Near-to-Near Transformation in Axisymmetrical Antenna Problems

Expressions for effective near-to-near (NTN) transformation of fields in structures of axial symmetry are presented. The results are applicable in the problems of axisymmetrical antenna feeds working in non-axisymmetrical reflector environment. The solution of the problem is based on an extension of the exact integration procedure for vector potentials of thin circular loop antennas, published previously by Werner. The Werner´s procedure is used directly to calculate contribution of components of the equivalent currents at the Huygens surface surrounding the antenna. New formulas are provided for the contribution of and current components. The accuracy of the present approach is verified against the results obtained by direct numerical integration in the 3-D space. Asymptotic behavior of the NTN transformation for large distances is also compared to the known results of the near-to-far transformation.