# How is noise figure calculated?

Table of Contents

## How is noise figure calculated?

To get a stable and accurate reading of the noise density, the optimum ratio of RBW (resolution bandwidth) and VBW (video bandwidth) is RBW/VBW = 0.3. Thus we can calculate the NF to be: -90dBm/Hz + 174dBm/Hz – 80dB = 4.0dB. The “Gain Method” can cover any frequency range, as long as the spectrum analyzer permits.

**How do you calculate noise power from a noise figure?**

To calculate the effective noise power of the thermal noise injected into the system over the frequency of interest, then PSD is integrated over the band. Example: If the band of interest is 1 MHz, then the effective thermal noise power comes out as: –174 dBm / Hz + 10log10(106) = –114 dBm / 1 MHz.

**How do you test noise figure of LNA?**

The ‘magic number’ for noise power is -174 dBm/Hz at room temperature. Take the difference between the measured noise power and the room temperature noise power (-174 dBm/Hz) and subtract the gain to get the noise figure.

### What is the ideal value of noise figure?

For an ideal amplifier, when a signal passes through the system, then no noise is added to the signal, and input SNR is equal to the output SNR and hence NF for the ideal amplifier is 1 or 0 dB.

**How can I improve my noise figure?**

Noise figure analyzer uncertainty can be significantly improved via the use of a pre-amplifier before the measurement system. The pre-amplifier should have substantial gain combined with a low noise figure. The fundamental goal of the pre-amplifier is a reduction in the overall “system” noise figure.

**What is a good noise figure?**

A typical professional or ham HF radio receiver may have a noise figure of 15 dB of more and function quite satisfactorily. A better level of performance is not necessary because of the high level of atmospheric noise.

#### What is the unit of noise figure?

Noise Figure (NF) is the Noise factor converted to Decibel (dB). It is a measure of degradation of the signal to noise ratio (SNR), caused by components in the RF signal chain, for a given bandwidth.

**What is the ideal value of noise figure in dB?**