qpskdet.asv

qpskmod.rar

function[xn,x]=qpskdet(y,Kmod,fs,fb,fc);
%
%Usage;[xn,x]=qpskdet(y,Kmod,fs,fb,fc); BBI2000
% Detection of QPSK and QDPSK
if nargin<6;fc=2; end;
if nargin<5;fb=1; end;
if nargin<4;fs=32;end;
if nargin<3;Kbase=2; end;
if nargin<2;Kmod=1;end;
if nargin<1;y=qpsk([0 0 0 1 1 1 1 0]) ;end;
Kmod=rem(Kmod,2);  Kmod=Kmod+(Kmod==0)*2;
dt=1/fs;t=0:dt:(length(y)-1)*dt;
I=y.*cos(2*pi*fc*t);Q=-y.*sin(2*pi*fc*t);
[b,a]=butter(2,2*fb/fs);
I=filtfilt(b,a,I); Q=filtfilt(b,a,Q);
m=2*fs/fb;N=length(y)/m;n=(.75:1:N)*m;
In=(sign(I(n))+1)/2;Qn=(sign(Q(n))+1)/2;
xn=[In;Qn];xn=xn(:);xn=xn';x=[I;Q];
if Kmod==1;
    tstr='QPSK,';
elseif Kmod==2;
    xn=dqpskcd(xn,2);tstr='QDPSK,';
end;
%--------------------------------------------------------------------------
if nargout<1;
    c='bbbbbbbbrrrrrrrr';
    subplot(211);plot(t,y);title('Input');
    subplot(212);plot(t,x);set(gca,'grid','on');v=axis;
    for i=1:2*N;
        ci=rem(i,16);ci=ci+(ci==0)*16;ci=c(ci);
        text((2*i-1)*m*dt/4,v(4)*.8,int2str(xn(i)),'color',ci);
    end;title('Output');
    set(gcf,'num',