Radar response approximations for buried plastic landmines

This paper analyzes the early-time radar response of buried penetrable targets such as plastic landmines. The Born approximation is used to derive simple analytical expressions relating target and soil properties to the early-time response. Understanding these dependencies is crucial for target identification under varying soil conditions. The derived expressions include the transfer function and the impulse response of a penetrable target embedded in an unbounded homogeneous lossy medium and illuminated by a uniform plane wave. Using a truncated circular cylinder having the dimensions of a PMA-3 mine as an example, the early time responses predicted by the Born approximation are compared against responses obtained by three-dimensional finite-difference time-domain (FDTD) simulations. The results demonstrate that with the Born approximation it is possible to predict the general shape of the target response, i.e. the number of amplitude peaks, as well as the amplitudes of those peaks that relate to backscatter from the top of the example target. To improve the fit between the predicted and simulated responses, two phenomenologically motivated modifications to the early-time response expressions are proposed. The modified expressions are able to accurately predict not just the general shape of the early-time response, but also the influence of the host medium conductivity on the target impulse response. Key words: ground penetrating radar, buried plastic landmines, identification, early-time response, Born approximation, impulse response, transfer function, FDTD simulation.