4-24.m

matlab数字信号与应用源代码4

%例程4－24    基于频率抽样方法1实现Ⅰ型FIR数字高通滤波器

clear all;        
N=61;
T1=0.1095;
T2=0.598;
alpha= (N-1)/2;
l=0:N-1;
wl= (2*pi/N)*l;
Hrs=[zeros(1,22),T1,T2,ones(1,14),T2,T1,zeros(1,21)]; %理想振幅采样响应
Hdr=[0,0,1,1];
wdl=[0,0.75,0.75,1];
k1=0:floor((N-1)/2);
k2=floor((N-1)/2)+1:N-1;
angH=[-alpha*(2*pi)/N*k1,alpha*(2*pi)/N*(N-k2)];  %相位约束条件
Hdk=Hrs.*exp(j*angH);                     %构成Hd(k)
h=real(ifft(Hdk,N));                      %实际单位冲激响应
[db,mag,pha,w]=freqz_m2(h,l);
[Hr,ww,a,L]=hr_type1(h);                 %实际振幅响应
subplot(221)
plot(wl/pi,Hrs,'.',wdl,Hdr)
title('频率样本Hd(k) :N=61')
axis([0 1 -0.1 1.2])
subplot(222)
stem(l,h)
title('实际单位脉冲响应h(n)')
subplot(223)
plot(ww/pi,Hr,wl/pi,Hrs,'.')
title('实际振幅湘响应H(w)')
axis([0 1 -0.1 1.2])
subplot(224)
plot(w/pi,db)
title('幅度响应(dB)')
axis([0 1 -80 10])