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function y = modmap(x, Fd, Fs, method, M, opt2, opt3)
%MODMAP Map a digital signal to an analog signal.
%
% Plotting syntaxes:
% MODMAP(METHOD...) plots the signal constellation associated with
% the specified mapping method.
%
% Mapping syntaxes:
% Y = MODMAP(X, Fd, Fs, METHOD...) maps the digital signal X to
% an analog signal Y. This syntax only maps; it does not modulate.
%
% More help for all syntaxes:
% ---------------------------
% For information about METHOD and subsequent parameters, and about
% using a specific technique, type one of these commands at the MATLAB
% prompt:
%
% FOR DETAILS, TYPE MAPPING/MODULATION TECHNIQUE
% modmap ask % M-ary amplitude shift keying
% modmap psk % M-ary phase shift keying
% modmap qask % M-ary quadrature amplitude shift keying
% modmap fsk % M-ary frequency shift keying
% modmap msk % Minimum shift keying
%
% For digital modulation, use DMOD for passband simulation and
% DMODCE for baseband simulation.
%
% See also DEMODMAP, DMOD, DMODCE, AMOD, AMODCE, APKCONST.
% Copyright 1996-2001 The MathWorks, Inc.
% $Revision: 1.16 $
opt_pos = 5; % position of 1st optional parameter
plot_const = 0;
if nargin < 1
feval('help','modmap')
return;
elseif isstr(x)
if exist('method', 'var')
tmp_sto = method;
end
method = lower(deblank(x));
if findstr(method, 'samp')
method = 'samp';
end
if nargin == 1
% help lines for individual modulation method.
if strcmp(method, '')
method = 'ask';
end
hand = fopen('modmap.hlp');
if hand<=0
error('The Communications Toolbox on your computer is not completely installed.')
else
x = fscanf(hand, '%c', Inf);
index_begin = findstr(x, [method,'_help_begin']);
index_end = findstr(x, [method,'_help_end']);
if index_end > index_begin
x = x(index_begin+12+length(method):index_end-1);
fprintf('%s', x);
disp(' ')
disp(' See also DEMODMAP, DMOD, DMODCE, AMOD, AMODCE, APKCONST.')
else
disp(['No help for ', method]);
end
end
fclose(hand);
return;
else
plot_const = 1;
opt_pos = opt_pos - 3;
M = Fd;
if nargin > opt_pos
opt2 = Fs;
end
if nargin > opt_pos+1
opt3 = tmp_sto;
end
end
else
if nargin < 3
error('Usage: Y=MODMAP(X, Fd, Fs, METHOD, OPT1, OPT2, OPT3) for modulation mapping');
elseif nargin < opt_pos-1
method = 'sample';
end
if length(Fs)~=1 | ~isfinite(Fs) | ~isreal(Fs) | Fs<=0
error('Fs must be a positive number.');
elseif length(Fd)~=1 | ~isfinite(Fd) | ~isreal(Fd) | Fd<=0
error('Fd must be a positive number.');
else
FsDFd = Fs / Fd;
if ceil(FsDFd) ~= FsDFd
error('Fs/Fd must be a positive integer.');
end
end
% determine M
if isempty(findstr(method, '/arb')) & isempty(findstr(method, '/cir'))
if nargin < opt_pos
M = max(max(x)) + 1;
M = 2^(ceil(log(M)/log(2)));
M = max(2, M);
elseif length(M) ~= 1 | ~isfinite(M) | ~isreal(M) | M <= 0 | ceil(M) ~= M
error('Alphabet size M must be a positive integer.');
end
end
if isempty(x)
y = [];
return;
end
[r, c] = size(x);
if r == 1
x = x(:);
len_x = c;
else
len_x = r;
end
if ~(strncmpi(method, 'qask', 4) | strncmpi(method, 'qam', 3) |...
strncmpi(method, 'qsk', 3)) & ...
(~isreal(x) | all(ceil(x)~=x) | any(any(x<0)) | any(any(x>M-1)))
error('Elements of input X must be integers in [0, M-1].');
end
yy = [];
for i = 1 : size(x, 2)
tmp = x(:, ones(1, FsDFd)*i)';
yy = [yy tmp(:)];
end
x = yy;
clear yy tmp;
end
method = lower(method);
if strncmpi(method, 'ask', 3)
if plot_const
plot([0 0], [-1.1 1.1], 'w-', [-1.1, 1.1], [0 0], 'w-', ([0:M-1] - (M - 1) / 2 ) * 2 / (M - 1), zeros(1, M), '*');
axis([-1.1 1.1 -1.1 1.1])
xlabel('In-phase component');
title('ASK constellation')
else
y = (x - (M - 1) / 2 ) * 2 / (M - 1);
if r==1 & ~isempty(y)
y = y.';
end
end
elseif strncmpi(method, 'fsk', 3)
if nargin < opt_pos + 1
Tone = Fd;
else
Tone = opt2;
end
if plot_const
maxTone = Tone*(M-1);
x = [0 : Tone : maxTone];
tmp = ones(1, M);
tmp(1) = 2;
stem(x, tmp);
axis([-1, maxTone+1, 0, 2]);
xlabel('Frequency (Hz)');
title('FSK constellation');
else
y = x * Tone;
if r==1 & ~isempty(y)
y = y.';
end
end
elseif strncmpi(method, 'psk', 3)
if plot_const
apkconst(M);
else
y = modmap(x, Fs, Fs, 'qask/cir', M);
end
elseif strncmpi(method, 'msk', 3)
% This is a special case of fsk.
if plot_const
stem([0 Fd], [2 1]);
axis([-1, Fd+1, 0, 2]);
xlabel('Frequency (Hz)');
title('MSK constellation');
else
M = 2;
Tone = Fd/2;
y = x * Tone;
if r==1 & ~isempty(y)
y = y.';
end
end
elseif ( strncmpi(method, 'qask', 4) | strncmpi(method, 'qam', 3) |...
strncmpi(method, 'qsk', 3) )
if findstr(method, '/ar') % arbitrary constellation
if nargin < opt_pos + 1
error('Incorrect format for METHOD=''qask/arbitrary''.');
end
I = M;
Q = opt2;
M = length(I);
if plot_const
axx = max(max(abs(I))) * [-1 1] + [-.1 .1];
axy = max(max(abs(Q))) * [-1 1] + [-.1 .1];
plot(I, Q, 'r*', axx, [0 0], 'w-', [0 0], axy, 'w-');
axis('equal');
axis('off');
text(axx(1) + (axx(2) - axx(1))/4, axy(1) - (axy(2) - axy(1))/30, 'QASK Constellation');
return;
else
% leave to the end for processing
end
elseif findstr(method, '/ci') % circular constellation
if nargin < opt_pos
error('Incorrect format for METHOD=''qask/circle''.');
end
NIC = M;
M = length(NIC);
if nargin < opt_pos+1
AIC = [1 : M];
else
AIC = opt2;
end
if nargin < opt_pos + 2
PIC = NIC * 0;
else
PIC = opt3;
end
if plot_const
apkconst(NIC, AIC, PIC);
return;
else
inx = apkconst(NIC, AIC, PIC);
I = real(inx);
Q = imag(inx);
M = sum(NIC);
end
else % square constellation
if plot_const
qaskenco(M);
return;
else
[I, Q] = qaskenco(M);
end
end
y = [];
x = x + 1;
if (min(min(x)) < 1) | (max(max(x)) > M)
error('An element in input X is outside the permitted range.');
end
for i = 1 : size(x, 2)
tmp = I(x(:, i));
y = [y tmp(:)];
tmp = Q(x(:, i));
y = [y tmp(:)];
end
elseif strncmpi(method, 'samp', 4)
%This is made possible to convert an input signal from sampling frequency Fd
%to sampling frequency Fs.
y = x;
if r==1 & ~isempty(y)
y = y.';
end
else % invalid method
error(sprintf(['You have used an invalid method.\n',...
'The method should be one of the following strings:\n',...
'\t''ask'' Amplitude shift keying modulation;\n',...
'\t''psk'' Phase shift keying modulation;\n',...
'\t''qask'' Quadrature amplitude shift-keying modulation, square constellation;\n',...
'\t''qask/cir'' Quadrature amplitude shift-keying modulation, circle constellation;\n',...
'\t''qask/arb'' Quadrature amplitude shift-keying modulation, user defined constellation;\n',...
'\t''fsk'' Frequency shift keying modulation;\n',...
'\t''msk'' Minimum shift keying modulation.']));
end
% [EOF]