PPT - Noise in Communication System - Electronics and Communication Engineering (ECE) PDF Download

 Page 2


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
• Analysis of Noise in Communication Systems
• Thermal  Noise
• Noise Voltage Spectral Density
• Resistors in Series
• Resistors in Parallel 
• Signal - to – Noise
• Noise Factor –
• System Noise Figure
•Additive White Gaussian Noise
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
• Analysis of Noise in Communication Systems
• Thermal  Noise
• Noise Voltage Spectral Density
• Resistors in Series
• Resistors in Parallel 
• Signal - to – Noise
• Noise Factor –
• System Noise Figure
•Additive White Gaussian Noise
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:-
•Interference, usually from a human source (man made)
•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 … 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
• Analysis of Noise in Communication Systems
• Thermal  Noise
• Noise Voltage Spectral Density
• Resistors in Series
• Resistors in Parallel 
• Signal - to – Noise
• Noise Factor –
• System Noise Figure
•Additive White Gaussian Noise
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:-
•Interference, usually from a human source (man made)
•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 … etc. 
Natural Noise
Naturally occuring external noise sources include atmosphere 
disturbance (e.g. electric storms, lighting, ionospheric effect etc), 
so called ‘Sky Noise’ or Cosmic noise which includes noise  from 
galaxy, solar noise and ‘hot spot’ due to oxygen and water vapour 
resonance in the earth’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
• Analysis of Noise in Communication Systems
• Thermal  Noise
• Noise Voltage Spectral Density
• Resistors in Series
• Resistors in Parallel 
• Signal - to – Noise
• Noise Factor –
• System Noise Figure
•Additive White Gaussian Noise
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:-
•Interference, usually from a human source (man made)
•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 … etc. 
Natural Noise
Naturally occuring external noise sources include atmosphere 
disturbance (e.g. electric storms, lighting, ionospheric effect etc), 
so called ‘Sky Noise’ or Cosmic noise which includes noise  from 
galaxy, solar noise and ‘hot spot’ due to oxygen and water vapour 
resonance in the earth’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 = Boltzmann’s constant = 1.38 x 10
-23
Joules per K
T = absolute temperature
B = bandwidth noise measured in (Hz)
R = resistance (ohms)