Keysight M8000 Series of BER Test Solutions User Guide 277Setting up Generator 5Bit RateBit rate is defined as bits per second. The Generator's clock rate sets thebit rate and serves as the frequency reference for the Data, Clock andTrigger outputs, your device, and the Analyzer (if it receives its clock fromthe Generator). It can be generated internally or supplied from an externalsource.When to Use an External Clock Source?The M8020A/M8030A/M8040A's internal clock can be used for mosttesting purposes.There are some circumstances, however, when an external clock source isrequired:• Synchronization with an external clockThe M8020A/M8030A/M8040A can be connected to an external clockto allow it to run as part of a larger external system.• Use of a modulated clockA frequency- or delay-modulated clock can be used to provide a smallamount of jitter to the clock signal.• Use of a precision clockA precision clock with very low phase noise can be used to enhance theinstrument's performance. This is especially interesting for longtermmeasurements.Bit Rate RangeThe M8040A provides symbol rate from 2.0 to 32.4 Gbaud for M8045AOption -G32 and 2.0 to 58.0 Gbaud (all specifications are valid up to 58Gbaud with over-programming up to 64.8 Gbaud) for M8045AOption -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 intoaccount when working at low bit rates. The limitations apply to theinstrument 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.
