matlabfft简单例子(国外英文资料).docVIP

matlabfft简单例子(国外英文资料) N=128; N=0:N-1; T=n/fs; F0=10;% sets sine signal frequency % generates sinusoidal signals X=sin (2*pi*f0*t); Figure (1); Subplot (231); Plot (T, x)% sinusoidal waveform in time domain Xlabel (t); Ylabel (y); Title (` sine signal, y=2*pi*10t time domain waveform ); Grid; % to do FFT transform and do frequency spectrum Y=fft (x, N);% performs the FFT transform Mag=abs (y);% for magnitude F= (0:length (y) -1)*fs/length (y);% corresponding frequency conversion Figure (1); Subplot (232); Plot (F, MAG):% do spectrogram Axis ([0100,0,80]); Xlabel (` frequency (Hz) ); Ylabel (amplitude); Title (sine signal y=2*pi*10t amplitude spectrum N=128); Grid; MATLABs FFT program 2009-11-08 16:30clc X% input signal M=nextpow2 (x);% x length corresponds to the minimum power m of 2 N=2^M; If length (x) N X=[x, zeros (1, N-length (x))]% if the length of X is not the power of 2, the integral power of zero to 2 End Nxd=bin2dec (fliplr (DEC2BIN ([1:N]-1, M) +1));% for 1:2^M sequence number in reverse order Y=x (NXD); X% will reverse order as the initial value of Y WN=exp (-i*2*pi/N); For L=1:M B=2^L/2;%, class L, each butterflys two input data is separated by B points, each level has B different rotation factors For J=0:B-1% J represents a different rotation factor P=J*2^ (M-L); WNp=WN^p; For k=J+1:2^L:N%, this butterfly operation spans an interval of 2^L Kp=k+B; the two factor of a butterfly operation that corresponds to the unit subscript T=y (KP) *WNp; the product of the butterfly operation Y (KP) =y (k) -t;% butterfly operations, attention must first be subtraction, and then add operations, or use intermediate variables to pass y (k) Y (k) =y (k) +t;% butterfly arithmetic End End End Y Y1=fft (x)% FFT is compared with the result of the function operation that is called directly *************************************************************************% % FFT practice and frequency analysis,% %*************************************************************************%