| Continuous Phase Modulation is a class of spectrally efficient digital modulation schemes with constant envelope and continuous phase, thereby widely used in the field of mobile communications, satellite communications and remote metering, etc.In this paper, a CPM data transmission system based on FPGA, DSP and AD chips was studied and developed. Firstly, two kinds of expressions of the CPM signals and their power density spectrum formula were introduced, on the basis of which the influence of modulation parameters on CPM spectral properties was simulated and analyzed. Then, a CPM modulation-demodulation system was designed, mainly including modulation, demodulation and synchronization, with further simulation on the performance of these schemes. In the system design, a kind of decomposition model for modulation was proposed, thus effectively reducing the implementation complexity and resource consumption; A kind of combined synchronization based on coarse synchronization and accurate synchronization was proposed.Viterbi algorithm based on the maximum likelihood criterion was used for decoding. Finally, a hardware platform for the CPM system was realized based on FPGA,DSP and AD chips development board. Extensive testing and analysis verified good performance of the platform. |
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