Following are few statements regarding noise in communication system:

a) Atmospheric noise, shot noise, solar noise are examples of external noise sources

b) Noise temperature is useful in dealing with UHF noise

c) Thermal agitation is the only source of noise in receiver

Choose the correct answer:

Statement a:

Noise in communication systems is generally divided into two categories-

i) External noise like atmospheric noise, industrial noise solar noise, and cosmic noise.

ii) Internal noise like shot noise, thermal noise, low and high-frequency noise. (Statement a is false)

Statement b:

Noise temperature is one way of expressing the level of available noise power introduced by a component or source. The power spectral density of the noise is expressed in terms of the temperature (in kelvins) that would produce that level of Johnson–Nyquist noise.

It is useful in dealing with UHF. (Statement b is True)

Statement c:

Internal and external noises are the main source of noise in the receiver (Statetemt c is false)

Note:

Thermal Agitation:

• It is also called Johnson-Nyquist noise
• It is distributed across the entire frequency spectrum range so it is also called as white noise
• Thermal noise is generally observed in the passive component like R, L & C due to the random movement of charge carriers electrons.
• Random noise power is

Pn = KTB

Where,

K = Boltz man's constant

T = temperature

B = Bandwidth over which noise is measured