]>
where the pair is a solution of the equations
(8.12) |
in such a way that a spectral factor
(8.13) |
should be invertible in the Callier–Desoer algebra (case of a countably many –impulses). In other words its numerator should be a stable quasipolynomial, which holds for
(8.14) |
Indeed, it is easy to check that , which is a necessary and sufficient condition for this quasipolynomial to have roots in the open left half complex plane (roots are located on a straight line parallel to , as for the open–loop–system quasipolynomial ).
In what follows, we assume that and in (8.13), and in other formulae in which they will appear, are determined by (8.14).