c4_qamdemo.m

通信系统仿真原理与无线应用第四张全部程序

%File: c4_qamdemo.m
echo on
levelx=input('Number of D levels >');
levely=input('Number of Q levels >');
m=input('Number of symbols >');
n=input('Number of samples per symbol>');
bw=input('Filter bandwidth,0<bw<1 >');%
%
[xd,xq]=qam(levelx,levely,m,n);
%
[b,a]=butter(6,bw);   %determine filter coefficients
yd=filter(b,a,xd);    %filter direct coefficient
yq=filter(b,a,xq);    %filter quadrature coefficient
%
subplot(2,2,1)         %first pane
plot(xd,xq,'o')        %unfiltered scatterplot
a=1.4;
maxd=max(xd);maxq=max(xq);
mind=min(xd);minq=min(xq);
axis([a*mind a*maxd a*minq a*maxq])
axis equal
xlabel('xd');ylabel('xq');
%
subplot(2,2,2)        %second pane 
plot(yd,yq)           %filtered scatterpolt
axis equal
xlabel('xd');ylabel('xq');
%
sym=30;               %number of symbols in time plot
nsym=(0:sym*n)/n;     %x axis vector for time plots
subplot(2,2,3)        %third pane
plot(nsym(1:sym*n),yd(1:sym*n))    %filtered direct component 
xlabel('symbol index');
ylabel('xd');
%
subplot(2,2,4)        %fourth pane
plot(nsym(1:sym*n),yq(1:sym*n))    %filtered quadrature component
xlabel('symbol index');
ylabel('xq');
%End of script file