Expanding a matrix with for loop

A product from a for loop is a 1 x 20 matrix alfa and 1 x 20 matrix m.

I would like to expand the matrix alfa to 40 x 20 matrix by adding an equidistant increment with linspace to every value in the row.

I tried the following:

for j=1:numel(alfa)

b(j)= linspace(alfa(j),2*alfa(j),40)

r0(b)=m(b)./(cosd(alfa(b)/2));

end

but it's not working and I can't think of a solution.

Please let me know if you have a suggestion.