Frequency Modulation (Fm) - PeakTech 4055 MV Bedienungsanleitung

4.6. Frequency modulation (FM)

In Frequency modulation, the frequency of the carrier is varied by the instantaneous voltage of
modulating waveform, all 16 waveforms could be used as carrier waveform, Of course, using DC or noise
as carrier wave is invalid. Before entering into frequency modulation, users should firstly set the
waveform, frequency and amplitude of carrier wave under continuity function.
Press【FM】key, the keyboard indicator of "FM" will be on, and the generator will enter into frequency
modulation function.
4.6.1 Modulation frequency:
Press【Menu】key to light "Mod_f" character, and then set modulation frequency value. In FM,
modulation frequency is usually far lower than carrier frequency.
4.6.2 Frequency deviation:
Press【Menu】key to light "Devia" character, and then set frequency deviation value. Frequency
deviation represents the frequency variation of carrier wave when the modulating waveform is with full
amplitude during FM process. When the amplitude of the modulating waveform is at positive peak value,
the output frequency is equal to the frequency of the carrier plus the frequency deviation, and when it is at
the negative peak value, the output frequency is equal to the carrier frequency minus the frequency
deviation. Therefore, the frequency deviation setting must conform to the following two conditions:
(Carrier frequency + frequency deviation) < The upper limit of the generator
4.6.3 Modulation waveform:
Press【Menu】key to light "Shape" character, the current modulation waveform sequence No. is shown,
input modulation waveform No. with the numeric keys or adjusting knob to select modulation waveform,
the modulation waveform may be any one of the 16 kinds of waveforms listed in the waveforms table in
section 4.2.9.
4.6.4. Sync output:
In FM, the generator outputs a sync signal from the front panel "Sync" connector, which is a square wave
with TTL level and 50% duty cycle, its frequency is equal to modulating wave frequency and its phase is
referenced to the phase of the modulating wave.
In FM, press【FM】key, the keyboard light of "FM" will be off, the generator will exit frequency
modulation function and return back to continuity function.
(Carrier frequency - frequency deviation) > 0
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