What are signals and different classifications of Signals in Communication

What are signals and different classifications of Signals in Communication
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Electronics and Communication is a wide topic which explains lot of theories and physical phenomena. Today our major part of life is dependent on the communication system. Here we will study one of the physical phenomena which are Signals. Here we are going to talk about the different type of signals in communication and how they are different from each other .

Signals consists of information in many form of variations. Signals are basically the function of one or more than one variable. It consists of the useful information about the nature and behavior of phenomena. Most common example of signals are the Voltage and Current.

Different Types of Signals in communication

Signals can be generally as Continuous time (x(t)) and Discrete Time (y(t)) Signals. Signals can be categorized into four types which are:

  1. Continuous Time Non-Periodic Signals
  2. Continuous Time Periodic Signals
  3. Discrete Time Non-Periodic Signals
  4. Discrete Time Periodic Signals

Classification of Signals

There are six major classification of any signal existing. These can be classified into:

  1. Continuous time and Discrete time Signals
  2. Analog and Digital Signals
  3. Periodic and Non-Periodic Signals
  4. Energy and Power Signals
  5. Deterministic and Random Signals
  6. Odd and Even Signals

Below we will know about each type of signal in brief.

Types of signals # 1

Continuous time and Discrete time Signal: Continuous signal are those signal which can be specified for each and every value of time ‘t’.

For example: x(t) = A cos(wt) where -∞ < t< ∞

continuous signal with time and amplitude

A signal which can be obtained for discrete values of ‘t’ is called discrete signal.

For Example: x(nT) = A cos(wnT) where n is only the integer values and t is defined over real number line.

Classification_of_Signals, discrete signal


  • These both qualify the nature along the horizontal x-axis i.e. time.

Types of signals # 2

Analog and Digital Signal: Signal which can take any value of amplitude in continuous range is Analog Signal i.e it can have infinite range of values. Signal whose amplitude can have only finite number of value is Digital Signal.


  • These both qualify the nature along the vertical y-axis i.e. amplitude.

Types of signals # 3


Periodic and Non-Periodic Signal: As the name suggest periodic, that means if the signal is periodic in nature i.e repeat itself after certain interval of time then it is periodic signal (P). For signal to be periodic it should be defined in infinite duration. For the signal which are in finite duration are non-periodic signals (NP).

While if the signal does not repeat itself after certain interval of time then it is non-periodic in nature.


  • Periodic Signal + Periodic Signal = In continuous time domain result in non-periodic signal
  • Periodic Signal + Periodic Signal = In discrete time domain result in periodic signal

Types of signals in communication # 4

Energy and Power Signal: Signal which follows and satisfies the below condition is called Energy Signal.

0\lt \int_{- \infty}^{\infty}|x(t))| ^{2}dt \lt \infty, signal equation

Signal which satisfies the below condition is called the Power Signal.

0\lt \lim_{{T->\infty}} 1/T \int_{<T>}^{}|x(t))| ^{2}dt \lt \infty Note:

  • Periodic Signals are always Power Signals.
  • Periodic Signals always have infinite energy hence these are not Energy signals.
  • Non-Periodic signals are bounded in nature hence acquire zero Power and are Energy signals.
  • No signal can be Power and Energy signal simultaneously.

Types of signals in communication # 5


Deterministic and Random Signals: Signal where physical description (Mathematical or Graphical) are known are known as Deterministic Signals.

Classification of Signals, deterministic

While the signals which are known for its probabilistic description (mean value, mean squared value and other) is called Random Signal.

Classification of Signals, random, signal

Types of signals # 6


Even and Odd Signal: There are condition which defines whether the signal is even or odd signal.

A signal is even if it follows:

  • x(t) = x(-t) for continuous time signal &
  • x[n] = x[-n] for discrete time signal

Odd signal are those which follows the following condition:

  • x(t) = – x(-t) for continuous time signal &
  • x[n] = – x[-n] for discrete time signal

x_{{odd}} (t)=(x(t) - x(-t))\div2

x_{{even}} (t)=(x(t) + x(-t))\div2

x_{{even}} [n]=(x[n] + x[-n])\div2

x_{{odd}} [n]=(x[n] - x[-n])\div2


  • The total area under the odd signal is always Zero, hence average value for same is zero.
  • A single signal may contain both even and odd part.

So, this was all about the Signals and their different types . For more about Classification of Signals and different types of signals in communication , Stay in touch . If you have any queries related to any such topics, do comment and we will surely entertain you. In case, any specific topics needs to be discussed on our website, we welcome & give our audience the first priority. Hit the like button and share the post with your friends who need help with this topic.

Also check our latest article on Arithmetic Coding Solved Numerical for Exams

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