Negacyclic codes over Z/sub 4/ of even length

This paper generalizes the results from Wolfmann (see ibid., vol.45, p.2527-2532, Nov. 1999 and vol.47, p.1773-1779, July 2001), classifying all negacyclic codes over Z/sub 4/ of even length using a transform approach. It is then shown which linear binary cyclic codes are images of negacyclic codes under the Gray map. In the process, the concatenated structure of both negacyclic codes and binary repeated-root cyclic codes is given.