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How to use TFastFourier


The application of TFastFourier is straightforward. First, put as many FFT components as needed on a form and specify the proper data array size(s) by setting the property SpectrumSize. In order to calculate the Fourier spectrum, fill in the RealSpec array property with the data and call the method Transform (don't forget to clear the data buffer by calling Clear before doing anything else). Optionally, you may set the property WeightingWindow, in order to suppress windowing artefacts. Thereafter the results of the transform is available from the array properties RealSpec (real part of the complex spectrum) and ImagSpec (imaginary part). The original data in RealSpec and ImagSpec will be lost.

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In addition, you may retrieve the corresponding power spectrum from the array property PowerSpec, the magnitude spectrum from the property Magnitude, the phase from the property Phase, and the coefficients of the corresponding Fourier series from the properties FourSerSinCoeff and FourSerCosCoeff. The root mean square value of the power of the signal in a given frequency interval can be obtained by using the function RMS. Please note that these array properties use an indexing scheme which is different from the one used for ImagSpec and RealSpec.

The inverse transformation can be achieved quite similarly: fill the properties RealSpec and ImagSpec with the Fourier spectrum and call the method InverseTransform. For high speed applications, the data buffer of the FFT algorithm may be accessed directly by the property FData.

You may also have a look at the sample programs which are delivered with the unit FOURIER.



Last Update: 2013-May-14