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# PPT - Noise in Communication System Electronics and Communication Engineering (ECE) Notes | EduRev

## Communication Theory

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## Electronics and Communication Engineering (ECE) : PPT - Noise in Communication System Electronics and Communication Engineering (ECE) Notes | EduRev

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contents:
?Introduction of noise
1) Thermal Noise
2).Shot Noise
3).Low Frequency or Flicker Noise
4).Excess Resister Noise
5).Burst or Popcorn Noise
?Types of noise
â€¢ Analysis of Noise in Communication Systems
â€¢ Thermal  Noise
â€¢ Noise Voltage Spectral Density
â€¢ Resistors in Series
â€¢ Resistors in Parallel
â€¢ Signal - to â€“ Noise
â€¢ Noise Factor â€“
â€¢ System Noise Figure
Page 3

contents:
?Introduction of noise
1) Thermal Noise
2).Shot Noise
3).Low Frequency or Flicker Noise
4).Excess Resister Noise
5).Burst or Popcorn Noise
?Types of noise
â€¢ Analysis of Noise in Communication Systems
â€¢ Thermal  Noise
â€¢ Noise Voltage Spectral Density
â€¢ Resistors in Series
â€¢ Resistors in Parallel
â€¢ Signal - to â€“ Noise
â€¢ Noise Factor â€“
â€¢ System Noise Figure
Introduction of Noise
Noise is a general term which is used to describe an unwanted
signal which affects a wanted signal. These unwanted signals arise
from a variety of sources which may be considered in one of two
main categories:-
â€¢Interference, usually from a human source (man made)
â€¢Naturally occurring random noise
Interference
Interference arises for example, from other communication
systems (cross talk), 50 Hz supplies (hum) and harmonics,
switched mode power supplies, thyristor circuits, ignition (car
spark plugs) motors â€¦ etc.
Page 4

contents:
?Introduction of noise
1) Thermal Noise
2).Shot Noise
3).Low Frequency or Flicker Noise
4).Excess Resister Noise
5).Burst or Popcorn Noise
?Types of noise
â€¢ Analysis of Noise in Communication Systems
â€¢ Thermal  Noise
â€¢ Noise Voltage Spectral Density
â€¢ Resistors in Series
â€¢ Resistors in Parallel
â€¢ Signal - to â€“ Noise
â€¢ Noise Factor â€“
â€¢ System Noise Figure
Introduction of Noise
Noise is a general term which is used to describe an unwanted
signal which affects a wanted signal. These unwanted signals arise
from a variety of sources which may be considered in one of two
main categories:-
â€¢Interference, usually from a human source (man made)
â€¢Naturally occurring random noise
Interference
Interference arises for example, from other communication
systems (cross talk), 50 Hz supplies (hum) and harmonics,
switched mode power supplies, thyristor circuits, ignition (car
spark plugs) motors â€¦ etc.
Natural Noise
Naturally occuring external noise sources include atmosphere
disturbance (e.g. electric storms, lighting, ionospheric effect etc),
so called â€˜Sky Noiseâ€™ or Cosmic noise which includes noise  from
galaxy, solar noise and â€˜hot spotâ€™ due to oxygen and water vapour
resonance in the earthâ€™s atmosphere.
Page 5

contents:
?Introduction of noise
1) Thermal Noise
2).Shot Noise
3).Low Frequency or Flicker Noise
4).Excess Resister Noise
5).Burst or Popcorn Noise
?Types of noise
â€¢ Analysis of Noise in Communication Systems
â€¢ Thermal  Noise
â€¢ Noise Voltage Spectral Density
â€¢ Resistors in Series
â€¢ Resistors in Parallel
â€¢ Signal - to â€“ Noise
â€¢ Noise Factor â€“
â€¢ System Noise Figure
Introduction of Noise
Noise is a general term which is used to describe an unwanted
signal which affects a wanted signal. These unwanted signals arise
from a variety of sources which may be considered in one of two
main categories:-
â€¢Interference, usually from a human source (man made)
â€¢Naturally occurring random noise
Interference
Interference arises for example, from other communication
systems (cross talk), 50 Hz supplies (hum) and harmonics,
switched mode power supplies, thyristor circuits, ignition (car
spark plugs) motors â€¦ etc.
Natural Noise
Naturally occuring external noise sources include atmosphere
disturbance (e.g. electric storms, lighting, ionospheric effect etc),
so called â€˜Sky Noiseâ€™ or Cosmic noise which includes noise  from
galaxy, solar noise and â€˜hot spotâ€™ due to oxygen and water vapour
resonance in the earthâ€™s atmosphere.
This type of noise is generated by all resistances (e.g. a resistor,
semiconductor, the resistance of a resonant circuit, i.e. the real part
of the impedance, cable etc).
Thermal Noise (Johnson Noise)
Experimental results (by Johnson) and theoretical
studies (by Nyquist) give the mean square noise
voltage as
) ( 4
2
2
_
volt TBR k V ?
Where  k = Boltzmannâ€™s constant = 1.38 x 10
-23
Joules per K
T = absolute temperature
B = bandwidth noise measured in (Hz)
R = resistance (ohms)
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