MATLAB 添加高斯噪声awgn函数(需要wgn函数)

function y=awgn(varargin)

%AWGN Add white Gaussian noise to a signal.

% Y = AWGN(X,SNR) adds white Gaussian noise to X. The SNR is in dB.

% The power of X is assumed to be 0 dBW. If X is complex, then

% AWGN adds complex noise.

%

% Y = AWGN(X,SNR,SIGPOWER) when SIGPOWER is numeric, it represents

% the signal power in dBW. When SIGPOWER is 'measured', AWGN measures

% the signal power before adding noise.

%

% Y = AWGN(X,SNR,SIGPOWER,STATE) resets the state of RANDN to STATE.

%

% Y = AWGN(..., POWERTYPE) specifies the units of SNR and SIGPOWER.

% POWERTYPE can be 'db' or 'linear'. If POWERTYPE is 'db', then SNR

% is

% % %

% % % % % If POWERTYPE

% To specify the power of X to be 0 dBW and add noise to produce % an SNR of 10dB, use:

X = sqrt(2)*sin(0:pi/8:6*pi);

Y = awgn(X,10,0);

is measured in dB and SIGPOWER is measured in dBW. 'linear', then SNR is measured as a ratio and SIGPOWER is measured in Watts. Example 1:

%

% Example 2:

% % To specify the power of X to be 3 Watts and add noise to

% % produce a linear SNR of 4, use:

% X = sqrt(2)*sin(0:pi/8:6*pi);

% Y = awgn(X,4,3,'linear');

%

% Example 3:

% % To cause AWGN to measure the power of X and add noise to

% % produce a linear SNR of 4, use:

% X = sqrt(2)*sin(0:pi/8:6*pi);

% Y = awgn(X,4,'measured','linear');

%

% See also WGN, RANDN, and BSC.

% Copyright 1996-2008 The MathWorks, Inc.

% $Revision: 1.9.4.6 $ $Date: 2008/08/22 20:23:43 $

% --- Initial checks

error(nargchk(2,5,nargin,'struct'));

% --- Value set indicators (used for the string flags)

pModeSet = 0;

measModeSet = 0;

% --- Set default values

sigPower = 0;

pMode = 'db';

measMode = 'specify';

state = [];

% --- Placeholder for the signature string

sigStr = '';

% --- Identify string and numeric arguments

for n=1:nargin

if(n>1)

sigStr(size(sigStr,2)+1) = '/';

end

% --- Assign the string and numeric flags

if(ischar(varargin{n}))

sigStr(size(sigStr,2)+1) = 's';

elseif(isnumeric(varargin{n}))

sigStr(size(sigStr,2)+1) = 'n';

else

error('comm:awgn:InvalidArg','Only string and numeric arguments are allowed.');

end

end

% --- Identify parameter signatures and assign values to variables

switch sigStr

% --- awgn(x, snr)

case 'n/n'

sig = varargin{1};

reqSNR = varargin{2};

% --- awgn(x, snr, sigPower)

case 'n/n/n'

sig = varargin{1};

reqSNR = varargin{2};

sigPower = varargin{3};

% --- awgn(x, snr, 'measured')

case 'n/n/s'

sig = varargin{1};

reqSNR = varargin{2};

measMode = lower(varargin{3});

measModeSet = 1;

% --- awgn(x, snr, sigPower, state)

case 'n/n/n/n'

sig = varargin{1};

reqSNR = varargin{2};

sigPower = varargin{3};

state = varargin{4};

% --- awgn(x, snr, 'measured', state)

case 'n/n/s/n'

sig = varargin{1};

reqSNR = varargin{2};

measMode = lower(varargin{3});

state = varargin{4};

measModeSet = 1;

% --- awgn(x, snr, sigPower, 'db|linear')

case 'n/n/n/s'

sig = varargin{1};

reqSNR = varargin{2};

sigPower = varargin{3};

pMode = lower(varargin{4});

pModeSet = 1;

% --- awgn(x, snr, 'measured', 'db|linear')

case 'n/n/s/s'

sig = varargin{1};

reqSNR = varargin{2};

measMode = lower(varargin{3});

pMode = lower(varargin{4});

measModeSet = 1;

pModeSet = 1;

% --- awgn(x, snr, sigPower, state, 'db|linear')

case 'n/n/n/n/s'

sig = varargin{1};

reqSNR = varargin{2};

sigPower = varargin{3};

state = varargin{4};

pMode = lower(varargin{5});

pModeSet = 1;

% --- awgn(x, snr, 'measured', state, 'db|linear')

case 'n/n/s/n/s'

sig = varargin{1};

reqSNR = varargin{2};

measMode = lower(varargin{3});

state = varargin{4};

pMode = lower(varargin{5});

measModeSet = 1;

pModeSet = 1;

otherwise

error('comm:awgn:InvalidSyntax','Syntax error.');

end

% --- Parameters have all been set, either to their defaults or by the values passed in,

% so perform range and type checks

% --- sig

if(isempty(sig))

error('comm:awgn:NoInput','An input signal must be given.');

end

if(ndims(sig)>2)

error('comm:awgn:InvalidSignalDims','The input signal must have 2 or fewer dimensions.');

end

% --- measMode

if(measModeSet)

if(~strcmp(measMode,'measured'))

error('comm:awgn:InvalidSigPower','The signal power parameter must be

numeric or ''measured''.');

end

end

% --- pMode

if(pModeSet)

switch pMode

case {'db' 'linear'}

otherwise

error('comm:awgn:InvalidPowerType','The signal power mode must be ''db'' or ''linear''.');

end

end

% -- reqSNR

if(any([~isreal(reqSNR) (length(reqSNR)>1) (isempty(reqSNR))]))

error('comm:awgn:InvalidSNR','The signal-to-noise ratio must be a real scalar.');

end

if(strcmp(pMode,'linear'))

if(reqSNR<=0)

error('comm:awgn:InvalidSNRForLinearMode','In linear mode, the signal-to-noise ratio must be > 0.');

end

end

% --- sigPower

if(~strcmp(measMode,'measured'))

% --- If measMode is not 'measured', then the signal power must be specified

if(any([~isreal(sigPower) (length(sigPower)>1) (isempty(sigPower))]))

error('comm:awgn:InvalidSigPower','The signal power value must be a real scalar.');

end

if(strcmp(pMode,'linear'))

if(sigPower<0)

error('comm:awgn:InvalidSigPowerForLinearMode','In linear mode, the signal power must be >= 0.');

end

end

end

% --- state

if(~isempty(state))

if(any([~isreal(state) (length(state)>1) (isempty(state)) any((state-floor(state))~=0)]))

error('comm:awgn:InvaildState','The State must be a real, integer scalar.');

end

end

% --- All parameters are valid, so no extra checking is required

% --- Check the signal power. This needs to consider power measurements on matrices

if(strcmp(measMode,'measured'))

sigPower = sum(abs(sig(:)).^2)/length(sig(:));

if(strcmp(pMode,'db'))

sigPower = 10*log10(sigPower);

end

end

% --- Compute the required noise power

switch lower(pMode)

case 'linear'

noisePower = sigPower/reqSNR;

case 'db'

noisePower = sigPower-reqSNR;

pMode = 'dbw';

end

% --- Add the noise

if(isreal(sig))

opType = 'real';

else

opType = 'complex';

end

y = sig+wgn(size(sig,1), size(sig,2), noisePower, 1, state, pMode, opType);