数字滤波器设计椭圆型数字滤波器确定数字滤波器的阶数N及参数Wc[N, Wc] =ellipord(Wp, Ws, Ap, As)DF系统函数分子、分母多项式的确定低通num,den|= ellip(N,Ap,As, Wc)高通[num,den]= ellip(N,Ap,As, Wc,'high')带通其中Wc=[W1, W2][num,den|= ellip(N,Ap,As,W)带阻其中Wc=[W1,W2][num,den]=ellip(N,Ap,As,Wc,'stop')
数字滤波器设计 椭圆型数字滤波器 确定数字滤波器的阶数N及参数Wc [N, Wc] = ellipord(Wp, Ws, Ap, As) DF系统函数分子、分母多项式的确定 低通 [num,den] = ellip(N,Ap,As,Wc) 高通 [num,den] = ellip(N,Ap,As,Wc,'high') 带通 [num,den] = ellip(N,Ap,As,Wc) 其中Wc=[W1, W2] 带阻 [num,den] = ellip(N,Ap,As,Wc,'stop') 其中Wc=[W1, W2]
[例]试设计满足下列指标的BW型数字带通滤波器Qpl=0.45元 rad, 2p2=0.55元 rad, A,≤3dB,2s,=0.40元 rad, 2s2=0.60元 rad, A,≥30dBWp-[0.45*pi,0.55*pi];Ws=[0.40*pi,0.60*pil;Ap=3;As=30;%BP-DFspecificationsNWe]=buttord(Wp/pi,Ws/pi,Ap,As);%Computerlow-passDForder[numd,dend]=butter(N,We)%Computeband-passDFcoefficientsomega=/WpWsh=freqz(numd,dend,omega); %ComputeAp and As of theDFfprintf(Ap1= %.4fin',-20*log10(abs(h(1);fprintf(Ap2=%.4fln,-20*log10(abs(h(2));fprintf(As1= %.4fln',-20*log10(abs(h(3));fprintf(As2= %.4fin',-20*log10(abs(h(4)));w-linspace(0.3*pi,0.7*pi,1000);h=freqz(numd,dend,w);plot(w/pi,20*log10(abs(h);%PlottheDFfrequency responsexlabel(Frequency in rad'), ylabel(Gain in dB');
Wp=[0.45*pi, 0.55*pi]; Ws=[0.40*pi, 0.60*pi]; Ap=3; As=30; % BP-DF specifications [N,Wc]=buttord(Wp/pi, Ws/pi, Ap, As) ; % Computer low-pass DF order [numd,dend]=butter(N,Wc) % Compute band-pass DF coefficients omega=[Wp Ws]; h = freqz(numd,dend,omega); %Compute Ap and As of the DF fprintf('Ap1= %.4f\n',-20*log10(abs(h(1)))); fprintf('Ap2= %.4f\n',-20*log10(abs(h(2)))); fprintf('As1= %.4f\n',-20*log10(abs(h(3)))); fprintf('As2= %.4f\n',-20*log10(abs(h(4)))); w=linspace(0.3*pi,0.7*pi,1000); h=freqz(numd,dend,w); plot(w/pi, 20*log10(abs(h))); % Plot the DF frequency response xlabel('Frequency in rad'); ylabel('Gain in dB'); [例] 试设计满足下列指标的BW型数字带通滤波器 Wp1=0.45π rad, Wp2=0.55π rad, Ap ≤3dB, Ws1=0.40π rad, Ws2=0.60π rad, As ≥30dB