Based upon the active line concept, the conversion mechanisms of microscopic low frequency noise (e.g. generation-recombination noise) located in the channel of a Field Effect Transistor (FET) which is driven by a large RF signal is demonstrated. The first consequence is that the based band (low frequency) input gate noise voltage spectral density is dependent on the magnitude of the input RF power applied to the FET. Moreover, the microscopic generation-recombination noise sources located in the channel are responsible of up-converted input gate noise voltage spectral density around the RF frequency