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7920 139th Ave SE
Newcastle, WA 98059

                     


FFTX

The FFT control allows one to quickly calculate the Fast Fourier Transform and the Inverse Fast Fourier Transform of a real or complex data set.   The control also includes the option of Welch windowing the data prior to FFT.  Included sample code demonstrates various examples of the FFT/IFFT usage, including how to use the control for creating a smoothing filter. Other uses for the control includes data convolution and deconvolution.

The control is robust and simple to use. To FFT data,  make a call to the FFT method, passing the data set, plus the number of data points. Upon return, the data  has been replaced by it's frequency domain transform. To take the inverse, make a similar call to the IFFT method. To use Welch windowing prior to FFT,  just set the Welch window property to true.

For a complex data set, make a call to the complex FFT method (CFFT) passing vectors of the real and imaginary components of the complex numbers. Use the complex IFFT (ICFFT) to take the complex inverse.


A simple CFFT/CIFFT example:

Private Sub Perform_FFT()

Redim dataX(1024) as double
Redim datareal(1024) as double, Redim dataimaginaray(1024) as  double
Redim datarealp (1024) as double, Redim dataimaginarayp(1024) as  double

Dim i as long,  N as long

'  example data
N=1024
For i = 0 To N - 1
        dataX(i)=CDBL(i)
        datareal(i) = 15.0 * Sin(2# * PI * dataX(i) * 12/N)  _
                          +12.0 * Sin(2# * PI * dataX(i) * 20/N) _
                          +15.0 * Sin(2# * PI * dataX(i) * 30/N) _
                          +50.0*rnd-25
        dataimaginary(i) = 0.0 
Next i

' take FFT of data
call FFTX1.CFFT(datareal(0), dataimaginary(0), number_of_data)

 ' take IFFT which will equal original dataset
call  FFTX1.ICFFT(datareal(0), dataimaginary(0), number_of_data)

end sub

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