stft.m

以矩形窗实现stft

load mtlb
load mtlb;
x=mtlb;
figure(1)
plot(0:4000,x);
xlabel('n');
ylabel('x(n)');
title('random unbalanced signal x');

n0=0;
R=128;
n1=4000;
n2=n0+R;
n=[n0:n1];
w=[(n-n0)>=0];
wd=[(n-n2-1)<=0];
WN=w.*wd;
figure(2)
stem(n,WN);
xlabel('n');
ylabel('W(N)');
title('Rectangular Window WN');
grid

x1=x';
y1=x1.*WN;
figure(3)
plot(n,y1);
xlabel('n');
ylabel('y1');
title('The first block')

k=1:128;
y3=[y1(n0+1:n2)];
figure(4)
plot(k,y3);
xlabel('k');
ylabel('y3');
title('The effective signal')

yn=fft(y3);
YN=abs(yn);
figure(5)
plot(k,YN);
xlabel('frequency(Hz)');
ylabel('Abs');
title('Frequency content of yn');

for i=1:60
    n2=n2+64;
    n3=n0+i*64;
    n=[n0:n1];
    w=[(n-n3)>=0];
    wd=[(n-n2)<=0];
    WN=w.*wd;
    x1=x';
    y1=x1.*WN;
    m=0:128;
    y2=[y1(n3:n2)];
    figure(i+5)
    plot(m,y2);
    xlabel('m');
    ylabel('y2');
    title('Every signal signal');
    ym=fft(y2);
    YM=abs(ym);
    figure(i+5+60)
    plot(m,YM);
    xlabel('frequency(Hz)');
    ylabel('Abs');
    title('frequency content of ym');
end