% 第七章: 例 7.17
% 頻率采樣技術: 帶通, 最優法 T1 & T2
%            ws1=0.2pi, wp1=0.35pi, wp2=0.65pi, ws2=0.8pi, Rp=1dB, As=60dB
%            T2 = 0.59417456, T1=0.109021
M = 40; alpha = (M-1)/2; l = 0:M-1; wl = (2*pi/M)*l;
T1 = 0.109021; T2 = 0.59417456;
Hrs = [zeros(1,5),T1,T2,ones(1,7),T2,T1,zeros(1,9),T1,T2,ones(1,7),T2,T1,zeros(1,4)];
Hdr = [0,0,1,1,0,0]; wdl = [0,0.2,0.35,0.65,0.8,1];
k1 = 0:floor((M-1)/2); k2 = floor((M-1)/2)+1:M-1;
angH = [-alpha*(2*pi)/M*k1, alpha*(2*pi)/M*(M-k2)];
H = Hrs.*exp(j*angH);
h = real(ifft(H,M));
[db,mag,pha,grd,w] = freqz_m(h,1);
[Hr,ww,a,L] = Hr_Type2(h);
subplot(1,1,1)
subplot(2,2,1);plot(wl(1:21)/pi,Hrs(1:21),'o',wdl,Hdr); 
axis([0,1,-0.1,1.1]); title('帶通: M=40,T1=0.5941, T2=0.109')
xlabel(''); ylabel('Hr(k)')
set(gca,'XTickMode','manual','XTick',[0,0.2,0.35,0.65,0.8,1])
set(gca,'YTickMode','manual','YTick',[0,0.59,0.109,1]); grid
subplot(2,2,2); stem(l,h); axis([-1,M,-0.4,0.4])
title('脈沖響應');ylabel('h(n)');text(M+1,-0.4,'n')
subplot(2,2,3); plot(ww/pi,Hr,wl(1:21)/pi,Hrs(1:21),'o');
axis([0,1,-0.1,1.1]); title('振幅響應')
xlabel('頻率（單位：pi）'); ylabel('Hr(w)')
set(gca,'XTickMode','manual','XTick',[0,0.2,0.35,0.65,0.8,1])
set(gca,'YTickMode','manual','YTick',[0,0.59,0.109,1]); grid
subplot(2,2,4);plot(w/pi,db); axis([0,1,-100,10]); grid
title('幅度響應'); xlabel('頻率（單位：pi）');
ylabel('Decibels');
set(gca,'XTickMode','Manual','XTick',[0,0.2,0.35,0.65,0.8,1]);
set(gca,'YTickMode','Manual','YTick',[-60;0]);
set(gca,'YTickLabelMode','manual','YTickLabels',['60';' 0'])
%