An algorithm of MSK demodulation based on differential composite grid was proposed. The MSK differential composite grid was constructed by phase deflection, and the optimal path in the composite grid was selected by comparing the likelihood function value to compensate the phase error of the Doppler frequency offset. Theoretical analysis and simulation show that the performance of the algorithm was still close to the theoretical lower bound of the MSK non-coherent demodulation error rate when the phase error caused by the Doppler frequency offset was of the order of 10-1rad magnitude. The algorithm extends the range of MSK demodulation anti-Doppler frequency offset, and is superior to similar algorithm in complexity and decision delay time, slightly higher than 1 symbol differential algorithm corresponding value, which provides a new means for demodulation of MSK under Doppler frequency offset.%提出了一种基于差分复合网格的MSK解调算法.通过相位偏转构建出最小频移键控(MSK, minimum shift keying)差分复合网格,比较似然函数值选择复合网格中的最优路径,以此抵消多普勒频偏产生的相位误差.理论分析和仿真表明,算法性能在多普勒频偏引起的相位误差为10-1rad数量级的情况下仍能接近MSK非相干解调误码率的理论限.该算法扩展了MSK解调抗多普勒频偏的范围,且在复杂度和判决时间上优于同类算法,略高于1符号差分算法对应值,为在多普勒频偏条件下MSK的解调提供了新的手段.
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