What is the formula for Equivalent Noise Temperature?

The Equivalent Noise Temperature formula is Te = T0 × (NF − 1), where Te—Equivalent noise temperature (K); T0—Reference temperature, standard 290K (K); NF—Noise factor (linear, not dB).

What does Te mean in the Equivalent Noise Temperature formula?

Te is Equivalent noise temperature (K).

Equivalent Noise Temperature

Q: How do you calculate Equivalent Noise Temperature?

Use the formula Te = T0 × (NF − 1). Equivalent noise temperature provides an alternative way to express the noise contribution of a component by stating what temperature a matched resistor at the input would need to be to produce the same amount of noise. Enter the values you know in the calculator above and it solves for the remaining variable.

Q: What should I watch out for when using Equivalent Noise Temperature?

A 1 dB noise figure corresponds to Te = 75K. A 3 dB NF gives Te = 290K. Satellite LNAs operate at 40-70K noise temperature (0.5-0.8 dB NF). Radio telescopes use cryogenic receivers at 5-15K. The sky noise temperature at microwave frequencies is about 3K (cosmic microwave background) plus atmospheric contributions.

Te = T0 × (NF − 1)

Calculator

Noise Temperature

Reference Temperature

Noise Factor (linear)

Result

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Formula

Te = T0 × (NF − 1)

Description

Equivalent noise temperature provides an alternative way to express the noise contribution of a component by stating what temperature a matched resistor at the input would need to be to produce the same amount of noise. A perfect noiseless amplifier has Te = 0K. The standard reference temperature is T0 = 290K. This representation is preferred in radio astronomy and satellite communications where system noise temperatures are very low (cryogenic LNAs achieve Te < 10K). Noise temperature adds directly for cascaded stages (when properly referred to the same point).

Variables

Te — Equivalent noise temperature (K)
T0 — Reference temperature, standard 290K (K)
NF — Noise factor (linear, not dB)

Practical Notes

A 1 dB noise figure corresponds to Te = 75K. A 3 dB NF gives Te = 290K. Satellite LNAs operate at 40-70K noise temperature (0.5-0.8 dB NF). Radio telescopes use cryogenic receivers at 5-15K. The sky noise temperature at microwave frequencies is about 3K (cosmic microwave background) plus atmospheric contributions.

Related Concepts

All Signal & RF formulas →

Wavelength Free Space Path Loss Signal-to-Noise Ratio Nyquist Sampling Rate Link Budget Antenna Gain Skin Depth Friis Noise Figure (3-stage)

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