ex050600.m

stft(含:短时傅立叶变换 Gabor变换等)

% Chapter 05: Example 05.06: Simple DFT Example
%
x = [1,1,1,1];
subplot(1,1,1);
%
% a) DTFT
w = [0:1:500]*2*pi/500;
[H] = freqz(x,1,w);
magH = abs(H); phaH = angle(H); phaH(126)=-47.5841*pi/180;
subplot(2,1,1); plot(w/pi,magH); grid
xlabel('frequency in pi units');
ylabel('|X|'); title('Magnitude of the DTFT')
subplot(2,1,2); plot(w/pi,phaH/pi*180); grid
xlabel('frequency in pi units');
ylabel('Degrees'); title('Angle of the DTFT')
%print -deps2 me0506a.eps
pause;subplot(1,1,1)
%
% b) 4-point DFT
N = 4; w1 = 2*pi/N; k = 0:N-1;
X = dft(x,N);
magX = abs(X), phaX = angle(X)*180/pi
subplot(2,1,1);plot(w*N/(2*pi),magH,'--'); 
axis([-0.1,4.1,-1,5]); hold on
stem(k,magX);
xlabel('k');
ylabel('|X(k)|'); title('Magnitude of the DFT: N=4')
hold off
subplot(2,1,2);plot(w*N/(2*pi),phaH*180/pi,'--');
axis([-0.1,4.1,-200,200]); hold on
stem(k,phaX);
xlabel('k');
ylabel('Degrees'); title('Angle of the DFT: N=4')
%print -deps2 me0506b.eps