用FFT分析离散时间周期信号的频谱实例，利用FFT分析离散时间周期信号的频谱，通过实验理解分辨率的概念和栅栏效应。-With a the FFT analysis the the frequency spectrum instance of of the discrete-time periodic signal, the use of the FFT analysis the the frequency spectrum of the discrete-time periodic signal