function w_black = Blackman(M);
%  M-點 Blackman 窗函數
%  -----------------------
% w_black = Blackman(M);
%
M1 = M-1;
m = [0:1:M1];
w_black = abs(0.42 - 0.5*cos(2*pi*m'/(M1)) + 0.08*cos(4*pi*m'/(M1)));