Sensitivity and tolerance analysis for oscillator circuits simulated by Van der Pol models

The paper presents an improvement of sensitivity and tolerance analysis method for the Voltage-Controlled Oscillator (VCO) circuits with Van der Pol model. The tolerance analysis method is based on the Monte Carlo Analysis (MCA) and on the Fast Monte Carlo Analysis (FMCA) based on the circuit transfer function. The circuit sensitivities are computed by means of the derivatives of the circuit transfer functions. A practical and reliable approach has been developed and implemented in a computation program for linear (nonlinear piecewise-linearized) analog circuits. The circuits can contain any type of passive elements, independent and controlled sources. Powerful modified nodal approaches to build the mathematical model combined with some symbolic computation strategies have been exploited, in order to reduce the computational effort and to minimize the numerical errors. A software tool was conceived as a useful and valuable support for research and design engineers.