Keysight M8000 Series of BER Test Solutions User Guide 277
Setting up Generator 5
Bit Rate
Bit rate is defined as bits per second. The Generator's clock rate sets the
bit rate and serves as the frequency reference for the Data, Clock and
Trigger outputs, your device, and the Analyzer (if it receives its clock from
the Generator). It can be generated internally or supplied from an external
source.
When to Use an External Clock Source?
The M8020A/M8030A/M8040A's internal clock can be used for most
testing purposes.
There are some circumstances, however, when an external clock source is
required:
• Synchronization with an external clock
The M8020A/M8030A/M8040A can be connected to an external clock
to allow it to run as part of a larger external system.
• Use of a modulated clock
A frequency- or delay-modulated clock can be used to provide a small
amount of jitter to the clock signal.
• Use of a precision clock
A precision clock with very low phase noise can be used to enhance the
instrument's performance. This is especially interesting for longterm
measurements.
Bit Rate Range
The M8040A provides symbol rate from 2.0 to 32.4 Gbaud for M8045A
Option -G32 and 2.0 to 58.0 Gbaud (all specifications are valid up to 58
Gbaud with over-programming up to 64.8 Gbaud) for M8045A
Option -G64.
The M8020A/M8030A provides bit rates from 256 Mbit/s up to 16.2 Gbit/s,
depending on the instrument's options.
However, several specific properties and limitations need to be taken into
account when working at low bit rates. The limitations apply to the
instrument according to the following hysteresis curve:
• If the bit rate falls below 615 Mbit/s, the limitations apply.
• If the bit rate exceeds 620 Mbit/s, the limitations no longer apply.
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