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FFT Filter Smoothing

FFT Filter smoothing is accomplished by removing Fourier components with frequencies higher than a cutoff frequency of:

where n is the number of data points specified by the user, and Δt is the time (or more generally the abscissa) spacing between two adjacent data points. Larger values of n result in lower cutoff frequencies, and thus a greater degree of smoothing. The function used to clip out the high-frequency components is a parabola with a maximum of 1 at zero frequency, and falling off to zero at the cutoff frequency defined above.

Origin and FFT Filter smoothing...

FFT Filter smoothing is accessible from Origin's Analysis menu or the Smoothing tool (Tools:Smooth). When selected, the Smoothing dialog opens.

The cutoff frequency is determined by the Number of Points, specified by user, according to the formula listed above.

The dialog also includes a Smoothed Line Color drop-down list and an Apply button. The Apply button can be used to perform the smoothing operation as many times as you want without ever leaving the dialog. As long as the dialog is open, the smoothed line replaced by the result of the latest calculations.