Question

List the types of noise and their sources. What are the various ways of enhancing Signal-toNoise ratio?

Answer 1

here,

noise is a random fluctuation in an electrical signal, a characteristic of all electronic circuits

Thermal noise is unavoidable at non-zero temperature

while other types depend mostly on device type

noise is an error or undesired random disturbance of a useful information signal in a communication channel

types of noise ,

Thermal noise
   generated by the random thermal motion of charge carriers (usually electrons), inside an electrical conductor, which happens regardless of any applied voltage.

   Shot noise
   Shot noise in electronic devices results from unavoidable random statistical fluctuations of the electric current when the charge carriers   traverse a gap

   Flicker noise
   is a signal or process with a frequency spectrum that falls off steadily into the higher frequencies, with a pink spectrum.

   Burst noise
   Burst noise consists of sudden step-like transitions between two or more levels (non-Gaussian), as high as several hundred microvolts, at random and unpredictable times

   Transit-time noise
   If the time taken by the electrons from traveling from emitter to collector becomes comparable to the period of the signal being amplified, that is, at frequencies above VHF and beyond, so-called transit-time effect takes place and noise input admittance of the transistor increases

   Coupled noise
   Energy external of the receiver can couple noise, also by energy conversion. Generally this is done by fundamental interaction, in electronics mainly by Inductive coupling and/or capacitive coupling.

   Signal-to-noise ratio (abbreviated SNR) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power, often expressed in decibels