A construction for modified generalized Hadamard matrices using QGH matrices

Let G be a group of order mu and U a normal subgroup of G of order u. Let G/U = {U1, U2, · · · , Um} be the set of cosets of U in G. We say a matrix H = [hij ] order k with entries from G is a quasi-generalized Hadamard matrix with respect to the cosets G/U if ∑ 1≤t≤k hith −1 jt = λij1U1 + · · · + λijmUm (∃λij1, · · · , ∃λijm ∈ Z) for any i ̸= j. On the other hand, in our previous article we defined a modified generalized Hadamard matrix GH(s, u, λ) over a group G, from which a TDλ(uλ, u) admitting G as a semiregular automorphism group is obtained. In this article, we present a method for combining quasi-generalized Hadamard matrices and semiregular relative difference sets to produce modified generalized Hadamard matrices.