Applications of multidimensional large- and small-signal impedances and S-parameters

This paper’s aim is two fold: calculated in multi-variable simulation. 1. to present extraction of impedances and S-parameters from currents and voltages. 2. to present a fresh look at applications of S-parameters in circuit design. First, we discuss stability analysis in which S-parameters are used in Bode and in Nyquist plots. In particular we present an example which illustrates the limitations of Barkhausen criterion (SrSn, > 1) and shows that the Bode plots might be misleading. We conclude that, while the Nyquist criterion remains valid and so does Bode but with very careful data representation, the Barkhausen criterion holds only when additional conditions are satisfied.