%wc=0.25*pi;N=33;
%alpha=(N-1)/2;
%n=0:1:N-1;
%m=n-alpha+eps;
%hd=sin(wc*m)./(pi*m);
hd=ideal_lp(wc,N);
wd1=hanning(N)';b1=hd.*wd1;
wd2=hamming(N)';b2=hd.*wd2;
wd3=blackman(N)';b3=hd.*wd3;
wd4=kaiser(N)';b4=hd.*wd4;
[H1,w]=freqz(b1,1);
[H2,w]=freqz(b2,1);
[H3,w]=freqz(b3,1);
[H4,w]=freqz(b4,1);
figure(1)
plot(w,abs(H1),':b',w,abs(H2),'-.g',w,abs(H3),'--r',w,abs(H4),'-c')
legend('漢寧窗低通濾波器','海明窗低通濾波器','布來克曼窗低通濾波器','凱澤窗低通濾波器')
figure(2)
plot(w/pi,20*log10(abs(H1)),':b',w/pi,20*log10(abs(H2)),'-.g',w/pi,20*log10(abs(H3)),'--r',w/pi,20*log10(abs(H4)),'-c')
legend('漢寧窗幅度響應（dB）','海明窗幅度響應（dB）','布來克曼窗幅度響應（dB）','凱澤窗幅度響應（dB）')
figure(3)
plot(n,b1,':b',n,b2,'-.g',n,b3,'--r',n,b4,'-c')
legend('漢寧窗h(n)','海明窗h(n)','布來克曼窗h(n)','凱澤窗h(n)')