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Open table with initial data and use Analysis → Fast Fourier Transform
menu item to perform FFT.
MagicPlot uses the algorithm of FFT that does not require the number of points to be the integer power of 2.
MagicPlot uses 'electrical engineering' convention to set the sign of the exponential phase factor of FFT as follows from the table below. 1)
Normalize Forward Transform | Forward Transform (Signal→Spectrum) | Inverse Transform (Spectrum→Signal) |
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Unchecked | ||
Checked |
Here are complex signal components and are complex spectrum components, .
The only difference is in the sign of exponential phase factor and multiplier.
Note: If you expect to get the original data when doing a inverse FFT of forward FFT set the Normalize Forward Transform
and Center Zero Frequency
check boxes identically for forward and inverse transforms.
Because of using atan2 function the phase is unwrapped and is in range (].
Center Zero Frequency | Sampling Column Values |
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Unchecked | |
Checked |
Here is given sampling interval of initial data.
Sampling Interval | Sampling interval of original data is used to compute the data in resulting sampling column. If Get from box is set, MagicPlot will calculate sampling interval as difference between two beginning values from given column. You can set sampling interval manually by checking Set manually box. Note that using of discrete Fourier transform implies that the samples in your original data are equally spaced in time/frequency, i.e. the sampling interval is constant. If the sampling interval is varying or real and/or imaginary data contains empty cells in the middle, the result of discrete Fourier transform will be incorrect. |
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Real, Imaginary | Columns with real and imaginary components of data. If your data is only real, select <all zeros> imaginary item |
Forward / Inverse | Transform direction (here Inverse equals to Backward) |
Normalize forward transform | Divide forward transform result by number of points N |
Center zero frequency | If selected, after forward Fourier transform the two parts of spectrum will be rearranged so that the lower frequency components are in the center; the opposite rearrangement of spectrum will be done before inverse transform if any. |