Question

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?

Answer 1

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)

∴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:

The angular frequency of the carrier signal is calculated as:

From equations (i) and (ii), we get:

The amplitude modulated waveform of the modulating signal is shown in the following figure.

(ii)Modulation index,