qam.m

16QAM的MATLAB调制解调仿真

function [y, fs, fb, fc]=qam (x, Kbase, fs, fb, fc);
%
%   Usage:[y, fs, fb, fc]=qam(x,kbase,fs,fb,fc);BBI2000
if nargin<5; fc=2;    end;
if nargin<4; fb=1;    end;
if nargin<3; fs=32;   end;
if nargin<2; Kbase=2; end;
if nargin<1
   x=[1 1 1 1 1 1 1 0 1 1 0 1 1 1 0 0];
   x=[x 1 0 1 1 1 0 1 0 1 0 0 1 1 0 0 0];
   x=[x 0 0 1 1 0 0 1 0 0 0 0 1 0 0 0 0];
   x=[x 0 1 1 1 0 1 1 0 0 1 0 1 0 1 0 0];
end;
T=length (x) /fb;   m=fs/fb;  nn=length(x);
dt=1/fs;   t=0: dt: T-dt;
Kbase=rem (Kbase, 2); Kbase=Kbase+(Kbase==0)*2;
tstr='QAM';
I=x(1: 2: nn-1);  [I, In]=two2four (I, 4*m);
Q=x(2: 2: nn);   [Q, Qn]=two2four (Q, 4*m);
if Kbase==2;
   I=bshape(I, fs, fb/4);
   Q=bshape(Q, fs, fb/4);
end;
y=I.*cos(2*pi*fc*t);y1=y;
n=length(y);
%----------------------
if nargout<1
   subplot(211);
   plot(t,y,t,I,t,Q,[0 T],[0 0],'b:');
   if Kbase==2;
      tstr=[tstr ' with the RC filter'];
   end;  title(' Signal');
   n=length(y);y=fft(y)/n;y=abs(y(1:fix(n/2))) *2;
   I=find(y<1e-04);y(I)=1e-04;y=20*log10(y);
   f1=m/n;f=0:f1:(length(y)-1)* f1;
   subplot(223);  plot(f,y,' r');grid on;
   title(' Specturm'); xlabel(' f/fb'); zoom xon;
   subplot (224);constel (y1, fs, fb, fc);xlabel (' Constellsstion');
   set(gcf,'num','off','name',[tstr ',' blanks(10) 'BBI2000']);
end;