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Friis's formula is used to calculate the total noise factor of a cascade of stages, each with its own noise factor and power gain (assuming that the impedances are matched at each stage). The total noise factor can then be used to calculate the total noise figure. The total noise factor is given as
In the above formula, P is measured in units of power, such as watts (W) or milliwatts (mW), and the signal-to-noise ratio is a pure number. However, when the signal and noise are measured in volts (V) or amperes (A), which are measures of amplitude, [note 1] they must first be squared to obtain a quantity proportional to power, as shown below:
Noise experts and some small specialized companies have slowly developed a limited number of calculation tools, which have increased in number and become more user-friendly, covering more application cases, and adding service elements to the noise calculation tools. The noise calculation process is complex in input (gathering data, correctly ...
The noise floor limits the smallest measurement that can be taken with certainty since any measured amplitude can on average be no less than the noise floor. A common way to lower the noise floor in electronics systems is to cool the system to reduce thermal noise, when this is the major noise source. In special circumstances, the noise floor ...
The noise factor (a linear term) is more often expressed as the noise figure (in decibels) using the conversion: = The noise figure can also be seen as the decrease in signal-to-noise ratio (SNR) caused by passing a signal through a system if the original signal had a noise temperature of 290 K. This is a common way of expressing the noise ...
Peak signal-to-noise ratio (PSNR) is an engineering term for the ratio between the maximum possible power of a signal and the power of corrupting noise that affects the fidelity of its representation.
is the carrier-to-noise ratio or signal-to-noise ratio, B is the channel bandwidth in hertz, and f s {\displaystyle f_{s}} is the symbol rate in baud or symbols per second.
Johnson–Nyquist noise (thermal noise, Johnson noise, or Nyquist noise) is the electronic noise generated by the thermal agitation of the charge carriers (usually the electrons) inside an electrical conductor at equilibrium, which happens regardless of any applied voltage.