# noise figure

Also found in: Acronyms, Wikipedia.

## noise figure

(noise factor) See noise.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

## Noise Figure

(or noise factor), the numerical characteristic of a radio receiver that indicates how much its sensitivity to an incoming signal is decreased by the effects of its internal noise (seeFLUCTUATIONS, ELECTRICAL).

The noise figure F is equal to the ratio of the total noise power at the output of an actual receiver Pact to the output noise power of a similar ideal (noiseless) receiver Pid under the condition that the only source of input noise in both cases is the thermal noise of the matched impedance (dummy antenna) at the temperature T0 = 290°K (seeNYQUIST FORMULA):

(1) F = Pact/Pid = Pact/kT0 Δ fG

Here, k is Boltzmann’s constant, Δf is the receiver’s passband in hertz, and G is the receiver’s power gain. The noise figure is also expressed in decibels: F (dB) = 10 log F. For an ideal receiver, F = 1 (or 0 dB), while for an actual receiver, F > 1. Often, the noise figure is described by the noise temperature Tn.

The noise figure is measured by means of standard noise generators or standard signal generators by determining how much the total power of the receiver’s output signal is increased with a calibrated signal Pgen at its input compared with the output power without the signal. When measuring by the “twofold excess” method, Pgen is adjusted so that the output-signal power is doubled. Then, Pact = GPgen, and the noise figure is calculated from equation (1).

Quantum mechanical amplifiers and cooled parametric amplifiers using semiconductor diodes, for which F ≈ 1.1 and Tn ≈ 30°K (when not cooled, F ≈ 1.3 and Tn ≈ 100°K), have the lowest noise figures. For amplifiers using traveling-wave tubes and tunnel diodes, F ≈ 3 to 10 and Tn ≈ 600° to 3000°K. Radio and television receivers have noise figures ranging from several units to several tens.

### REFERENCES

Kuz’min, A. D. Izmerenie koeffilsienla shuma priemno-usilitel’nykh ustroistv. Moscow-Leningrad, 1955.
Sukhodoev, I. V. Shumy eleklricheskikh tsepei (Teoriia). Moscow, 1975.

I. T. TROFIMENKO

## noise figure

[′nȯiz ‚fig·yər]
(electronics)
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Thus, a common source installation is recommended if you wish to allow the high output power, low noise figure, good linearity, and efficiency.
Gain, noise figure, output power, and Q-Factor at different values of attenuation coefficient are illustrated in Figure 7.
The noise figure of the cascade can be calculated by the formula 
Simulations have been carried out to estimate the effects of ASE noise, noise figure, and chromatic dispersion on performance of the network in different pump configurations.
Applications include vector noise figure, gain compression, IMD, true differential and NVNA.
Noise figure measurements enable test engineers to determine potential degradation of signal-to-noise ratio from system components in applications including radar, wireless communications, and digital communications.
In addition to the balanced amplifier application, these devices are a perfect solution for the first and second stages of a base station LNA due to the excellent combination of low noise figure and linearity.
Noise figure as a measurement parameter came into use in the early 1940s.
Typical performance includes 6.5-dB noise figure and + 14-dBm output at P1dB.
Transmit power is [greater than or equal to] +17 dBm and receive noise figure is 6 dB.
This means that we calculate receiver sensitivity in dBm as a function of kTB, the receiver-system noise figure, and the required signal-to-noise ratio.

Site: Follow: Share:
Open / Close