5.5.4. Modulation source
Press
【
Menu
】
key, select “Source” option and then set modulation source, there are only two values to
choose: 0 and 1. Set the value as 0 to choose internal modulation source, and set it as 1 to choose external
modulation source. If external modulation source is chosen, connect a modulation signal to the
《
Modulation
In
》
port on the rear panel of the generator. When external modulation signal reaching to full amplitude as
±5V, the display of modulation depth accords with its real value. Or the display of modulation depth is
incorrect.
5.5.5. Sync output
In AM, 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 frequency and its phase is
referenced to the phase of the modulating signal.
In AM, press
【
AM
】
key again, the “AM” indicator will be off, and the generator exits AM function and returns
back to continuous function.
5.6. Phase modulation (PM)
In PM, the phase of the carrier is varied by the instantaneous voltage of the modulating waveform, all the 16
kinds of waveforms listed in the waveforms table could be used as carrier waveform. Before entering into
phase modulation, the users should set the waveform, frequency and amplitude value of the carrier wave
first under CHA continuous function.
Press
【
PM
】
key to light “PM”, and the CHA output phase modulation signal.
5.6.1. Phase deviation
Press
【
Menu
】
key and select “Devia” option, and then set phase deviation value. Phase deviation
represents the variation of carrier phase while the modulating waveform is with full amplitude in phase
modulation. When the amplitude of the modulating waveform is at positive peak value, the phase of the
outputted signal increase one phase shift, and when it is at the negative peak value, the phase of the
outputted signal decrease one phase shift.
5.6.2. Modulation frequency
Press
【
Menu
】
key and select “Mod_f” option and then set modulation frequency value. In PM, modulation
frequency is usually far lower than carrier frequency.
5.6.3. Modulation waveform
Press
【
Menu
】
key and select “Shape” option, set modulation waveform by setting waveform No., the
modulation waveform may be any one of the 16 kinds of waveforms listed in the waveforms table.
5.6.4. Modulation source
Press
【
Menu
】
key, select “Source” option and then set modulation source, there are only two values to
choose: 0 and 1. Set the value as 0 to choose internal modulation source, and set it as 1 to choose external
modulation source. If external modulation source is chosen, connect a modulation signal to the
《
Modulation
In
》
port on the rear panel of the generator. When external modulation signal reaching to full amplitude as
±5 V, the display of phase deviation accords with its real value. Or the display of phase deviation is incorrect.
3.6.5 Sync output: in PM, 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 frequency and its
phase is referenced to the phase of the modulating signal.
In PM, press
【
PM
】
key, the “PM” indicator will be off, the generator exits PM function and returns back to
continuous function.
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