Abstract

Among the noise parameters expressed in the reflection coefficient form ( Fo, IFOI, /Fo and rn ), the noise resistance rn is of critical importance lo the design of low-noise receivers. Very low values of rn allow for optimizing the performance of broad band amplifiers in receiver front-ends. We here present an analysis performed on typical circuit models of FET's which was aimed at assessing the key elements influencing the behavior of rn at microwave frequencies. We found that the noise performance can be improved by tuning the value of the input (gate, source) inductances which are responsible of the U shaped curves typically observed for rn in MESFET's and HEMT's.