simtarget.m

阵列信号处理的工具箱

function radarSig3D = simtarget(steeringMatrix, pri, lambda, pulseMod, sampleTime, targetPowers, targetVel, targetRanges, targetTypes, targetStartPhases, noPulses, noRangeBins, targCorrMx, propSpeed, pulIx, ranIx, spaIx, extraIx, cpiIx, trialIx)

%SIMTARGET is the core simulating engine for simulating narrowband radar
%          signals from targets
%
%Synopsis:
%  radarSig3D = simtarget(steeringMatrix, pri, lambda, pulseMod,...
%                         sampleTime, targetPowers, targetVel, ...
%                         targetRanges, targetTypes, noPulses, ...
%                         noRangeBins, targCorrMx);
%
%Description:
%  Simulates narrowband radar signals and stores the data in a 3D matrix
%  ( Number Pulses x Number Of RangeBins x Number Of Channels )
%  The range to the target is translated into a corresponding range bin
%  with the function "ran2ranbin" where all targets that are beyond the
%  range described by the "noRangeBin" input parameter are folded back
%  to the beginning of the range bins in a modulo fashion. Target ranges
%  are also used to determine the start phase of each target. These phases
%  are then altered from pulse to pulse according to the target's velocity
%  Range bins correspond to a time shift that is faster then between pulses,
%  this leads to a phase shift between range bins aswell (much slower
%  rate though). The simulated radarsignal is also convolved with the
%  pulse modulation code. This convolution is performed on the range
%  dimension. There is also a possibility to correlate targets with each
%  other. Finally the simulated radar signal is moved into beamspace
%  with the help of the steering vector.
%
%  This function is called upon by "simradarsig" and should be
%  hidden from the everyday user.
%
%Input:
%  steeringMatrix (CxMatrixT)  : The steering matrix describing the
%                                antenna geometry.
%  pri (RealScalarT)           : Pulse repetition interval [s].
%  lambda (RealScalarT)        : Wavelength [m].
%  pulseMod (CxVectorT)        : Pulse modulation weights. see "getmod".
%  sampleTime (RealScalarT)    : Time between range bins [s].
%  targetPowers (CxVectorT)    : Power received from each targets [W].
%  targetVel (CxVectorT)       : Radial velocities to radar antenna for
%                                each target [m/s].
%  targetRanges (CxVectorT)    : Distance between target and radar [m].
%  targetTypes (StingVectorT)  : List of the target types.
%  noPulses (IntScalarT)       : Number of pulses in simulation.
%  noRangeBins (IntScalarT)    : Number of range bins.
%  targCorrMx (CxMatrixT)      : Correlations between the targets.
%                                (noPulses x noPulses)
%  propSpeed (RealScalarT)     : Propagation speed of the beam [m/s].
%
%Output:
%  radarSig3D (CxMatrixT)      : 3D matrix with the simulated data.
%                                pulses x rangebins x channels.
%
%--------
%Notations:
%  Data type names are shown in parentheses and they start with a capital
%  letter and end with a capital T. Data type definitions can be found in
%  [1] or by "help dbtdata".
%
%Examples:
%
%Software Quality:
%
%Known Bugs:
%  1) Only targets of type "swerling0" (constant) is implemented.
%
%  2) Targets beyond the umambiguous range, i.e. in a range bin beyond
%     "noRangeBins" should not show up in first pulse, but instead in the
%     pulse corresponding to the distance of the target.
%
%  3) In a situation with targets in some of the last range bins and when
%     pulse modulation is chosen the pulse code should spill over to the
%     next pulse.
%
%References:
%  [1]: Bj鰎klund S., Rejdemyhr D. Athley F.: "DBT, A MATLAB Toolbox
%       for Radar Signal Processing. Reference Guide",
%       FOA-D--9x-00xxx-408--SE, To be published.
%  [2]: Kingsley S., Quegan S.: "Understanding Radar Systems",
%       McGraw-Hill 1992.
%
%See also:
%  deftarget, simradarsig, simnoise, simclutter, simjammer, defwave,
%  getmod.

%   *  DBT, A Matlab Toolbox for Radar Signal Processing  *
%  (c) FOA 1994-2000. See the file dbtright.m for copyright notice.
%
%  Initiation    : 980511 David Rejdemyhr (davrej).
%  Latest change : $Date: 2000/10/16 15:21:56 $ $Author: svabj $.
%  $Revision     : 1.0 $
%*************************************************************************

%-------------------------------------------------------------------------
%----                 Constants used in function                      ----
%-------------------------------------------------------------------------

  noTargets = length(targetPowers);
  pulseMod = pulseMod.';
  corrFlag = sum(sum(eye(noTargets)-targCorrMx));
    % Equal to zero when there's no correlation


%-------------------------------------------------------------------------
%----                    Simulate the signals.                        ----
%-------------------------------------------------------------------------

  %- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  %--- Create empty preRadarSig variable. Each row corresponds to a    ---
  %--- range bin. Each Column corresponds to a target.                  ---
  %- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

  preRadarSig = zeros(noRangeBins, noTargets);


  % -- Convert Targetrange to corresponding RangeBin --

  targetRangeBins = ran2ranbin(targetRanges, sampleTime, propSpeed,...
                              noRangeBins);

  %- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  %--- An index to a 2D matrix is a linear array columnwise. I.e. 2nd  ---
  %--- column and 5th row is 2*noRows + 5                              ---
  %- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

  idxes2D = ((1:noTargets) - 1) * noRangeBins + targetRangeBins;
  preRadarSig(idxes2D) = sqrt(targetPowers) .* exp(j*targetStartPhases);

  %- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  %--- We now have a signal where the rows represent range bins and the ---
  %--- columns represent targets                                       ---
  %- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


  %- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  %--- Calculate velocity dependent phase shifts due to target motion   ---
  %--- within a single pulse, i.e. different positions of the targets  ---
  %--- at each subpulse. One of the two's are there because of that    ---
  %--- the wave travelles back and forth.                              ---
  %- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

  phShifts = ((1:length(pulseMod))-1) * 2*pi * 2 * sampleTime / lambda;


  %- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  %--- Convolute with the modulation array including phaseshift due to ---
  %--- motion of target between subpulses (rangebins). Only if         ---
  %--- pulemodulation differs from zero.                               ---
  %- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

  if ~isempty(pulseMod)
    for targIdx = 1:noTargets
      data = preRadarSig(:,targIdx);
      convolved = conv(data,pulseMod .* ...
                       exp(j*phShifts*targetVel(targIdx)));
      preRadarSig(:,targIdx) = convolved(1:length(data));
    end%for
  end%if


  %- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  %--- Calculate velocity dependent weights, i.e. phaseshifts for each ---
  %--- source due to its radial speed and variation of source power    ---
  %--- between pulses. Consider sterling cases aswell.                 ---

  pulseWeights = zeros(noPulses, noRangeBins, noTargets);

  phaseShifts = ((1:noPulses)-1).' * 2*pi * 2 * targetVel * pri / lambda;

  for targIdx = 1:noTargets

    targetType = targetTypes{targIdx};

    if (strcmp(targetType,'constant') | ...
        strcmp(targetType,'swerling0') | ...
        strcmp(targetType,'swerling5') | ...
        strcmp(targetType,'marcum')),

      pulseWeights(:, 1, targIdx) = ones(noPulses,1) .* ...
                                    exp(j*phaseShifts(:,targIdx));

    elseif strcmp(targetType,'swerling1'),


    elseif strcmp(targetType,'swerling2'),


    elseif strcmp(targetType,'swerling3'),


    elseif strcmp(targetType,'swerling4'),


    elseif strcmp(targetType,'custom'),

    elseif strcmp(targetType,'randn'),
      pulseWeights(:, 1, targIdx) = randn(noPulses,1) .* ...
                                    exp(j*phaseShifts(:,targIdx));

    end %if
  end %for

  pulseWeights = repmat(pulseWeights(:,1,:),[1, noRangeBins, 1]);


  % -- Extend this matrix to a 3D matrix. The new dim is the pulses --

  preRadarSig3D = zeros(noPulses, noRangeBins, noTargets);
  preRadarSig3D1(1,:,:) = preRadarSig;
  preRadarSig3D = repmat(preRadarSig3D1(1,:,:),[noPulses,1,1]);

  preRadarSig3D(:,:,:) = preRadarSig3D(:,:,:) .* pulseWeights;

  %- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  %--- We now have a 3D-signal where the 1:st index represent pulses   ---
  %--- and the 2:nd index represents rangebins and  3:rd index         ---
  %--- represent the targets.                                          ---
  %- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -


  % -- If needed then correlate the targets with supplied correlation matrix. --

  if ( ~isempty(targCorrMx) & ...
       (corrFlag ~= 0) )
    % Compute the square root of the covariance matrix with SVD
    % and color the random variables with the square root of the
    % noise covariance matrix.
    [U,SIG,V] = svd(targCorrMx);
    for rangeIdx = 1:noRangeBins
      preRadarSig3D(:,rangeIdx,:) = ...
        (U*sqrt(SIG)*squeeze(preRadarSig3D(:,rangeIdx,:)).').';
    end %for
  end %if


  % -- Take the step into beamspace with help of the steering matrix --
  profileTest = 0;
    % = 1 when measuring the excution time. Otherwise = 0.

  noChannels = size(steeringMatrix,1);
  radarSig3D = zeros(noPulses, noRangeBins, noChannels);
  for pulseIdx = 1:noPulses
    if (noTargets == 1 | noRangeBins == 1)
      % The (above) if statement is needed due to behavior of squeeze.
      if (profileTest)
        tmp1 = preRadarSig3D(pulseIdx,:,:);
        tmp2 = squeeze(tmp1);
        tmp3 = steeringMatrix * tmp2;
        tmp4 = tmp3.';
        radarSig3D(pulseIdx,:,:) = tmp4;
        %radarSig3D(:,:,pulseIdx) = tmp4;
      else
        % Normal operation.
        radarSig3D(pulseIdx,:,:) = (steeringMatrix * ...
                                  squeeze(preRadarSig3D(pulseIdx,:,:))).';
        %radarSig3D(:,:,pulseIdx) = (steeringMatrix * ...
        %                          squeeze(preRadarSig3D(pulseIdx,:,:))).';
      end%if
    else
      radarSig3D(pulseIdx,:,:) = (steeringMatrix * ...
                                  squeeze(preRadarSig3D(pulseIdx,:,:)).').';
    end %if
  end %for

  %------------------------------------------------------------------------------
  %- Finally we have a 3D-signal where the 1st index represent pulses and    --
  %- the 2nd index represents rangebins and 3rd index represent the channels  -
  %------------------------------------------------------------------------------

%End Of File -------------------------------------------------------------