An Accurate Equivalent Behavioral Model of Antenna Radiation Using a Mode-Matching Technique Based on Spherical Near Field Measurements

A new and simple method for modeling an antenna under test (AUT) from spherical near-field (NF) measurements is presented. This method utilizes NF data to determine an equivalent behavioral model composed of magnetic and electric dipoles placed over a fictitious sphere surrounding the AUT. A spherical wave expansion (SWE) of the measured NF is developed to derive a linear relation between the transmission coefficients of the AUT and the transmission coefficients of each dipole. Dipole transmission coefficients are determined using the translational and rotational addition theorems. Finally, a least square method is employed to compute the excitation of each current source. Once the equivalent model is obtained, it can be used to study the behavior of the original AUT in different environments. Computations with electromagnetic simulation data illustrate the accuracy of the proposed method and the reliability of the derived model.