% m_l.m
% generate the m 
% m 序列長度為P=2^n-1
% 設輸入為n=5，查常用本原多項式表得其本原多項式為1+x^2+x^5


% clear [0 1 1 1 0 0 0 1]
 n=8;
fbcon=[];
switch n
    case 2
        fbcon=[1 1];
    case 3
        fbcon=[1 0 1];
    case 4
        fbcon=[1 0 0 1];
    case 5
        fbcon=[0 1 0 0 1];
    case 6
        fbcon=[1 0 0 0 0 1];
    case 7 
        fbcon=[0 0 1 0 0 0 1];
    case 8 
        fbcon=[0 1 1 1 0 0 0 1];
    case 9
        fbcon=[0 0 0 1 0 0 0 0 1];
    otherwise
        disp('輸入數據不支持！');
end

N=2^n-1;
register=[zeros(1,n-1) 1];
out(1)=register(n);
for i=2:N
    newregister(1)=mod(sum(fbcon.*register),2);
    for j=2:n
        newregister(j)=register(j-1);
    end
 
     register=newregister;
%     out(i)=register(n);
    if register(n)==0
        out(i)=-1;
    else
        out(i)=1;
    end
end
% 
 xc=xcorr(out,'biased');
 aaa=fft(xc,1024);
 % w=(0:511)/512*(3000/2);%
 figure,plot(abs(aaa));