What is Noise Figure and How to Improve it with a Low Noise Amplifier

Noise Figure describes the amount of noise a component, amplifier, or an entire radio receive chain contributes to the RF signal being received. It can also be defined as the logarithmic unit (dB) derived from the ratio of the signal to noise ratio (SNR) into the device or circuit versus the SNR out of the device. High NF reduces receive clarity and intelligibility.

Although passive components contribute some noise to a signal path, this document will only deal with the NF of amplifiers and chains of amplifiers. This understanding will then be used to demonstrate the improvement in receive quality from adding a low noise amplifier (LNA) to the antenna input (i.e., front end) of a receiver, such as the NuWaves µHILNATM LNA described in
this Application Note.