Amplitude Modulation

Amplitude Modulation

Modulation is the process by which one or more properties of the digital or analog signal are varied so that the signal can travel longer distance from its source to destination. We know that the sound wave travels through the medium (air) but while in transit it gets absorbed by objects and hence it won’t travel larger distance. For making it travel large distance it needs to be send such that it won’t be absorbed by the objects in between or the effect of absorption should be very less. For doing this signal has to be modulated such that it can travel the distance.

What is Amplitude Modulation?

AM is the simplest way of modulating a signal. Production of amplitude modulated signals is easy. Also, the requirements are feasible. When an amplitude modulated signal is created, the amplitude of the created signal represents the original baseband signal to be transmitted. This amplitude forms an envelope over the underlying high-frequency carrier wave. Here, the overall envelope of the carrier is modulated to carry the audio signal. However, AM waves are interrupted by electrical and other disturbances which make them weak and noisy.Amplitude ModulationAmplitude Modulation Circuit:Amplitude Modulation CircuitWhere,
M (t) = information bearing signal,
C(t) = Carrier wave
F(t) = amplitude modulated wave.
The signal is passed through the modulator and finally we will be able to get Amplitude Modulated Wave.

Advantages and Disadvantages of Amplitude Modulation:


  1. Simple Implementation.
  2. Less complex circuitry.
  3. Cheaper components so easy to build AM transmitter and receiver.


  1. Power usage in modulation is not efficient.
  2. Bandwidth requirement is very high, the reason is it has to send two sideband along with carrier.
  3. Prone to noise and hence AM transmission is highly noisy.
  4. Difficult to tune in absence of the carrier.

To remove these disadvantages several different approaches are used, some of them are discussed below:
DSBSC (Double Sideband Suppressed Carrier): In this scheme both the side bands are sent while the carrier is suppressed to reduce the wastage of power in the carrier.
SSBSC (Single Sideband Suppressed Carrier): In this scheme one of the side band is sent while the carrier and the other side band are suppressed to reduce the wastage of power in the carrier and the side band.
Vestigial Sideband: It is a compromise between DSB and SSB. In this scheme one complete side band is sent along with the partial other side band.