State Variables and Feedback Theory
E.S. Kuh · IEEE Transactions on Circuit Theory · 1969
The state-space characterization of a linear timeinvariant system can be viewed in terms of a general multiple-loop feedback configuration. The return difference matrix and the null return difference matrix with respect to theAmatrix are derived and related to the poles and zeros of the transfer function. A useful formula for sensitivity of the transfer function with respect to an element of theAmatrix is also obtained.