A COMPLETE ELECTROMAGNETIC SIMULATION OF THE SEPARATED-APERTURE SENSOR FOR DETECTING BURIED LAND MINES

The detection of buried land mines is a problem of military and humani tarian importance. Electromagnetic sensors (ground-penetrating radars) use signals at radio and microwave frequencies for this purpose, In t he past, electromagnetic sensors for land-mine detection have been emp irically developed and optimized, This has involved experimental tests that are complicated, time consuming, and expensive. An alternative, which has only recently become available, is to carry out initial deve lopment and optimization using accurate numerical simulations. One obj ective of this paper is to show, for the first time, that such simulat ions can be done using the finite-difference time-domain (FDTD) method . The separated-aperture sensor has been under investigation by the Un ited States Army for land-mine detection for many years. It consists o f two parallel dipole antennas housed in corner reflectors that are se parated by a metallic septum. It is a continuous-wave sensor tuned to a particular frequency (typically 790 MHz). When the sensor is over em pty ground, the coupling between the antennas is very small, As the se nsor is moved over a buried mine, the coupling between the antennas in creases indicating the presence of the mine. In this paper, the comple te electromagnetic system composed of the separated-aperture sensor, a ir and soil, and buried land mine is modeled using the FDTD method. Th e finite computational volume is truncated with an absorbing boundary condition: the generalized perfectly matched layer, Detailed studies m ade with the simulation increase the understanding of this sensor. Res ults computed from the simulation are in good agreement with experimen tal measurements made at Georgia Tech and,vith measurements made by th e United States Army.