a School of Electrical Engineering and Telecommunications, University of New South Wales, Sydney 2052, NSW, Australia
b Mathematisches Institut, Universität Würzburg, Am Hubland, D-97074, Würzburg, Germany
Abstract:
A solution X of a discrete-time algebraic Riccati equation is called unmixed if the corresponding closed-loop matrix Φ(X) has the property that the common roots of det(sI−Φ(X)) and det(I−sΦ(X)*) (if any) are on the unit circle. A necessary and sufficient condition is given for existence and uniqueness of an unmixed solution such that the eigenvalues of Φ(X) lie in a prescribed subset of .