ex072400.m

关于滤波器性能的各种转换 帮助菜鸟在较短时间内精通滤波器性能的MATLAB表示

% 第七章 例 7.24
% 用PM算法进行的带通滤波器设计
%
ws1 = 0.2*pi; wp1 = 0.35*pi; wp2 = 0.65*pi; ws2 = 0.8*pi;
Rp = 1.0; As = 60;
delta1 = (10^(Rp/20)-1)/(10^(Rp/20)+1);
delta2 = (1+delta1)*(10^(-As/20));
deltaH = max(delta1,delta2); deltaL = min(delta1,delta2);
weights = [1 delta2/delta1 1];
delta_f =min((ws2-wp2)/(2*pi), (wp1-ws1)/(2*pi));
M = ceil((-20*log10(sqrt(delta1*delta2))-13)/(14.6*delta_f)+1)
f = [0 ws1/pi wp1/pi wp2/pi ws2/pi 1];
m = [0 0 1 1 0 0];
h = remez(M-1,f,m,weights);
[db,mag,pha,grd,w] = freqz_m(h,[1]);
delta_w=2*pi/1000;
ws1i=floor(ws1/delta_w)+1; wp1i = floor(wp1/delta_w)+1;
ws2i=floor(ws2/delta_w)+1; wp2i = floor(wp2/delta_w)+1;
Asd = -max(db(1:1:ws1i))
M = M+1;
h = remez(M-1,f,m,weights);
[db,mag,pha,grd,w] = freqz_m(h,[1]);
Asd = -max(db(1:1:ws1/delta_w))
M = M+1;
h = remez(M-1,f,m,weights);
[db,mag,pha,grd,w] = freqz_m(h,[1]);
Asd = -max(db(1:1:ws1/delta_w))
M = M+1;
h = remez(M-1,f,m,weights);
[db,mag,pha,grd,w] = freqz_m(h,[1]);
Asd = -max(db(1:1:ws1/delta_w))
M
[Hr,omega,P,L] = ampl_res(h);
%
% Plots
figure(1); subplot(1,1,1)
subplot(2,2,1); stem([0:1:M-1],h); title('实际脉冲响应')
axis([0,M-1,-0.4,0.5]);ylabel('h(n)');text(M,-0.4,'n')
set(gca,'XTickMode','manual','XTick',[0,M-1])
set(gca,'YTickMode','manual','YTick',[-0.4:0.2:0.5])
subplot(2,2,2);plot(w/pi,db);title('幅度响应');
axis([0,1,-80,10]); xlabel(''); ylabel('分贝数')
set(gca,'XTickMode','manual','XTick',f)
set(gca,'YTickMode','manual','YTick',[-60,0]);
set(gca,'YTickLabelMode','manual','YTickLabels',['60';' 0']);grid
subplot(2,2,3);plot(omega/pi,Hr);title('振幅响应');
axis([0 1 -0.1 1.1]); xlabel('频率（单位：pi）'); ylabel('Hr(w)')
set(gca,'XTickMode','manual','XTick',f)
set(gca,'YTickMode','manual','YTick',[0,1]);grid
delta_w = 2*pi/1000; sp_edge1 = ws1/delta_w+1; sp_edge2 = ws2/delta_w+1;
subplot(2,2,4);
sb1w = omega(1:1:ws1i)/pi; sb1e = Hr(1:1:ws1i); 
pbw = omega(wp1i:wp2i)/pi; pbe = Hr(wp1i:wp2i)-1;
sb2w = omega(ws2i:501)/pi; sb2e = Hr(ws2i:501); 
plot(sb1w,sb1e,pbw,pbe*(delta2/delta1),sb2w,sb2e);
title('加权误差');
axis([0,1,-deltaL,deltaL]);
xlabel('频率（单位：pi）'); ylabel('Hr(w)')
set(gca,'XTickMode','manual','XTick',f)
set(gca,'YTickMode','manual','YTick',[-deltaL,0,deltaL]);
set(gca,'XGrid','on','YGrid','on')