说明：  对信号进行傅里叶变换，并绘出频谱图，功率谱，对数谱等。然后对信号进行反傅里叶变换恢复出原始信号，并绘出其各种谱图
(The Fourier transform of the signal, and plot the frequency spectrum, power spectrum, the number spectrum. And inverse Fourier transform to recover the original signal and plot its various spectrum signal)