[datuman]

f这项处理的不对。

频谱分析建议记住这些：

x Sampled data
m = length(x) Window length (number of samples)
fs Samples/unit time
dt = 1/fs Time increment per sample
t = (0:m-1)/fs Time range for data
y = fft(x,n) Discrete Fourier transform (DFT)
abs(y) Amplitude of the DFT
(abs(y).^2)/n Power of the DFT
fs/n Frequency increment
f = (0:n-1)*(fs/n) Frequency range
fs/2 Nyquist frequency