2.3.6 Fast Fourier transform FFT Improving the efficiency of the computation of the dFt exploits one or both of the following special properties of the quantities 1)Symmetry A (2235) 2)Periodicity W=WN Wk+N)n (2236)Improving the efficiency of the computation of the DFT exploits one or both of the following special properties of the quantities : 1) Symmetry 2) Periodicity 2.3.6 Fast Fourier transform (FFT) kn WN ( ) ( ) * kn N k N n WN = W − (2.235) ( ) (k N )n N k n N N kn WN W W + + = = (2.236)