Hankel singular values and vectors of a class of infinite dimensional systems for control and approximation problems

This paper considers the problem of computing singular values and singular vectors of Hankel operators of a class of infinite dimensional systems. The class consists of plants that are a product of a general inner function and a rational function. It is shown that there is a transcendental equation characterizing the singular values and that the singular vectors are calculated from the null vector of a matrix. This extends the results in the literature to include the approximation problem having a general inner part.