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function [x,y]=qaskenco(msg,M) 
%QASKENCO Map a message to a QASK square signal constellation. 
%   QASKENCO(M) plots a QASK square constellation with M-ary number M. 
%   M must be an integer power of 2. 
% 
%   QASKENCO(MSG, M) plots the location of MSG in constellation with 
%   M-ary number M. The elements in MSG must be integers in the range 
%   [0, M-1]. 
% 
%   [X, Y] = QASKENCO(M) outputs the in-phase and quadrature components 
%   of the QASK square constellation in variables X and Y respectively. 
% 
%   [X, Y] = QASKENCO(MSG, M) encodes the message signal given in MSG 
%   into in-phase and quadrature component variables X and Y. 
% 
%	The output signal constellations are scaled such that the minimum 
%   distance between adjacent signal points is 2. 
% 
%   This function generates a Gray code with K = log2(M) bits, when K 
%   is an even integer. When K is an odd integer, this function generates a 
%   non-Gray-code near-square constellation. 
% 
%   See also QASKDECO. 
 
%   Copyright 1996-2001 The MathWorks, Inc. 
%   $Revision: 1.15 $ 
 
if nargin < 1 
    disp('Usage: QASKENCO(M)'); 
end; 
 
plot_type = []; 
if nargin == 1 
    M = msg; 
    plot_type = 'N'; 
elseif isstr(M) 
    plot_type = M; 
    M = msg; 
end; 
 
if M < 0 
    error('M must be a positive number.'); 
end; 
 
K = log2(M); 
if floor(K) ~= K 
	error('M must equal an integer power of 2.'); 
end; 
 
if ~isempty(plot_type) 
    msg = 0:M-1; 
end; 
 
if any(msg<0) | any(msg>M-1) 
	error('Input message to QASKENCO must be integers in the range [0, M-1].'); 
end 
 
msg = msg + 1; 
% define a table for the coding. 
[tabx, taby] = QASKConstlation(K); 
 
if nargout > 0 % Encode the message 
    x = tabx(msg); 
    y = taby(msg); 
else % Plot the constellation 
    if isempty(plot_type) 
	plot_type = 'N'; 
    end 
 
	lims = max(max([tabx(msg) taby(msg)])) * [-1 1]; 
    axx =  lims + [-1 1]; 
    if findstr(lower(plot_type), 'n') 
       handle = plot(tabx(msg), taby(msg), 'r.',... 
          [max(tabx(msg)) min(tabx(msg))],[0 0], 'k-',... 
          [0 0], [max(taby(msg)) min(taby(msg))], 'k-'); 
        set(handle(1),'Markersize',12); 
        set(get(handle(1),'parent'), ... 
            'box','off',... 
            'defaulttextfontsize', 9,... 
            'Ylim',axx,... 
            'Xlim',axx ); 
        for i = 1 : length(msg) 
            text(tabx(msg(i)), taby(msg(i)), num2str(msg(i)-1)); 
        end; 
    else 
        handle = plot(tabx(msg), taby(msg), plot_type,... 
                 axx, [0 0], 'k-', [0 0], axx, 'k-'); 
    end 
    axis('square'); 
    set(handle(2), 'Xdata', get(get(handle(2), 'parent'), 'Xlim')); 
    set(handle(3), 'Ydata', get(get(handle(3), 'parent'), 'Ylim')); 
	set(gca, 'xtick', lims(1):2:lims(2), 'ytick', lims(1):2:lims(2)); 
	pos = get(gcf, 'position'); 
	pos = [pos(1) pos(2)-(pos(3)-pos(4)) pos(3) pos(3)]; 
	set(gcf,'position',pos); 
    xlabel('In-phase'); ylabel('Quadrature'); title('QASK Constellation'); 
end; 
 
%------------------------------------------------------------------ 
function [xt, yt] = QASKConstlation(K) 
% Output the constellation in-phase and quadrature components. 
 
xx = constlay(K, 1); 
 
[leny, lenx] = size(xx); 
[xt, yt]= meshgrid([1-lenx : 2 : lenx-1], [leny-1 : -2 : 1-leny]'); 
 
xx = xx(:); 
xt = xt(:); 
yt = yt(:); 
 
tmp = isnan(xx); 
if ~isempty(tmp) 
  xx(tmp) = []; 
  xt(tmp) = []; 
  yt(tmp) = []; 
end; 
 
[xx, tmp] = sort(xx); 
xt = xt(tmp); 
yt = yt(tmp); 
 
% [EOF]