function noise3D = simnoise(noiseSources, noPulses, noRangeBins, noChannels);%SIMNOISE is the core simulating engine for simulating noise sources.%%Synopsis:%  noise3D = simnoise(noiseSources, noPulses, noRangeBins, noChannels);%%Description:%  Simulates radarsignals and stores the data in a 3D matrix%  ( Number Pulses x Number Of RangeBins x Number Of Channels )%  The simulator assumes that the noise is borne in the antenna channels,%  in contrast to in the antenna elements or outside of the antenna. This%  implies that the noise signals does not pass through the analog%  beamformer modelled by the steering matrix, e.g. the steering matrix is%  not needed in calculations.%  The noise that is simulated is a complex gaussian noise with mean 0 and%  variance equal to the wanted power. The power of the noise is the same%  in all channels. Since the noise is deployed directly in the antenna%  channels, the signal-to-noise-ratio is ambiguous and dependent of the%  steering matrix. If the steering matrix has components whos absolute%  values is different from "1", then the target's power will vary from%  antenna channel to antenna channel and thus will SNR vary equally much.%%  This function is called upon by the function "simradarsig" and is%  normally not used by the end user.%%Input:%  noiseSources (NoiseDefT)  : Cellarray of the noise sources that will be%                              simulated.%  noPulses (IntScalarT)     : Number of pulses in simulation.%  noRangeBins (IntScalarT)  : Number of rangebins in simulation.%  noChannels (IntScalarT)   : Number of channels of the antenna.%%OutPut:%  noise3D (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:%%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.%%  [3]: Horner R.A., Johnson, C.R.: "Topics in matrix Analysis",%       Cambridge University Press 1991.%%See also:%  defnoise, simradarsig, simtarget, simclutter, simjammer.%   *  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 15:21:54 $ $Author: svabj $.%  $Revision     : 1.0 $%*************************************************************************%-------------------------------------------------------------------------%----                     Initialize variables.                       ----%-------------------------------------------------------------------------noise3D = 0;%-------------------------------------------------------------------------%----                  Initialize random generator.                   ----%-------------------------------------------------------------------------randn('seed',sum(100*clock));rand('seed',sum(100*clock));%-------------------------------------------------------------------------%----                     Simulate noise signals.                     ----%-------------------------------------------------------------------------for noiseIdx = 1:length(noiseSources.Types)  if (noiseSources.Types{noiseIdx} == 'Gaussian')    if (1)      noise3Dpre = sqrt(noiseSources.Powers{noiseIdx}/2) * ...                  (randn(noPulses, noRangeBins, noChannels) + ...                  j*randn(noPulses, noRangeBins, noChannels));    else      % This branch is used to test the execution time.      noise3Dpre = randn(noPulses, noRangeBins, noChannels);      noise3Dpre = noise3Dpre + j*randn(noPulses, noRangeBins, noChannels);      noise3Dpre = noise3Dpre * sqrt(noiseSources.Powers{noiseIdx}/2);    end%if%  elseif  else    dbtwarning('Desired noise type was unknown to simulator, proceeding with no noise.');    noise3D = 0;  end %if  if ~isempty(noiseSources.CorrMxs{noiseIdx})    % Compute the square root of the source covariance matrix with SVD    % and color the random variables with the square root of the    % noise covariance matrix.    [U,SIG,V] = svd(noiseSources.CorrMxs{noiseIdx});    usqrtsig = U*sqrt(SIG);    for rangeIdx = 1:noRangeBins      noise3Dpre(:,rangeIdx,:) = (usqrtsig* ...        squeeze(noise3Dpre(:,rangeIdx,:)).').';    end %for  end %if  noise3D = noise3D + noise3Dpre;end %for%End Of File -------------------------------------------------------------