%--------------------------------------------------------------------------
%  exa070301 , for example 7.3.1 and fig 7.3.3;
%  計算和顯示利用Johnston優化設計方法所得到的濾波器的頻率響應
%  濾波器序號：16A
% -------------------------------------------------------------------------
clear;

h0=[0.001050167,-0.005054526,-0.002589756,0.0276414,-0.009666376,-0.09039223,...
    0.09779817,0.4810284,0.4810284,0.09779817,-0.09039223,-0.009666376,...
    0.0276414,-0.002589756,-0.005054526,0.001050167];
Fs=1;

h1=qmf(h0,1);

[H0,w]= freqz(h0,1,256,Fs);
[H1,w]= freqz(h1,1,256,Fs);

subplot(221)
h0=abs(H0);
h1=abs(H1);
ah0=20*log10(h0+0.000000001);
ah1=20*log10(h1+0.000000001);
plot(w,ah0,'k-',w,ah1,'b-');
grid on;

sumh=h0.*h0+h1.*h1;
sum=10*log10(sumh);
subplot(222)
plot(w,sum);grid;