Realization of the DB boundary condition

In this paper we find a realization for the DB-boundary conditions, which imposes vanishing normal derivatives of the normal components of the D and B fields. The implementation of the DB boundary, requiring vanishing normal components of D and B, is known. It is shown that the realization of the DB boundary can be based on a layer of suitable metamaterial, called the wave-guiding quarter-wave transformer, which transforms the DB boundary to the DB boundary. In an appendix, the mixed-impedance boundary, which is a generalization of both DB and DB boundaries, is shown to transform to another mixed-impedance boundary through the same transformer.