Frequency Modulation (Fm) - Rigol DSG821 User Manual

Chapter 2 Front Panel Operations

Frequency Modulation (FM)

During frequency modulation (FM), the modulating signal changes the frequency of
the RF carrier waveform.
Press MOD  FM/ØM to enter the frequency/phase modulation parameter setting
menu.
To Turn on Frequency Modulation
Press FM/ØM to select "FM" and then press Switch to select "On" or "Off".

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Note:
same time. In addition, if a sweep manner is selected and the step sweep time is
lower than 200 ms, "You can turn on the FM or ØM when sweep time is greater than
200ms" will be displayed in the user interface when frequency modulation is turned
on.
To Select the Modulation Source
Press Source to select "Int" or "Ext" modulation source.
1. Internal Source
2. External Source
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On: turn on the FM function. The FM label in the function status area in the user
interface is illuminated.
Off: turn off the FM function and this is the default state.
The frequency modulation and phase modulation cannot be turned on at the
When "Int" is selected, the internal modulation source is turned on. At this point,
the instrument provides the modulating signal and you can set the modulation
rate and modulation waveform of the modulating signal.
When "Ext" is selected, Rate and Waveform are grayed out and disabled. The
RF signal generator receives the external modulating signal input from the [EXT
MOD IN] connector (as shown in the figure below) at the rear panel. This
modulating signal can be any waveform.
Note:
The input amplitude of the external modulating signal cannot exceed
+/-3 V (HighZ). To ensure the modulation performance, the input amplitude of
the external modulating signal should be less than 1 Vpp.
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