music1.doc

这是多重信号分类的经典算法

clear all;
close all;
%*****Setting the system and the signal parameters**********************************
NumOfAntennas = 12; 				
NumOfSamples = 1000; 				
d_lamda = 0.5; 				% The ratio d/lamda

SNR=[20 20 25 25 20];                          %The Interferer signals in db
Amp=[]; Amp = sqrt(2)*10.^(SNR/20);         %Normalized amplitudes of the users

Theta_in_Deg=[0 22 -15 -20 -50];          % The DOA of the signals wrt the broadside(the normal to the array line)
Theta_in_Radians=Theta_in_Deg*pi/180;

Allowed_Noise_db=-40;
Noise_db=-40;
Noise=[];
Noise = sqrt(2)*10^(Noise_db/20)*exp(-j*1*pi*randn(NumOfAntennas,NumOfSamples)  );    % Gaussian noise, variance = 1.0 for real and imag part, i.e. variance of noise = 2

Phi=[]; Phi = 2*pi*d_lamda*sin(Theta_in_Radians);
A=[];
for StrCounter=1:length(Theta_in_Deg)                           %Creating Steering vectors
    A(:,StrCounter)=exp(-j*Phi(StrCounter)).^[0:NumOfAntennas-1]';
end

S=[];
for SignalCounter=1:length(Theta_in_Deg)                        %Creating the signals
        S(SignalCounter,:) = Amp(SignalCounter)*exp(-j*1*pi*randn(1,NumOfSamples));
end

X = A*S + Noise;
%************************************************************************************
%Here the input samples are ready in the X(NumOfAntennas,NumOfSamples)
%************************************************************************************



%Creating the Covariance Matrix------------------------------------
clear CovMatrix V D ThetaAxis temp a;
CovMatrix(NumOfAntennas,NumOfAntennas)=0;
for counter1=1:NumOfSamples;
    CovMatrix=CovMatrix+X(:,counter1)*X(:,counter1)';
end
CovMatrix=CovMatrix/NumOfSamples;
%------------------------------------------------------------------

%Getting the eigen values and the eigen vectors--------------------
[V,D]=eig(CovMatrix)

for counter=1:NumOfAntennas
    if D(counter,counter)>sqrt(2)*10^(Allowed_Noise_db/20) 
        NumOfSignals=NumOfAntennas-counter+1;break
    end
end
%------------------------------------------------------------------

%Creating P_MUSIC--------------------------------------------------
      %Creating Vn
      Vn=V(:,1:NumOfAntennas-NumOfSignals);
      %-----------  

        ResolutionInDeg=0.1;
        Theta_Axis_Deg=-90:ResolutionInDeg:90;
  for counter2=1:180/ResolutionInDeg+1
      %Creating (A) matrix for a given theta (counter2)
      IntegersSet=0:NumOfAntennas-1;
      IntegersSet=IntegersSet.';  
      ThetaAxis=2*pi*Theta_Axis_Deg(counter2);
      temp=-i*2*pi*d_lamda*sin(ThetaAxis);
      a=exp(temp*IntegersSet);
      %------------------------------------------------
     P_MUSIC(counter2)=(a'*a)/(a'*Vn*Vn'*a);
%    P_MUSIC(counter2)=1/(a'*Vn*Vn'*a);
  end
 %------------------------------------------------------------------
      

figure
%semilogy(Theta_Axis_Deg , abs(P_MUSIC));  xlabel('Degrees');  ylabel('MUSIC spectrum') ;  grid;
plot(Theta_Axis_Deg , abs(P_MUSIC));  xlabel('Degrees');  ylabel('MUSIC spectrum') ;  grid;