Minimal Square Spectral Factors via Triples
Mitchell A. Petersen, André C. M. Ran · SIAM Journal on Matrix Analysis and Applications · 2001
We consider the problem of parametrizing the set of square minimal spectral factors of a rational matrix function taking positive semidefinite values on the imaginary axis in terms of invariant subspaces and of the minimal unitary left divisors of a certain unitary function. We shall use an approach which involves null-pole triples.