PAM Decomposition of Ternary CPM With Duobinary Encoding

In this paper, we investigate the pulse amplitude modulation (PAM) decomposition and the spectral efficiency of duobinary continuous phase modulation (CPM), where duo- binary CPM represents a ternary CPM whose symbols are generated using a duobinary encoder. We show that this precoder ensures a higher spectral efficiency compared with binary CPM and we propose a PAM decomposition characterized by the presence of a single main pulse and by uncorrelated pseudo-symbols for a half integer modulation index value for this ternary CPM. We show that shaped offset quadrature phase shift keying belongs to this CPM family and we provide a new reduced complexity trellis detector capable of reaching identical performance as the one introduced by Perrins as well as new linear detectors.