1) Noise is an unwanted signal that affects communication systems and can originate from both human-made and natural sources. Interference comes from sources like other communication systems while natural noise includes atmospheric, solar, and cosmic noise. 2) Internal noise in devices includes thermal noise, which originates from the random motion of electrons in conductors due to temperature, and shot noise, which comes from the discrete nature of electric charge. 3) External or natural noise sources are atmospheric noise from lightning, solar noise from the sun, and cosmic noise from outside the earth's atmosphere. Industrial noise also affects signals.

1. Analog Communication
Systems
Vishal Jain
18BEC10093

2. 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.
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3. Introduction of Noise
External Noise -
• Atmospheric Noise
• Solar Noise
• Cosmic Noise
• Industrial Noise
Internal Noise -
• Thermal Noise
• Shot Noise
• Flicker Noise
• Partition Noise
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4. External Noise -
Atmospheric Noise –
• Atmospheric noise is radio noise caused by natural atmospheric processes,
primarily lightning discharges in thunderstorms. On a worldwide scale, there
are about 40 lightning flashes per second – ≈3.5 million lightning discharges
per day.
• Effect in whole spectrum till 80MHz.
• Also called statics.
Solar Noise –
• Noise that originates from the Sun is called solar noise. Under normal
conditions there is constant radiation from the Sun due to its high
temperature. Electrical disturbances such as corona discharges, as well as
sunspots can produce additional noise.
• From 20MHz to 120MHz
• Highly effect when sun activity is on peak.
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5. External Noise -
Cosmic Noise –
• Cosmic noise and galactic radio noise is random noise that originates outside
the Earth's atmosphere. It can be detected and heard in radio
receivers. Cosmic noise characteristics are similar to those of thermal noise.
• Exp FRB, Gamma Burst, Quasars
• Intensity is so low.
Industrial Noise –
• This type of noise originates from industries, vehicles.
• Because of electrical noise, machines in industries etc.
• Effects whole spectrum.
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6. Shot Noise -
• Shot noise or Poisson noise is a type of noise which can be modeled by
a Poisson process. In electronics shot noise originates from the discrete
nature of electric charge. Shot noise also occurs in photon counting in
optical devices, where shot noise is associated with the particle nature of
light.
Shot Noise
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7. Thermal Noise (Johnson Noise)
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8. Thermal Noise
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9. Thermal Noise
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10. Registers in Series
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11. Registers in Parallel
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12. Signal to Noise Ratio (SNR)
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