2015 Vol. 4, No. 5
A novel concept for suppressing the problem of multipath ghosts in Ground Penetrating Radar (GPR) and Through-Wall Imaging (TWI) is presented. Ghosts (i.e., false targets) mainly arise from the use of the Born or single-scattering approximations that lead to linearized imaging algorithms; however, these approximations neglect the effect of multiple scattering (or multipath) between the electromagnetic wavefield and the object under investigation. In contrast to existing methods of suppressing multipath ghosts, the proposed method models for the first time the reflectivity of the probed objects as a probability function up to a normalized factor and introduces the concept of random subaperture by randomly picking up measurement locations from the entire aperture. Thus, the final radar image is a joint probability distribution that corresponds to radar images derived from multiple random subapertures. Finally, numerical experiments are used to demonstrate the performance of the proposed methodology in GPR and TWI imaging.
In this paper, we present a Modified Two-Scale Microwave (MTSM) scattering model to describe the scattering coefficient of naturally rough surfaces. The surface roughness is assumed to be Gaussian in the proposed model so that the surface height z(x, y) can be split into large- and small-scale components by the wavelet packet transform according to electromagnetic wavelength. We used the Kirchhoff Model(KM) and Small Perturbation Method (SPM) to estimate the backscattering coefficient of large- and small-scale roughness, respectively. The tilting effect caused by the slope of large-scale roughness was corrected when calculating the contribution of backscattering to small-scale roughness. The backscattering coefficient of the MTSM comprised the total backscattering contributions of surfaces with both scales of roughness. The MTSM was tested and validated using the Advanced Integral Equation Model (AIEM) for dielectric randomly rough surfaces. The accuracy of the MTSM showed favorable agreement with AIEM, both when the incident angle was less than 30 (i30) and when the surface roughness was small (ks=0.354).