bshape.m

此程序实现了用matlab仿真qpsk的调制过程

function y=bshape(x,fs,fb,N,alfa,delay)
%
%
if nargin<6;
    delay=8;
end;
if nargin<5;
    alfa=.5;
end;
if nargin<4;
    N=16;
end;
if nargin<3;
    fb=1;
end;
if nargin<2;
    fs=16;
end;
if nargin<1;
    x=pulse(randint(1,100));
end;
b=firrcos(N,fb,2*alfa*fb,fs);
y=filter(b,1,x);
y=y/max(abs(y));
m=fs;
%------------------------------------------------
if nargout<1;
    dt=1/m;
    t=0:dt:(length(y)-1)*dt;
    subplot(211);
    plot(t,x,t,y);
    v=axis;
    axis([v(1:2) v(3)-v(4)*.2 v(4)*1.2]);
    title('Pulse signal');
    subplot(224);
    n=length(y);
    eyescat(y(m:n),fb,fs,delay);
    y=fft(y)/n;
    y=abs(y(1:fix(n/4)))*2;
    I=find(y<1e-04);
    y(I)=1e-04;
    y=20*log10(y);
    x=fft(x)/n;
    x=abs(x(1:fix(n/4)))*2;
    I=find(x<1e-04);
    x(I)=1e-04;
    x=20*log10(x);
    f1=m/n;
    f=0:f1:(length(y)-1)*f1;
    subplot(223);
    plot(f,x,f,y);
    title('Power Spectrum');
    xlabel('f/fb');
    zoom xon;
end;