Fresnel Zone Criterion to Implement Locality in the Method of Moments and PO-MoM Hybrid Method for the Reduction of Unknowns

Keita ITO  Tetsu SHIJO  Makoto ANDO  

IEICE TRANSACTIONS on Electronics   Vol.E94-C   No.1   pp.72-79
Publication Date: 2011/01/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E94.C.72
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Electromagnetic Theory
method of moments,  physical optics,  geometrical theory of diffraction,  hybrid method,  radar cross section,  

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Locality of high frequency electromagnetic scattering phenomena is embodied and imported to the Method of Moments (MoM) to reduce computational load. The proposed method solves currents on small areas only around inner and edge stationary phase points (SPPs) on the scatterer surfaces. The range of MoM area is explicitly specified in terms of Fresnel zone number as a function of frequency, source and observer positions. Based upon this criterion, scatterer of arbitrary size and shape can be solved with almost frequency independent number of unknowns. In some special cases like focusing systems, locality disappears and the method reduces to the standard MoM. The hybrid method called PO-MoM is complementarily introduced to cope with these cases, where Fresnel zone number with analogous but different definition is used. The selective use of Local-MoM and PO-MoM provides frequency insensitive number of unknowns for general combination of source and observation points. Numerical examples of RCS calculation for two dimensional flat and curved surfaces are presented to demonstrate the accuracy and reduction of unknowns of this method. The Fresnel zone, introduced in the scattering analysis for the first time, is a useful indicator of the locality or the boundary for MoM areas.