98 Keysight EXG and MXG X-Series Signal Generators User’s GuideOptimize PerformanceUsing External Leveling (N5173B/83B Only)Option 1E1 Output Attenuator Behavior and UseWhen using the internal detector, the Option 1E1 output attenuator enables signal generatorpower levels down to -130 dBm at the RF Output connector. It accomplishes this by addingattenuation to the output signal after the ALC detection circuit. The output power value (shown inthe Amplitude area of the display) is the resultant of the Set Atten and Set ALC Level values (seepage 95). With the external detector selected, the output attenuator no longer attenuates theoutput signal since the feedback for the detection circuit has been moved beyond the outputattenuator. Because the attenuator no longer affects the amplitude of the output signal, the outputamplitude is determined by only the Set ALC Level softkey.With external leveling selected, the signal generator enables attenuator hold and the power rangeapproximates the range of a standard option (no attenuator) signal generator (see the Data Sheet).As stated earlier, the actual output power may vary due to the external detector and thecoupler/power splitter performance characteristics.Even though the output attenuator no longer affects the output power, it is still useful to drive theALC circuit to its mid–power point of approximately 0 dBm, which is optimal for the internal levelingcircuitry and typically provides the best amplitude flatness results. This is useful with power valuesof -5 dBm or less. For example, to drive the ALC to approximately mid–power with a -20 dBmpower setting, add 25 dB of attenuation. This sets the ALC circuit to 5 dBm (-20 + 25).Configure External LevelingBasic Setup Process— If working with a single frequency signal, perform Steps 1 through 5.— If working with multiple frequencies:a. Perform Steps 1 through 4.b. Perform a user flatness correction, see “Using Flatness Correction” on page 82.— If working with a sweep:a. Perform Steps 1 through 4.b. Setup the sweep, see “Configuring a Swept Output” on page 46.1. Setup the equipment, see “Equipment Setup” on page 992. Configure the carrier signal, see “Configuring the Carrier” on page 993. Select external leveling, see “Selecting External Leveling” on page 99.When the internal detector (Internal selection) is reselected, the signalgenerator does not turn the attenuator hold off.If there is too much attenuation, it will drive the ALC circuit too high andcause the signal generator to go unleveled. Ensure that you decrease theattenuation as you increase the power level.
