Realization of the ${\rm D}^{\prime}{\rm B}^{\prime}$ Boundary Condition

In this letter, we find a realization for the D'B' 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 D'B' boundary can be based on a layer of suitable metamaterial, called the wave-guiding quarter-wave transformer, which transforms the DB boundary to the D'B' boundary. This is demonstrated by a numerical example. In an appendix, the mixed-impedance boundary, which is a generalization of both DB and D'B' boundaries, is shown to transform to another mixed-impedance boundary through the same transformer.