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 spec