PeakTech 4035 Bedienungsanleitung Seite 91

modulation signal, larger the offset of frequency modulation or depth of amplitude modulation. When using
exterior modulation, the offset of frequency modulation or depth of amplitude modulation cannot be settled
by the keyboard. In the state of exterior modulation, pressing the key of (Option 4) and selecting "FM Devia"
or "AM Depth", it will change to the state of interior modulation. It must be paid attention that the exterior
modulation signal should be taken out. Otherwise, the operation of interior modulation cannot be normal.
7.7 Amplitude modulation (AM)
In AM, the amplitude of the carrier is varied by the instantaneous voltage of the modulating waveform, the
carrier waveform is sine wave usually, but square, ramp or arbitrary waveform can also be used.
7.7.1 Carrier setting:
Press 〖CarrFreq〗softkey to select "carrier frequency" or "carrier amplitude". It is able to set carrier
frequency and amplitude at any moment while the AM signal is outputted.
7.7.2 Modulating waveform frequency:
In amplitude modulation, the modulating frequency is always much lower than the carrier frequency. If
internal modulating signal is used, you can set the modulating frequency within the range of 2 mHz~20 kHz.
If external modulating signal is used, the modulating frequency setting is ignored.
7.7.3 Modulation depth:
It represents the maximum variation in the amplitude of the carrier wave in amplitude modulation. If the
maximum amplitude of the modulated waveform is called as Amax, the minimum amplitude as Amin, then
the modulation depth can be expressed as the following formula:
Modulation depth %=(Amax － Amin)／A
If Amax=A，Amin=0, the modulation depth setting will be up to 100%. If Amax=0.8A, Amin=0.2A, the
modulation depth setting will be up to 60%. If Amax=0.5A, Amin=0.5A, the modulation depth setting will be
up to 0%. That is to say, when modulation depth is 0, carrier amplitude is half of the amplitude setting.
7.7.4 Modulating waveform shape:
It is able to set modulating waveform shape if internal modulating signal is used. Press 〖SineModu〗
softkey to select "sine modulation", "square modulation", "triangle modulation" or "ramp modulation".
Modulating waveform shape setting would be ignored if external modulating signal is used.
7.7.5 Modulating source:
The function generator will accept an internal or external modulation source for AM. Press 〖Int Modu〗
softkey to select "external source". The modulating signal is inputted from the rear panel "Modulation In"
connector for AM. If the amplitude of the external modulating signal is ±5 V, the modulation depth setting
and the display value accord with the real modulation depth. Otherwise, the modulation depth setting and
display value are not accurate.
7.7.6 Sync output:
In AM, the generator outputs a sync signal from the front panel "Sync" connector, which is square wave with
TTL level and 50% duty cycle, its frequency if equal to modulating frequency and its phase is referenced to
the phase of the modulating signal.
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