Frequency Shift Keying (Fsk); External Trigger - PeakTech 4055 MV Bedienungsanleitung

4.10. Frequency shift keying (FSK)

In FSK, the frequency of the carrier shifts between "carrier frequency" and "hop frequency" alternately, the
rate at which the output shifts is determined by hop rate.
All 16 waveforms could be used as carrier wave.
Of course, using DC or noise signal as carrier wave is invalid.
Before entering into FSK, users should firstly set the waveform, frequency and amplitude of carrier wave
under continuity function.
Press【FSK】key to light "FSK" keyboard indicator, the generator enter into FSK function.
4.10.1. Hop rate:
Press【Menu】key to light "Rate" character, then set hop rate value.
In FSK, the modulation waveform is fixed as a square wave with 50% duty cycle, the frequency of the
square wave is the hop rate.
4.10.2. Hop frequency:
Frequency shift keying is similar with FM whose modulating waveform is square.
"Hop frequency" is similar with "Frequency offset", with the difference of, frequency offset is an offset
value that the frequency of carrier wave positive or negative, whose setting range is relational with the
frequency of carrier wave, hop frequency could be set arbitrarily within whole frequency range, it has no
relationship with carrier frequency.

4.10.3. External trigger:

After entering into FSK function, the generator uses internal trigger source as default, outputs FSK signal
based on hop rate set.
Press【trig】key, the "trig" keyboard indicator will be on and the generator enters into FSK mode with
external trigger.
The trigger signal with TTL level is inputted from the rear panel "Trig In" connector.
If the level of the trigger signal is low, the frequency of the output signal is that of the carrier, if the level of
the trigger signal is high, the frequency of the output signal is the hop frequency.
When using external trigger, the setting of hop rate is ignored. When using external trigger, press
【FSK】key, the "trig" keyboard indicator will be off and the generator resume to internal trigger mode.
4.10.4 Sync output:
In FSK, 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 the hop rate. If the output signal is the
carrier, a low level sync signal is outputted. If the output is hop frequency, a high level sync signal is
outputted.
In internal trigger FSK, press【FSK】key again, the "FSK" keyboard indicator will be off, the generator
exits FSK function and returns back to continuity function.
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