Two previously studied classes of electromagnetic media, labeled as those of Q media and P media, are decomposed according to the natural decomposition introduced by Hehl and Obukhov. Six special cases based on either non-existence or sole existence
of the three Hehl-Obukhov components, are defined for both medium classes.
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.
