Characteristics of the Electromagnetic Field in the Near- and Far-Field and their Application to Interference Mitigation

Abstract

A radio frequency (RF) propagation model that can accurately predict the power received by one antenna from an RF signal that is transmitted by another antenna over an imperfectly conducting ground has many applications in link budget analysis and interference mitigation. Common theoretical RF propagation models such as the Two-ray Reflection Model or models based on solving Maxwell’s equations using the parabolic equation methods can reliably generate such predictions only in the far-field of the antennas, where antenna gain patterns can be used with the models. This paper will examine a model derived from Maxwell’s equations. The model solves the problem of electromagnetic propagation over a half-space that applies to both the near- and far-field. The model’s theoretical equations are corroborated with field measurements. The paper concludes with recommendations on how the propagation characteristics of RF signals in the near-field can be used to mitigate interference from earth station transmitters to commercial base station antennas.