test06-02 PCM模拟调制

clear all;
close all;
dt=0.01;

t=0:dt:10;
xt=sin(4*pi*t);

fs=10;
sdt=1/fs;
t1=0:sdt:10;
st=sin(4*pi*t1);
[out]=pcm_encode(st);
[out1]=pcm_decode(out,1);
figure(1);
subplot(411);
plot(t,xt);
title('原始信号');
subplot(412);
plot(t1,st);
title('抽样信号');
subplot(413);
plot(out);
title('编码信号');
subplot(414);
plot(out1);

title('译码恢复信号');

//////////////////////////////

function [out]=pcm_decode(in,v)
n=length(in);
in=reshape(in',8,n/8)';
slot(1)=0;
slot(2)=16;
slot(3)=32;
slot(4)=64;
slot(5)=128;
slot(6)=256;
slot(7)=512;
slot(8)=1024;
step(1)=1;
step(2)=1;
step(3)=2;
step(4)=4;
step(5)=8;
step(6)=16;
step(7)=32;
step(8)=64;
for i=1:n/8
ss=2*in(i,1)-1;
tmp=in(i,2)*4+in(i,3)*2+in(i,4)+1;
st=slot(tmp);

dt=(in(i,5)*8+in(i,6)*4+in(i,7)*2+in(i,8))*step(tmp)+0.5*step(tmp);
out(i)=ss*(st+dt)/2048*v;
end

///////////////////////

function[out]=pcm_encode(st)
x=st*2048;
n=length(x);
for i=1:n;
if x(i)>0
out(i,1)=1;
else
out(i,1)=0;
end
if 0<=abs(x(i))&abs(x(i))<16
out(i,2)=0;out(i,3)=0;out(i,4)=0;
step=1;
%起始电平
st=0;
elseif 16<=abs(x(i))&abs(x(i))<32
out(i,2)=0;out(i,3)=0;out(i,4)=1;step=1;st=16;
elseif 32<=abs(x(i))&abs(x(i))<64
out(i,2)=0;out(i,3)=1;out(i,4)=0;step=2;st=32;
elseif 64<=abs(x(i))&abs(x(i))<128
out(i,2)=0;out(i,3)=1;out(i,4)=1;step=4;st=64;
elseif 128<=abs(x(i))&abs(x(i))<256
out(i,2)=1;out(i,3)=0;out(i,4)=0;step=8;st=128;
elseif 256<=abs(x(i))&abs(x(i))<512
out(i,2)=1;out(i,3)=0;out(i,4)=1;step=16;st=256;
elseif 512<=abs(x(i))&abs(x(i))<1024
out(i,2)=1;out(i,3)=1;out(i,4)=0;step=32;st=512;
else
out(i,2)=1;out(i,3)=1;out(i,4)=1;step=64;st=1024;
end
if (abs(x(i))>=2048)
%处理过载现象
out(i,2:8)=[1 1 1 1 1 1 1];
else
%计算段内码
tmp=floor((abs(x(i))-st)/step);
%十进制转二进制数，%如果不减48，最后4位是ASCII数
% 49 48 48 48
t=dec2bin(tmp,4)-48;
out(i,5:8)=t(1:4);
end
end
out=reshape(out',1,8*n);