Using FDFD Technique in Two-Dimensional TE Analysis for Modeling Clutter in Wall Penetrating Radar

Finite difference frequency domain (FDFD) computational electromagnetic modeling is implemented to perform a two-dimensional analysis for the application of wall penetrating radar (WPR). Resolving small targets of interest, embedded in a strong clutter environment of unknown configuration, is difficult. Field interaction between clutter elements will dominate the received fields back-scattered from the scene. Removing the effects of clutter ultimately relies on the accuracy of the model. Analysis starts with a simple model that continues to build based on the dominant scattering features of the scene. FDFD provides a steady state frequency response to a discrete excitation. Taking the fast Fourier transform of the wideband response of the scene, at several external transmit/receive locations, produces 2D images of the clutter, which are used to mature the model. 1. Introduction Previous work on EM field modeling for WPR commonly used time domain-based techniques to determine the true time-varying fields that are backscattered from the interaction of an excitation with the full 2D dielectric map of a scene. Several time domain approaches to resolving the inner layout of a building use ray tracing techniques with UWB radar imaging [1]. In WPR, depending on the application (counter-terrorism, urban warfare, etc.), several aspects of the scene can be important. For typical WPR applications, a sensor transmits from a remote location into a dielectric barrier (clutter) of unknown internal configuration containing an unknown number of targets of interest (TOIs). For monostatic radar, the scattered field received at the sensor contains the direct scattered energy due to clutter plus the TOIs plus the interactions between them. Precise TOI localization requires isolating the scattered energy due to the TOIs alone. The focus of this paper is around generating an accurate model of the clutter in the frequency domain. Due to the geometric complexity and inhomogeneity involved in a typical scene, precise model formulation containing minor detail of the internal structure becomes difficult. Instead, emphasis is placed on characteristics that contribute most to the scattered field. These include the overall dimensions and layout of the infrastructure, with focus on the orientation of the internal walls, doorway locations, and relatively large, static internal objects. TOIs typically have a significantly smaller radar cross-section (RCS) profile compared to the surrounding clutter and therefore contribute significantly less to the scattered field of the total scene.