Dependence of the noise resistance of microwave FET's from the device characteristics

The noise parameters F/sub 0/, /spl Gamma//sub 0/ and r/sub n/ are a complete representation of the noise performance of any linear twoport. We focus upon r/sub n/ which is a measure of the noise figure degradation when the source reflection coefficient departs from the optimum value /spl Gamma//sub 0/. In the present paper, the behaviour of r/sub n/ is analysed as a function of the main elements of the noisy electrical model which reproduces the device performance. Such a study is aimed at evidencing the factors which allow for decreasing either the values and the frequency-dependence of r/sub n/. By optimizing r/sub n/, great improvements can be obtained in the performance of broad-band microwave low-noise amplifiers.