Abstract-An extension of the multilevel fast multipole algorithm (MLFMA), originally developed for targets in free space, is presented for the electromagnetic scattering from arbitrarily shaped three-dimensional (3-D), electrically large, perfectly conducting targets above or embedded within a lossy half space. We have developed and implemented electric-field, magnetic-field, and combined-field integral equations for this purpose. The nearby terms in the MLFMA framework are evaluated by using the rigorous half-space dyadic Green's function, computed via the method of complex images. Non-nearby (far) MLFMA interactions, handled efficiently within the multilevel clustering construct, employ an approximate dyadic Green's function. This is expressed in terms of a direct-radiation term plus a single real image

Abstract-The low-frequency natural response of conducting, permeable targets is investigated. We demonstrate that the source-free response is characterized by a sum of nearly purely damped exponentials, with the damping constants strongly dependent on the target shape, conductivity, and permeability, thereby representing a potential tool for pulsed electromagnetic induction (EMI) identification (discrimination) of conducting and permeable targets. This general concept is then specialized to the particular case of a body of revolution (BOR), for which the Method-of-Moments (MoM)-computed natural damping constants from several targets are compared with measurements. Moreover, theoretical natural (equivalent) surface currents and damping coefficients are shown for other targets of interest. Finally, we investigate the practical use of such natural signatures in the context of identification, wherein Cramer-Rao bound (CRB) studies address signal-to-noise ratio (SNR) considerations.

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Abstract-A method of moments (MoM) analysis is developed for electromagnetic scattering from a dielectric body of revolution (BOR) embedded in a layered medium (the half-space problem constituting a special case). The layered-medium parameters can be lossy and dispersive, of interest for simulating soil. To make such an analysis tractable for the wide-band (short-pulse) applications of interest here, we have employed the method of complex images to evaluate the Sommerfeld integrals characteristic of the dyadic layered-medium Green's function. Example wideband scattering results are presented, wherein fundamental wave phenomenology is elucidated. Of particular interest, we consider wide-band scattering from a model plastic mine, buried in soil, with the soil covered by a layer of snow.Index Terms-Method of moments, subserfice sensing, timedomain scattering.