Characteristic current decomposition and radar cross-section analysis for perfectly electrically conducting bodies.

We review the characteristic current decomposition, first introduced by Garbacz (1968, A generalized expansion for radiated and scattered field. Ph.D. Dissertation, Ohio State University, Columbus) and then by Harrington & Mautz (1971, Theory of characteristic modes for conducting bodies. IEEE Trans. Antennas Propag., AP-19, 622–628). Our approach is based on the study of the scattering operator, or scattering matrix, the unitarity property of which plays a central role. The spectral decomposition of this operator leads to a particular characteristic far fields (or eigenfar-fields), from which a set of characteristic currents can be derived. These currents are those of Garbacz, Harrington and Mautz. They satisfy a generalized eigenequation involving usual integral operators split according to the regular/singular decomposition of the free space Green kernel. We provide proof of existence, denseness and orthogonality for these sets of characteristic modes (both currents and far fields). In addition to its theoretical interest, our analysis is motivated by its application to radar cross-section (RCS) analysis, where this particular decomposition turns out to be a powerful tool, especially for objects of small dimensions compared with the wavelength of the incident wave. Numerical computations are presented for a general three-dimensional object and the electrical field integral equation, including the first characteristic currents and their analyses in terms of their impact on the monostatic RCS. [ABSTRACT FROM AUTHOR]