Equivalent current excitation for an aperture antenna embedded in an arbitrarily shaped impedance surface

It is demonstrated, via the equivalence principle, that if the aperture fields are known, one can explicitly obtain the equivalent current excitation required for modeling an aperture in an arbitrarily shaped impedance surface, when the aperture surface is closed, by replacing it with an impedance surface. It is also demonstrated that the impedance condition over the antenna body and the closed aperture can be nonuniform and anisotropic and that different choices are possible for the value of the surface impedance of the surface that closes the aperture. It is expected that the procedures described will be most useful in approximately modeling aperture antennas embedded in nonplanar impedance surfaces where the aperture electric field is known.