fsk调制解调程序.txt

不仅仅是闲了二进制二进制随机序列的频率调制

clear all
close all
i=10;%基带信号码元数
j=5000;
a=round(rand(1,i));%产生随机序列
t=linspace(0,5,j);
f1=10;%载波1频率
f2=5;%载波2频率
fm=i/5;%基带信号频率
B1=2*f1;%载波1带宽
B2=2*f2;%载波2带宽
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%产生基带信号
st1=t;
for n=1:10
    if a(n)<1;
        for m=j/i*(n-1)+1:j/i*n
            st1(m)=0;
        end
    else
        for m=j/i*(n-1)+1:j/i*n
            st1(m)=1;
        end
    end
end
st2=t;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%基带信号求反
for n=1:j;
    if st1(n)>=1;
        st2(n)=0;
    else
        st2(n)=1;
    end
end;
figure(1);
subplot(411);
plot(t,st1);
title('基带信号');
axis([0,5,-1,2]);
subplot(412);
plot(t,st2);
title('基带信号反码');
axis([0,5,-1,2]);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%载波信号
s1=cos(2*pi*f1*t)
s2=cos(2*pi*f2*t)
subplot(413),plot(s1);
title('载波信号1');
subplot(414),plot(s2);
title('载波信号2');
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%调制
F1=st1.*s1;%加入载波1
F2=st2.*s2;%加入载波2
figure(2);
subplot(411);
plot(t,F1);
title('s1*st1');
subplot(412);
plot(t,F2);
title('s2*st2');
e_fsk=F1+F2;
subplot(413);
plot(t,e_fsk);
title('2FSK信号')
nosie=rand(1,j);
fsk=e_fsk+nosie;
subplot(414);
plot(t,fsk);
title('加噪声信号')
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%相干解调
st1=fsk.*s1;%与载波1相乘
[f,sf1] = T2F(t,st1);%通过低通滤波器
[t,st1] = lpf(f,sf1,2*fm);
figure(3);
subplot(311);
plot(t,st1);
title('与载波1相乘后波形');
st2=fsk.*s2;%与载波2相
[f,sf2] = T2F(t,st2);%通过低通滤波器
[t,st2] = lpf(f,sf2,2*fm);
subplot(312);
plot(t,st2);
title('与载波2相乘后波形');
for m=0:i-1;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%抽样判决
if st1(1,m*500+250)<0.25;
for j=m*500+1:(m+1)*500;
at(1,j)=0;
end
else
for j=m*500+1:(m+1)*500;
at(1,j)=1;
end
end
end;
subplot(313);
plot(t,at);
axis([0,5,-1,2]);
title('抽样判决后波形')