Simplification of linear time-invariant systems by moment approximants †

Abstract Given a system S characterized by a transfer function, a practical method is developed for finding a system S∗ with proper rational transfer function of small denominator degree, such that the step response of S∗ is, in an appropriate sense, the baat approximant to the step response of S. The method is extended to multivariable systems. Various relations between moment and Pade approximants are derived.