Using the Sensitivity Analysis of the Noise Spectral Density and the Sensitivity Analysis of the Noise Figure for Practical Circuit Design

Although the sensitivity analysis is implemented in contemporary software tools for computer-aided design, kinds of available sensitivities are limited. For example, Spice or Micro-Cap calculate DC or small-signal AC sensitivities, and SpectreRF contains a periodic noise analysis or a parametric sensitivity analysis that can be efficiently used for determining the phase noise. In this paper, some novel types of the noise sensitivity analysis are described, which are not implemented in the usually applied circuit simulators. First, a procedure for determining the sensitivities of the noise figure was suggested. Second, an improvement of the algorithm for computing the noise figure was described, which incorporates circuit matching and eliminates necessary subtraction of the output noise generated by the load resistance at each frequency. Third, a new formula was derived for a computation of the sensitivities of the noise figure. The sensitivity analysis of the noise spectral density is demonstrated by means of an analytically solved example. The application of the sensitivity analysis of the noise figure for improving the noise properties of a microwave integrated circuit is described in a detailed way as well. Finally, using a sophisticated multi-objective optimization is suggested for a better selection of the operating point instead of classical circuit matching. This method was utilized for a practical design of an antenna preamplifier for a GPS/Galileo/GLONASS/Compass receiver.