
2-22 Programming Guide
Programming Commands and Examples ESG Family Signal Generators
:FM Subsystem
:FM Subsystem
The frequency modulation subsystem is used to set the modulation controls and the
parameters associated with frequency modulated signals.
External Frequency Modulation Source Coupling
:FM[1]|2:EXTernal[1]|2:COUPling AC|DC
:FM[1]|2:EXTernal[1]|2:COUPling?
This command sets the external coupling for the frequency modulation source. The choices
are AC or DC coupling. This command does not change the currently active source, nor
does it switch the current modulation on or off. The modulating signal may be the sum of
several signals, either internal or external sources. If the coupling is set to DC, then both
the AC and DC signal components pass. AC coupling passes only AC signal components.
The external 1 source has multiple uses but can be used for only one modulation at a time.
If, for example, you were using the external 1 source in an amplitude modulation
configuration for
AM Path 1, and then you configured FM Path 2 to also use the external 1
source, the signal generator would turn off
AM Path 1 and assign the external 1 source to
your
FM Path 2 configuration. Notice that for these purposes, the external 1 AC-coupled
source is the same as the external 1 DC-coupled source.
*RST Value: DC
Frequency Modulation Deviation
:FM[1]|2[:DEViation] <val><unit>
:FM[1]|2[:DEViation]?
Use this command to set the frequency modulation deviation for the
FM Path 1 and
FM Path 2 configurations. The current value for FM deviation is displayed in the active
entry area. The range of values allowed depends on the carrier frequency. For the ESG-A
and ESG-D Series, the maximum peak deviation for a frequency is calculated by
multiplying N by 10 MHz. For the ESG-AP and ESG-DP Series, N is multiplied by 1 MHz.
(The following table lists the values for N and the resulting maximum peak deviations.)
Carrier Frequency N
Maximum Peak
Deviation
(ESG-A & ESG-D)
Maximum Peak
Deviation
(ESG-AP & ESG-DP)
250 kHz to
≤ 249.999 MHz 1 10 MHz 1 MHz
> 249.999 MHz to
≤ 500 MHz 0.5 5 MHz 0.5 MHz
> 500 MHz to ≤ 1 GHz 1 10 MHz 1 MHz
> 1 GHz to
≤ 2 GHz 2 20 MHz 2 MHz
> 2 GHz to 4 GHz 4 40 MHz 4 MHz
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