IIR数字滤波器matlab的实现程序.docVIP

数字信号实验四程序： function [b,a] =afd_butt(Omegp,Omegs,Ap,As); % b = Ha(s)分子多项式的系数 % a = Ha(s)分母多项式的系数 % Omegp = 通带截止频率 单位为rad/s; Ωp 0 % Omegs =阻带起始频率单位为rad/s; Ωs Ωp 0 % Ap = Passband ripple in +dB; (Ap 0) % As = Stopband attenuation in +dB; (As 0) if Omegp= 0 error(Passband edge must be larger than 0) end if Omegs=Omegp error(Stopband edge must be larger than Passband edge) end if (Ap = 0) | (As 0) error(PB ripple and/or SB attenuation must be larger than 0) end N = ceil((log10((10^(Ap/10)-1)/(10^(As/10)-1)))/(2*log10(Omegp/Omegs)) ); fprintf(\n*** Butterworth Filter Order = %2.0f \n,N) OmegaC = Omegp/((10^(Ap/10)-1)^(1/(2*N))); [b,a]=u_buttap(N,OmegaC); function [b,a] = afd_chb1(Omgp, Omgs,Ap,As); if Omgp= 0 error(Passband edge must be larger than 0) end if Omgs = Omgp error(Stopband edge must be larger than Passband edge) end if (Ap = 0) | (As 0) error(PB ripple and/or SB attenuation ust be larger than 0) end ep = sqrt(10^(Ap/10)-1); A = 10^(As/20); OmegaC =Omgp; OmegaR = Omgs/Omgp; g = sqrt(A*A-1)/ep; N = ceil(log10(g+sqrt(g*g-1))/log10(OmegaR+sqrt(OmegaR*OmegaR-1))); fprintf(\n*** Chebyshev-1 Filter Order = %2.0f \n,N) [b,a]=u_chb1ap(N,Ap,OmegaC); 1-1a、clear; close all; wp=0.4*pi; ws=0.6*pi; Ap=0.5; As=50; T=1;Fs=1/T; OmegaP=wp/T; OmegaS=ws/T; [cs,ds]=afd_butt(OmegaP,OmegaS,Ap,As); [b,a]=impinvar(cs,ds,Fs); [h,w]=freqz(b,a); subplot(2,2,1);plot(w/pi,abs(h));title(幅度响应);grid; subplot(2,2,2);plot(w/pi,angle(h));title(相位响应);grid; %subplot(2,2,3);plot(w/pi,20*log10(abs(h)));title(幅度响应dB);grid; n=[0:1:59];imp=[1;zeros(59,1)];y=filter(b,a,imp); subplot(2,2,4);plot(n,y);title(脉冲响应);grid; 1-1b、clear; close all; wp=0.4*pi; ws=0.6*pi; Ap=0.5; As=50; T=1;Fs=1/T; OmegaP=wp/T; OmegaS=ws/T; [cs,ds]=afd_chb1(OmegaP,OmegaS,Ap,As); [b,a]=impinvar(cs,ds,Fs); [h,w]=freqz(b,a); subplot(2,2,1);plot(w/pi,abs(h));title(幅度响应);grid; subplot(2,2,2);plot(w/pi,angle(h));title(