Keysight A Series User Manual page 611

AM/FM Metrics (SA Only and Option 355)
Using AM/FM Metrics
Table 26-1 Measurement Details
Modulation Metrics
FM deviation
Carrier power
Keysight N9927-90020 User's Guide
The FM deviation reflects the amount of the frequency modulation to which
the baseband signal modulates the carrier signal. The quantity being
measured is the peak frequency deviation that is the maximum frequency
excursion from the carrier frequency.
This measures the power of the carrier signal without the modulation. Ideally,
power for a sinusoidal carrier signal is concentrated around its carrier
frequency.
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