jiaosutiaozhi.m

关于模拟调制解调的源代码

function[M,m,df]=fftseq(m,tz,df)
fz=1/tz;
if nargin==2
    n1=0;
else n1=fz/df;
end
n2=length(m);
n=2^(max(nextpow2(n1),nextpow2(n2)));
M=fft(m,n);
m=[m,zeros(1,n-n2)];     df=fz/n;
echo on
t0=0.15;
tz=0.0005;
fc=200;
kf=50;
fz=1/tz;
t=[0:tz:t0];
df=0.25;
m=[ones(1,t0/(3*tz)),-2*ones(1,t0/(3*tz)),zeros(1,t0/(3*tz)+1)];
int_m(1)=0;
for i=1:length(t)-1
    int_m(i+1)=int_m(i)+m(i)*tz;
end
[M,m,df1]=fftseq(m,tz,df);
M=M/fz;
f=[0:df1:df1*(length(m)-1)]-fz/2;
u=cos(2*pi* fc*t+2*pi*kf*int_m);
[U,u,df1]=fftseq(u,tz,df);
U=U/fz;
Pause;       subplot(2,1,1)
plot(t,m(1:length(t)))
axis([0 0.15-2.1 2.1]);       xlabel('时间')
title('未调信号');            subplot(2,1,2)
plot(t,u(1:length(t)))
axis([0 0.15-2.1 2.1]);       xlabel('时间')
title('调制信号');       pause
subplot(2,1,1)
plot(f,abs(fftshift(M)))
xlabel('频率');          title('信号的频谱')
subplot(2,1,2)
plot(f,abs(fftshift(U)))
title('调频信号的频谱');    xlabel('频率')