ch32快速傅里葉變換fft-資料下載頁(yè)
2025-09-20 22:22本頁(yè)面
【導(dǎo)讀】DFT:N2次的復(fù)數(shù)乘法,N(N-1)次的復(fù)數(shù)加。法,N很大時(shí),計(jì)算量相當(dāng)可觀,N=1024,種算法”的文章,提出快速傅立葉變換，成為DSP發(fā)展史上的里程碑。FFT只是DFT的一種算法,不是新的變換,使得DFT的乘法計(jì)算量由N2降低到,N=1024,乘法計(jì)算量為5120,僅為原來(lái)的%. DFT運(yùn)算中含有大量的重復(fù)運(yùn)算,此時(shí),只需一次復(fù)數(shù)乘。把一個(gè)序列分為長(zhǎng)度減半的偶序列和奇。進(jìn)一步把N/2序列分解成兩個(gè)N/4序列,一。以L=3,N=8為例，需要三級(jí)分解,要使得X正常排序,輸入序列的順序打亂,以二進(jìn)制數(shù)碼倒置順序排列,即碼位倒置,
【正文】 ing Nankai University, CY LI, FFT of sin(x) 0 10 20 30101sin(n), T=1s0 10 20 3005101520x(n)=sin(n) 的 FFT 的的的0 20 40 60101sin(n), T=0 20 40 600102030x(n)=sin(n) 的 FFT 的的的Biomedical signal processing Nankai University, CY LI, fft in MATLAB ?fft and ifft, for one dimension ?fft2, ifft2, fftn, two and multidimensions, ?fftshift, ifftshift, shift the DC ponent to the middle of the spectrum, Biomedical signal processing Nankai University, CY LI, fft ? FFT(X) is the discrete Fourier transform (DFT) of vector X. For matrices, the FFT operation is applied to each column. For ND arrays, the FFT operation operates on the first nonsingleton dimension. ? FFT(X,N) is the Npoint FFT, padded with zeros if X has less than N points and truncated if it has more. ? FFT(X,[],DIM) or FFT(X,N,DIM) applies the FFT operation across the dimension DIM. ? For length N input vector x, the DFT is a length N vector X, with elements ? N ? X(k) = sum x(n)*exp(j*2*pi*(k1)*(n1)/N), 1 = k = N. ? n=1 ? The inverse DFT (puted by IFFT) is given by ? N ? x(n) = (1/N) sum X(k)*exp( j*2*pi*(k1)*(n1)/N), 1 = n = N. ? k=1
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