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数字信号处理课程的有关实验

  %直接设计数字滤波器  
    wp=0.2*pi;
    ws=0.3*pi;
    Rp=1;
    Rs=15;
    Ts=0.02*pi;
    Fs=1/Ts;
    wp1=0.2;                     %归一化指标        
    ws1=0.3;
    [N,Wn]=buttord(wp1,ws1,Rp,Rs);  %选择滤波器的最小阶数   
    [bz,az]=butter(N,Wn); 
    [H,W]=freqz(bz,az);%绘制频率响应曲线
    figure(1),plot(W*Fs/(2*pi),abs(H)),grid,xlabel('频率／Hz'),ylabel('频率响应幅度');
    x=[-4,-2,0,-4,-6,-4,-2,-4,-6,-6,-4,-4,-6,-6,-2,6,12,8,0,-16,-38,...
-60,-84,-90,-66,-32,-4,-2,-4,8,12,12,10,6,6,6,4,0,0,0,0,0,-2,...
-4,0,0,0,-2,-2,0,0,-2,-2,-2,-2,0];
y=filter(bz,az,x);      %滤波
figure(2),
subplot(2,1,1),plot(x),title('原始信号');
subplot(2,1,2),plot(y),title('滤波后信号');