336 Keysight EXG and MXG X-Series Signal Generators User’s GuideUsing Real–Time Phase Noise Impairments for N5172B/82B with Option 432 and 653/655/656/657DAC Over–Range Conditions and ScalingDAC Over–Range Conditions and ScalingWhen using phase noise impairment, it is possible to create a DAC over–range condition, whichcauses the signal generator to generate an error. To minimize this condition with the phase noiseimpairment feature, the Keysight X-Series signal generator incorporates an automatic DAC over–range protection feature that scales down the I/Q data. Because it can scale the data by more thanwhat is actually need, it typically decreases the dynamic range of the waveform. This is especiallynoticeable when using a constant amplitude signal such as GSM.For the Dual ARB Player, the automatic over–range protection can be turned off (on is the factorydefault). The control for the Dual ARB DAC over–range protection feature is located in the key pathas shown in Figure 12-3.Figure 12-3 Dual ARB DAC Over–Range Protection Softkey LocationIn the Dual ARB Player, to avoid excessive scaling or to just perform scaling manually, turn theover–range protection off and use the Waveform Runtime Scaling softkey to eliminate DAC over–range conditions.When the automatic feature is disabled, the other options to eliminate a DAC over–range conditionare to reduce the f2 value, or the Lmid value, or both until the condition corrects itself.For details on each key, use key helpas described on page 56.When the DAC over–range protection is off,eliminate over–range conditions bydecreasing the scaling value (see “SettingWaveform Runtime Scaling” onpage 204).Default setting is On.Turn off to manually control scaling whileusing the phase noise impairment option.Manually adjust the scaling using theWaveform Runtime Scaling softkeyshown above.
