%例程4－19   Ⅲ、Ⅳ型理想帶通濾波器的單位沖激響應 計算

function hd=ideal_bp2(Wcl,Wch,N)
%compute the ideal bandpass fiter unit pulse respondence hd(n)
%wcl: low cutoff frequency
%wch: high cutoff frequency
%N: window length
%hd: unit pulse respondence

alpha= (N-1)/2;
n=0:1:N-1;
m=n-alpha+eps;
hd=[cos(Wch*m)-cos(Wcl*m)]./(pi*m);