Reconstruct time series from FFT components. There is a time shift error.

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Haifei Chen 2024-6-24，18:38

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评论： Haifei Chen 2024-6-25，4:38

Hello,

I'd like to extract various frequency components (amplitue, frequecny, phase) by applying FFT to a time series. Then to check if I get the correct numbers, reconstruct the time series by summing up the cosine components. As shown in the figure attached, there seems to be a growing time shift. What went wrong in my script? This issue is absent for my another set of data though.

Thank you!

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Answer 1

Paul 2024-6-25，3:49

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编辑：Paul 2024-6-25，3:56

在 MATLAB Online 中打开

Hi Haifei,

You may want to investigate why the data is not uniformly sampled and how that impacts the analysis. Does the other set of data exhibit the same behavior?

load fftData.mat

t = t_exp';

x = y_exp';

plot(diff(t))