# Different Types of Signals

Signals can be classified into different categories, as given below.

- Continuous-time and discrete-time signals
- Periodic and non-periodic signals
- Odd and even signals

# Continuous-time and Discrete-time Signals

Signals are represented mathematically as function of one or more independent variables. We classify signals as being either continuous-time (functions of a real-valued variable) or

**(functions of an integer-valued variable).***discrete-time*In other words, a continuous-time signal has a value defined for each point in time and a discrete-time signal is defined only at discrete points in time.

**(a) Continuous-time signal**

**(b) Discrete-time signal**

# Periodic and Non-Periodic Signals

A signal

*f*(*t*) is said to be periodic if*f*(

*t*) =

*f*(

*t*Â±

*nT*)

where

*n*is a positive integer and '*T*' is the period. Thus, a periodic signal repeats itself every*T*seconds. Some periodic signals are shown in the figure.**Periodic signals**

A signal not satisfying the above condition of Eq. is called a non-periodic signal. Examples of some non-periodic signals are

*eâ€™*,*t*, etc.# Odd and Even Signals

A signal

*f*(*t*) is said to be odd if*f*(

*t*) = â€“

*f*(â€“

*t*)

Some examples of odd signals are sine functions, triangular functions and square function, as shown in figure.

**Odd signals**

A signal

*f*(*t*) is said to be even if*f*(

*t*) =

*f*(â€“

*t*)

Some examples of even signals are shown in figure.

**Even signals**