The goal of all communications systems is the same: to produce a signal that was applied at the transmitter as input, suffered the link losses and distortions (such as cable attenuation, dispersion, fading, and reflections), and then was recovered by the demodulator or detector in the receiver section. When the signal reaches the detection stage, it is accompanied by an additional signal voltage that varies in time in an entirely unpredictable manner. This unpredictable voltage waveform is a random process called noise. All signals accompanied by such a waveform are described as contaminated or corrupted by noise. Therefore, one of the parameters that needs to be kept in mind when designing any kind of receiver is its noise performance. The noise performance of a system is defined by the system's noise figure; 10 log(F) = (NF). This affects the receiver's C/N (carrier to noise), or Eb/no bit energy per noise, which directly affects the detection quality carrier-to-noise ratio (CNR) and bit error rate (BER), respectively.
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