Author_Institution :
Dept. of Radio Eng., Southeast Univ., Nanjing, China
Abstract :
Finding fast solutions for the electromagnetic (EM) scattering by dielectric objects buried in lossy earth is very important in near-surface geophysical exploration and landmine detection. Although conjugate gradient fast Fourier transform (CG-FFT) algorithms are much more efficient than the conventional method of moments (MoM), they are still not fast enough because many iterations are required. Consequently, some approximate methods, like the Born approximation and the extended Born (ExBorn) approximation, are usually used in the detection of buried objects. The ExBorn approximation is the more accurate, but it requires O(N/sup 2/) computational complexity (N is the number of unknowns). Recently, we proposed a fast ExBorn method using the FFT technique (Cui, T.J. et al., IEEE APS Int. Symp., vol.II, p.570-3, 2002), where the computational complexity is proportional to CN log N with a small coefficient C. Hence, ExBorn is much more efficient than the CG-FFT algorithm. However, the ExBorn approximation is less accurate when the target contrast is high. We derive high-order ExBorn approximations, all of which have closed-form expressions. Using the FFT technique, these approximations can be evaluated at a cost of O(N log N). Compared with full-wave analysis, high-order ExBorn approximations are more accurate than ExBorn.
Keywords :
approximation theory; buried object detection; computational complexity; dielectric bodies; electromagnetic wave scattering; fast Fourier transforms; geophysical techniques; landmine detection; EM scattering; FFT; MoM; buried dielectric objects; closed-form expressions; computational complexity; conjugate gradient fast Fourier transform algorithms; high-order extended Born approximations; iterations; landmine detection; lossy earth; method of moments; near-surface geophysical exploration; target contrast; Approximation methods; Buried object detection; Closed-form solution; Computational complexity; Dielectric losses; Earth; Electromagnetic scattering; Fast Fourier transforms; Landmine detection; Moment methods;