Frequency Modulation (Fm) - Rigol DG900 Pro Series User Manual

Modulation
4. Turn on the CH1 and CH2 outputs.
Modulation Frequency
After the internal modulation source is selected, click or tap the AM Freq input field
and set the modulation frequency with the pop-up numeric keypad. The available
range is from 2 mHz to 1 MHz, and the default is 100 Hz. The resolution is 1 μHz.
TIP
When an external modulation source is selected, this setting is grayed out and disabled.
Modulation Depth
Modulation depth is a percentage that represents the amplitude variation. Click or tap
the Depth input field to set the modulation depth. AM depth ranges from 0% to
120%. The default is 100%, and the resolution is 0.01%.
• At 0% depth, the amplitude is one-half of the carrier's amplitude setting.
• At 100% depth, the amplitude is identical to the carrier's amplitude setting.
• At greater than 100% depth, the output amplitude will not exceed the maximum
output amplitude (refer to
When an external modulation source is selected, the AM modulation amplitude is
also controlled by the ±5 V signal level on the rear-panel [AUX IN/OUT] connector.
For example, if the modulation depth is set to 100%, then the output will be at the
maximum amplitude when the modulating signal is at +5 V. The output will be at the
minimum amplitude when the modulating signal is at -5 V.
DSSC
DG900 Pro supports two forms of amplitude modulation, Normal and Double
Sideband Suppressed Carrier (DSSC). In "normal" AM, the modulated wave consists of
the carrier wave and two sidebands. Such a modulation is inefficient because the
carrier wave carries no information. If this carrier is suppressed and the saved power
is distributed to the two sidebands, then such a process is called Double Sideband
Suppressed Carrier (DSSC).
By default, the "DSSC" is off. Click or tap the DSSC on/off switch to turn on or off the
DSSC function.
6.2

Frequency Modulation (FM)

In Frequency Modulation (FM), a modulated waveform consists of a carrier waveform
and a modulating waveform. The frequency of the carrier waveform is varied by the
instantaneous voltage of the modulating waveform. In the "Modulation Setting
Interface" (
"FM" and set its parameters.
DG900 Pro User Guide
50
Table 5.2 Range of Amplitude
Figure 6.1
), click or tap the "Modulation Type" drop-down button to select
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).