Efficient representation of induced currents on large scatterers using the generalized pencil of function method

It is shown that the currents induced over large and smooth scatterers can often be represented by a series of complex exponentials with only a few terms. The generalized pencil of function method is employed to extract these exponentials from the numerical solution of the scattering problem derived by using the method of moments. Illustrative examples include a partially-coated two-dimensional scatterer modeling a helicopter blade and the three-dimensional problem of scattering by a thin plate. The ultimate objective of this effort is to solve a class of large-body scattering problems, for arbitrary angles of incidence including the grazing angle, by utilizing the numerically-derived, complex exponential type of basis functions extrapolated to higher frequencies. It is well known that the physical optics approximation for the induced current becomes inaccurate when the angle of incidence is close to grazing, and the asymptotic methods, e.g., the GTD can become unwieldy for scatterers with edge treatments and those with complex geometrical shapes. The approach based upon the use of numerically derived entire domain basis functions on a portion of the body is proposed as a means to circumventing this difficulty