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1、数字信号处理课程设计报告课程名称数字信号处理实验项目IIR数字滤波器设计指导教师学院光电信息与通信工程_专业电子信息工程班级/学号学生实验日期__________成绩_____________________实验目的1、熟悉IIR数字滤波器的设计原理与方法。2、掌握数字滤波器的计算机软件实现方法。3、通过观察对实际心电图信号的滤波作用，学习数字滤波器在实际中的应用。实验仪器及材料计算机，MATLAB软件实验容及要求1．设计巴特沃斯低通数字滤波器对人体心电信号进行滤波(1)人体心电图信号在测量过程中会受到工业高频干扰，所以必须经过低通
2、滤波处理，才能作为判断心脏功能的有用信息。以下为一个实际心电图信号采样序列x(n)，其中存在高频干扰，抽样周期Ts=1秒。在实验中，以x(n)作为输入序列，滤除其中干扰成分。x(n)=[-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]对序列x(n)用FFT做频谱分析，生成x(
3、n)的频谱图。(2)设计一个巴特沃斯低通IIR数字滤波器H(z)。设计指标参数为：在通带频率低于0.2π时，最大衰减小于1dB；在阻带[0.3π,π]频率区间上，最小衰减大于15dB。写出数字滤波器H(z)的表达式，画出滤波器的幅频响应曲线。(3)用所设计的滤波器对实际心电图信号采样序列x(n)进行滤波处理，编写程序，求滤波后的序列y(n)，并分别画出滤波前后的心电图信号波形图和频谱图。y(n)=[0,0,0,0,0,0,0,0,-0.14025,0.40279,-0.56085,0.33328,0.023981,-0.18809,
4、0.11843,-0.1038,0.11576,-0.1225,0.099815,-0.13769,0.095249,-0.0070273,0.018867,0.090543,-0.11257,-0.070884,0.17676,-0.55407,0.24813,-0.34732,-0.30428,0.59426,-0.29574,-0.063869,0.34018,-0.73334,1.0293,-0.57107,-0.2461,0.83605,-0.83026,0.45459,0.011551,-0.25667,0.23896,
5、-0.17361,0.20829,-0.28417,0.28765,-0.2035,0.02865,0.066164,0.077916,-0.36052,0.53517,-0.5571]源程序clearall，clcx=[-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];%未
6、经滤波的心电图信号L=length(x);l=0:L-1;y=fft(x,L);Wp=0.2*pi;Ws=0.3*pi;Rp=1;Rs=15;[N,Wn]=buttord(Wp,Ws,Rp,Rs,'s');[b,a]=butter(N,Wn,'s');[numa,dena]=impinvar(b,a,1);w=linspace(0,pi,1024);h=freqz(numa,dena,w);norm=max(abs(h));numa=numa/norm;[z,p]=tf2zp(b,a);figure(1)plot(w,20*log1
7、0(abs(h)/norm));grid;xlabel('数字频率');ylabel('幅度响应dB');figure(2)plot(w,abs(h));grid;xlabel('数字频率');ylabel('幅度响应
8、H(e^(jw))
9、');figure(3)zplane(z,p);xx=filter(b,a,x);yy=fft(xx,L);figure(4)subplot(2,1,1)stem(l,x);title('未经滤波的心电图信号');xlabel('n');subplot(2,1,2)stem(l,xx);title
10、('经滤波之后的心电图信号');xlabel('n');figure(5)subplot(2,1,1)plot(l,abs(y));title('未经滤波的心电图信号的频谱');subplot(2,1,2)plot(l,abs(yy)
