数字信号处理实验-实验七.doc

数字信号处理实验报告实验名称：用双线性变换法设计IIR数字滤波器学生姓名： zxx 学生学号： 学生班级： 上课时间： 周二上午 指导老师： 实验七：书中例7.1程序：wp=100*2*pi;ws=200*2*pi;Rp=2;Rs=15;Fs=500;Ts=1/Fs;wp1=wp*Ts;ws1=ws*Ts;wp2=2*Fs*tan(wp1/2);ws2=2*Fs*tan(ws1/2);N,Wn=buttord(wp2,ws2,Rp,Rs,s);Z,P,K=buttap(N);Bap,Aap=zp2tf(Z,P,K);b,a=lp2lp(Bap,Aap,Wn);bz,az=bilinear(b,a,Fs);H,W=freqz(bz,az);subplot(2,1,1);plot(W/pi,abs(H);grid;xlabel(频率);ylabel(幅度);subplot(2,1,2);plot(W/pi,20*log10(abs(H);grid;xlabel(频率);ylabel(幅度（dB）);其图形：题目：（1）编写用双线性变换法设计巴特沃兹低通IIR数字滤波器的程序，要求通带内频率低于0.2rad时，容许幅度误差在1dB之内，频率在0.3到之间的阻带衰减大于10dB。程序：%wp=0.2*pi;%ws=0.3*pi;Rp=1;Rs=10;Fs=500;Ts=1/Fs;%wp1=wp*Ts;%ws1=ws*Ts;wp1=0.2*pi;ws1=0.3*pi;wp2=2*Fs*tan(wp1/2);ws2=2*Fs*tan(ws1/2);N,Wn=buttord(wp2,ws2,Rp,Rs,s);Z,P,K=buttap(N);Bap,Aap=zp2tf(Z,P,K);b,a=lp2lp(Bap,Aap,Wn);bz,az=bilinear(b,a,Fs);H,W=freqz(bz,az);subplot(2,1,1);plot(W/pi,abs(H);grid;xlabel(频率);ylabel(幅度);subplot(2,1,2);plot(W/pi,20*log10(abs(H);grid;xlabel(频率);ylabel(幅度（dB）);其图形：（2）用双线性变换法设计巴特沃兹低通IIR数字滤波器的程序，要求使用buttord,butter和bilinear函数。滤波器技术指标：取样频率1Hz，通带内临界频率0.2Hz,通带内衰减减小于1dB,阻带临界频率0.3Hz,阻带内衰减大于25dB.程序：wp=0.2*2*pi;ws=0.3*2*pi;Rp=1;Rs=25;Fs=1;Ts=1/Fs;wp1=wp*Ts;ws1=ws*Ts;wp2=2*Fs*tan(wp1/2);ws2=2*Fs*tan(ws1/2);N,Wn=buttord(wp2,ws2,Rp,Rs,s);Z,P,K=buttap(N);Bap,Aap=zp2tf(Z,P,K);b,a=lp2lp(Bap,Aap,Wn);%b,a=butter(N,Wn);bz,az=bilinear(b,a,Fs);H,W=freqz(bz,az);subplot(2,1,1);plot(W/pi,abs(H);grid;xlabel(频率);ylabel(幅度);subplot(2,1,2);plot(W/pi,20*log10(abs(H);grid;xlabel(频率);ylabel(幅度（dB）);其图形：（3）以/64为取样间隔，在屏幕上打印出数字滤波器的频率区间0,上的幅频响应特性曲线。程序：wp=0.2*2*pi;ws=0.3*2*pi;Rp=1;Rs=25;Fs=1;Ts=1/Fs;wp1=wp*Ts;ws1=ws*Ts;wp2=2*Fs*tan(wp1/2);ws2=2*Fs*tan(ws1/2);N,Wn=buttord(wp2,ws2,Rp,Rs,s);b,a=butter(N,Wn,s);bz,az=bilinear(b,a,Fs);H,W=freqz(bz,az,64,2*pi);subplot(2,1,1);stem(W/pi,abs(H);grid;xlabel(频率);ylabel(幅度);subplot(2,1,2);stem(W/pi,20*log10(abs(H);grid;xlabel(频率);ylabel(幅度（dB）);其图形：（4）在屏幕上打印出H（z）的分子，分母多项式系数。bz = 0.0179 0.1072 0.2681 0.3575 0.2681 0.1072 0.0179az =1.0000 -0