Spectrally-efficient constant-amplitude digital modulation schemes for communication satellite applications. Task 3: Transmitter implementation

In this task we investigate implementation aspects of different CPM modulators are investigated. Only CPM schemes with fixed modulation index h are considered. In the following we first give the general structures are given the practical implementation aspects are discussed with a few special cases. The basic conceptual transmitter structure is shown. Because of the exact relation needed between the symbol rate and the modulation index this structure is not easily converted into a practical implementation. However, a solution based on this structure is investigated. The three other transmitter structures are studied. The general quadrature transmitter structure, refered to as the ROM structure, is considered. The structure based on a simple PSK modulator followed by a phase locked loop with a certain loop transfer function is also investigated. This structure has certain limitations concerning the g(t)-pulses that can be implemented. It is also limited in the maximum modulation index.