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楼主 |
发表于 2007-7-12 13:34
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谢谢热心帮助，下面附上wgn的源码！
function y = wgn(varargin)
%WGN Generate white Gaussian noise.
% Y = WGN(M,N,P) generates an M-by-N matrix of white Gaussian noise.
% P specifies the power of the output noise in dBW.
%
% Y = WGN(M,N,P,IMP) specifies the load impedance in Ohms.
%
% Y = WGN(M,N,P,IMP,STATE) resets the state of RANDN to STATE.
%
% Additional flags that can follow the numeric arguments are:
%
% Y = WGN(..., POWERTYPE) specifies the units of P. POWERTYPE can
% be 'dBW', 'dBm' or 'linear'. Linear power is in Watts.
%
% Y = WGN(..., OUTPUTTYPE); Specifies the output type. OUTPUTTYPE can
% be 'real' or 'complex'. If the output type is complex, then P
% is divided equally between the real and imaginary components.
%
% Example: To generate a 1024-by-1 vector of complex noise with power
% of 5 dBm across a 50 Ohm load, use:
% Y = WGN(1024, 1, 5, 50, 'dBm', 'complex');
%
% Example: To generate a 256-by-5 matrix of real noise with power
% of 10 dBW across a 1 Ohm load, use:
% Y = WGN(256, 5, 10, 'real');
%
% Example: To generate a 1-by-10 vector of complex noise with power
% of 3 Watts across a 75 Ohm load, use:
% Y = WGN(1, 10, 3, 75, 'linear', 'complex');
%
% See also RANDN, AWGN.
% Copyright 1996-2003 The MathWorks, Inc.
% $Revision: 1.11.4.3 $ $Date: 2004/04/12 23:01:28 $
% --- Initial checks
error(nargchk(3,7,nargin));
% --- Value set indicators (used for the strings)
pModeSet = 0;
cplxModeSet = 0;
% --- Set default values
p = [];
row = [];
col = [];
pMode = 'dbw';
imp = 1;
cplxMode = 'real';
seed = [];
% --- Placeholders for the numeric and string index values
numArg = [];
strArg = [];
% --- Identify string and numeric arguments
% An empty in position 4 (Impedance) or 5 (Seed) are considered numeric
for n=1:nargin
if(isempty(varargin{n}))
switch n
case 4
if(ischar(varargin{n}))
error('The default impedance should be marked by [].');
end;
varargin{n} = imp; % Impedance has a default value
case 5
if(ischar(varargin{n}))
error('The default seed should be marked by [].');
end;
varargin{n} = []; % Seed has no default
otherwise
varargin{n} = '';
end;
end;
% --- Assign the string and numeric vectors
if(ischar(varargin{n}))
strArg(size(strArg,2)+1) = n;
elseif(isnumeric(varargin{n}))
numArg(size(numArg,2)+1) = n;
else
error('Only string and numeric arguments are allowed.');
end;
end;
% --- Build the numeric argument set
switch(length(numArg))
case 3
% --- row is first (element 1), col (element 2), p (element 3)
if(all(numArg == [1 2 3]))
row = varargin{numArg(1)};
col = varargin{numArg(2)};
p = varargin{numArg(3)};
else
error('Illegal syntax.')
end;
case 4
% --- row is first (element 1), col (element 2), p (element 3), imp (element 4)
%
if(all(numArg(1:3) == [1 2 3]))
row = varargin{numArg(1)};
col = varargin{numArg(2)};
p = varargin{numArg(3)};
imp = varargin{numArg(4)};
else
error('Illegal syntax.')
end;
case 5
% --- row is first (element 1), col (element 2), p (element 3), imp (element 4), seed (element 5)
if(all(numArg(1:3) == [1 2 3]))
row = varargin{numArg(1)};
col = varargin{numArg(2)};
p = varargin{numArg(3)};
imp = varargin{numArg(4)};
seed = varargin{numArg(5)};
else
error('Illegal syntax.');
end;
otherwise
error('Illegal syntax.');
end;
% --- Build the string argument set
for n=1:length(strArg)
switch lower(varargin{strArg(n)})
case {'dbw' 'dbm' 'linear'}
if(~pModeSet)
pModeSet = 1;
pMode = lower(varargin{strArg(n)});
else
error('The Power mode must only be set once.');
end;
case {'db'}
error('Incorrect power mode passed in. Please use ''dBW'', ''dBm'', or ''linear.''');
case {'real' 'complex'}
if(~cplxModeSet)
cplxModeSet = 1;
cplxMode = lower(varargin{strArg(n)});
else
error('The complexity mode must only be set once.');
end;
otherwise
error('Unknown option passed in.');
end;
end;
% --- Arguments and defaults have all been set, either to their defaults or by the values passed in
% so, perform range and type checks
% --- p
if(isempty(p))
error('The power value must be a real scalar.');
end;
if(any([~isreal(p) (length(p)>1) (length(p)==0)]))
error('The power value must be a real scalar.');
end;
if(strcmp(pMode,'linear'))
if(p<0)
error('In linear mode, the required noise power must be >= 0.');
end;
end;
% --- Dimensions
if(any([isempty(row) isempty(col) ~isscalar(row) ~isscalar(col)]))
error('The required dimensions must be real, integer scalars > 1.');
end;
if(any([(row<=0) (col<=0) ~isreal(row) ~isreal(col) ((row-floor(row))~=0) ((col-floor(col))~=0)]))
error('The required dimensions must be real, integer scalars > 1.');
end;
% --- Impedance
if(any([~isreal(imp) (length(imp)>1) (length(imp)==0) any(imp<=0)]))
error('The Impedance value must be a real scalar > 0.');
end;
% --- Seed
if(~isempty(seed))
if(any([~isreal(seed) (length(seed)>1) (length(seed)==0) any((seed-floor(seed))~=0)]))
error('The State must be a real, integer scalar.');
end;
end;
% --- All parameters are valid, so no extra checking is required
switch lower(pMode)
case 'linear'
noisePower = p;
case 'dbw'
noisePower = 10^(p/10);
case 'dbm'
noisePower = 10^((p-30)/10);
end;
% --- Generate the noise
if(~isempty(seed))
randn('state',seed);
end;
if(strcmp(cplxMode,'complex'))
z = randn(2*row,col);
y = (sqrt(imp*noisePower/2))*(z(1:row,:)+j*z(row+1:end,:));
else
y = (sqrt(imp*noisePower))*randn(row,col);
end; |
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发表于 2007-7-11 09:56
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发表于 2007-7-11 10:07
