sq4qam_gray_demap.m

一些关于调指和解调的小程序

function out=sq4QAM_Gray_demap(input)

K=length(input);

d=1/sqrt(2);                  %%% The minimum distance between constellations is 2*d
x=[d,-d];                     %%% coordinate matrix
y=[d,-d];

for i=1:K
    temp(i,:)=[real(input(i)),imag(input(i))]; %%% 复数矩阵变成实数矩阵，便于处理
end

%%%------Minimun Euclidean distance demodulate-----------------
%%% 解调采用比较横纵坐标，找最接近的横纵坐标的方法，相当于量化的思想
%%% X-coordinate demapping -----------------------------------------------
for i=1:K
    for k=1:2               %%% 先比较横坐标
        dis(k)=temp(i,1)-x(k);
    end
    [di,num]=min(abs(dis));
    temp(i,1)=x(num);        %%% 横坐标解调出来，并保存到原来矩阵中
    
    if x(num)==x(1)
        t_out(i,2)=0;
    else t_out(i,2)=1;
    end
    
end

%%% Y-coordinate demapping -----------------------------------------------
for i=1:K
    for k=1:2                %%% 先比较纵坐标
        dis(k)=temp(i,2)-y(k);
    end
    [di,num]=min(abs(dis));
    temp(i,2)=y(num);        %%% 纵坐标解调出来，并保存到原来矩阵中
   
    
    if x(num)==y(1)
        t_out(i,1)=0;
    else t_out(i,1)=1;
    end
end

for i=1:K
    for m=1:2
        out(2*(i-1)+m)=t_out(i,m);     %%% P/S transform, the out is a serial binary sequence
    end
end