在MATLAB环境下设计带阻滤波器的程序

clear all;

fp=[200 500];通带上下限
fs=[300 400];阻带
rp=3;rs=18;衰减db
Fs=2000;
wp=fp*2*pi/Fs;
ws=fs*2*pi/Fs;
%
% Firstly to finish frequency prewarping;
wap=2*Fs*tan(wp./2)
was=2*Fs*tan(ws./2);
[n，wn]=buttord(wap，was，rp，rs，'s');
% Note: 's'!
[z，p，k]=buttap(n);
[bp，ap]=zp2tf(z，p，k)
%
bw=wap(2)-wap(1)
w0=sqrt(wap(1)*wap(2))
[bs，as]=lp2bs(bp，ap，w0，bw)
%带阻
[h1，w1]=freqs(bp，ap);
figure(1)
plot(w1，abs(h1));grid;
ylabel(' lowpass G(p)')
%
w2=[0:Fs/2-1]*2*pi;
h2=freqs(bs，as，w2);
% Note: z=(2/Ts)(z-1)/(z+1);
[bz1，az1]=bilinear(bs，as，Fs) %双线性变换
[h3，w3]=freqz(bz1，az1，1000，Fs);
figure(2)
plot(w2/2/pi，20*log10(abs(h2))，w3，20*log10(abs(h3)));grid;
ylabel('Bandpass AF and DF')
xlabel(' Hz')