Coded nonlinear continuous phase modulation

A class of nonlinear continuous phase modulation (CPM) signals is introduced by extending nonlinear continuous phase frequency shift keying (CPFSK) signals. Coding is considered to further improve the performance of nonlinear CPM signals. Numerical results indicate that both uncoded and coded CPM signals achieve attractive minimum Euclidean distances. Gains of over 1.8 dB over previous schemes have been reported at the same number of states. The spectral properties of nonlinear CPM signals are kept close to those of full response linear CPM with a modulation index of 0.5. It is shown that both uncoded and coded nonlinear CPM signals can be realized by using a finite state machine and a standard FM modulator.<>