%%%%%%%%%%%数字频带传输仿真实验
clear all;
clc;
N=500;%码元个数
Ts=1;%码元周期
fc=2;%载波频率
num=100;%单个码元的采样点数
signal=rand(N,1);
for i=1:N
if(signal(i)>0.5)
signal(i)=1;
else
signal(i)=0;
end
end
%%%%%%%%%2ASK信号
t=0:1/num:Ts*N-1/num;
w=sin(2*pi*fc*t);%载波
s=zeros(1,N*num);
for i=1:N
for j=1:num
if(signal(i))
s((i-1)*num+j)=1;
else
s((i-1)*num+j)=0;
end
end
end
e2psk=s.*w;%产生2ASK信号
subplot(2,1,1)
plot(e2psk);
title('2ASK信号时域波形');
axis([1,2000,-1.3,1.3]);
grid on
[f,sf]=t2f(t,e2psk);
subplot(2,1,2)
plot(f,10*log10(abs(sf).^2/t(end)));
title('2ASK信号功率谱');
axis([-2*fc,2*fc,-80,20]);
grid on
%%%%%%%%%2FSK信号
s1=zeros(1,N*num);
s2=zeros(1,N*num);
t=0:1/num:Ts*N-1/num;
w1=sin(2*pi*fc*t);%载波1
w2=sin(2*pi*2*fc*t);%载波2----频率是载波1频率的2倍
for i=1:N
for j=1:num
if(signal(i))
s1((i-1)*num+j)=1;
s2((i-1)*num+j)=0;
else
s1((i-1)*num+j)=0;
s2((i-1)*num+j)=1;
end
end
end
e2fsk=s1.*w1+s2.*w2;%产生2FSK信号
figure
subplot(2,1,1)
plot(e2fsk)
title('2FSK信号时域波形');
axis([1,2000,-1.3,1.3])
grid on
[f,sf]=t2f(t,e2fsk);
subplot(2,1,2)
plot(f,10*log10(abs(sf).^2/t(end)));
title('2FSK信号功率谱');
% plot(f,abs(sf))
axis([-4*fc,4*fc,-80,20])
grid on
%%%%%%%%%%2PSK信号
t=0:1/num:Ts*N-1/num;
w=sin(2*pi*fc*t);%载波
for i=1:N
for j=1:num
if(signal(i))
s((i-1)*num+j)=1;
else
s((i-1)*num+j)=-1;
end
end
end
e2psk=s.*w;%产生2PSK信号
figure
subplot(2,1,1)
plot(e2psk);
title('2PSK信号时域波形');
axis([1,2000,-1.3,1.3]);
grid on
[f,sf]=t2f(t,e2psk);
subplot(2,1,2)
plot(f,10*log10(abs(sf).^2/t(end)));
title('2PSK信号功率谱');
axis([-2*fc,2*fc,-80,20]);
grid on
