This paper presents the utilization of the Method of Auxiliary Sources (MAS) to localize active source positions of radiation by a desired predefined pattern or measured near-field distribution. The active sources position is based on the uniqueness of the wave field's analytical continuation along its propagation and, by means of the converging and diverging wave's function, localizes the positions of the field's singularities. Determining the coordinates of these active source locations with appropriate polarization and placing in these locations the field sources as a corresponding current, we can restore complete near-field distribution or a desired field pattern. The objective of this paper is to study the nature of the near-field regions (reactive and radiative zones), as well as transition zones in some particular cases. This paper presents the source localization methodology along with simulation and measurement results. The proposed methodology is used for directive antenna synthesis to realize a desired pattern with minimal side lobes and reactive fields, and also could be used efficiently for far-field prediction or EMI source localization by near-field scanning.