Symmetry transformations and time reversal of currents and fields in bounded (Bi)anisotropic media

Arbitrary current distributions and the electromagnetic wave fields generated by them in (bi)anisotropic media, bounded by dyadic impedance walls, are considered. Sufficient conditions are found for transformed currents and fields (rotated, reflected, or inverted) to satisfy either Maxwell's equations (leading to an equivalent problem in the transformed medium), or else an adjoint set of equations, leading to a modified Lorentz reciprocity relation between the given and transformed currents and fields. The adjoint transformations which lead to Lorentz-type reciprocity are shown to be equivalent to time reversal in a rotated or reflected medium. Some applications are discussed.