This document defines and describes different types of systems. A system takes a signal as input and transforms it into an output signal. There are several ways to classify systems, including whether they are static or dynamic, causal or non-causal, linear or non-linear, time-invariant or time-varying, stable or unstable, and invertible or non-invertible. For example, a static system is memoryless and its output depends only on the present input values, while a dynamic system is one with memory where the output depends on past and future input values.

1. Systems
By
Md. Fazle Rabbi
16CSE057

2. 4.2
What is System?
 Systems process input signals to produce output signals.
 A system is combination of elements that manipulates one
or more signals to accomplish a function and produces
some output
A communication system is generally composed of three
subsystems, the transmitter, the channel and the receiver. The
channel typically attenuates and adds noise to the transmitted
signal which must be processed by the receiver
Example

3. 4.3
How is a System Represented?
A system takes a signal as an input and transforms it
into another signal

4. 4.4
Types of System
Both continuous-time and discrete-time systems are
further classified as follows:
1. Static (memoryless) and dynamic (memory) systems
2. Causal and non-causal systems
3. Linear and non-linear systems
4. Time-invariant and time varying systems
5. Stable and unstable systems.
6. Invertible and non-invertible systems
7. Continuous and Discrete systems

5. 4.5
Static and Dynamic System
A static system is memoryless system
It has no storage devices
its output signal depends on present values of the
input signal
For example

6. 4.6
Static and Dynamic System cont’d
 A dynamic system possesses memory
 It has the storage devices
 A system is said to possess memory if its output signal
depends on past values and future values of the input
signal
For example

7. 4.7
Causal and Non-Causal System
Causal system : A system is said to be causal
if the present value of the output signal
depends only on the present and/or past
values of the input signal.
Example:
y[n]=x[n]+1/2x[n-1]

8. 4.8
Non-causal system : A system is said to be
anticausal if the present value of the output
signal depends only on the future values of
the input signal.
Example:
y[n]=x[n+1]+1/2x[n-1]
Causal and Non-Causal System

9. 4.9
Linear & Non Linear System
A system is said to be linear if it satisfies the principle of
superposition
For checking the linearity of the given system, firstly we
check the response due to linear combination of inputs
Then we combine the two outputs linearly in the same
manner as the inputs are combined and again total
response is checked
If response in step 2 and 3 are the same, the system is
linear otherwise, it is non linear.

10. 4.10
Superposition Property
Superposition property means a system which
produces an output y1(n) for an input x1(n) and an
output y2(n) for an input x2(n) must produce an
output y1(n) + y2(n) for an input x1(n) + x2(n).

11. 4.11
Time Invariant and Time Variant System
A system is said to be time invariant if a time delay or
time advance of the input signal leads to a identical
time shift in the output signal.

12. 4.12
Stable and Unstable System
A system is said to be bounded-input bounded-output
stable (BIBO stable) if every bounded input results in
a bounded output.

13. 4.13
Invertible and Non-invertible System
 Invertible : Input Signal can be recovered
 Non-Invertible : Input Signal can’t be recovered
from output signal

14. 4.14
Thank You