4. ALC

The following figure is a composite of all supported instruments, so some parameters may not apply to your instrument.

4. ALC: ALC Trigger Source bus (M9381A)

4. ALC: ALC Mode (M9381A)

ALC

Double-click or use the drop-down menu to enable or disable the automatic level control.

On − the ALC circuit constantly monitors and controls the output power level.
Off − no automatic leveling occurs.

ALC Bandwidth

Choices:

MXG/EXG: Auto, 200 Hz, 2 kHz,20 kHz

ESG/PSG: Auto, 100 Hz, 1 kHz, 10 kHz, 100 kHz

Default: Auto

ALC bandwidth control is not available for the N5182A MXG.

Select the ALC loop bandwidth from the drop-down list. Choose Auto to let the signal generator automatically select the optimized bandwidth for the current signal setup.

For waveforms with varying amplitudes, a high crest factor, or both, set the ALC loop bandwidth to 100 Hz, which is the default bandwidth set when an ARB format is turned on. Limiting the loop bandwidth of the ALC circuit prevents the ALC from sampling the fast rising edges of high-crest pulsed waveforms.

Power Search Reference

Choice: Fixed | Modulation | RMS

Default: Modulation

Double-click or use the drop-down menu to select one of the following reference signal types when doing a power search.

Fixed − power search uses a fixed 0.5 V reference
Modulation − power search uses the AC bias from the actual modulating signal
RMS − power search uses a DC bias value equivalent to the value derived from the file header or the calculated value from the current I/Q data

Set ALC to Off to enable this parameter.

This parameter is not available for all instrument models and may be greyed out or not shown in GUI.

RF During Power Search

Choice: Normal | Minimum

Default: Normal

Double-click or use the drop-down menu to select the level of the output power control during a power search routine.

Normal − performs power searches without setting the internal step attenuator to its maximum setting. Glitches and power changes may be present during the search.
Minimum − sets the signal generator's step attenuator to its maximum setting during power search to protect sensitive circuits.

Set ALC to Off to enable this parameter.

ALC Trigger Source bus (M9381A)

Choice: AUTO | PXI0 | .. | PXI7

Default: None

Double-click or use the drop-down menu to select a bus for ALC hold signal path on PXI backplane. This parameter is only available when connected to the M9381A.

ALC Mode (M9381A)

Choice: : Off | HOLD | TRACK

Default: Off

Double-click or use the drop-down menu to select ALC mode. This parameter is only available when connected to the M9381A.