untitled5.m

y3k=fft(u,(m+n-2)/4) i=1:(m+n-2)/4 subplot(5,2,9) stem(i,u) title( 滤波后上采样 ) k=1:(m+n-2

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1
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1
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];

x=x';
w=0.04*fs,fc=fs/4,m=7801;
    y=zeros(1,4*m);
 for i=1:m,
     y(4*i)=x(i);
 end

  i=1:4*m;
subplot(5,2,1);stem(i,y);
title('下采样');
y1k=fft(y,4*m);
k=1:4*m;
subplot(5,2,2);stem(k,y1k);
title('下采样频谱');
xlabel('k');ylabel('y1k');

for i=1:(m-1)/4,
    h(i)=x(4*i);
end
y2k=fft(h,(m-1)/4);

  i=1:(m-1)/4;
subplot(5,2,3);stem(i,h);
title('上采样');

  k=1:(m-1)/4;
subplot(5,2,4);stem(k,y2k);
title('上采样频谱');
xlabel('k');ylabel('y2k');

n=138;wc=2*fc/fs;
j=fir1(n-1,wc,blackman(n));
hk=fft(j,n);
k=1:n;
subplot(5,2,5);stem(k,hk);
title('滤波器的频谱');
g=conv(j,x);
gk=fft(g,m+n-1);
 k=1:m+n-1;
subplot(5,2,6);stem(k,gk);

title('滤波后的频谱');
xlabel('k');ylabel('gk');
    f=zeros(1,4*(m+n-1));
 for i=1:m+n-1,
     f(4*i)=g(i);
 end

  i=1:4*(m+n-1);
subplot(5,2,7);stem(i,f);
title('滤波后下采样');

fk=fft(y,4*(m+n-1));
 k=1:4*(m+n-1);
subplot(5, 2,8);stem(i,fk);
title('滤波后下采样频谱');
xlabel('k');ylabel('fk');

for i=1:(m+n-2)/4,
    u(i)=g(4*i);
end
y3k=fft(u,(m+n-2)/4);

  i=1:(m+n-2)/4;
subplot(5,2,9);stem(i,u);
title('滤波后上采样');

  k=1:(m+n-2)/4;
subplot(5,2,10);stem(k,y3k);
title('上采样频谱');
xlabel('k');ylabel('y3k');