Electromagnetic pulse propagation and scattering from terrain: experimental observation and comparison with theory

We consider the problem of electromagnetic propagation over variable terrain from both an experimental and a theoretical standpoint. The experimental data were collected by MIT Lincoln Laboratory during an airborne multipath propagation experiment in the fall of 1996. The experiment utilized two planes equipped with UHF and VHF antennas and explored the time-difference-of-arrival (TDOA) observed between the direct and reflected signal in a pulsed radar system. The data was collected over a variety of terrains in New Mexico and Maine ranging from smooth desert floor to rough mountainous terrain. In this paper measurements from selected data sets are compared to theoretical results from Lincoln Laboratory propagation code SEKE which has been modified for wide bandwidth signals using Fourier techniques. This work may be useful for the evaluation of multipath-based height-finding techniques for airborne radars. By estimating the TDOA between the direct and reflected signals one can estimate the target height geometrically. This height-finding technique requires sufficient signal bandwidth to resolve the multiple pulses as well as a propagation environment that will support specular reflections. The goal of this work is to increase our understanding of the propagation environment and to improve our modeling capacity for wide-bandwidth signals over various terrains.