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Selecting Modulation Source
•
The Generator can offer both an internal and external modulation source.
With PWM enabled the modulation source
defaults at internal source. To modify the
parameter, turn the multipurpose knob
after switching on PWM interface or press
Params→Mod→Source→Ext MHz
to modify.
•
Note: Enable PWM function first before
selecting modulation source. Press
Menu→Mod→Type→PWM
to switch on the
PWM function.
Internal Source
When you select Internal Source, the modulating waveform can be: sine, square, up
ramp, down ramp, arbitrary, noise. The default is sine.
Once PWM is enabled, the modulating shape defaults at sine. To modify the parameter,
switch on PWM interface, turn the multipurpose knob or press
Params→Wave MHz
softkeys to modify.
•
Square: 50% Duty Cycle
•
UpRamp: 100% Symmetry
•
DownRamp: 0% Symmetry
•
Arbitrary: When arbitrary waveform is selected as the modulation shape, the
waveform is automatically sampled and limited to 1,000 points.
•
Noise: White Gaussian
External Source
•
When you select external source, modulation shape and modulation frequency
items won’t show on the parameter list and the carrier is modulated by an external
waveform.
•
PWM duty cycle deviation is controlled by ±5V signal level presented on the
external analogue input connector (Modulation In) on the rear panel.
•
For instance, if the duty cycle deviation in the parameter list is set to 15%,
when external modulation 5V is applied, duty cycle of the carrier (Pulse
waveform) will increase by 15%; the deviation will be smaller for external signal
with lower level.
Setting Modulating Frequency
•
When internal source is selected, the modulation frequency can be set up. With
PWM enabled, the modulation frequency is 100Hz by default.
•
To modify the parameter, switch on PWM interface, then use multipurpose knob
and direction buttons or press
Params→ModFreq
to select.
•
The modulation frequency range from 50kHz to 20MHz. If external source
is selected, modulation shape and modulation frequency will not be on the
parameter, and the carrier (impulse wave) will be modulated by an external
waveform with a modulation frequency from 0Hz to 20kHz.
Setting Duty Cycle Deviation
Duty cycle deviation represents the variation in duty cycle of modulated waveform from
