equivalent input noise and noise figure

The received signal after low noise amplifier (LNA) is very small so that noise would degrade the information. It is very important to determine how small of the signal that the circuit can handle. The term “equivalent input noise voltage” gives us a parameter that how small of the input signal strength of the circuit (sensitivity). The calculation is to measure the root-mean-square output noise voltage and divided by the voltage conversion gain.

In the study of wireless communication, the performance of noise is determined by in terms of signal-to-noise ratio (SNR). For system point of view, every circuit is regarded as a noise sources and added noise at every stage before the baseband circuit. Therefore, the SNR at output is always lower than the input. Thus, we define a term “Noise Figure” which tell us the ratio of SNR of input with respected to output.

The noise due to soure is always refering to the white noise from 50 ohm input source impedence so that the noise due to source in measurement and simulation. The spectral density of soure can be obtained by:

Re: Equivalent Input Noise and Noise Figure

Noise Figure (NF) is the ratio (in dB) between the signal-to-noise ratio applied to the input of the microwave component and the signal-to-noise ratio measured at its output. It is an indication of the amount of noise added to a signal by the component during normal operation. Lower noise figures mean less degradation and better performance.