Principles of Communication Modulation - Principles of Communication

What is Principles of Communication Modulation?

A signal can be something like a sound wave which comes out when you shout. This shout can be received merely up to a certain distance. But for the similar wave to travel over a long distance, you’ll need a method which adds asset to this signal, without worrying the parameters of the original signal.

What is Signal Modulation?

A message carrying signal has to get communicated over a space and for it to create a trustworthy communication; it needs to take the help of a high frequency signal which should not move the original characteristics of the message signal.

The characteristics of the message signal, if altered, the message limited in it also alters. Therefore it is a necessity to take care of the message signal. A high frequency signal can travel up to a longer distance, without getting pretentious by external conflicts. We take the help of such high frequency signal which is called as a carrier signal to transmit our message signal. Such a procedure is merely called as Modulation.

Modulation is the procedure of altering the parameters of the carrier signal, in accordance with the on the spot values of the modulating signal.

Need for Modulation

The baseband signals are mismatched for direct transmission. For such a signal, to travel lengthier distances, its strength has to be increased by reducing with a high frequency carrier wave, which doesn’t move the parameters of the modulating signal.

Advantages of Modulation

The antenna used for communication, had to be precisely large, if modulation was not presented. The range of communication gets partial as the wave cannot travel to a distance without getting distorted.

Resulting are some of the benefits for applying modulation in the communication systems.

  • Antenna size gets reduced.
  • No signal mixing occurs.
  • Communication range increases.
  • Multiplexing of signals occur.
  • Adjustments in the bandwidth is allowed.
  • Reception quality improves.

Signals in the Modulation Process

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

Message or Modulating Signal

The signal which comprises a message to be transmitted is called as a message signal. It is a baseband signal, which has to experience the procedure of modulation, to get transmitted. Therefore, it is also called as the modulating signal.

Carrier Signal

The high frequency signal which has an assured phase, frequency, and amplitude but comprises 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 subsequent signal after the procedure of modulation is called as the modulated signal. This signal is a combination of the modulating signal and the carrier signal.

Types of Modulation

There are numerous types of modulations. Contingent upon the modulation techniques used, they are categorized as shown in the resulting figure.


The kinds of modulations are generally classified into continuous-wave modulation and pulse modulation.

Continuous-wave Modulation

In the continuous-wave modulation, a high frequency sine wave is used as a carrier wave. This is further divided into amplitude and angle modulation.

  • If the amplitude of the high frequency carrier wave is varied in agreement with the immediate amplitude of the modulating signal, then such a technique is called as Amplitude Modulation.
  • If the angle of the carrier wave is different, in accordance with the instant value of the modulating signal, then such a technique is called as Angle Modulation.

The angle modulation is further divided into frequency and phase modulation.

  • If the frequency of the carrier wave is varied, in accordance with the instantaneous value of the modulating signal, then such a technique is called as Frequency Modulation.

  • If the phase of the high frequency carrier wave is varied in accordance with the instantaneous value of the modulating signal, then such a technique is called as Phase Modulation.

Pulse Modulation

In Pulse modulation, a periodic sequence of rectangular pulses is used as a carrier wave. This is additionally separated into analog and digital modulation.

In analog modulation method, if the amplitude, duration or position of a pulse is different in accordance with the instant values of the baseband modulating signal, then such a technique is called as Pulse Amplitude Modulation (PAM) or Pulse Duration/Width Modulation (PDM/PWM), or Pulse Position Modulation (PPM).

In digital modulation, the modulation method used is Pulse Code Modulation (PCM) where the analog signal is changed into digital form of 1s and 0s. As the subsequent is a coded pulse train, this is called as PCM. This is additionally developed as Delta Modulation (DM), which will be talk over in subsequent chapters. Therefore, PCM is a method where the analog signals are changed into a digital form.

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