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function yy=apkconst(nir, air, pir, plot_type) 
%APKCONST Plot a combined circular ASK-PSK signal constellation. 
%   APKCONST(NUMSIG, AMP, PHASE) plots a circle signal constellation whose kth 
%   circle has NUMSIG(k) evenly spaced constellation points at radius AMP(k). 
%   One point on the kth circle has phase PHASE(k). NUMSIG, AMP, and PHASE are 
%   vectors of the same length. 
% 
%   APKCONST(NUMSIG, AMP) is the same as the syntax above, except that one 
%   point on each circle has zero phase. 
% 
%   APKCONST(NUMSIG) is the same as the syntax above, except that the kth 
%   circle has radius k. 
% 
%   Y = APKCONST(...) outputs a complex vector whose real part is the in-phase 
%   component and whose imaginary part is the quadrature component.  This 
%   syntax does not produce a plot. 
 
%   Copyright 1996-2001 The MathWorks, Inc. 
%   $Revision: 1.11 $ 
 
error(nargchk(1,4,nargin)); 
 
m = length(nir); 
if nargin <= 1 
    air = [1:m]; 
end; 
 
if nargin <= 2 
    pir = zeros(1,m); 
end; 
 
if nargin <= 3 
    plot_type = 'r*'; 
end; 
 
if isempty(plot_type) 
    plot_type = 'r*'; 
end 
 
if nargout < 1 
    plot_flag = 1; 
else 
    plot_flag = 0; 
end; 
 
j=sqrt(-1); 
z = exp(j*[0:100]*pi/50); 
x=real(z); y=imag(z); 
if plot_flag 
    cax = newplot; 
    hold_state = ishold; 
    plot(x*max(air), y*max(air)); 
    if ~hold_state 
        hold on 
    end; 
    zz=axis*1.05; 
    plot(zz(1:2),[0,0],'k'); 
    plot([0,0],zz(3:4),'k'); 
end; 
z=[]; 
for i = 1:m 
    for k = 1:nir(i) 
        z = [z air(i)*exp(j*((k-1)*2*pi/nir(i)+pir(i)))]; 
    end; 
    if plot_flag 
        if (i ~= m) 
            plot(x*air(i), y*air(i)); 
        end; 
    end; 
end; 
% plot the ASK/PSK signal. 
if plot_flag 
    if findstr(lower(plot_type), 'n') 
        tmp = plot(z, 'r.'); 
	set(tmp, 'MarkerSize', 12) 
	for i = 1 : length(z) 
            text(real(z(i)), imag(z(i)), num2str(i-1)); 
	end 
    else 
        tmp = plot(z, plot_type); 
        if findstr(lower(plot_type), '.') 
            set(tmp, 'MarkerSize', 12) 
	end; 
    end 
 
    if ~hold_state 
        axis('equal'); 
        axis('off'); 
        text(zz(1)+(zz(2)-zz(1))/4, zz(3)-(zz(4)-zz(3))/15, 'ASK/PSK Constellation'); 
        hold off; 
    end; 
else 
    yy = z; 
end;