椭圆数字带通且比雪夫2带阻滤波器.doc

椭圆数字带通滤波器
wp1=*pi;wp2=*pi; %滤波器的通带截止频率
ws1=*pi;ws2=*pi; %滤波器的阻带截止频率
Rp=1;As=15; %滤波器的通阻带衰减指标
ripple=10^(-Rp/20); %滤波器的通带衰减对应的幅度值
Attn=10^(-As/20); %滤波器的阻带衰减对应的幅度值
%转换为模拟滤波器的技术指标
Fs=2000;T=1/Fs;
Omgp1=wp1*Fs;Omgp2=wp2*Fs;Omgp=[Omgp1,Omgp2];
Omgs1=ws1*Fs;Omgs2=ws2*Fs;Omgs=[Omgs1;Omgs2];
bw=Omgp2-Omgp1;w0=sqrt(Omgp1*Omgp2);
%模拟原型滤波器计算
[n,Omgc]=ellipord(Omgp,Omgs,Rp,As,'s') %计算阶数n和截止频率
[z0,p0,k0]=ellipap(n,Rp,As); %设计归一化的巴特沃思模拟滤波器原型
ba1=k0*real(poly(z0)); %求原型滤波器的系数b
aa1=real(poly(p0)); %求原型滤波器的系数a
[ba,aa]=lp2bp(ba1,aa1,w0,bw); %变换为模拟dai通滤波器
%用脉冲响应不变法计算数字滤波器系数
[bd,ad]=impinvar(ba,aa,Fs)
[C,B,A]=dir2par(bd,ad) %转换成bing联型
%求数字系统的频率特性
[H,w]=freqz(bd,ad);
dbH=20*log10((abs(H)+eps)/max(abs(H)));
subplot(2,2,1);plot(w/pi,abs(H));
ylabel('|H|');title('幅度响应');axis([0,1,0,]);
set(gca,'XTickMode','manual','XTick',[0,,,1]);
set(gca,'YTickMode','manual','YTick',[0,Attn,ripple,1]);grid
subplot(2,2,2);plot(w/pi,angle(H)/pi);
ylabel('\phi');title('相位响应');axis([0,1,-1,1]);
set(gca,'XTickMode','manual','XTick',[0,,,1]);
set(gca,'YTickMode','manual','YTick',[-1,0,1]);grid
subplot(2,2,3);plot(w/pi,dbH);title('幅度响应(dB)');
ylabel('dB');xlabel('频率(\pi)');axis([0,1,-40,5]);
set(gca,'XTickMode','manual','XTick',[0,,,1]);
set(gca,'YTickMode','manual','YTick',[-50,-15,-1,0]);grid
subplot(2,2,4);zplane(bd,ad);
axis([-,,-,]