Noise figure/factor and equivalent noise tempeture

[sqx]

By defiltration, NF = (N_noise_due_to_input + N_added)/N_due_to_input

When we talk about the noise factor of a LNA under a 50 ohm system, is the input noise regarding the thermal noise of a 50 ohm source resistor? So that the output noise due to input source is K*T*B*Gain?

But let's say we have an antenna with 50 ohm impedance, and it has a equivalent noise temperature which is different from the environment, should the noise factor change?

 

[stenzer]

Hi,

this designe note [1] explains how a noise figure can be converted into its corresponding voltage noise spectral density.

[1] https://www.analog.com/media/en/reference-design-documentation/design-notes/dn439f.pdf

greets