justhomework/Matlab/comm/lab5_0.m

clc
clear
%================================================
%已知抽样值以△为单位
%================================================
x = 500
pcmcode = pcmEnCode(x)
amp = pcmDeCode(pcmcode)
qerror = x-amp
%================================================
%已知抽样值为实际电压值，则需先转换为以△为单位
%================================================
M = 5
d = M/2^11;
x = 2.5
x0 = round(x/d)
pcmcode = pcmEnCode(x0);
amp0=pcmDeCode(pcmcode);
amp0 = amp0*d
qerror=x-amp0


function pcmcode = pcmEnCode(s)
    start_t=[0,2.^(4:11)];
    width_t=[1,1,2,4,8,16,32,64];
    pcm=0;
    if s>0 
        pcm=pcm+bitshift(1,7);
    else
        s=abs(s);
    end
    for i = 0:7
        if s < start_t(i+2)
            pcm=pcm+bitshift(i,4);
            pcm=pcm+floor((s-start_t(i+1))/width_t(i+1));
            break
        end
    end
    pcmcode=dec2bin(pcm,8);
end

function amp = pcmDeCode(pcmcode)
    start_t=[0,2.^(4:11)];
    width_t=[1,1,2,4,8,16,32,64];
    code=bin2dec(pcmcode);
    ucode=bitand(code,0b01111111);
    k=bitshift(ucode,-4);
    m=bitand(ucode,0b00001111);
    amp=start_t(k+1)+double(m)*width_t(k+1)+width_t(k+1)/2;
    if code<=128 
        amp=-amp;
    else 
        amp=amp;
    end
end