stardoa.m

阵列信号处理的工具箱

function [StartDOA] = stardoa(R,thetaprev,method,tol)

% *****************************************************************************
%   *  DBT, A Matlab Toolbox for Radar Signal Processing  *
% (c) FOA 1994-2000. See the file dbtright.m for copyright notice.
%
%  function StartDOA = stardoa(R,thetaprev,method,tol)
%
%
%  Finds the Startvalues for parametric algorithms
%
%  R    Covariance Matrix
%  thetaprev
%  method 'ap' (Alternating Projection) is implemented
%     'ap' by default
%  tol    0.01 by default
%
%  Ex. Calculating of two start values
%     doaStart(1) = stardoa(R,-1);    %find the first DOA
%   doaStart(2) = stardoa(R,[doaStart(1)]); %find the other one
%   edoa = doapar1('wsf',R, doaStart);  %use it in a DOA algorithm
%
%

%
%  Start        : 970715 Amir Heydarkhan (amihey).
%  Latest change: $Date: 2000/10/16 15:22:12 $ $AEthor: amihey $.
%  $Revision: 1.11 $
% *****************************************************************************

if nargin < 2,
  tol = 0.01*pi/180;
  method = 'ap';
  thetaprev = -1;
elseif nargin < 3,
  tol = 0.01*pi/180;
  method = 'ap';
elseif nargin < 4,
  tol = 0.01*pi/180;
end

antenna = R.antenna;
%lambda = antenna.lambda;
waveform = R.waveform;
lambda  = waveform.wavelength;

E = R.corrMat;
E = sqrtm(E);

[cE,rE] = size(E);
d = length(thetaprev);


if method == 'ap',
%----------------------------------------------------------
% Alternating Projection
%----------------------------------------------------------

  if thetaprev == -1,
    Q2 = eye(cE);
  else
    rand('uniform')
    while (min(abs(thetaprev(1:d-1)-thetaprev(2:d))) < tol )
      thetaprev = thetaprev+ 5*tol*rand(size(thetaprev));
      thetaprev = sort(thetaprev);
    end

    A = spastemat(antenna, thetaprev, lambda);
    [Q2,R0] = qr(A);Q2 = Q2(:,d+1:cE);
  end


  %--------------
  %a coarse grid
  %--------------

  beamwidth = asin(2/cE);   % Beamwidth for half-wavelength spaced ELA
  if tol < beamwidth/4
    delta = beamwidth/4;
  else
    delta = tol;
  end

  global phitab

 if isempty(phitab)
    thmin = d2r(-80);   %form -80 to 80 degrees
    thmax = d2r(80);
  else
    thmax = max(phitab);
    thmin = min(phitab);
  end

  thhat = thmin:delta:thmax;

  Abig = spastemat(antenna, thhat, lambda);
  QA = Q2'*Abig;
  B = (E'*Q2)*QA;

  P = diag(real(B'*B))./diag(real(QA'*QA));

  [Pp,index] = max(P);

  StartDOA = thhat(index);

%----------------------------------------------------------
%
%----------------------------------------------------------

%elseif method == 'ddd',


%----------------------------------------------------------
%
%----------------------------------------------------------

%elseif method == 'ddd',

%----------------------------------------------------------
% The method is not implemented yet!!!
%----------------------------------------------------------

else
  disp('the method is not implemented yet!!!')
end