iir.m

Matlab设计FIR,IIR

close all,clear all ,clc;

mp1=2*tan(0.2*pi/2);mp2=2*tan(0.3*pi/2);ms1=2*tan(0.1*pi/2);ms2=2*tan(0.4*pi/2);%预畸变
r=mp2-mp1;                                %参考频率

rp1=mp1/r;rp2=mp2/r;rs1=ms1/r;rs2=ms2/r;  %归一化模拟带通滤波器的边界频率
r0=sqrt(rp1*rp2);

mpL1=(rp1^2-r0^2)/rp1;                    %归一化模拟低通原型滤波器
mpL2=(rp2^2-r0^2)/rp2;
msL1=(rs1^2-r0^2)/rs1;  
msL2=(rs2^2-r0^2)/rs2;
mp=mpL2;
ms=min(abs(msL1),abs(msL2));

ap=1;as=25;                               %转换成模拟低通滤波器后的参数
[N,mc]=buttord(mp,ms,ap,as,'s')           %确定模拟低通原型的阶数和 截止频率
[zl,pl,kl]=buttap(N);
[num,den]=zp2tf(zl,pl,kl);
zplane(zl,pl);                            %模拟低通滤波器的零极点图
figure;

wo=sqrt(mp1*mp2);                         %模拟带通的中心频率
[bt,at] = lp2bp(num,den,wo,mp2-mp1+0.1);  %将模拟低通滤波器转换为模拟带通滤波器
[zb,pb,kb]=tf2zp(bt,at);
zplane(zb,pb);                            %模拟带通的零极点图
figure;

fs=1;                                     %双线性变换法求得数字带通
[zd,pd,kd]=bilinear(zb,pb,kb,fs);         
[b,a]=zp2tf(zd,pd,kd);
zplane(zd,pd);                            %数字带通的零极点图
figure;
freqz(b,a);