2.3. 1 Discrete Fourier Transform DFT) uFig 2.63(a): a nonperiodic continuous signal x(t)and its Fourier transform spectrum X(. The spectrum is continuous OFig. 2.63 (b): a periodic continuous signal and the frequency spectrum is or discrete F:X()=「x(012dt (2201) JFT:x()=∑X()e2m (2202) where f=ky(k=0,±1±2…) Af: fundamental frequencys❑Fig. 2.63 (a): a nonperiodic continuous signal x(t) and its Fourier transform spectrum X(f). The spectrum is continuous. ❑Fig. 2.63 (b): a periodic continuous signal, and the frequency spectrum is or discrete. where Δf: fundamental frequency, 2.3. 1 Discrete Fourier Transform (DFT) ( ) ( ) − − = 2 2 1 2 : T T j f kt k x t e dt T FT X f  (2.201) ( )  ( )  =− = k j f t k k IFT x t X f e 2 : (2.202) f = kf (k = 0,1,2, ) k T f 1  =