• A signal can be anything like a sound wave which comes out when you shout. This shout can be heard only up to a certain distance. But for the same wave to travel over a long distance, you’ll need a technique which adds strength to this signal, without disturbing the parameters of the original signal.

• A message carrying signal has to get transmitted over a distance and for it to establish a reliable communication, it needs to take the help of a high frequency signal which should not affect the original characteristics of the message signal.

• High frequency signal which is called as a carrier signal to transmit our message signal. Such a process is simply called as Modulation.

• Modulation is the process of changing the parameters of the carrier signal, in accordance with the instantaneous values of the modulating signal.

• For a signal, to travel longer distances, its strength has to be increased by modulating with a high frequency carrier wave, which doesn’t affect the parameters of the modulating signal.

Advantages of Modulation:

• Antenna size gets reduced.

• No signal mixing occurs.

• Communication range increases.

• Adjustments in the bandwidth is allowed.

• Reception quality improves.

Following are the three types of signals in the modulation process.

• Message or Modulating Signal: The signal which contains a message to be transmitted, is called as a message signal. It is a baseband signal, which has to undergo the process of modulation, to get transmitted. Hence, it is also called as the modulating signal.

• Carrier Signal: The high frequency signal which has a certain frequency, and amplitude but contains no information, is called a carrier signal. It is an empty signal. It is just used to carry the signal to the receiver after modulation.

• Modulated Signal: The resultant signal after the process of modulation, is called as the modulated signal. This signal is a combination of the modulating signal and the carrier signal.