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Noise figure (NF) and noise factor (F) are figures of merit that indicate degradation of the signal-to-noise ratio (SNR) that is caused by components in a signal chain. These figures of merit are used to evaluate the performance of an amplifier or a radio receiver, with lower values indicating better performance.
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
Signal to noise ratio may be abbreviated as SNR and less commonly as S/N. PSNR stands for peak signal-to-noise ratio. GSNR stands for geometric signal-to-noise ratio. [13] SINR is the signal-to-interference-plus-noise ratio.
Noise figure (NF) is noise factor (F) expressed in decibels. F is the ratio of the input signal-to-noise ratio (SNR i) to the output signal-to-noise ratio (SNR o). F quantifies how much the signal degrades with respect to the noise because of the presence of a noisy network.
The Y-factor method is a common measurement technique for this purpose. [1] By using a noise diode, the output noise of an amplifier is measured using two input noise levels, and by measuring the output noise factor (referred to as Y) the noise figure of the amplifier can be determined without having to measure the amplifier gain.
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 ...
The attenuation coefficient of a volume, denoted μ, is defined as [6] =, where Φ e is the radiant flux;; z is the path length of the beam.; Note that for an attenuation coefficient which does not vary with z, this equation is solved along a line from =0 to as:
"Attenuators have a noise factor F equal to their attenuation ratio L" I just can't see how this can be correct, for example an attenuator made of capacitors (voltage divider) will not introduce any new noise so the SNRin and SNRout will be the same, therfore the noise figure of such an attenuator will be zero, I am sure that there are many other examples where the NF is zero or irrelevant.