Basics of Electronic Communication

Chapter 1
BASICS OF ELECTRONICS
COMMUNICATION
12 MARKS
08 HOURS
Ms. Kavita Giri
Lecturer (ET)
Government Residential Womens
Polytechnic, Latur

Contents
1.1 The elements of basic electronic communication systems.
1.2 Electromagnetic spectrum – different bands and their applications.
1.3 Transmission modes – simplex, half duplex, full duplex
Synchronous and Asynchronous
1.4 Sources of Noise
1.5 Definition of noise figure and SNR.
22334 – Principles of Electronic Communication
Ms. Kavita Giri, Lecturer (ET), Govt. Residential Womens Polytechnic, Latur

Learning Outcomes
 After completion of this chapter you should be able to:
 Define different terms related to electronic communication.
 Describe the functioning of communication system.
 Identify the various bands in the EM spectrum.
 Identify the various forms of electronic communication.
 Classify different types of noise based on its source.

1.1 Introduction to electronic communication
 The word communication arises from the Latin word
“commūnicāre”, which means ‘to share’.
 Communication is the basic step for the exchange of information.
 For example, a baby in a cradle, communicates with a cry that she
needs her mother. A cow moos loudly when it is in danger. A
person communicates with the help of a language.
 Communication is the bridge to share.

 Communication can be defined as
the process of exchange of
information through means such as
words, actions, signs, etc., between
two or more individuals.
….1.1 Introduction to electronic
communication

 For any living being, while co-existing, there occurs the necessity of exchange
of some information.
 Whenever a need for exchange of information arises, some means of
communication should exist.
 While the means of communication, can be anything such as gestures, signs,
symbols, or a language, the need for communication is inevitable.
 Language and gestures play an important role in human communication,
while sounds and actions are important for animal communication.
 However, when some message has to be conveyed, a communication has to
be established.
1.1.2 Need for
communication

1.1.3 Elements of communication system
Sender
(Transmitter)
Channel Receiver
Person who sends
the message
Source of
information
Sends the message by
speaking, writing or by
doing gestures
Medium through which
message signal travels
channel could
be ‘air’
sender sends the message
signal (sound waves
containing message)
through the air medium
person who receives
the message
has no information
to share but
receives
all TV sets and radios are
receivers.

1.1.3 Elements of communication system

1.2 Communication System
 Communication means sending, receiving and processing of
information between two or more devices.
 Some examples of communication system include radio
broadcasting, television broadcasting, radio telegraphy, mobile
communication, computer communication etc.
A collection of elements (devices) which works together to
establish a communication between the sender and receiver is
called a communication system.

……1.2 Communication System
Block Diagram of a
Communication System

Information
Source
This information
originates in the
information source.
The information
generated by the
source may be in the
form of sound
Input
Transducer
The input transducer
converts the non-
electrical signal
(sound signal or light
signal) into an
electrical signal.
A microphone is a
Transmitter
The transmitter is a
device which
the signal produced
by the source into a
form that is suitable
for transmission over
a given channel or
……1.2 Communication
System

Channel
Medium through
which the signal
travels.
Channel reduces
the signal strength.
Mainly caused by
the addition of
Noise
unwanted signal
that enters the
communication
system via the
communication
channel.
interferes with the
Receiver
Receives the signal
(electrical signal)
from the channel
and converts the
signal (electrical
signal) back to its
original form.

Output
Transducer
Converts the electrical
signal into a non-
electrical signal (sound
signal, light signal, or
both sound and light
signal).
The loudspeaker converts
Destination
Final Stage
Humans at some place are
considered as the destination.
A destination is a place where
humans consume the
information.

1.3 The Electromagnetic spectrum
Radiation
• Whenever a high frequency current flows through a conductor,
the power measured on both the ends is not same.
• A part of the power is dissipated in the resistance of conductor
and a part of it escapes into the free space. This escaped part is
radiation.
Propagation
• This radiated power then propagates in the free space in the
form of electromagnetic waves (EM).
The process of signal travel from transmitter to receiver has been divided into two parts as:

1.3 The Electromagnetic spectrum
Radiation Propagation

…..1.3 The Electromagnetic spectrum
 Electromagnetic waves (or radio waves)
are nothing but oscillations which
propagate in free space.
 They travel at the speed of light.
 These waves consists of moving fields of
electric and magnetic forces, thus known
as electromagnetic (EM) waves.
 The frequency of EM signal ranges from
few Hz to several GHz.
This entire range of frequencies of
EM waves is called as
Electromagnetic Spectrum.

https://youtu.be/1JpwDaOHppA

Sr. No. Frequency Band Applications
01 300 Hz to 3KHz Voice or audio communication
(Used in telephone lines)
02 VLF – 3KHz to 30KHz Submarine, military, navy communication
03 LF – 30KHz to 300KHz Marine, Navigation, also used as subcarrier frequency
04 MF – 300KHz to 3MHz MW band of AM radio broadcast
05 HF- 3MHz to 30MHz SW i.e., short wave band of AM radio
06 VHF – 30MHz to 300MHz TV and FM radio broadcasting
07 UHF – 300MHz to 3GHz UHF TV channels, mobile phones
08 SHF – 3GHz to 30GHz Satellite and Radar
09 EHF – 30GHz to 300GHz Satellite and Radar

1.4 Types of electronic communication
Electronic
Communication
Systems
Direction of
Information
transfer
Simplex
Half
Duplex
Full
Duplex
Nature of
information
Signal
Analog Digital
Technique
of
transmissio
n
Baseban
d
transmiss
ion
Modulati
on
techniqu
e

 1. In simplex mode the data transmits in one
direction only, from one system to another system.
 2. The sender device that sends data can only send
data and cannot receive it. On the other hand the
receiver device can only receive the data and cannot
send it.
 3. Television is an example of simplex mode
transmission as the broadcast sends signals to our
TV but never receives signals back from our TV. This
is a unidirectional transmission.
…..1.4 Types of electronic communication
1.4.1.1 Simplex
Communication

1.4.1.1 Simplex
Communication
Transmitter Receiver
Channel

 Advantages of Simplex Mode:
The full capacity of the transmission medium is utilized as the
transmission is one way and cannot have traffic issues.
 Disadvantages of Simplex Mode:
No bidirectional communication is possible. Two devices cannot
communicate with each other using simplex mode of transmission.
1.4.1.1 Simplex
Communication

 1. In half duplex mode transmission can be done both ways
which means if two systems are connected with half-duplex
mode of transmission, they both can send and receive data
but not at the same time.
 2. If one device is sending data then other device cannot
send data until it receives the data which is already in
transmission. You can say that the communication is not
simultaneous.
 3. The radio communication device that our soldiers use at
the battle fields are the examples of half duplex mode
transmission as they send message and then say over and
then the person on other hand send his message and this
1.4.1.2 Half Duplex
Communication

1.4.1.2 Half Duplex
Communication
Trans-
Receiver1
Trans-
Receiver2
Alpha!!! There
is an
emergency…
Alpha come in…
Delta Over.
Delta!!!
Message
received. Just
reporting…
Alpha Over.
Trans-
Receiver1
Trans-
Receiver2
Transmits
Transmits
Receives
Receives

 Advantages of Half-Duplex mode:
Both devices can send and receive data.
Whole bandwidth can be utilized as at a time only one signal
transmits.
 Disadvantages of Half-Duplex mode:
The disadvantage in half duplex mode is that the other device
cannot send data until it receives the data which is already in
transmission, this can cause delays to the communication.
1.4.1.2 Half Duplex
Communication

 1. In full duplex mode both the
connected devices can send and
receive data simultaneously. The
mobile phone we use is an example
of full duplex mode where we can
communicate simultaneously.
 2. Both the devices can send and
receive the data at the same time.
1.4.1.3 Full Duplex Communication

…..1.4 Types of electronic
communication
Transceiv
er A
Transceiv
er B
Channel

 Advantages of Full Duplex mode:
No delays in communication as both can send and receive data
simultaneously.
 Disadvantages of Full Duplex mode:
No proper bandwidth utilization as the same line is used for sending and
receiving data at the same time.

 An analog
communication system is a
communication system where
the information signal sent from
point A to point B can only be
described as an analog signal.
 An example of this is Monica
speaking to Carl over the
telephone.
1.4.2.1 Analog Communication
System
Hello Carl…
How are you??

 A digital communication system is a
communication system where the information
signal sent from A to B can be fully described as a
digital signal.
 For example, Here, data is sent from one
computer to another over a wire. The computer at
point A is sending 0s or 1s to the computer at
point B;
 0 is being represented by −5 V for a duration of
time T and a 1 is being represented by a +5 V for
the same duration T.
1.4.2.2 Digital Communication
A
B

1.4.3.1 Baseband Transmission
 The input signal to a communication
system is either analog i.e., sound or
picture or digital i.e., computer data.
 Sound or picture is converted into
electrical signal.
 The electrical equivalent of the original
information signal is known as the
baseband signal.
 The communication system in which the
baseband signals are transmitted directly 22334 – Principles of Electronic Communication

1.5 Applications of
Communication
 AM and FM radio broadcasting
 TV broadcasting
 Telemetry
 Cable TV systems
 FAX, Pager,
 Telephones
 Mobile Phones
 Radar

1.8 Noise
 Noise is an unwanted signal which interferes
with the original message signal and corrupts
the parameters of the message signal.
 This alteration in the communication process,
leads to the message getting altered.
 It is most likely to be entered at the channel or
the receiver.
 It is quite random and unpredictable.
Measures are usually taken to reduce it,
though it can’t be completely eliminated.
 Most common examples of noise are −
• Hiss sound in radio receivers
• Buzz sound amidst of telephone
1.8.1 What is
Noise?

 Noise limits the operating range of the systems
Noise indirectly places a limit on the weakest signal that can be
amplified by an amplifier. The oscillator in the mixer circuit may limit its
frequency because of noise. A system’s operation depends on the
operation of its circuits. Noise limits the smallest signal that a receiver
capable of processing.
 Noise affects the sensitivity of receivers
Sensitivity is the minimum amount of input signal necessary to obtain
the specified quality output. Noise affects the sensitivity of a receiver
system, which eventually affects the output.
……1.8 Noise
1.8.2 Effects of
Noise

……1.8 Noise
1.8.3 Classification of
Noise
Noise
External
Atmosp
heric
noise
Extra-
terrestri
al noise
Industri
al
noise.
Internal
Therma
l
agitatio
n noise
Shot
noise
Transit-
time
noise
Miscella
neous
Noise

……1.8 Noise
1.8.3.1 External Noise
 This noise is produced by the external sources which may occur in
the medium or channel of communication, usually.
 This noise cannot be completely eliminated.
 The best way is to avoid the noise from affecting the signal.
 Types of external noise are −
1. Atmospheric noise
2. Extra-terrestrial noise
3. Industrial noise

……1.8 Noise
1. Atmospheric Noise
 Atmospheric noise or static is caused by lighting
discharges in thunderstorms and other natural
electrical disturbances occurring in the atmosphere.
 These electrical impulses are random in nature. Hence
the energy is spread over the complete frequency
spectrum used for radio communication.
 Atmospheric noise accordingly consists of spurious
radio signals with components spread over a wide
frequency range.
 It is propagated over the earth in the same way as the
desired radio waves of the same frequencies, so that a
given receiving point, the receiving antenna picks up
not only the signal but also the static from all the
thunderstorms, local or remote. 22334 – Principles of Electronic Communication

……1.8 Noise
2. Extra-terrestrial Noise
A) Solar Noise:
• This is the electrical noise emanating from the sun.
• Under quite conditions, there is a steady radiation of noise from the sun.
• This results because sun is a large body at a very high temperature (exceeding
6000°C on the surface), and radiates electrical energy in the form of noise over a
very wide frequency spectrum including the spectrum used for radio
communication.
• The intensity produced by the sun varies with time.
• In fact, the sun has a repeating 11-Year noise cycle.
• During the peak of the cycle, the sun produces some amount of noise that causes
tremendous radio signal interference, making many frequencies unusable for

……1.8 Noise
2. Extra-terrestrial Noise
B) Cosmic Noise:
• Distant stars are also suns and have high temperatures.
• These stars, therefore, radiate noise in the same way as our sun.
• The noise received from these distant stars is thermal noise (or
black body noise) and is distributing almost uniformly over the
entire sky.
• We also receive noise from the center of our own galaxy (The

……1.8 Noise
3. Industrial Noise
• It is the electrical noise produced by such sources
as automobiles and aircraft ignition, electrical
motors and switch gears, leakage from high
voltage lines, fluorescent lights, and numerous
other heavy electrical machines.
• Such noises are produced by the arc discharge
taking place during operation of these machines.
• Such man-made noise is most intensive in
industrial and densely populated areas.
• Man-made noise in such areas far exceeds all
other sources of noise in the frequency range

……1.8 Noise
1.8.3.2 Internal Noise
 This noise is produced by the receiver components while functioning.
 The components in the circuits, due to continuous functioning, may
produce few types of noise.
 This noise is quantifiable.
 A proper receiver design may lower the effect of this internal noise.
 Types of internal noise are −
1. Thermal Noise
2. Shot Noise
3. Transit time Noise
4. Miscellaneous Noise

……1.8 Noise
1. Thermal Noise (Johnson noise or White noise)
• Conductors contain a large number of free electrons and ions strongly bound by
molecular forces.
• The ions vibrate randomly about their normal (average) positions, however, this
vibration being a function of the temperature.
• Continuous collisions between the electrons and the vibrating ions take place.
• Thus there is a continuous transfer of energy between the ions and electrons.
• This is the source of resistance in a conductor.
• The movement of free electrons constitutes a current which is purely random in
nature and over a long time averages zero.
• There is a random motion of the electrons which give rise to noise voltage called
thermal noise. 22334 – Principles of Electronic Communication

……1.8 Noise
2. Shot Noise
 Shot noise is produced by the random movement of electrons
or holes across a PN junction.
 Even through current flow is established by external bias
voltages, there will still be some random movement of
electrons or holes due to discontinuities in the device.
 An example of such a discontinuity is the contact between the
copper lead and the semiconductor materials.
 The interface between the two creates a discontinuity that
causes random movement of the current carriers.

……1.8 Noise
3. Transit time Noise
 Transit time is the duration of time that it takes for a current carrier
such as a hole or current to move from the input to the output.
 The devices themselves are very tiny, so the distances involved are
minimal.
 Yet the time it takes for the current carriers to move even a short
distance is finite.
 At low frequencies this time is negligible. But when the frequency of
operation is high and the signal being processed is the magnitude as
the transit time, then problem can occur. 22334 – Principles of Electronic Communication

……1.8 Noise
1.8.3.2 Internal Noise 4. Miscellaneous
Noise
Flicker noise or modulation noise
It is the one appearing in transistors
operating at low audio frequencies.
Flicker noise is proportional to the
emitter current and junction
temperature.
However, this noise is inversely
proportional to the frequency. Hence
it may be neglected at frequencies
above about 500 Hz and it, Therefore,
Partition noise
It occurs whenever current has to
divide between two or more paths,
and results from the random
fluctuations in the division.
It would be expected, therefore, that
a diode would be less noisy than a
transistor (all other factors being
equal) If the third electrode draws
current (i.e.., the base current).
It is for this reason that the inputs of

1.9 Signal to Noise Ratio & Noise Figure
 Signal to Noise Ratio
 Signal-to-Noise Ratio (SNR) is
the ratio of the signal power
to the noise power.
 The higher the value of SNR,
the greater will be the quality
of the received output.
 Noise Figure
 The ratio of output SNR to the
input SNR can be termed as
the Noise Figure.
 It is denoted by F.
 It describes the performance of
a device.

Basics of Electronic Communication

Basics of Electronic Communication

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