Comments on "Cryogenic noise parameter measurements of microwave devices"

For original paper see Rolfes et al. (IEEE Trans. Instrum. Meas., vol.50, p.373-6, 2001 April). With regard to the original paper, the present author wishes to make remarks on the following statements presented in the abstract: "In contrast to existing concepts, the seven-state method makes it possible to determine the minimum noise figure F/sub min/ and the equivalent noise resistance R/sub n/, except for a constant term m with the help of noise power measurements with a noise source operated at ambient temperature only. The optimum generator admittance Y/sub opt/ and the input admittance Y/sub in/ of the device under test are completely calculable from cold noise power measurements. An additional measurement of Y/sub in/ with a network vector analyzer as needed for other techniques is not necessary.".