co4.m

国外大学的同志作出来的好程序

function [st, st_rate]=co4(x1, x2, x3);
%Get the complex orthogonal matrix.
%x1, x2, x3 can be vectors.
if nargin~=3,
   disp('[co4]Error: Three inputs are required.');
   return;
end
if size(x1, 1)>1 && size(x1, 2)>1 | size(x2, 1)>1 && size(x2, 2)>1 | size(x3, 1)>1 && size(x3, 2)>1,
    disp('[co4]Error: Input should be vectors.');
    return;
end
if [length(x1), length(x2), length(x3)]/length(x1)~=ones(1, 3);
    disp('[co4]Error: All input vector should have the same length.');
    return;
end

%make x1 and x2 vectors.
if size(x1, 2)>1,
    x1=x1.';
end
if size(x2, 2)>1,
    x2=x2.';
end
if size(x3, 2)>1,
    x3=x3.';
end


%dimension of the space-time code
%p is the number of inputs for a block per transmitter
%q is the number of outputs for a block per transmitter
%space_len is the number of transmitters
space_len=4;p=3;q=4;
time_len=q*length(x1);

%rate of the orthogonal codes.
st_rate=p/q;

%construct Alamouti matrix.
st=zeros(time_len, space_len);
index1=1:q:time_len;
index2=index1+1; index3=index2+1; index4=index3+1;

st(index1, :)=[x1         x2         0    x3];
st(index2, :)=[-conj(x2)  conj(x1)   x3   0];
st(index3, :)=[0          -conj(x3)  x1   conj(x2)];
st(index4, :)=[-conj(x3)  0          -x2  conj(x1)];