Noise Figure


Noise Figure (NF) is a measure used in communication systems to quantify the performance of a device with respect to its signal-to-noise ratio. It is usually expressed in decibels (dB) and indicates the degradation in signal strength caused by the device when compared to an ideal, noiseless component. A lower noise figure signifies better performance in minimizing the addition of noise to the received signal.

Key Takeaways

  1. Noise Figure is a measurement that represents the degradation in signal-to-noise ratio caused by adding an electronic device, such as an amplifier or a mixer, to a communication system.
  2. It is expressed in decibels (dB) and indicates the difference between the noise output of an ideal (noise-free) device and the actual noise output of the device being measured, with both devices having equal gain or loss.
  3. Lower Noise Figure values are desirable, as they indicate a component that adds less noise and thus contributes to improved overall system performance.


The term “Noise Figure” is important in the field of technology, particularly in telecommunications and electronic systems, as it quantifies the level of degradation in the signal-to-noise ratio (SNR) of a device or system.

This degradation is caused by the inherent noise produced by various electronic components, such as amplifiers and receivers, within the system.

By measuring the Noise Figure, engineers can assess the performance of these devices and determine their suitability for specific applications, enabling the optimization and development of communication systems with minimal noise interference.

A low Noise Figure indicates superior performance and higher reception quality, making it a crucial factor in maintaining the fidelity of signals as they pass through various stages of a communication network or electronic system.


Noise Figure (NF) is a crucial parameter in the assessment and design of communication systems, particularly in networks that demand high precision, such as satellite and fiber-optic communication systems. The primary purpose of Noise Figure, a dimensionless value expressed in decibels (dB), is to quantify the degradation of signal quality introduced by an electronic device, or system components, when amplifying the weak input signals.

In simpler terms, NF indicates the difference in performance between a theoretically ideal device and the actual component under scrutiny, accounting for noise introduced in the processing of a signal. By analyzing the Noise Figure, engineers can determine the effectiveness of components in maintaining signal quality and make informed decisions to enhance the overall performance of a communication system.

Moreover, the NF serves as a vital factor in understanding the level of additional noise contributed by an amplifier, apart from its inherent thermal noise, as it amplifies a signal. This additional noise may stem from manufacturing imperfections and variations in components or materials, which, subsequently, contribute to overall system noise floor and affect transmitted data accuracy.

By comparing the Noise Figure values of various components within a system or between different products, designers can select the most appropriate devices for specific applications, achieving optimal system performance. In summary, the Noise Figure is an indispensable metric for gauging the effectiveness of electronic devices and systems in preserving signal integrity while processing weak input signals, enabling engineers to optimize communication networks.

Examples of Noise Figure

Noise Figure (NF) is a term used to quantify the performance of a communication system by measuring how much it degrades the signal-to-noise ratio (SNR). In the real-world context, this performance parameter is important in various systems like cellular communication networks, satellite communication, and radio astronomy. Here are three real-world examples:

Cellular Communication Networks: In cellular networks, base station receivers need to handle various signal sources, such as communication signals from multiple users, interference, and environmental noise. A low noise figure for the receiver is essential to provide a clear and reliable signal to users. The noise figure of the low noise amplifiers (LNAs) and other components utilized in the receiving chain directly affect the communication quality.

Satellite Communication Systems: In satellite communications, a key component is the satellite’s transponder that amplifies and redirects signals back to Earth. To ensure optimal communications, these systems need to minimize noise figure to avoid interference and signal degradation. In this case, the noise figure of the satellite’s low noise block downconverter (LNB) directly impacts the overall system performance. A low noise figure for the LNB is critical for maintaining clear signals and reducing potential disruptions in satellite communication systems.

Radio Astronomy: Radio telescopes collect extremely weak signals from distant celestial bodies to study the universe. Radio astronomers need to minimize the noise figure in their signal processing chains to maximize their observations’ sensitivity and accuracy. To achieve this, low-noise preamplifiers and components are used to reduce the noise figure as much as possible, allowing for more precise measurements and more accurate data interpretation.

FAQ: Noise Figure

What is Noise Figure?

Noise Figure (NF) is a measure of the degradation of the signal-to-noise ratio (SNR) of a system or device, such as an amplifier, receiver, or mixer, due to the presence of intrinsic noise. It’s expressed in decibels (dB) and represents the relationship between the input and output SNR levels.

Why is Noise Figure important in communication systems?

Noise Figure is crucial in communication systems because it determines the overall performance and sensitivity of the system. A lower Noise Figure indicates better performance and higher signal quality. In wireless communication systems, low Noise Figure devices are essential to maximize the received signal strength, minimize data errors, and increase the range.

How is Noise Figure calculated?

Noise Figure is calculated using the following formula: NF = 10 * log10(F), where NF is the Noise Figure in decibels (dB) and F is the noise factor, which is the ratio of input SNR to output SNR.

What factors can affect Noise Figure?

Several factors can affect Noise Figure, including the temperature, frequency of operation, type and quality of components used, and amplifier gain. In general, as temperature and frequency increase, the Noise Figure also tends to increase. High-quality components and careful design can help minimize the Noise Figure.

What is a typical Noise Figure value for a receiver?

The typical Noise Figure value for a receiver varies depending on the application and frequency range. For example, in satellite communication systems, the Noise Figure for a low-noise block downconverter (LNB) is generally between 0.5 dB and 3 dB. In cellular systems, the Noise Figure for a base station receiver is typically in the range of 1.5 dB to 3 dB.

Related Technology Terms

  • Signal-to-Noise Ratio (SNR)
  • Amplifier Gain
  • Receiver Sensitivity
  • Thermal Noise
  • Noise Temperature

Sources for More Information


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