One solution for constant envelope modulation

A comparative study of constant envelope modulation schemes, QPSK, OQPSK, MSK, and QMCPFSK, for use in nonlinear satellite channel communications is presented. A superior QMCPFSK (quasi-multilevel continuous phase frequency shift keying) modulation scheme is proposed in which sidelobe levels are low and detection performance on nonlinear band-limited communication channels is efficient. The bit error rate (BER) performance and power spectral densities of a QMCPFSK modem using OQPSK-raised cosine Nyquist shaping and an amplitude limiter are presented. The study results indicate that the BER of the QMCPFSK is more superior to the others in a comparatively narrow band model of channel allocation selected close to delta fT = 1.5 (delta f: channel separation frequency, T: symbol duration time).