Noise parameters of the cryogenic LNA expressed following Meys’ noise wave representation, based on two waves at the LNA input. T_a represents the non-correlated part of the wave going into the amplifier (it is the noise temperature measured using a matched load at the source). T_b represents the non-correlated part of the noise wave emitted from the LNA towards the source. Finally, T_c represents the modulus of the noise waves correlation (see Meys 1978).