A characterization of minimal square spectral factors
Lorenzo Finesso, Giorgio Picci · IEEE Transactions on Automatic Control · 1982
Two different well-known approaches to the spectral factorization problem\Phi(s)=W(s)W'(-s)are connected together by relating the geometric properties of the solution set of the underlying algebraic Riccati equation to the structure of the "all-pass" factor of each minimal solutionW(s).