Closed-Form Expressions of Fields Radiated From an Annular Ring of Magnetic Current

Closed-form expressions of fields radiated from an annular aperture of magnetic current are derived in this article. The derivation is based on the spherical functions expansion for the scalar Green's function and the direct integration procedure for the evaluation of the vector potential. The derived field expressions are valid everywhere above the ground plane on which the annular aperture is mounted for arbitrary inner and outer aperture radii a and b, except the region included between the hemispheres of radii a and b and concentric with the aperture. The new derived field expressions are in excellent agreement with the corresponding fields available in the literature in their common region of validity, which reveals the correctness of these field expressions.