Localization of Signals in the Near-Field of an Antenna Array

The problem of locating signals transmitted in the proximity of an antenna array has been studied extensively in the signal processing literature. In this paper, we consider the standard array manifold models used in these works and show that they differ, sometimes significantly, from the model based on electromagnetic theory. In particular, the standard models do not correspond to the equations governing an electromagnetic field near an antenna or an array. They also do not take into account the characteristics of the near-field source, such as the type and orientation of the transmitting antenna, which may have a profound impact on the signals received by the array. We use selected numerical examples based on a numerical electromagnetic code to illustrate the various issues raised herein.