Research On CPFSK Modulation And Demodulation Technology

CPFSK(Continuous Phase Frequency Shift Keying) is a class of nonlinear modulation scheme with memory,which is bandwidth-and power-efficient. However, CPFSK still suffers with the complexity of demodulator and synchronization. Usually, we use MLSD (Maximum-Likelihood-Sequence-Detection) algorithm to demodulate the signal of CPFSK, which is very complex. So, this paper concentrates on a simplified algorithm of demodulation of CPFSK, and it has a very practical significance and value.This article has a concrete study on two presentations on CPFSK signal, the Laurent decomposition of CPFSK signal and CPFSK signal with Rimoldi tilted phase. On the method of Laurent decomposition of CPFSK, CPFSK signal is expressed as a linear combination of a set of PAM signals. On the base of traditianal CPFSK signal, we introduce a titled phase factor to change it into CPFSK signal with titled phase. Then, this paper introduces the expressive formulas of them. Next, this paper introduces the Viterbi algorithm and the coherent demodulators of each CPFSK signal, then paper analyses the performance of CPFSK signal with different parameter through simulation. Result shows that the bit error rate performances with a little loss, and the complexity of demodulator is simplified. Finally, this paper has a study on the mothed of the synchronization and demodulation of each CPFSK signal. We estimate the frequency offset, timing error and the initial phase. The process to implement the algorithm and final emulational results of various performance are recorded.