wp1=3000*pi;                  %通帶截止角頻率   
ws1=6000*pi;                  %阻帶截止角頻率
wsam1=30000*pi;               %采樣角頻率
fsam1=wsam1/(2*pi);           %采樣截止頻率
passrad=(wp1+ws1)/2/fsam1;    %截止頻率
A=3.3;
wdelta=(ws1-wp1)/fsam1; 
N=ceil(2*pi/wdelta*A);         %濾波器的階數(shù)
w1=hamming(N+1);               %用海明窗實現(xiàn)
L=N/2+1;
n=1:1:N+1;
hd=sin(passrad*(n-L))./(pi*(n-L));            %理想低通濾波器
if(N==ceil(N/2)*2)
   hd(L)=passrad/pi;
end
h1=hd.*w1';                            %加窗
[mag1,rad]=freqz(h1);
plot(rad,20*log10(abs(mag1)));         %頻譜顯示