IIR数字滤波器的设计clear;closeallt=1;fs=4000;wpu=0.65*pi,wpl=0.45*pi;wsu=0.75*pi,wsl=0.30*pi;wpz=[0.45,0.65];wsz=[0.30,0.75];wp=2/t*tan(wpz/2);ws=2/t*tan(wsz/2);rp=1;as=40;[n,wc]=buttord(wp,ws,rp,as,'s');%计算带通滤波器阶数N和3dB截止频率wc[b,a]=butter(n,wc,'s');%计算带通滤波器系统函数分子分母多项式系数向量b,a[bz,az]=bilinear(b,a,fs);[nd,wdc]=buttord(wpz,wsz,rp,as);[bd,adz]=butter(nd,wdc);hk=freqz(bd,adz)subplot(2,2,1)plot(abs(hk))xlabel('Hz');ylabel('幅度');title('幅度函数曲线')subplot(2,2,2)plot(angle(hk))xlabel('\omega/\pi');ylabel('phi(omega)');title('相频特性曲线')FIR数字滤波器的设计[n,wn,bta,ftype]=kaiserord([0.30.450.650.8],[010],[0.010.10870.01]);h1=fir1(n,wn,ftype,kaiser(n+1,bta),'noscale');[hh1,w1]=freqz(h1,1,256);figure(1)subplot(2,1,1)plot(w1/pi,20*log10(abs(hh1)))gridxlabel('归一化频率w');ylabel('幅度/db');subplot(2,1,2)plot(w1/pi,angle(hh1))gridxlabel('归一化频率w');ylabel('相位/rad');
