www.pudn.com > voiceprocessingtoolbox.rar > fft4.m

% Add a "Blackman window" 
% w = blackman(M); % if you have the signal processing toolbox 
M=64; 
w = .42-.5*cos(2*pi*(0:M-1)/(M-1))+.08*cos(4*pi*(0:M-1)/(M-1)); 
figure(5); 
subplot(3,1,1); plot(w,'*'); title('The Blackman Window'); 
xlabel('Time (samples)'); ylabel('Amplitude'); 
text(-8,1,'a)');  
 
% Also show the window transform: 
xw = [w,zeros(1,(zpf-1)*M)]; % zero-padded window (col vector) 
Xw = fft(xw);                 % Blackman window transform 
spec = 20*log10(abs(Xw));     % Spectral magnitude in dB 
spec = spec - max(spec);      % Usually we normalize to 0 db max 
spec = max(spec,-100*ones(1,nfft)); % clip to -100 dB 
subplot(3,1,2); plot(fni,spec,'-'); axis([0,1,-100,10]); grid; 
xlabel('Normalized Frequency (cycles per sample))');  
ylabel('Magnitude (dB)'); 
text(-.12,20,'b)');  
 
% Replot interpreting upper bin numbers as negative frequencies: 
nh = nfft/2; 
specnf = [spec(nh+1:nfft),spec(1:nh)];  % see also Matlab's fftshift() 
fninf = fni - 0.5; 
subplot(3,1,3); 
plot(fninf,specnf,'-'); axis([-0.5,0.5,-100,10]); grid; 
xlabel('Normalized Frequency (cycles per sample))');  
ylabel('Magnitude (dB)');