A modulating signal is a square wave, as shown in Fig. 15.14.
The carrier wave is given by
(i) Sketch the amplitude modulated waveform
(ii) What is the modulation index?
It can be observed from the given modulating signal that the amplitude of the modulating signal, A m = 1 V
It is given that the carrier wave c (t) = 2 sin (8πt)
Therefore, Amplitude of the carrier wave, A c = 2 V
Time period of the modulating signal T m = 1 s
The angular frequency of the modulating signal is calculated as: ωm = 2π/Tm
= 2π rad s-1 .......(i)
The angular frequency of the carrier signal is calculated as: ωc = 8π rad s-1 ....(ii)
From equations (i) and (ii), we get:
= ωc = 4ωm
The amplitude modulated waveform of the modulating signal is shown in the following figure.
( ii ) Modulation index, m = Am/Ac = 1/2 = 0.5
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