Classification of Signals
Signals classified on the basis of various categories. Some of the basis categories and its classification is discussed below:
On the Basis of Type
Signals can be classified on the basis of its type into following two groups:
- Analog Signal
- Digital Signal
Analog Signal
In analog signal, the physical quantities such as current or voltage varies continuously with time. These signals get stored in the form of wave signal. It also has low impedance. Example- Sinusoidal wave, triangular wave, etc.
Digital Signal
In digital signal, the physical quantities such as current or voltage can have only one of the two possible values at a time, i.e., digital signal have only levels, either zero or some maximum finite value of current or voltage. These signals get stored in the form of binary bit. It is having high impedance which may reach to 100 megaohms.
On the Basis of Time
Signals can be classified on the basis of its nature into following two groups:
- Continuous Time Signal
- Discrete Time Signal
Continuous Time Signal
In continuous-time signal at each point of time, signal will have some continuous values. These of signals can be analyzed using techniques such as Fourier or Laplace transformations. It requires more space than discrete-time signal because it has to be firstly sampled before transmission. This signal has infinite bandwidth and can be represented using signals like sine or cosine waves.
Discrete Time Signal
In discrete-time signal at each point of time, signal will have distinct or discontinuous values. These types of signals can be analyzed using techniques like discrete Fourier transformations or z-transformations. It requires less space than continuous-time signal as they are represented by some specific set of numbers. Discrete-time signal has finite bandwidth.
On the Basis of Nature
Signals can be classified on the basis of its nature into following two groups:
- Periodic Signal
- Aperiodic Signal
Periodic Signal
A periodic signal have constant frequency and have a characteristic signal which repeats itself at regular intervals, i.e., it has a repeating waveform. At some specific frequencies this type of signal has high concentration of energy. These signals are commonly used in communication centers. Some of the common examples of periodic signals are square wave, triangular wave, sine wave, etc.
Aperiodic Signal
A aperiodic signal also referred as non-periodic signal does not repeat itself at regular intervals, i.e., it does not have repeating waveform. non- periodic signal’s energy is distributed over whole range of frequencies. Non-periodic signals are commonly used in study of chaotic systems. Some of the common examples of aperiodic signals are noise, speech, etc.
On the basis of Behaviour
Electric signals can be classified on the basis of its behaviour into following two groups:
- Deterministic signal
- Random Signal
Deterministic signal
Deterministic signal is the type of signal that follows a fixed and regular pattern means it can be determined and accurately produced. This type of signal has well-defined wavelength, frequency and phase.
Random Signal
Random signal is a type of signal that has irregularity means it cannot be determined and cannot be accurately produced. This type of signal lacks regularity and has out of phase wavelength, frequency and pulse width.
On the basis of Symmetry
Signals can be classified on the basis of its symmetry into following two groups:
- Even Signal
- Odd Signal
Even Signal
The signal which is symmetrical about its vertical axis is called as even signal. Hence, it is also called as symmetrical signal. Even signal has same value of current or voltage for both positive and negative time interval.
Mathematically, it is represented as:
f(t) = f(-t)
Example of even signal is cosine signal.
Odd Signal
The signal which lacks symmetry about its vertical axis but has rotational symmetry (Anti symmetrical about origin) is called as odd signal. Hence, it is also called as asymmetrical signal. Odd signal has negative value of current or voltage when positive time interval(t) is replaced by negative time interval(-t).
Mathematically, it is represented as:
f(t) = -f(-t)
Example of odd signal is sinusoidal signal.
What are the Different Types of Signals?
An electrical signal is a physical quantity that varies with time. It varies with any dependent or independent quantity. A signal can either be one-dimensional or multi-dimensional. When the function which varies with time depends only on a single variable then that type of signal is referred to as a one-dimensional signal. Examples of such signals are audio signals, biometrics like pulse or heartbeat, light wave signals, etc. On the other hand, a signal that is dependent on more than one time-dependent variable, then that type of signal is known as a multi-dimensional signal. Examples of two-dimensional signals are electromagnetic signals, video signals, etc. A signal is a mathematical representation of energy.
Thus, signal is a time-dependent function that can be dependent on one or more than one physical quantity for the transference of data and information with or without the presence of the medium. Electromagnetic wave signals can travel in a vacuum whereas sound and electrical signals require a medium for their propagation.
Table of Content
- Signals
- Characteristics of Signal
- Operations on Signal
- Classification of Electric Signals
- Applications of Signals
- Advantages of Signals
- Disadvantages of Signals