Alc Off Mode; Power Search Mode - Agilent Technologies X Series User Manual

ALC Off Mode

Turning ALC off deactivates the signal generator's automatic leveling circuitry. Turning ALC off is
useful when the modulation consists of very narrow pulses that are below the pulse width
specification of the ALC or when up converting external IQ signals and the modulation consists of
slow amplitude variations or bursts that the automatic leveling would remove or distort. When using
the internal IQ baseband generator, the best technique is to use the ALC hold marker function vs.
ALC off for the types of signals just described.
NOTE
After the ALC has been turned off, power search must be executed to set the proper output
power level requested on the front panel. Power search is executed automatically by default,
but the these settings can be overridden by using the Manual mode

Power Search Mode

NOTE The power search mode cannot be used with bursted signals input via the external IQ inputs.
The MXG/EXG has three power search modes (for internal and external I/Q modulation) and four
power search references (for external I/Q modulation only). Refer to
Power search executes a routine that temporarily activates the ALC, calibrates the power of the
current RF output, and then disconnects the ALC circuitry.
Power Search Modes (Applies to External and Internal I/Q Modulation)
• Auto — A power search is executed at each frequency or power change, and at each change to the
AM, burst, pulse, or I/Q modulation state.
• Span — When Power Search is set to Span, pressing Do Power Search executes the power search
calibration routine over a range of user- defined frequencies. The power search is stored and used
when the signal generator is tuned within a user- defined range. After the Span softkey is pressed,
select either Full or User. If User is selected, then the start and stop frequencies need to be
selected.
• Manual — When Power Search is set to Manual, pressing Do Power Search executes the power search
calibration routine for the current RF frequency and amplitude. In this mode, if there is a change
in RF frequency or amplitude, you will need to press Do Power Search again.
Power Search References (Only applies to Internal I/Q Modulation)
The four Power Search References control the power search function. These four references select the
reference voltage used while the RF signal is being I/Q modulated. (Power search references are not
used for analog modulation: FM, φM, or pulse modulation.)
CAUTION
If the power search reference has the incorrect RMS voltage, the output power will be
incorrect. Refer to
Waveform Sample Point"
Waveform."
NOTE A successful power search is dependent on a valid power search reference.
Agilent X-Series Signal Generators User's Guide
Figure 5- 23, "Calculating the Output Power Error for a Single
and Figure 5- 24, "Calculating the RMS Voltage of the
Optimizing Performance
Using Unleveled Operating Modes
Figure 5- 22 on page 118.
119