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The noise figure is the difference in decibel (dB) between the noise output of the actual receiver to the noise output of an "ideal" receiver with the same overall gain and bandwidth when the receivers are connected to matched sources at the standard noise temperature T 0 (usually 290 K).
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 ...
Antenna gain-to-noise-temperature (G/T) is a figure of merit in the characterization of antenna performance, where G is the antenna gain in decibels at the receive frequency, and T is the equivalent noise temperature of the receiving system in kelvins.
An important consequence of this formula is that the overall noise figure of a radio receiver is primarily established by the noise figure of its first amplifying stage. Subsequent stages have a diminishing effect on signal-to-noise ratio .
In RF applications, noise power is defined using the relationship P noise = kTB, where k is the Boltzmann constant, T is the noise temperature, and B is the noise bandwidth. Typically the noise bandwidth is determined by the bandwidth of the intermediate frequency (IF) filter of the radio receiver. Thus, we can define the noise temperature as:
Noise figure measurements can be made with a noise diode, a power supply for the noise diode, and a spectrum analyser. They can also be made with a specialist noise figure meter. The advantage of the noise figure meter is that it will automatically switch the noise diode on and off, giving a continuous reading of Y; it will also have the ...
Figure 1. Johnson's 1927 experiment showed that if thermal noise from a resistance of with temperature is bandlimited to bandwidth, then its root mean squared voltage is in general, where is the Boltzmann constant.
Effective input noise temperature; Noise-equivalent power, a measure of sensitivity for photodetectors; Relative intensity noise, in a laser beam; Antenna noise temperature, measure of noise in telecommunications antenna; Received noise power, noise at a telecommunications receiver; Circuit noise level, ratio of circuit noise to some reference ...