matlab函数qammod源代码

MATLAB 函数 `qammod` 的源代码如下：

function y = qammod(x,M,varargin)
%QAMMOD Quadrature Amplitude Modulation modulation.
%   Y = QAMMOD(X,M) outputs the complex envelope Y of the modulation of
%   the message signal X using quadrature amplitude modulation. M is the
%   modulation order and must be an integer power of 2. If X is a matrix,
%   the function treats each column as a separate channel.
%
%   Y = QAMMOD(X,M,S) uses constellation mapping specified by S. S must
%   be a complex column vector with M elements. The elements in S must be
%   unique and have unit magnitude. The default constellation mapping for
%   QAM is Gray-coded.
%
%   Y = QAMMOD(X,M,S,SYMORDER) specifies the symbol order. The default
%   symbol order is 'gray'. Other options include 'bin' and 'sym'.
%
%   % Example:
%   %   Modulate a random signal using 16-QAM
%
%   data = randi([0 3],100,1);            % Random data stream
%   modSignal = qammod(data,16);          % 16-QAM modulated signal
%   scatterplot(modSignal);               % Plot constellation diagram
%
%   See also QAMDEMOD, MODULATE, DEMODULATE, PAMMOD, PSKMOD, FSKMOD.

%   Copyright 2001-2019 The MathWorks, Inc.

%   References:
%   [1] Simon, M. K. and Alouini, M.-S., Digital Communication over
%       Fading Channels, 2nd Ed., Wiley, 2005.
%   [2] Proakis, J. G., Digital Communications, 3rd Ed., McGraw-Hill, 1995.

narginchk(2, 4);
validateattributes(x,{'double','single'},{'column','finite'},'','X');
validateattributes(M,{'numeric'},{'integer','scalar','positive'},'','M');

% Default symbol mapping is Gray-coded
defaultConstellation = qammod([],M,'gray');

if nargin > 2
    validateattributes(varargin{1},{'double','single'},{'column','finite','nonnan','nonempty'},'','S');
    if numel(varargin) > 1
        symOrder = varargin{2};
    else
        symOrder = 'gray';
    end
    constellation = varargin{1};
else
    constellation = defaultConstellation;
    symOrder = 'gray';
end

if nargin > 3
    validateattributes(symOrder,{'char'},{'nonempty'},'','SYMORDER');
    symOrder = validatestring(symOrder,{'bin','gray','sym'},'','SYMORDER');
end

% Validate inputs
if ~isreal(constellation)
    error(message('comm:qammod:InvalidConstellation'));
end
validateattributes(constellation,{'double','single'},{'column','finite','nonnan','nonempty'},'','S');
validatestring(symOrder,{'bin','gray','sym'},'','SYMORDER');

% Calculate number of bits per symbol
k = log2(M);

% Validate input
if mod(length(x), k) ~= 0
    error(message('comm:qammod:InvalidInputLength', k));
end

% Modulate using index mapping
if strcmp(symOrder,'bin') || strcmp(symOrder,'sym')
    if strcmp(symOrder,'bin')
        x = bi2de(x,'left-msb');
    end
    xMsg = de2bi(x,k,'left-msb');
    xMsg = reshape(xMsg.',[],1);
    xIndex = bi2de(xMsg,'left-msb') + 1; % Convert to decimal index
else % Gray coding
    xMsg = reshape(x,k,[]);
    xGray = sum(xMsg .* repmat(2.^(k-1:-1:0)',1,size(xMsg,2)),1); % Convert to decimal index
    xIndex = gray2bin(xGray,'qam',M) + 1;
end

% Map the message to a point in the constellation
y = constellation(xIndex);

end

该函数实现了各种 QAM 调制方式，包括二进制、格雷码和符号映射。你可以根据自己的需求进行调用和修改。