sa_ex7_11.m

Smart antennas for wireless communication - With MATLAB (Gross F.B. - 2005 - McGraw-Hill)

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

tic
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);

[V,Dia]=eig(Rrr);
[Y,Index]=sort(diag(Dia));   % sorts the eigenvalues from least to greatest
 EN=V(:,Index(1:M-D));      % calculate the noise subspace matrix of eigenvectors
                           % using the sorting done in the previous line

for k=1:360;
   th(k)=-pi/6+pi*k/(3*360);
   clear a
a=[1];
   for jj=2:M
      a = [a exp(-1j*jj*pi*sin(th(k)))];
   end
  a=a';
P(k)=1/abs(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])
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