GW Instek GRF-1300A - Manual (Page 73)

RF Communication and Signals Experiments
And the carrier signal is
u
c
(t) = U
cm
cosω
c
t = U
cm
cos2πf
c
t
An FM signal varying to changes in the modulating signal is shown
in Figure 6-1.
Figure 6-1.
An FM signal
varying to the
change of a
modulating
signal
t
t
t
u
Ω
c
u
u
In the positive half-period of the modulating signal, the
frequency of the modulated signal is higher than the frequency of
the carrier signal. At the peak of the positive half-period, the
angular frequency of the modulated signal is at its peak.
In the negative half-period of the modulating signal, the
frequency of the modulated signal is lower than the frequency of
the carrier signal, and its angular frequency is at its lowest. The
angular frequency ω of an FM wave changes in response to changes
in the modulation signal.
Then ω=ω
c
+ΔωcosΩt
In this formula, ω
c
is the angular frequency of the carrier wave, Δω
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