Enhanced Modes of the Sensitivity Analysis for RF Design

The majority of standard tools for computer aided design can perform only limited types of the sensitivity analysis: Spice determines operating-point sensitivities, and Affirma RF contains a parametric sensitivity analysis that can be used for determining phase noise, for example. In the paper, some types of the sensitivity analysis in the frequency domain are described which are not present in the standard simulators—especially, a procedure is suggested for determining the sensitivities of noise figure. First, an improvement of the method for computing the noise figure is presented, which incorporates necessary circuit matching and eliminates the subtraction of output noise from load at each frequency. Second, a simple formula is derived for computing the sensitivities of the noise figure. The sensitivity analysis in the frequency domain is generally demonstrated by means of a distributed microwave amplifier first, and then using the sensitivity analysis of the noise figure for improving the noise properties of a monolithic microwave amplifier is described.