Discrete Fourier Transform:-
The Discrete Fourier Transform (DFT) of a signal may be defined by
Where ` ' means ``is defined as'' or ``equals by definition'', and
The inverse DFT (the IDFT) is given by
In the signal processing literature, it is common to write the DFT and its
inverse in the more pure form below, obtained by setting in the
previous definition:
Where denotes the input signal at time (sample) , and denotes the
th spectral sample. This form is the simplest mathematically, while the
previous form is easier to interpret physically.