122 Keysight EXG and MXG X-Series Signal Generators User’s Guide
Optimizing Performance for All Models
Using Unleveled Operating Modes
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.
Power Search Mode
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 Figure 5-23 on page 121.
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, fM, or pulse modulation.)
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.
The power search mode cannot be used with bursted signals input via the
external IQ inputs.
If the power search reference has the incorrect RMS voltage, the output
power will be incorrect. Refer to Figure 5-24, "Calculating the Output
Power Error for a Single Waveform Sample Point" and Figure 5-25,
“Calculating the RMS Voltage of the Waveform.”
A successful power search is dependent on a valid power search reference.
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