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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
If the noise has expected value of zero, as is common, the denominator is its variance, the square of its standard deviation σ N. The signal and the noise must be measured the same way, for example as voltages across the same impedance. Their root mean squares can alternatively be used according to:
To determine the noise figure of an amplifier one uses a noise diode at the input to the amplifier and determines the output noise Y with the diode switched on and off. Knowing both Y and the ENR, one can then determine the amount of noise contributed by the amplifier and hence can calculate the noise figure of the amplifier.
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 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 ...
G/T Calculation. G/T is the figure of merit for a satellite system. G is the Receive antenna gain. T is the system noise temperature. System noise temperature = antenna noise temperature + Receiver noise temperature (LNA) Antenna noise temperature is the noise power seen at the receive output of the antenna. (To LNA)
For color images with three RGB values per pixel, the definition of PSNR is the same except that the MSE is the sum over all squared value differences (now for each color, i.e. three times as many differences as in a monochrome image) divided by image size and by three.