On linear $q$-ary completely regular codes with $\rho=2$ and dual antipodal

Abstract

We characterize all linear $q$-ary completely regular codes with covering radius $\rho=2$ when the dual codes are antipodal. These completely regular codes are extensions of linear completely regular codes with covering radius 1, which are all classified. For $\rho=2$, we give a list of all such codes known to us. This also gives the characterization of two weight linear antipodal codes.