Analytical behavior of the noise resistance and the noise conductance for a network with parallel and series feedback

An analysis is presented of the changes of the noise parameters of a two-port network when noisy series and parallel feedback immittances are applied. Exact formulas for the noise parameters R/sub n/, g/sub n/, and /spl rho//sub n/ are given as functions of the feedback for a given network. It is proved that R/sub n/ always reaches a minimum when a reactive series feedback is considered. The same results are demonstrated for g/sub n/ since a duality principle is pointed out. The results are valid for a wide range of linear microwave two-port networks, either passive or active, and they are used to confirm the data from previously published work.