u_pcm.m

PCM编码把模拟信号转换为数字编码

function[sqnr,a_quan,code]=u_pcm(a,n)
%函数实现u率的非均匀量化编码
%a为输入序列
% n为编码电平级数
amax=max(abs(a));       
a_quan=a/amax;          %对输入信号序列归一化处理
b_quan=a_quan;
d=2/n;
q=d.*[0:n-1];
q=q-((n-1)/2)*d;
for i=1:n
    a_quan(find((q(i)-d/2<=a_quan)&(a_quan<=q(i)+d/2)))=q(i).*ones(1,length(find((q(i)-d/2<=a_quan)&(a_quan<=q(i)+d/2))));
    b_quan(find(a_quan==q(i)))=(i-1).*ones(1,length(find(a_quan==q(i))));
end         % 量化电平取量化间隔中间值
a_quan=a_quan*amax; 
nu=ceil(log2(n));  
code=zeros(length(a),nu);
 for i=1:500
     p(i)=2^i;
 end
r=sin(p);                         

 for i=1:500
     b_quan(i)=r(i);%加噪声
 end
  for i=1:length(a)       %产生一个以输入信号序列中元素个数为行数，每个级数所需比特数为列数的矩阵
    for j=nu:-1:0
        if(fix(b_quan(i)/(2^j))==1)
            code(i,(nu-j))=1;
            b_quan(i)=b_quan(i)-2^j;
        end
    end
end
    sqnr=20*log10(norm(a)./norm(a-a_quan))  %噪声理解为原信号减去量化后的所得电平的差值