chebyshev.m

butterworth+chebcv的matlab 程序

%Impulse Invariance Transformation
%chebyshev Lowpass Filter Design
wp=0.2*pi;ws=0.3*pi;
Rp=1;As=15;
T=1;Fs=1/T;
OmegaP=(2/T)*tan(wp/2);
OmegaS=(2/T)*tan(ws/2);
Ripple=10^(-Rp/20);
Attn=10^(-As/20);
 %设计出所需的模拟低通滤波器
[b,a]=afd_cheby(OmegaP,OmegaS,Rp,As,Fs);
 %应用双线性法进行变换
%[b,a]=bilinear(cs,ds,T);

%[C,B,A]=dir2cas(b,a)
%plot
%求得相对、绝对频响及相位、群迟延响应
figure(1);
[db,mag,pha,grd,w]=freqz_m(b,a);
subplot(2,2,1);plot(w/pi,mag);
title('幅频特性');
xlabel('w(/pi)');
ylabel('|H(jw)|');
axis([0,1,0,1.1]);
set(gca,'XTickMode','manual','XTick',[0 0.2 0.3 0.5 1]);
set(gca,'YTickMode','manual','YTick',[0 Attn Ripple 1]);
text(0.2,Ripple,'\leftarrow1/sqrt(\epsilon^2+1)')
grid
subplot(2,2,2);
plot(w/pi,db);
title('幅频特性(db)');
xlabel('w(/pi)');
ylabel('dB');
axis([0,1,-40,5]);
set(gca,'XTickMode','manual','XTick',[0 0.2 0.3 0.5 1]);
set(gca,'YTickMode','manual','YTick',[-40 -As -Rp 0]);
grid
subplot(2,2,3);
plot(w/pi,pha/pi);
title('相频特性');
xlabel('w(/pi)');
ylabel('pha(/pi)');
axis([0,1,-1,1]);
set(gca,'XTickMode','manual','XTick',[0 0.2 0.3 0.5 1]);
set(gca,'YTickMode','manual','YTick',[-1 0 1]);
grid
subplot(2,2,4);
plot(w/pi,grd);
title('群延时');
xlabel('w(/pi)');
ylabel('Sample');
axis([0,1,0,12]);
set(gca,'XTickMode','manual','XTick',[0 0.2 0.3 0.5 1]);
grid