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Phase Modulation (PM)
PM is similar to FM, but the phase of the carrier waveform is varied, rather than the frequency:
y(t)=sin[ω
t+d•m(t) ]
c
where m(t) is the modulating signal and d is the phase deviation.
Frequency-Shift Keying (FSK) Modulation
FSK is similar to FM, except the carrier frequency alternates between two preset values, the carrier frequency and
the hop frequency. Sometimes the hop and carrier frequencies are called "Mark" and "Space," respectively. The rate
at which the switching between these values occurs is determined by an internal timer or the signal on the front
panel Ext Trig connector. Frequency changes are instantaneous and phase-continuous.
The internal modulating signal is a square wave with 50% duty cycle.
The top trace below represents the modulating signal; the bottom trace represents the modulated carrier.
Binary Phase Shift Keying (BPSK)
BPSK is similar to FSK, except it is the carrier's phase, rather than its frequency, that switches between two values.
The rate at which the switching between these values occurs is determined by an internal timer or the signal on the
front panel Ext Trig connector. Phase changes are instantaneous.
The internal modulating signal is a square wave with 50% duty cycle.
Pulse Width Modulation (PWM)
PWM is only available for the Pulse waveform, and the pulse width varies according to the modulating signal. The
amount by which the pulse width varies is called the width deviation, and it can be specified as a percentage of the
waveform period (that is, duty cycle) or in units of time. For example, if you specify a pulse with 20% duty cycle and
then enable PWM with a 5% deviation, the duty cycle varies from 15% to 25% under control of the modulating
signal.
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Keysight EDU33210 Series User's Guide
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