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Hi, Thank u all for being so nice and supporting . Now there is another technique of getting higher resolution fft i have learned from mathematical journal without taking long sample here is steps involved in it (1)On input Data perform FFT using Nres NFFT = Length of data (2)Take chunk of data perform IFFT on it (3) Do FFT on it Higher resolution (4) Again do IFFT on chunk of data (5) Do FFT on it using very narrow resolution The journal says this algorithm of Zoom fft is recursive and can be implemented when i tried to implement on matlab i get serious errors clear all; fs = 400 ; % sampling rate Nres = 0.1 ; %spectral resolution of fft Nfft = fs/Nres ; % number of points in fft i.e 4000 t = (0:Nfft-1)/fs ; %length of signal in time domain sig1 = sin(2*pi*t*100); %100 Hz sinousidal signal sig2 = sin(2*pi*t*100.3) ; %100.5Hz sinousidal signal sig0 = sig1+sig2 ; %Adding signal together blocksize = 4000; wnd = hanning(blocksize)' ; %Hanning window olap = 0.5; %Overlap by half a block each time len = length(sig0); overlap = 0.5 ; % overlap by half block each time for k = 1:overlap:len/blocksize ss = (k-1)*blocksize+1; %First block index ee = k*blocksize ; %Last block index sndw = fft(wnd.*sig0(ss:ee)); end Now am confused where to put ifft and fft Regards Maria --------------------------------- |
Higher resolution FFT
Started by ●January 21, 2004
