% MUSIC AOA estimation for a M = 6 element array with noise variance = .1


M=6;
D = 2;  % number of signals
sig2=.1;
th1=-5*pi/180;
th2=5*pi/180;

a1=[1];
a2=[1];
for i=2:M
    a1=[a1 exp(-1j*i*pi*sin(th1))];
    a2=[a2 exp(-1j*i*pi*sin(th2))];
end
A=[a1.' a2.'];

Rss=[1 0;0 1];      % source correlation matrix with uncorrelated signals
%Rrr=A*Rss*A'+sig2*eye(M);
for jj=1:10
f1=randn;
f2=randn;
t1=A*[f1 f2]';
t2=(rand(6,1)-.5)*.2;
R(:,jj)=t1+t2;
end

Rrr
[V,D]=eig(Rrr);
 EN=[V(:,1:4)];      % calculate the noise subspace matrix of eigenvectors
for k=1:180;
   th(k)=-pi/6+pi*k/(3*180);
   clear a
a=[1];
   for jj=2:M
      a = [a exp(-1j*jj*pi*sin(th(k)))];
   end
  
P(k)=1/abs(conj(a)*EN*EN'*a.'); 
end
figure;
plot(th*180/pi,10*log10(P/max(P)),'k')
grid on
xlabel('Angle')
ylabel('|P(\theta)|')
axis([-30 30 -30 10])