Pls help me generate circulant matrix

I want to create M x M circulant matrix where M=128

h1=gallery('circul',M:M/2);
h2=gallery('circul',M:M/2);
h=horzcat(h1,h2);

But I get error with this coding.

pls see this link for more info

http://www.eurasip.org/Proceedings/Eusipco/Eusipco2007/Papers/b2l-c02.pdf

in page 2 (2.2 mimo-ofdm sytem)

Answer 1

[Honglei Chen]

You may want to use

M:-1:M/2

in your code, or something like that.

M:M/2

returns an empty vector so there is nothing to construct from it.

BTW, you can also use linspace. Say you want 5 points between M and M/2, just do

linspace(M,M/2,5)

[Jan]

@melody: You do not have to create two equal matrices to join them. h = [h1, h1] is ok.

Answer 2

[Emmanuel Ijiga]

M = 20;

input = randi([0 15], 1, M); %Random Input values between 0 and 15

CM = zeros(M,M); %Initialize M X M Circulant Matrix (CM)

CM(1,:) = input; %place the input values in the first row of CM

for kk = 1:(size(CM,1) - 1)

CM(kk+1,1) = CM(kk,end);

 CM(kk+1,2:end) = CM([kk],[1:end - 1])

end