function [ a ] = yulewalker( phi , N )
for i=1:N+1
    for j=1:N+1
        R(i,j)=phi(abs(i-j)+1);
    end
end
b(1)=0;
for i=2:N+1
    b(i)=phi(i);
end
alpha=(-1/phi(1))*b*inv(R);
a(1)=phi(1)/(phi(1)*alpha(1)+1);

for i=2:N+1
    a(i)=a(1)*alpha(i);
end
end