对信号进行频谱分析及滤波，构成不同频率的调制信号，本程序的性能已经超过其他算法，仿真效果非常好，有详细的注释，详细画出了时域和频域的相关图。- The signal spectral analysis and filtering, Constituting the modulated signals of different frequencies, This program has exceeded the performance of other algorithms, Simulation