ti_03_16.m

是关于通信仿真的几个程序

echo on
T0=2;
ts=1/100;
fc=1000;
kf=25;
fs=1/ts;
t=[0:ts:2];
df=0.3;
m=0.1*ones(1,length(t));
m(10:100)=t(10:100);
m(101:190)=-t(101:190)+2; 
int_m(1)=0;
for i=1:length(t)-1
    int_m(i+1)=int_m(i)+m(i)*ts;
   echo off;
end
echo on;
[M,m,df1]=fftseq(m,ts,df);
M=M/fs;
f=[0:df1:df1*(length(m)-1)]-fs/2;
u=cos(2*pi*fc*t+2*pi*kf*int_m);
[U,u,df1]=fftseq(u,ts,df);
U=U/fs;
A=[0.001 0.01 0.05 0.1 0.3];
for i=1:5
    snr=1/A(i)
signal_power=spower(u(1:length(t)));
noise_power=signal_power/snr;
noise_std=sqrt(noise_power);
noise=noise_std*randn(1,length(u));
r=u+noise;
[R,r,df1]=fftseq(r,ts,df);
R=R/fs;
[v,phase]=env_phas(r,ts,1000);
phi=unwrap(phase);
dem=(1/(2*pi*kf))*(diff(phi)/ts);
pause;
subplot(3,1,1);
plot(t,m(1:length(t)));
xlabel('Time');
title('消息信号');
subplot(3,1,2);
plot(t,u(1:length(t)));
xlabel('Time');
title('已调信号');
subplot(3,1,3);
plot(t,r(1:length(t)));
xlabel('Time');
title(['加噪声信号且n/s=',num2str(A(i))]);
pause;
subplot(3,1,1);
plot(f,abs(fftshift(M)));
xlabel('Frequency');
title('消息信号的幅度谱');
subplot(3,1,2);
plot(f,abs(fftshift(U)));
xlabel('Frequency');
title('已调信号的幅度谱');
subplot(3,1,3);
plot(f,abs(fftshift(R)));
xlabel('Frequency');
title(['加噪声信号的幅度谱且n/s=',num2str(A(i))]);
pause;
subplot(2,1,1);
plot(t,m(1:length(t)));
xlabel('Time');
title('消息信号');
subplot(2,1,2);
plot(t,dem(1:length(t)));
xlabel('Time');
title('解调信号');
end
snr;