Fast Mesh-based physical optics for large-scale electromagnetic analysis

[摘要] ENGLISH ABSTRACT: At sufficiently high frequencies, the electrical size of scattering objects become verylarge. The electromagnetic field simulation of such objects becomes prohibitively expensivewith physically rigorous (full wave) computational electromagnetics methods. Insuch cases, methods based on asymptotic assumptions can be employed instead, to approximatelysolve Maxwell's equations. The physical optics (PO) approximation for aconducting surface, is a well-known asymptotic assumption. The multiple-reflection PO(MRPO) method is obtained by applying the PO approximation recursively, to modelmultiple reflections occurring internally to an object. The overall research goal of thiswork is to significantly accelerate the mesh-based MRPO for electromagnetic scatteringanalysis. A standard representation was chosen for the surface current, namely Rao-Wilton-Glisson (RWG) basis functions on a mesh of triangle elements. Since the MRPOis an extension of the single-reflection PO (SRPO), the main bottleneck in the SRPO,namely incident field shadowing determination, is addressed first. An adaptive, multilevel,buffer-based shadowing determination algorithm is developed which is robustly optimal,yielding O(N) time-scaling results for extreme test cases (N denotes the number ofmesh elements). Secondly, the first ever, comprehensively accelerated version of the meshbasedMRPO method (which rigorously takes internal shadowing into account), denotedfast MRPO (FMRPO), is developed. The FMRPO uses the multi-level, fast multipolemethod (MLFMM) to accelerate internal reflected field calculations. The inter-groupinteraction criterion of the MLFMM is altered to account for shadowing. Inter-groupshadowing status flags are efficiently evaluated. The runtime scaling of the conventionalMRPO is O(Nˆ2), while the runtime of the FMRPO scales as quasi-O(N log N), dependingon the specific geometry. Results are presented for practical geometries with largerelectrical sizes than have ever before been considered with the MRPO, but which can nowfor the first time be solved in realistically fast runtimes. With the FMRPO there is nofundamental limit to the electrical size of the scattering objects that can be solved.

[发布机构] Stellenbosch University