Multivariable Nyquist-Bode and multivariable Root-Locus techniques

The theory of algebraic functions is used to extend to multivariable systems the basic techniques used in classical single-loop feedback theory for studying gain as a function of frequency and closed-loop frequency as a function of gain. This enables the basic building blocks of the classical frequency-response approach : poles, zeros, Nyquist diagrams, and root-locus-diagrams, to be used for multivariable feedback systems.