Full wave modeling of RF propagation between low-to-the-ground antennas

Recently, there has been a great deal of interest in unattended ground sensors (UGS) for remote monitoring applications. Since the antennas are located near the ground, interaction between the RF signal and the terrain can significantly affect the propagation of the signal. Some of these effects include multiple scattering and backscattering from the roughness of the terrain surface, blockage of the signal by obstructions on the propagation path, and coupling to ground wave modes. In addition, the ground in the near field can also significantly affect the radiation pattern of the antenna. We have applied the moving window finite difference time domain (MWFDTD) method to study near-the-surface propagation. The MWFDTD model is based on the full-wave finite difference time domain (FDTD) method. In this paper we demonstrate the utility of MWFDTD for modeling the propagation of RF signals from very-near-the-ground antennas located over rough terrain surfaces.