An Elias bound on the Bhattacharyya distance of codes for channels with a zero-error capacity

In this paper, we propose an upper bound on the minimum Bhattacharyya distance of codes for channels with a zero-error capacity. The bound is obtained by combining an extension of the Elias bound introduced by Blahut, with an extension of a bound previously introduced by the author, which builds upon ideas of Gallager, Lovász and Marton.