1)编写DFT子函数（计算并画出幅频特性），以后可调用。

2）N=32，M=32，128，256时，分析频率分辨率、频谱的光滑程度。

3）N=64，256，512时，分析频率分辨率和频谱的光滑程度。

-1) the preparation of DFT Functions (calculated and drawn amplitude-frequency characteristics), the future can be called. 2) N = 32, M = 32,128,256, the analysis of the frequency resolution, the degree of smooth spectrum. 3) N = 64,256,512, the analysis of the frequency spectrum resolution and the degree of smoothness.