exa5_15.m

matlab应用实例。如：FIR、IIR数字滤波器设计等。

%-----------------------------------------------------------------------------
% exa060401_fresam1.m , for example 6.4.1
% use frequency sampling method 1 to design highpass digital filter
%-----------------------------------------------------------------------------

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)]; %理想振幅响应采样
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])