exa5_16.m

matlab应用实例。如：FIR、IIR数字滤波器设计等。

%-----------------------------------------------------------------------------
% exa060402_fresam2.m , for example 6.4.2
% use frequency sampling method 2 to design bandpass digital filter
%-----------------------------------------------------------------------------

N=41;
T1 = 0.1095;
alpha = (N-1)/2;
l = 0:N-1;
wl = (2*pi/N)*l;
Hrs = [zeros(1,6),T1,ones(1,7),T1,zeros(1,11),T1,ones(1,7),T1,zeros(1,6)]; % 理想振幅响应采样
Hdr = [0,0,1,1,0,0];
wdl = [0,0.3,0.3,0.7,0.7,1];
k1 = 0:floor((N-1)/2);
k2 = floor((N-1)/2)+1:N-1;
angH = [pi/2-alpha*(2*pi)/N*(k1+0.5),-pi/2+alpha*(2*pi)/N*(N-k2-0.5)]; % 相位约束条件
Hdk = Hrs.*exp(j*angH); % 构成Hd(k)
h1 = ifft(Hdk,N); 
n = 0:1:N-1;
h = real(h1.*exp(j*pi*n/N));% 实际单位冲激响应
[db,mag,pha,w] = freqz_m2(h,[1]);
[Hr,ww,a,L] = hr_type3(h); % 实际振幅响应
subplot(221)
plot(wl/pi+1/N,Hrs,'.',wdl,Hdr)
title('频率样本Hd(k):N=41')
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+1/N,Hrs,'.')
axis([0 1 -0.1 1.2])
title('实际振幅响应H(w)')
subplot(224)
plot(w/pi,db)
title('幅度响应(dB)')
axis([0 1 -80 10])