Write two basic modes of communication. Explain the process of amplitude modulation. Draw a schematic sketch showing how amplitude modulated signal is obtained by superposing a modulating signal over a sinusoidal carrier wave.

Two basic modes of communication are-

1.Point to Point Communication

2.Broadcast Communication

In AM, the amplitude of the carrier wave is varied in accordance with the amplitude of the modulating wave.

Let, the carrier wave be given by-

$c\left(t\right)=A_{c}sin{\omega }_{c}t$

Modulating signal is given by;

$m\left(t\right)=A_{m}sin{\omega }_{m}t$

${\omega }_c$ is the angular frequency of the message signal.

Therefore, modulated signal is given by-

$m\left(t\right)=(A_c+A_{m}sin{\omega }_{m}t)sin{\omega }_{c}t$

$=A_c(1+\frac{A_m}{A_c}sin{\omega }_{m}t)sin{\omega }_{c}t$

$\frac{A_m}{A_c}=m$ ( therefore, Modulation Index).

AM signal is produced by superimposing a modulating signal over a sinusoidal carrier wave.