ex_sample.m

matlab 通信仿真。好

clear
clf
t0=10;    %  define the length of time
ts=0.001;  % define sample duration
ts1=0.01;  % 欠采样周期
ts2=0.005;  % 正确采样周期
fs=1/ts;fs1=1/ts1;fs2=1/ts2;
df=0.5;   % 定义频率分辨率

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%             原信号情况                         %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

t=[-t0/2:ts:t0/2];  %定义时间序列
%定义采样函数的平方，即信号序列
x=sin(200*t);
m=x./(200*t);
w=t0/(2*ts)+1;  % 确定t=0的点
m(w)=1;      % t=0的点的信号值为1
m=m.*m; m=50.*m;
[M,mm,dfy]=fftseq(m,ts,df);
M=M/fs;
f=[0:dfy:dfy*length(mm)-dfy]-fs/2;
pause;
subplot(2,1,1);
plot(t,m);
xlabel('时间');
title('原信号的波形');
axis([-0.15 0.15 -1 50]);

subplot(2,1,2);
plot(f,abs(fftshift(M)));
xlabel('频率');
title('原信号的频谱fh约为64Hz');
axis([-500 500 0 1]);
pause
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                 欠采样情况                          %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
clf
t1=[-t0/2:ts1:t0/2];  %定义时间序列
%定义采样函数的平方，即信号序列
x1=sin(200*t1);
m1=x1./(200*t1);
w1=t0/(2*ts1)+1;  % 确定t=0的点
m1(w1)=1;      % t=0的点的信号值为1
m1=m1.*m1;
m1=50.*m1;
[M1,mm1,dfy1]=fftseq(m1,ts1,df);
M1=M1/fs1;
N1=[M1,M1,M1,M1,M1,M1,M1,M1,M1,M1,M1,M1,M1];
f1=[-7*dfy1*length(mm1):dfy1:6*dfy1*length(mm1)-dfy1]-fs1/2;


pause;
subplot(2,1,1);
stem(t1,m1);
xlabel('时间');
title('采样不足信号的波形');
axis([-0.15 0.15 -1 50]);

subplot(2,1,2);
plot(f1,abs(fftshift(N1)));
xlabel('频率');
title('采样不足信号的频谱fs=100Hz<2fh');
axis([-500 500 0 1]);
pause
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%                正确采样情况                          %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
clf
t2=[-t0/2:ts2:t0/2];  %定义时间序列
%定义采样函数的平方，即信号序列
x2=sin(200*t2);
m2=x2./(200*t2);
w2=t0/(2*ts2)+1;  % 确定t=0的点
m2(w2)=1;      % t=0的点的信号值为1
m2=m2.*m2;
m2=50.*m2;
[M2,mm2,dfy2]=fftseq(m2,ts2,df);
M2=M2/fs2;
N2=[M2,M2,M2,M2,M2,M2,M2,M2,M2,M2,M2,M2,M2];
f2=[-7*dfy2*length(mm2):dfy2:6*dfy2*length(mm2)-dfy2]-fs2/2;


pause;
subplot(2,1,1);
stem(t2,m2);
xlabel('时间');
title('正确采样信号的波形');
axis([-0.15 0.15 -1 50]);

subplot(2,1,2);
plot(f2,abs(fftshift(N2)));
xlabel('频率');
title('正确采样信号的频谱fs=200Hz>2fh');
axis([-500 500 0 1]);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%