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What is Modulation?

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Modulation can be digital or analog. Input wave of analog scheme varies continuously like a sine wave. Voice is sampled at some rate then compressed and turned into a bit-stream then superimposed on the carrier signal, in digital modulation. This all happens because the communication systems have used a powerful and beautiful technique called Modulation. 


The process by which data/information is converted into electrical/digital signals for transferring that signal over a medium is called modulation. It increases strength for maximum reach of the signals. The process of extracting information/data from the transmitted signal is called demodulation. A Modem is a device that performs both modulation and demodulation processes. The various forms of modulation are designed to alter the characteristic of carrier waves. The most commonly altered characteristics of modulation include amplitude, frequency, and phase.

Carrier signal: The signals which contain no information but have a certain phase, frequency, and amplitude are called carrier signals.

Modulated signals: The signals which are the combination of the carrier signals and modulation signals are modulated signals. The modulated signal is obtained after the modulation of the signals.

Types of modulation:

1. Amplitude modulation: It is a type of modulation in which only the amplitude of the carrier signal is varied to represent the data being added to the signals whereas the phase and the frequency of the signal are kept unchanged.

Amplitude Modulation

Amplitude Modulation

2. Frequency modulation: It is a type of modulation in which only the frequency of the carrier signal is varied to represent the frequency of the data whereas the phase and the amplitude of the signals are kept unchanged.

Frequency Modulation

3. Phase modulation: It is a type of modulation in which the phase of the carrier signal is varied to represent the data being added to the signal. Different information values are represented by different phases. For example: ‘1’ may be represented by 0° while ‘0’ by 180°.

Phase Modulation

What is the need for modulation?

  • Size of antenna: As we know that the size of the antenna is inversely proportional to the frequency of the radiated signal and antenna size must be 1/10th of the wavelength. If the frequency signals are more than 5KHz in that case it is quite impossible to set up an antenna of that size. So, by using the modulation technique the size of the antenna is reduced.
  • Wireless communication: Modulation provides a wireless connection to transmit the signals to a longer distance. Earlier we used wire systems (like the telephone) to transfer information with the help of telephonic wires but it was not possible to spread the wires all over the world for communication. By using the modulation technique, the cost of wire is saved and even information can be transferred to longer distances faster. 

 Working of Modulation:  

Information/data can be added to the carrier signal by varying its amplitude, frequency, and phase. Basically, modulation is applied to electromagnetic signals like radio waves, optics, and computer networks. It can also be applied to direct current that can be treated as a degenerate carrier wave with a fixed amplitude and frequency of 0 Hz by turning it off and on as in a digital current loop and in Morse code telegraphy. 

Advantages of modulation:

  • It reduces the size of the antenna.
  • It reduces the cost of wires.
  • It prohibits the mixing of signals.
  • It increases the range of communication.
  • It improves the reception quality.
  • It easily multiplexes the signals.
  • It also allows the adjustment of the bandwidth.

Disadvantages of modulation:

  • The cost of the equipment is higher.
  • The receiver and the transmitter are very complicated.
  • For better communication, the antennas for the FM system must be kept closed.
  • It is not efficient for large bandwidth. 
  • Power wastage takes place.
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Last Updated : 24 May, 2022
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