In this ppt you will find all the basic concepts about signals and its properties.

1. Active Learning Assignment
Electrical Engg. Dept.
oName: Harsh M Shah
oEn no:140410109091
oClass:SY Elect. 2
oSubject: Signals & Systems
oTopic: Classification Of Signals

2.  Signals are variables that carry information.
 It is described as a function of one or more
independent variables.
 Basically it is a physical quantity.It varies
with some independent or dependent
variables.
 Signals can be One-dimensional or
multidimensional.
INTRODUCTION TO SIGNALS

3. Types Of Signals
1.Continous & Discrete Time signals
2.Periodic & Non-periodic signals
3.Deterministic & Random signals
4.Symmetrical & Antisymmetrical
signals
5.Energy & Power signals

4.  Continuous time (CT) and discrete time
(DT) signals
CT signals take on real or complex values as a
function of an independent variable that ranges over
the real numbers and are denoted as x(t).
DT signals take on real or complex values as a
function of an independent variable that ranges over
the integers and are denoted as x[n].
Note the subtle use of parentheses and square
brackets to distinguish between CT and DT signals.

5. ANALOG SIGNALS
Human Voice – best example
Ear recognises sounds 20KHz or less
AM Radio – 535KHz to 1605KHz
FM Radio – 88MHz to 108MHz

6. DIGITAL SIGNALS
 Represented by Square Wave
 All data represented by binary values
 Single Binary Digit – Bit
 Transmission of contiguous group of bits is a
bit stream
 Not all decimal values can be represented by
binary
1 0 1 0 1 0 1 0

7. PERIODIC VS. APERIODIC SIGNALS
 Periodic signals have the property that x(t +
T) = x(t) for all t.
 The smallest value of T that satisfies the
definition is called the period.
 Shown below are an aperiodic signal (left)
and a periodic signal (right).

8.  A causal signal is zero for t < 0 and an non-
causal signal is zero for t > 0
 Right- and left-sided signals
A right-sided signal is zero for t < T and a left-
sided signal is zero for t > T where T can be
positive or negative.
CAUSAL VS. NON-CAUSAL

9. BOUNDED VS. UNBOUNDED
 Every system is bounded, but meaningful signal is
always bounded

10. EVEN VS. ODD
 Even signals xe(t) and odd signals xo(t) are defined
as
xe (t) = xe (−t) and xo (t) = −xo (−t).
 Any signal is a sum of unique odd and even signals.
Using
x(t) = xe(t)+xo(t) and x(−t) = xe(t) − xo(t), yields
xe(t) =0.5(x(t)+x(−t)) and xo(t) =0.5(x(t) − x(−t)).

11. POWER AND ENERGY SIGNALS
 Power Signal
 Infinite duration
 Normalized power is
finite and non-zero
 Normalized energy
averaged over infinite
time is infinite
 Mathematically
tractable
 Energy Signal
 Finite duration
 Normalized energy is
finite and non-zero
 Normalized power
averaged over infinite
time is zero
 Physically realizable
• Although “real” signals are energy signals, we
analyze them pretending they are power signals!