Publications

This work describes the computation of scatterers that lay on the body of a real target which are depicted in radar images. A novelty of the approach is the target echoes collected by the radar are formulated into the first Fornasini-Marchesini (F-M) state space model to compute poles that give rise to the scatterer locations in the two-dimensional (2-D) space. Singular value decomposition carried out on the data provides state matrices that capture the dynamics of the target. Furthermore, eigenvalues computed from the state transition matrices provide range and cross-range locations of the scatterers that exhibit the target silhouette in 2-D space. The maximum likelihood function is formulated with the state matrices to obtain an iterative expression for the Fisher information matrix (FIM) from which posterior Cramer-Rao bounds associated with the various scatterers are derived. Effectiveness of the 2-D state-space technique is tested on static range data collected on a complex conical target model; its accuracy to extract target length is judged and compared with the physical measurements. Validity of the proposed 2-D state-space technique and the Cramer-Rao bounds are demonstrated through data collected on the target model.

A novel RCS component prediction model approach to producing both fast and accurate scattering from an electrically large open-ended cylindrical cavity (circular cross section) is presented. The component model is a hybrid approach which easily permits individual scattering mechanisms to be coherently combined to produce a high fidelity signature. For this problem, the component model included scattering produced from the interior of the cavity calculated via the waveguide modal approach combined with the scattering produced from the cavity's finite thick rim opening (i.e., annulus) computed via the Method of Moments (MoM) and finally combined with the cavity's external base ring edge diffraction computed via PTD. Narrowband and wideband signature analysis for the circular cylindrical cavity configuration are presented to validate the component prediction model with static range measurements, and another prediction result computed using MoM for X- band frequencies and linear polarization. Excellent agreement is achieved among the data sets: measurement and prediction (component and MoM model).

In this paper we present a resonance-based classification technique for the identification of plastic-cased antipersonnel (AP) land mines buried in lossy and dispersive soils under rough surfaces by a stepped-frequency ultra-wideband (UWB) downward-looking ground penetrating radar (GPR) with an array of receivers. For this application the multistatic ground probing sensor is positioned just above the ground surface and operates from UHF to C-Band frequencies. Novel physics-based models based on the finite difference frequency domain (FDFD) technique simulate the characteristic resonating multi-aspect target frequency responses for several realistic buried land mine detection scenarios. Matched filter detection results are presented which assess the GPR's performance in identifying a simulated mine buried under a rough surface at varying depths in dry sand and a dispersive clay loam soil from other false targets such as buried rocks.

This paper investigates the feasibility of detecting plastic antipersonnel land mines buried in lossy, dispersive, rough soils using a stepped-frequency ultra wideband (WB) ground-penetrating radar (GPR). Realistic land mine scenarios were modeled using a two-dimensional (2D) finite difference firequency domain (FDFD) technique. Assuming normal incidence plane wave excitation, the scattered fields were generated over a large frequency bandwidth (.5 to 5 GHz) for a variety of mine-like shapes, different soil types, and multiple receiver locations. The simulation results showed that for a ground penetration sensor located just above the soil surface, the strong reflection signals received from the rough ground surface obscured the buried target's fiquency response signal. The simulated GPR WB frequency response data at each receiver location was transformed to the time domain using the fast fourier transform. Time domain processing permits high resolution measurement of target features that are invariant to the ground roughness and also that are dependent on the soil characteristics as well as the burial depth and size of the mine, Specifically, two or more characteristic timing peaks are observed in the simulation results suggesting that the ultra-wideband spectral radar response may yield particular advantages not exploited by currently employed detection systems. It is also shown that by using time-gating to remove the strong ground reflection signals, the target signals are selectively enhanced (as expected), but more surprisingly, the target frequency response signature is almost completely recovered.