ms22r2.m

《数字信号处理实验(MATLAB版)》这

%直接法设计数字低通滤波器
ws=0.3;              %数字滤波器的阻带截止频率
wp=0.2;              %数字滤波器的通带截止频率
Rp=1;As=20;          %输入滤波器的通阻带衰减指标
[n,wn]=cheb2ord(wp,ws,Rp,As); %计算阶数n和截止频率
[b,a]=cheby2(n,As,wn)   %直接求数字高通滤波器系数
[H,w]=freqz(b,a);     %求数字系统的频率特性
dbH=20*log10((abs(H)+eps)/max(abs(H))); %化为分贝值
subplot(2,2,1),plot(w/pi,abs(H));
title('|H(jω)|');axis([0,1,0,1.1]);
set(gca,'XTickMode','manual','XTick',[0,wp,ws,1]);
set(gca,'YTickMode','manual','YTick',[0,0.707,0.891,1]);grid
subplot(2,2,2),plot(w/pi,angle(H));
title('Φ(ω)');set(gca,'XTickMode','manual','XTick',[0,wp,ws,1]);
set(gca,'YTickMode','manual','YTick',[-pi,0,pi]);grid
subplot(2,2,3),plot(w/pi,dbH);
title('G');axis([0,1,-50,1]);
set(gca,'XTickMode','manual','XTick',[0,wp,ws,1]);
set(gca,'YTickMode','manual','YTick',[-50,-20,0,0.1]);grid
subplot(2,2,4),zplane(b,a);
title('零极点分布图');