Refer to figures.
Amplitude modulation is a process by which the wave signal is transmitted by modulating the amplitude of the signal.
It is often called as AM and is commonly used in transmitting a piece of information through a radio carrier wave.
Amplitude modulation is mostly used in the form of electronic communication.
Currently, this technique is used in many areas of communication such as in portable two-way radios, citizens band radio, VHF aircraft radio and in modems for computers.
Amplitude modulation is also used to mention the mediumwave AM radio broadcasting.
In general, amplitude modulation definition is given as a type of modulation where the amplitude of the carrier wave is varied in some proportion with respect to the modulating data or the signal.
As for the mechanism, when amplitude modulation is used there is a variation in the amplitude of the carrier.
Here, the voltage or the power level of the information signal changes the amplitude of the carrier.
In AM, the carrier does not vary in amplitude.
However, the modulating data is in the form of signal components consisting of frequencies either higher or lower than that of the carrier.
The signal components are known as sidebands and the sideband power is responsible for the variations in the overall amplitude of the signal. (refer to annex1)

The AM technique is totally different from frequency modulation and phase modulation where the frequency of the carrier signal is varied in the first case and in the second one the phase is varied respectively.

Why Do We Need Modulation?

Practically speaking, modulation is required for;

• High range transmission

• Quality of transmission

• To avoid the overlapping of signals.

Difference Between AM And FM

Amplitude modulation and frequency modulation are used to transmit data using the method of modifying a carrier signal.
The AM technique is totally different from frequency modulation and phase modulation where the frequency of the carrier signal is varied in the first case and in the second one the phase is varied respectively. (refer to annex 2)

Amplitude Modulation

Amplitude modulation is a modulation technique where the amplitude of a carrier varies depending on the information signal.
AM radio broadcast signals use lower carrier frequencies, this helps them to travel long distances. Sometimes AM signals can be able to bounce off the ionosphere.
The distance travelled by the AM is much larger than the FM.

Frequency Modulation

In this module, the frequency of the carrier wave is modified according to the signal that carries information.
The radio signals have large bandwidth than AM radio signals, which helps to offer much better sound quality.
Frequency modulation also enables to transmit stereo signals.