Transcript LectureNotes1 - UniMAP Portal

Welcome to the subject
EKT 231
COMMUNICATION SYSTEM
LECTURERS
1.
2.
En. Rosnazri Bin Ali
04-9851626
[email protected]
Pn. Siti Rafidah Bt. Abdul rahim
04-9798909
[email protected]
SYNOPSIS
The aim of this subject is :
to introduce the students with the basic principles and components of
communications system.
This subject will cover various topics such as:





Introduction to Communication System,
Analog Modulation and Demodulation (e.g. Amplitude Modulation),
Angle Modulation (Frequency Modulation and Phase Modulation),
Digital Modulation,
Noise in Communication System, Transmission System and Transmission
Lines.
OBJECTIVES




To understand the basic components in a wire line
and wireless communication system for analog and
digital transmission.
To emphasize on the importance of modulation and
demodulation of analog signals along with associated
system design issues.
To introduce the student with the types of analogue
and digital modulation techniques those are used in
present telecommunication system.
To characterize amplitude, double-sideband and
single sideband modulated waveforms in the time and
the frequency domains.
OBJECTIVES (Cont’d)





To characterize frequency and phase modulated signals
in the time domain and tone modulated signals in the
frequency domain.
To study the quantization process in a pulse code
modulation system in terms of how it is created and
how to minimize its effect.
To study the characteristic of noise and its effect on the
communications system.
To study and analyze the modulated analog and digital
signals performance in the presence of additive noise.
To enhance the students’ knowledge on transmission
line those are used in communication system.
References

Wayne Tomasi, “ Electronic Communication
Systems Fundamentals Through Advanced” 5th Ed,
Prentice Hall, 2004.

Paul Young, “Electronics Communications
Techniques”, 5th Edition, Prentice Hall, 2004.

Mullet , “Basic Telecommunications:The Physical
Layer”, Thomson Learning, 2003.
Assessment

Final Exam = 50 %

Coursework = 50 %
Test x2
 Labs


= 15 %
= 30 % (lab work 20%, lab
test 10%)
Assignments/quizzes = 5%
CHAPTER 1
INTRODUCTION TO
COMMUNICATION SYSTEM
Definitions

Communications:
 Transfer of information from one place to
another.
 Should be efficient, reliable, and secured.

Communication system:
 components/subsystems act together to
accomplish information transfer/exchange
Definitions (Cont’d)
Electronic communication system
 transmission, reception and processing
of information between two or more
locations using electronic circuits.
 Information source
 analog/digital form

Information, message and signals



Information
 The commodity produced by the source for
transfer to some user at the destination.
Message
 The physical manifestation of information as
produced by the information source.
Signals
 A physical embodiment of information –
voltage signal or current signal
Need For Communication

Importance of communication:
exchange of information between two
parties separated in distances in a more
faster and reliable way.
Information transfer system block diagram
Information sources
> Audio
Processing
> Video
(modulator)
> Data
(with their respective
transducers)
Reproduced information
Audio
Video
Data
Transducers
Transmitter
Transmission
medium
Receiver /
Processing
(demodulator)
Think!

Have you ever pictured yourself living in a
world without any communication system?
Development and progress


Communications between human beings
 Form of hand gestures and facial expressions
 Verbal grunts and groans
Long distance communications
 Smoke signals
 Light, mirror reflection
 Telegraph
 Telephone
Cont’d…

Wireless radio signals
 Spark-gap transmitter
 Continuous carrier wave transmitter (with the
invention of triode vacuum tubes)
 Commercial radio broadcasting
 Satellite communications
 Mobile telephones
Early wireless telegraph station
(using spark-gap transmitter)
Transmitter
Receiver
Notice that the person is wearing a belt that full with vacuum tubes !
Vacuum tube
The first transistor
Brief History in Communication
Year
1844
1862
1876
1888
1895
1904
1906
Events
Telegraph – Samuel B. Morse
Prediction of electromagnetic
waves propagation through a vacuum
– James Clerk Maxwell
Telephone – Alexander Graham Bell
Proved of EM waves existence –
Heinrich Hertz
Wireless telegraph – G. Marconi
Invention of diode vacuum tube – John
Fleming
Invention of triode vacuum tube – Lee
de Forest
cont’d….
Year
1906
1920
1923
1933
1941
1948
Events
Amplitude modulation (AM) –
Reginald Fessenden
1st radio broadcast (AM, in US)
Television - Vladimir Zworykin
Frequency modulation (FM) –
Edwin H. Armstrong
FM radio broadcast (US)
Invention of transistor
cont’d….
1957
1966
1972
1989
First satellite (Sputnik,
Russia)
Optical links using laser and
fiber optics
Cellular Telephone
Internet
Analog vs. Digital


Analog
 Continuous Variation
 Assume the total range of
frequencies/time
 All information is transmitted
Digital
 Takes samples:
 non continuous stream of on/off pulses
 Translates to 1’s and 0’s
Analog vs. Digital
Digital CS
Advantages:
-Privacy preserved(data
encrypted)
-Can merge different data
-error correction
- high immunity to noise

Disadvantages:
-synchronization problem
is relatively difficult
Analog CS
Disadvantages:
-No privacy preserved
-Cannot merge different
data
-No error correction
capability
- Susceptible to noise
Advantages:
-synchronization problem
is relatively easier.

Basic Requirements of
Communication System




Rate of information transfer:
 how fast the information can be transferred
Purity of signal received:
 whether the signal received is the same as the
signal being transmit
Simplicity of the system
 the simpler the system, the better
Reliability
Trade-off between analog and digital
modulations
Analog modulation
Wide bandwidth
medium
Simple modulation
and hardware
Digital modulation
Complex modulation
and hardware
Simple demodulation
and hardware
Narrow bandwidth
medium
Complex
demodulation
and hardware
Signals and Systems Defined



A signal is any physical phenomenon which
conveys information
Systems respond to signals and produce new
signals
Excitation signals are applied at system
inputs and response signals are produced at
system outputs
A Communication System as a
System Example


A communication system has an information
signal plus noise signals
This is an example of a system that consists of an
interconnection of smaller systems
Signal Types
Conversions Between Signal Types
Sampling
Quantizing
Encoding
Sound Recording System
Recorded Sound as a Signal Example

“s” “i” “gn” “al”
W2-1
Elements of Communication
System(CS)
Elements of CS(cont’d)

Information
The communication system exists to convey a
message.
 Message comes from information source
 Information forms - audio, video, text or data

cont’d…

Transmitter:
Processes input signal to produce a transmitted signal
that suited the characteristic of transmission channel.
 E.g. modulation, coding, mixing, translate
 Other functions performed - Amplification, filtering,
antenna
 Message converted to into electrical signals by
transducers
 E.g. speech waves are converted to voltage variation
by a microphone

Elements of CS(cont’d)

Channel (transmission media):
a medium that bridges the distance from source to
destination. Eg: Atmosphere (free space), wires,
coaxial cable, fiber optics, waveguide
 signals undergoes degradation from noise ,
interference and distortion

Elements of CS(cont’d)

Receiver:
to recover the message signal contained in the
received signal from the output of the channel, and
convert it to a form suitable for the output
transducer.
 E.g. mixing, demodulation, decoding
 Other functions performed: Amplification, filtering.
 Transducer converts the electrical signal at its input
into a form desired by the system used

Various forms of communication
system




Broadcast: radio and television
Mobile communications
Fixed communication system- land line
Data communication-internet