CARRIER-TO-NOISE RATIO VERSUS NOISE FIGURE.- NOISE TERMINOLOGY
noise is the hazard that can obscure or distort a signal.
as can be seen in the graphs, noise is increased until the amplitude modulation (am) information is completely masked by noise.
another type of noise measurement quantifies the difference between the noise and the rf signal peak, that is, the signal-to-noise ratio (snr) measurement.
in catv, this is called carrier-to-noise ratio because the video tv carrier level compared to the system noise level is measured.
this carrier-to-noise ratio (c/n) is measured in unreferenced db because it is the ratio of two levels.
noise power is amplified in the amplifier by g(db). besides, the amplifier adds a measure of its own noise to the output, because of the inherent noise of internal amplifier components.
the measure of the amplifier characteristics is noise figure, or nf.
let us see the relationship of noise power density, amplifier gain and noise figure.