说明：  编写matlab程序，仿真2DPSK调制信号在高斯信道下分别采用相干解调及差分相干解调两种解调方式时的性能，并与理论分析结果相比较。
(Write matlab procedures, simulation 2DPSK modulated signals in Gaussian channel performance respectively coherent demodulation and coherent demodulation difference when the two demodulation, and compared with the theoretical analysis.)