronization is set to 10
–3
, since the generated bit error rate is lower
than this value, the BERTWave evaluates pattern synchronization has
been achieved.
To prevent obtaining pattern synchronization at the incorrect position
like this, the Sync Threshold bit error rate must be smaller than the
reciprocal number of the programmable pattern length. For example,
when the pattern length is 16,384 bits, Sync Threshold should be 1E-5.
The maximum Programmable Pattern length is 1305600 bits. When the
file data length is over 1305600 bits, the first 1305600 bits are used for
the test pattern.