Fit sinc square to FFT peak

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Tobias Reichold 2019-8-25

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评论： Matt J 2019-8-25

Good evening,

I have an FFT peak to which I need to fit a sinc square function to obtain an improved estimate for the peak location and peak width. However there doesn't seem to be a function to perform this properly. Has someone done this before/knows the correct function? Below is the figure in question. Any help would be much appreciated.

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Matt J 2019-8-25

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A more direct method would be to use the Curve Fitting Toolbox to fit a Fourier Series

https://www.mathworks.com/help/curvefit/list-of-library-models-for-curve-and-surface-fitting.html#btbcxno-1

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Tobias Reichold 2019-8-25

Not quite. Basically I have a sinusoidal fringe pattern I extract from an optical spectrum line. I have recovered the fringe frequency by taking a 1D fft and getting the frequency in cycles as shown previously. But rather than just taking the point of highest magnitude (other than the DC term) I thought fitting a sinc squared would be better as it immediately gives the peak position and width. But I didn't find any function to implement this.

Matt J 2019-8-25

I don't really understand though why your model is a sinc-squared. A sinc-squared spectrum is the Fourier transform of a triangular time domain pulse.

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