function [a_quan,code]=u_pcm(a,n)
amax=max(abs(a));
a_quan=a/amax;
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
a_quan=a_quan*amax;
nu=ceil(log2(n));
code=zeros(length(a),nu);
for i=1:length(a)
    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