## FFT

Most spectral analysis tools in SIGVIEW are based on the FFT algorithm. Its main purpose is to transform the signal from its time-domain representation into the frequency-domain representation. For the detailed mathematical description of the algorithm and its interpretation, please refer to the following internet resources:

http://en.wikipedia.org/wiki/Fast_Fourier_transform

http://www.fftw.org/links.html

And a wonderful web page with a free book on digital signal processing can be found at:

By preparing a signal before using the FFT algorithm, changing FFT calculation parameters or post-processing its results, many different variations of the FFT transformation can be applied. One of the most important features in SIGVIEW is the possibility to change most of these parameters and easily observe and compare the results.

To apply FFT transformation to your signal in SIGVIEW, select some window containing a signal and choose the “Signal tools/FFT” option. An FFT result window will be created containing the FFT result, calculated according to your current Spectral analysis defaults. You can change the parameters for the already calculated FFT sequence anytime by selecting the “Edit/Properties” option from the main menu or the “Properties” option from the context menu. The dialog for the editing of FFT parameters is the same as the Spectral analysis defaults dialog – you can find the detailed description of its values and options here.

To display the changes in the FFT result through time, you can use separate a Time FFT function or Tracking changes as 3D graphics function in combination with the normal FFT calculation.