# Signals and Systems ŌĆō Properties of Even and Odd Signals

## Even Signal

A signal is said to be an even signal if it is symmetrical about the vertical axis or time origin, i.e.,

­Øæź(­ØæĪ) = ­Øæź(−­ØæĪ); for all ­ØæĪ … continuous time signal

­Øæź(­Øæø) = ­Øæź(−­Øæø); for all ­Øæø … discrete time signal

## Odd Signal

A signal is said to be an odd signal if it is anti-symmetrical about the vertical axis, i.e.,

­Øæź(−­ØæĪ) = −­Øæź(­ØæĪ); for all ­ØæĪ … continuous time signal

­Øæź(−­Øæø) = −­Øæź(­Øæø); for all ­Øæø … discrete time signal

## Properties of Even and Odd Signals

Addition and Subtraction Properties of Even and Odd Signals

• The addition or subtraction of two odd signals is also an odd signal, i.e.,

odd signal ± odd signal = odd signal

• The addition or subtraction of two even signals is also an even signal, i.e.,

even signal ± even signal = even signal

• The addition or subtraction of an odd signal and an even signal is a signal which is neither even nor odd, i.e.,

odd signal ± even signal = neither even nor odd

• The addition of the dc component and even signal is an even signal, i.e.,

DC component + even signal = even signal

• The addition of the dc component and odd signal is a signal that is neither even nor odd, i.e.,

DC component + odd signal = neither even nor odd

### Multiplication Properties of Even and Odd Signals

• The product of two even signals is also an even signal, i.e.,

even signal × even signal = even signal

• The product of two odd signals is an even signal, i.e.,

odd signal × odd signal = even signal

• The product of an even signal and an odd signal (or an odd signal and an even signal) is an odd signal, i.e.,

odd signal × even signal = even signal × odd signal = odd signal

### Division Properties of Even and Odd Signals

• The division of two odd signals results an even signal, i.e.,

$$\mathrm{\frac{odd\: signal}{odd \: signal}= even\: signal}$$
• The division of two even signals results an even signal, i.e.,

$$\mathrm{\frac{even\: signal}{even \: signal}= even\: signal}$$
• The division of an odd signal by an even signal results an odd signal, i.e.,

$$\mathrm{\frac{even\: signal}{odd \: signal}= odd\: signal}$$

### Differentiation Properties of Even and Odd Signals

• The differentiation of an odd signal is an even signal, i.e.,

$$\mathrm{\frac{\mathrm{d} }{\mathrm{d} t}\left ( odd\:signal \right )= even\: signal}$$
• The differentiation of an even signal is an odd signal, i.e.,

$$\mathrm{\frac{\mathrm{d} }{\mathrm{d} t}\left ( even\:signal \right )= odd\: signal}$$

### Integration Properties of Even and Odd Signals

• The integration of an odd signal is an even signal, i.e.,

$$\mathrm{\int \left ( odd\: signal \right )= even\: signal}$$
• The integration of an even signal is an odd signal, i.e.,

$$\mathrm{\int \left ( even\: signal \right )= odd\: signal}$$

## Important Expressions for Even and Odd Signals

Some important expressions for the continuous-time and discrete-time even and odd signals are given in the table below −

Continuous-Time SignalDiscrete-Time Signal
$\mathrm{\int_{-\infty }^{\infty }\:x_{0}\left ( t \right )dt = 0}$
$\mathrm{\sum_{n=-\infty }^{\infty }\: x_{0}\left ( n \right )= 0}$
$\mathrm{\int_{-\infty }^{\infty }\:x_{e}\left ( t \right )dt = 2\int_{0}^{\infty }\:x_{e}\left ( t \right )dt}$
$\mathrm{\sum_{n=-\infty }^{\infty }\: x_{e}\left ( n \right )= x\left ( 0 \right )+2\sum_{n=1}^{\infty }\: x_{e}(n)}$
$\mathrm{\int_{-\infty }^{\infty }\:x_{e}\left ( t \right ).\:x_{0}\left ( t \right )dt = 0}$
$\mathrm{\sum_{n=-\infty }^{\infty }\: x_{e}\left ( n \right ).\: x_{0}\left ( n \right )= 0}$
$\mathrm{\int_{-\infty }^{\infty }\:x^{2}\left ( t \right )dt =\int_{-\infty }^{\infty }\: x_{e}^{2}\left ( t \right )dt\, +\, \int_{-\infty }^{\infty }\: x_{0}^{2}\left ( t \right )dt}$
$\mathrm{\sum_{n=-\infty }^{\infty }\:x^{2}\left ( n \right )dt = \sum_{n=-\infty }^{\infty }x_{e}^{2}(n)\, +\, \sum_{n=-\infty }^{\infty }x_{0}^{2}(n)}$