Closed-form Green's functions for cylindrically stratified media are derived in terms of spherical waves and surface-wave contributions. The methodology is based on a two-level approximation of the spectral-domain Green's functions. In the first step, the large argument behavior of the zeroth-order Hankel functions is used for the extraction of the quasistatic images from the spectral-domain Green's functions with the use of the Sommerfeld identity. In the second step, the remaining part of the Green's functions are approximated in terms of pole-residue expressions via the rational function fitting method. This robust, efficient, and fully numerical approach does not call for an analytical cumbersome extraction of the surface wave poles, prior to the spectrum fitting. Moreover, it can be applied in both the near-and far-field. Numerical results for the Green's functions of one-layer and two-layer structures are presented to verify the accuracy and efficiency of this approach.Index Terms-Closed-form Green's functions, cylindrically stratified media, discrete complex images method (DCIM), rational function fitting method (RFFM).
Abstract-In this paper, an improved CBFM/p-FFT algorithm is presented, which can be applied to solve electromagnetic scattering problems of large-scale periodic composite metallic/dielectric arrays, even when the array has electrically small periodicity or separating distance.Using characteristic basis function method (CBFM), scattering characteristics of any inhomogeneous targets can be represented by special responses derived from a set of incident plane waves (PWs). In order to reserve the dominant scattering characteristics of the targets and remove the redundancy of the overfull responses, a singular value decomposition (SVD) procedure is applied, then, new series of basis functions are built based on the left singular vectors after SVD whose corresponding singular values beyond a predefined threshold. However, the algorithm of CBFM combined with method of moments (MoM) still requires a lot of memory and CPU resources to some large scale problems, so the precorrectedfast Fourier transform (p-FFT) method is applied based on the novel built basis functions, with which, the required memory and solve time for solution can be reduced in an extraordinary extent. For a near correction technique is applied to process the interactions between cells placed within a distance less than a predefined near-far field threshold, arrays with electrically small periodicity can be analyzed accurately. Moreover, the incomplete LU factorization with thresholding (ILUT) preconditioner is applied to improve the condition number of the combined algorithm, which improves the convergence speed greatly.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.