说明：  对信号进行FFT，绘制出频率变化振幅，以及Nyquist频率之前随频率变化的振幅，进行谱分析，对归一化频率0~1进行分析。
(The signal is FFT, the amplitude of frequency change is drawn, and the amplitude of the frequency changes with the frequency before the Nyquist frequency. The spectral analysis is carried out, and the normalized frequency 0~1 is analyzed.)