通信MATLAB仿真_原创精品文档.pdfVIP

N=32;

x=zeros(1,N);

x(1)=1;

clearall

N=32;

x=zeros(1,N);

x(1)=1;

xn=0:N-1;

stem(xn,x)

axis([-13301.1])

t=0:0.01*pi:6*pi;

x=sin(t);plot(t,x);

N=32;

x=ones(1,N);

x(1)=1;

clearall

N=32;

x=ones(1,N);

x(1)=1;

xn=0:N-1;

stem(xn,x)

t=0:0.01*pi:6*pi;

f1=50;

f2=2000;

a=sin(2*pi*f1*t);b=cos(2*pi*f2*t);

y=a.*b;

plot(t,y);

clearall;

closeall;

clc;

t0=0.5;

t=0:0.01:0.5;

s=t.*(t0t=t0/4)+(-t+t0/4).*(t=t0/4t=3*t0/4)+(t-t0).*(t=3*t0/4tt0);

plot(t,s);

4、（1）信号的DSB调制与解调

clearall;

closeall;

clc;

t0=0.15;

dt=0.0001;

t=[0:dt:1];

fc=250;

phi0=0;

ct=cos(2*pi*fc*t+phi0);%载波信号

fm=10;

fun=@(t)1.*(t=0t=t0/3)+(-2).*(t=t0/3t=2*t0/3)+0.*(t=2*t0/3);

mt=fun(t);

ut=1.5*mt.*ct;

figure(1)

subplot(3,1,1),plot(t,mt),title(mt调制信号)

subplot(3,1,2),plot(t,ct),title(ct载波信号)

subplot(3,1,3),plot(t,ut),title(ut已调信号)

[m,n]=size(ut);

ni=0.05*randn(m,n);

u0=ut+ni;

figure(2)

subplot(3,1,1),plot(t,ni),title(ni高斯白噪声)

subplot(3,1,2),plot(t,u0),title(u0=ut+ni已调信号+高斯白噪声)

w1=2*dt*(fc-2*fm);

w2=2*dt*(fc+2*fm);

[b,a]=butter(4,[w1,w2],bandpass);

u1=filter(b,a,u0);

subplot(3,1,3),plot(t,u1),title(u1信号进入带通滤波器)

figure(3)

u2=u1.*ct;

subplot(3,1,1),plot(t,u2),title(u2与载波相乘后的波形)

B=2*fm;

wn3=2*dt*B;

[b,a]=butter(4,wn3,low);

u3=filter(b,a,u2);

subplot(3,1,2),plot(t,-u3),title(u3解调后的信号)

subplot(3,1,3),plot(t,-u3),holdon,title(解调后的信号与原调制信号比较)

plot(t,mt,r);

dt=t(2)-t(1);%采样周期

f=1/dt;%采样频率(Hz)

X=fft(ut);%计算x的快速傅立叶变换X

N=1/dt;

F=X(1:N/2+1);%F(k)=X(k)(k=1:N/2+1)

f=f*(0:N/2)/N;%使频率轴f从零开始

figure(4)

subplot(3,1,1),plot(f,abs(F)),title(dsb调制信号频谱图);xlim([0,fc*2]);

xlabel(Frequency);

ylabel(|F(k)|)

2）SSB方式

clearall;

closeall;

clc;

t0=0.15;

dt=0.0001;

t=[0:dt:1];

fc=250;

phi0=0;

ct=cos(2*pi*fc*t+phi0);%载波信号

fm=10;