Communication Engineering - Types of Noise in Communication

Summary

This video on communication engineering discusses the concept of noise in communication systems. Noise, defined as an unwanted signal that interferes with the original signal, can degrade the quality and performance of communication. The video explains the two main types of noise: external and internal, detailing their sources, effects, and classifications. External noise comes from outside the system, such as atmospheric and industrial noise, while internal noise is generated within the system components. The video also elaborates on various noise types, including thermal, flicker, and partition noise, and their impact on communication systems.

Takeaways

• 📢 Noise is an unwanted signal that interferes with the original message signal, corrupting its parameters.
• 🌐 Noise can enter a communication system either through the channel or the receiver.
• 📉 Noise is random, unpredictable, and lacks a specific pattern, frequency, or amplitude, making it difficult to fully eliminate.
• 📻 Common effects of noise include hiss in radio receivers, snow in TV receivers, and buzz in telephonic conversations.
• 📊 Noise affects the performance of communication systems by limiting operating range, reducing sensitivity, and impacting overall system performance.
• 🔍 Noise is classified into two broad groups: external noise (from sources outside the communication system) and internal noise (from within the system).
• 🌩️ External noise includes atmospheric noise (e.g., lightning and thunderstorms), industrial noise (e.g., electrical equipment), and extraterrestrial noise (e.g., solar and cosmic radiation).
• ⚙️ Internal noise originates from the components within the communication system and includes shot noise, partition noise, flicker noise, transit time noise, and thermal noise.
• 🔥 Atmospheric noise occurs mainly in low and medium frequency bands, while industrial noise is prevalent in urban and industrial areas.
• 🔧 Internal noise can be reduced through proper receiver design, and types like thermal noise are caused by the random motion of molecules and electrons.

Q & A

What is noise in communication systems?

Noise is an unwanted signal that interferes with the original message signal, corrupting its parameters. It can enter either through the communication channel or at the receiver, making it difficult to predict or eliminate completely.

How does noise affect the quality of a communication signal?

Noise causes fluctuations in the signal, making it unpredictable and random. It limits the operating range, sensitivity, and overall performance of the communication system, impacting signal quality.

What are the two broad categories of noise in communication systems?

Noise is broadly categorized into two types: external noise and internal noise. External noise originates outside the communication system, while internal noise is generated within the system or receiver components.

What is external noise and how is it classified?

External noise is generated outside the communication system and cannot be controlled or eliminated. It is classified into atmospheric noise, extraterrestrial noise, and industrial noise, all of which impact signal quality.

What causes atmospheric noise, and how does it affect communication?

Atmospheric noise, also known as static noise, is caused by natural phenomena such as lightning and thunderstorms. It spreads across a wide frequency spectrum, especially affecting low and medium frequencies.

What is industrial noise and how can it be reduced?

Industrial noise, also called man-made noise, is produced by electrical devices such as motors, switch gears, and transmission lines. It is prevalent in industrial areas and can be statistically analyzed, but reducing it requires shifting the communication system to less populated areas.

What is solar and cosmic noise, and how do they impact communication?

Solar noise comes from the sun, which radiates electrical energy due to its high temperature. Cosmic noise originates from distant stars, which also emit thermal noise. Both contribute to external noise in space-based communication.

What is internal noise and how does it differ from external noise?

Internal noise is generated by components within the communication system or receiver. Unlike external noise, it can be quantified, and its effects can be reduced through careful receiver design.

What is thermal noise, and why is it called 'white noise' or 'Johnson noise'?

Thermal noise, also known as white noise or Johnson noise, is a random noise generated in resistive components due to the random motion of electrons. It is constant across a wide frequency spectrum and affects signal quality.

How can internal noise, such as partition or flicker noise, be minimized in communication systems?

Partition noise occurs when current divides between two paths, and flicker noise increases as frequency decreases. Using less noisy components, such as MOSFETs, and optimizing circuit design can help reduce these types of internal noise.

Outlines

00:00

🔊 Introduction to Communication Noise

The video introduces the topic of noise in communication systems, defining noise as an unwanted signal that interferes with the original signal. It explains how noise can corrupt the message signal and how it can enter through the channel or receiver. Noise is unpredictable and has no pattern, making it impossible to eliminate completely but manageable through reduction. Examples of noise in radio, TV, and telephone systems are discussed, emphasizing its impact on signal quality and communication system performance.

05:01

📊 Classification of Noise

Noise is categorized into two major types: external and internal noise. External noise is generated outside the communication system and cannot be controlled or quantitatively analyzed. Atmospheric, extraterrestrial, and industrial noise fall under this category. Internal noise, on the other hand, originates within the communication system, such as from receiver components, and can be quantitatively measured. Both types of noise affect system performance, though they arise from different sources.

10:05

🌩️ External Noise Types and Their Effects

This section delves into external noise, describing atmospheric noise caused by thunderstorms and electrical disturbances, which affects signal quality across a wide frequency spectrum. Industrial noise, or man-made noise, is generated by machines, aircraft, and power lines, often found in dense urban areas. Extraterrestrial noise, including solar and cosmic noise, is discussed as radiation from the sun and distant stars, with its effect depending on frequency range and location.

15:06

🔧 Internal Noise and How It Affects Communication

Internal noise originates from within the communication system due to the random behavior of components like charge carriers in active devices. Various types of internal noise include short noise from random electron behavior, partition noise from current division, flicker noise at low frequencies, and thermal noise caused by the random motion of atoms and electrons. Each of these internal noise types impacts signal quality, but through careful system design, they can be minimized.

Keywords

💡Noise

Noise refers to any unwanted signal that interferes with the original communication signal, distorting or corrupting it. In the video, noise is described as random, unpredictable, and impossible to eliminate completely. It can enter the system at the channel or receiver, affecting the signal quality and limiting communication system performance.

💡External Noise

External noise is generated outside the communication system, often from sources like atmospheric disturbances, industrial equipment, or extraterrestrial bodies. The video categorizes external noise into atmospheric, industrial, and extraterrestrial noise, all of which degrade signal quality in different ways.

💡Internal Noise

Internal noise originates within the communication system itself, typically from components like receivers and circuits. Unlike external noise, internal noise can be quantified and minimized through better system design. Examples include short noise, partition noise, and thermal noise.

💡Atmospheric Noise

Also known as static noise, atmospheric noise is caused by natural electrical disturbances such as lightning in thunderstorms. The video emphasizes that this type of noise affects signals across a wide frequency range and is particularly strong in low- and medium-frequency bands.

💡Industrial Noise

Also referred to as man-made noise, industrial noise arises from human-made electrical sources like motors, aircraft, and high-voltage transmission lines. It is particularly strong in urban areas and can be statistically analyzed to assess its impact on communication systems.

💡Solar Noise

Solar noise is a form of extraterrestrial noise caused by the sun's radiation of electrical energy. Since the sun has a very high temperature, it emits noise over a wide frequency spectrum, affecting radio communications. This noise is constant and part of the broader category of space noise.

💡Cosmic Noise

Cosmic noise, another form of extraterrestrial noise, comes from distant stars. Like the sun, these stars emit thermal noise, though the noise received on Earth is weak due to the vast distance. The video explains that cosmic noise is uniformly distributed across the sky.

💡Thermal Noise

Also known as Johnson noise or white noise, thermal noise arises from the random motion of electrons in resistive components. The video highlights that this noise is inherent in electronic systems and can be minimized with better design. It is constant and present in all resistive elements.

💡Short Noise

Short noise occurs due to the random behavior of charge carriers, especially in active devices like electron tubes and semiconductors. The video explains that this noise is caused by the random emission or diffusion of electrons, impacting the performance of communication systems.

💡Flicker Noise

Flicker noise, also known as low-frequency or 1/f noise, appears at frequencies below a few kilohertz. It increases in power as frequency decreases, and the video relates it to slow changes in components like oxide-coated cathodes in vacuum tubes.

Highlights

Noise is defined as an unwanted signal that interferes with the original signal.

Noise can corrupt the message signal parameters and can enter at the channel or receiver.

Noise is random and unpredictable, with no specific pattern, frequency, or amplitude.

Noise reduction is crucial for improving communication system performance but cannot be completely eliminated.

Examples of noise include electrical disturbances in radio receivers, snow in TV receivers, and buzz in telephonic conversations.

Noise can limit the operating range, sensitivity of receivers, and overall performance of a communication system.

Noise is classified into external and internal noise, with external noise originating outside the communication system.

External noise includes atmospheric noise, extraterrestrial noise, and industrial noise.

Atmospheric noise, also known as static noise, is produced by natural electrical disturbances like lightning.

Industrial noise, or man-made noise, comes from sources like automobiles, electrical motors, and heavy electrical equipment.

Extraterrestrial noise includes solar noise from the sun and cosmic noise from distant stars.

Internal noise is generated within the communication system or receiver and can be quantified and reduced with proper design.

Types of internal noise include shot noise, partition noise, flicker noise, transit time noise, and thermal noise.

Shot noise arises from the random behavior of charge carriers in active devices.

Partition noise occurs when a current is divided between two or more paths in a circuit.

Flicker noise, or 1/f noise, increases with a decrease in frequency and is observed below a few kilohertz.

Transit time noise is observed in semiconductor devices when the transit time of charge carriers affects the signal.

Thermal noise, also known as white noise or Johnson noise, is generated by the random motion of molecules, atoms, or electrons.

Transcripts

[Music]

hello everyone

welcome to video lecture series of

communication engineering

today's topic is types of noise in

communication

in this video i will be talking about

the noise

what do you mean by noise and the

classification of noise

so let us begin

what is noise how can you define this

particular

term so noise you can define that it is

an

unwanted signal which interfere with the

original signal so when noise interfere

with the original message signal then it

is going to corrupt the

message signal parameters and noise can

enter

at the channel whatever the medium of

the communication

means it can enter at the channel itself

or at the

receiver so these are the two

possibilities where the noise can

enter and corrupt the original signal

you can see in this particular diagram

some variation is being shown on the

x-axis time is being taken on the y-axis

amplitude and now here you

can observe the impact of noise on the

signal how signal is fluctuating

means at any instant of time it's

difficult to predict means there is no

specific pattern

no certain pattern you can observe it

means

noise is a kind of signal which has

no pattern it has no constant frequency

or

amplitude so noises are random and it is

actually

unpredictable right so random nature

is of noise and measures are usually

taken

because our requirement is to reduce the

noise as much as possible in the

communication system

to improve the system performance but

noise cannot be completely eliminated it

can be reduced as much as possible but

it's difficult or

impossible almost to eliminate it

completely

so there are some of the examples of

noise

like noise you can observe in the case

of the

radio receivers so in receivers several

electrical disturbances produce noise

and therefore modifying the required

signal is an

in an unwanted form so in the case of

the radio receivers noise may produce

his type of pattern in the

output means at the output which you are

listening at the loudspeaker so his type

of pattern

similarly if you talk about tv receivers

noise may produce

snow and snow it actually it becomes

superimposed on the

picture output so snow or flicker is the

case of the

television receivers similarly you can

observe a

buzz kind of sound in the case of the

telephonic conversation so you can say

that

noise is a factor which is going to

impact a lot

a lot the signal quality and noise may

limit the performance of a

communication system

so what are the various effects of noise

noise can limit the operating range of

the system noise effect the sensitivity

of the receivers noise limit the

performance of

overall communication system so the

there are various factors you can see

how much spurious this is

now let's discuss the classification of

noise

there are various ways of classifying

the noise

but conveniently noise may be classified

into two broad groups and these groups

are

external noise and internal noise so

noise has been classified into two major

groups

one group is external noise and other is

the internal noise

external noise the first type the first

group

so external noise it can be defined as

that type

of noise which is generated

externally to the communication system

externally means

whose sources are external to the

communication

systems and external noise cannot be

analyzed quantitatively

there are various types of noise which

may fall into this category those are

atmospheric noise extraterrestrial noise

industrial noise

all of these kinds of noise i will be

talking in much detail

so noise is what noise is any random

interference to a

weak signal the second type of noise

categorization which is the

internal noise so internal noise is a

type of noise which is generated

internally from the name itself it is

clear it is generated

internally or within the communication

system or

receiver like an internal noise it may

be treated quantitatively

there are various types of internal

noise

the various types are short noise

partition noise low frequency noise or

flicker noise high frequency or transit

time noise

and thermal noise so these are the

various types of noise which

fall into the category of external noise

or

internal noise so let's talk about each

of them in detail

first is the external noise so here i

will be talking about the external noise

you must remember that external noise it

is defined

as a type of noise which is produced by

external sources means it may occur in

the medium or the channel of the

communication

this type of noise cannot be completely

eliminated

and external noise are analyzed

qualitatively means quantitatively

analysis is not possible so these are

the various factors

and in addition to this you must

remember that for a geographically point

or a location external noise cannot be

controlled means extend this particular

type of noise

control it's not possible but reduction

in the noise

can only be done it means to reduce the

effect of external noise the only way is

to

shift the communication system to the

other place

because these are the contributed by the

external factors

so if the communication system is to be

shifted to the other place or

other location which has comparatively

smaller external noise factors then this

particular

kind of noise can be reduced or

minimized

and because of this particular reason

the satellite earth stations are

generally located in the

noise free valleys there is always a

possibility to shift

the earth stations from one place to the

another place right

so those earth stations are located in

the noise free valleys

as i have told you that there are three

types of external noise

first is the atmospheric noise

atmospheric noise it is also known as a

static noise this is a very important

point

and it is produced by lightning

discharge in

thunderstorms or other natural

electrical disturbances

which occur in the atmosphere so these

various atmospheric imp effects they

creates a noise

and which is going to impact the signal

quality

it means when we are talking about the

thunderstorm or other electrical

disturbances in the atmosphere so these

electric

pulses they are random in nature it

means

this energy is spread over the complete

frequency spectrum

which is used for the radio

communication so atmospheric noise

it contains spurious radio signals which

are distributed over a

wide frequency range right and the

field strength of atmospheric noise that

varies approximately

inversely with the frequency means there

is a

inverse variation with the frequency it

means

large atmospheric noise is produced in

low

and medium frequency bands whereas

a small noise is produced in vhf

and uhf so for vhf

band and uhf band these are used

for the small noise means if the

application is to be done

in these bands the impact of noise will

be less

atmospheric noise becomes less severe at

frequencies

above 30 megahertz

second type of noise is the industrial

noise

industrial noise it is also known as a

man-made noise

man made

noise so this is the type of noise which

is produced by

various sources like automobiles

aircraft ignition

electrical motors switch gears leakage

from high voltage transmission lines

and various other heavy electrical

equipments

so such type of noise is produced by

actually

arc discharge that takes place during

the operation

of all types of machines or equipments

and industrial noise or man-made noise

this is

quite intensive in the industrial area

or dense populated urban areas

see industrial noise in such areas are

very strong

in comparison to other sources of noise

in the frequency range which

extends from 1 megahertz to 600

megahertz

so industrial or man-made noise that is

highly variable

and hence can be analyzed statistically

so this type of noise can be analyzed

statistically

third is the extraterrestrial noise

so there are various types of

extraterrestrial noise

or space noise depending upon their

sources so the various types are divided

into

two categories one is the solar noise

and other is the cosmic noise

see what is solar noise solar noise is

the electrical noise

which is emanating from the sun under

the steady state conditions what

happened there is a regular radiation of

noise from the sun

see this radiation of noise from sun

why this is because sun is a big body at

an

extremely high temperature and it

radiates electrical energy in the form

of noise over a wide frequency spectrum

which includes like various

applications may occur over there

so it means because sun is having a very

high temperature

and it also radiates so that is going to

contribute certain amount of noise and

that is known as a

solar noise the second type of noise

which

we are talking about the

extraterrestrial that is the cosmic

noise

see you are aware that there are various

distant stars

in the space and those distant stars can

also be considered as a sun

because these distant stars have high

temperatures

and they radiate noise in the same

manner as the sun does

but the noise received from these

distant stars in thermal noise

and that is distributed almost uniformly

over the

entire sky means there is a uniform

distribution

in the entire sky so this type of

galactic noise that is quite intense

but since it comes from very distinct

source

so the angle subtended by the earth that

is very small

it means the strength of galactic noise

which is received

on the earth it gets almost

diminished right so this is how you can

explain the various types of noise

which comes into the category of

external noise

now we are talking about the internal

noise

so internal noise is a type of noise

which is produced by

receiver component while functioning

because of the components in the circuit

or due to the continuous functioning

some of the

components may produce certain noise

this type of noise is

quantifiable and a proper receiver

design

may lower the effect of this internal

noise if the receiver designing is to be

done

in a very accurate manner this

particular type of noise can be

reduced there are various types of

internal noise let us discuss them first

is the

short noise so short noise it arises in

the

active devices this is an important

factor

it arises in the active devices and why

because of the random behavior of the

charge carriers

so because of random behavior of charge

carrier short noise

exist like in the case of the electron

tubes

short noise is generated due to the

random emission of electrons from

cathode

while in semiconductor devices short

noise is generated due to

random diffusion of minority carriers

or you can say simply because of the

random generation

and recombination of electron hole pair

so this is how short noise may occur

in the like receiver design or in

any of the other component and it

impacts the signal quality

second is partition noise

partition wise this is generated in a

circuit

it is generated in a circuit itself

whenever a current has to be divided

between

two or more paths so when a current is

being divided

in between two or more path this type of

noise occurs

it means partition noise results from

the

random fluctuations in the division

or it is expected that in such type of

cases

diode must be less noisy than the

transistor see what happened the

partition noise

the it has a spectrum like a flat

spectrum

and there are three terminal components

in which

control terminal draws less current and

are less noisy

you have studied the various three

terminal components like transistors

feds etc so what happened in a recent

time metal oxide semiconductor field

effect transistors which is mosfet

they have been developed which draws

almost

zero gate bias current and because of

this reason these devices have

low partition noise and they find

applications in low noise microwave

amplification so now you can understand

how partition noise can be

reduced next type of noise is the

flicker noise

so flicker noise or low frequency noise

it is also known as a

low frequency noise so at low frequency

means uh below few kilohertz a

particular type of noise appear

which is known as a flicker noise and

the power spectral density of this

particular noise

increases with decrease in the frequency

so this particular noise flicker noise

or it sometimes

it may be written as 1 upon f noise

what happen in the case of the vacuum

tubes the main cause of the flicker

noise is what

slow changes which takes place in the

oxide structure of oxide coated cathodes

and migration of impurity ions

right so mathematically you can write

the power density spectrum of flicker

noise

that is inversely proportional to the

frequency

means s of w this is inversely

proportional to

1 upon f

next type of noise is the transit time

noise it is also known as a

high frequency noise so it is generally

observed in a semiconductor devices

when the transit time of charge carriers

crossing a junction that is compared

with the time period of the signal

right so some charge carriers diffuse

back to the source or ammeters and this

particular process gives rise

to the input admittance

in which conduction sorry conductance

component

increases with frequency right and

when conductance component increases

with frequency

so it has a noise current source which

is associated with the parallel

so what happens the conductance which

increases with frequency the power

spectral density will also increase

and the type of noise can be observed as

a transit type of noise

last type of internal noise that is the

thermal noise

so the thermal noise or white noise

or johnson noise these are the

similar terms it is a random noise

which is generated in a register or

in a resistive components of a complex

impedance because of rapid and random

motion of the

molecules atoms or electrons

so this type of noise is called as a

thermal noise

so i hope now you will be able to define

each and every type of noise in detail

thank you so much for watching this

video