  In this paper we address the problem of closed-form spectral evaluation of
CPM. We show that the multi-h CPM signal can be conveniently generated by a PTI
SM. The output is governed by a Markov chain with the unusual peculiarity of
being cyclostationary and reducible; this holds also in the single-h context.
Judicious reinterpretation of the result leads to a formalization through a
stationary and irreducible Markov chain, whose spectral evaluation is known in
closed-form from the literature. Two are the major outcomes of this paper.
First, unlike the literature, we obtain a PSD in true closed-form. Second, we
give novel insights into the CPM format.
