Two-Step Equivalent Sources Method for Electromagnetic Near-Field Calculations at Microwave Frequencies

In this paper, we propose a two-step equivalent sources method (ESM) to calculate the total electric and magnetic fields in the vicinity of a dielectric scatterer located in the near-field of a radiating Hertz dipole. The electric component is determined by calculating equivalent bounded surface charges at the boundary of the dielectric object, resulting in a reduced linear system of equations compared to other ESMs that require the whole volume to be discretized. Singularities in the electric field of the surface point charges are avoided by introducing uniformly charged triangular sheets. A second set of equivalent sources is derived to account for the magnetic field. While these fictitious magnetic field sources are distributed over the whole volume of the object, no further matrix inversion is required as will be presented herein. Even with a relatively coarse discretization of 284 surface and 552 volume elements, an error of less than 0.2% with respect to a reference solution obtained from a finite element method is achieved. The small error, together with the significantly reduced computation time, demonstrate the high accuracy and efficiency of the proposed method.