Complex Resonant Frequencies for the Identification of Simple Objects in Free Space and Lossy Environments - Abstract

Abstract

The frequency-domain method of moments (MoM) has been used to analyze the induced current characteristics for an arbitrarily shaped, perfectly conducting, thin wire antenna and scatterer. The time-domain response of the current is obtained from the frequency domain data via an inverse fast Fourier transform (FFT) when the wire is excited by a Gaussian pulse. The numerical results of the transient current show that the late-time responses for both the radiation and scattering of a straight wire are almost identical, but that their early-time responses are quite different. The poles and residues of the time-domain response that contain the complex resonant frequencies of the scattering object are then extracted via the generalized pencil-of-function (GPOF) method. It is numerically demonstrated that the complex resonant frequencies of the object are their natural frequencies since they do not depend on the excitation sources. The time-domain response reconstructed by using the poles and residues is in excellent agreement with that obtained by FFT of the frequency domain data. The complex resonances for the transient scattering of an L-shaped wire are also analysed. As an application of this method to the radiation and scattering of buried bodies, the scattering from a strip on the surface of a lossy half-space is investigated and its complex resonances are recognized.