Physical Optics Radiation Integrals with Frequency-Independent Number of Division utilizing Fresnel Zone Number Localization and Adaptive Sampling Method

Takayuki KOHAMA  Makoto ANDO  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E97-C   No.12   pp.1134-1141
Publication Date: 2014/12/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E97.C.1134
Type of Manuscript: PAPER
Category: Electromagnetic Theory
Keyword: 
Physical Optics,  Adaptive Sampling Method,  Radiation Integral,  Fresnel zone,  Localization,  

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Summary: 
The physical optics (PO) approximation is one of the widely-used techniques to calculate scattering fields with a reasonable accuracy in the high frequency region. The computational load of PO radiation integral dramatically increases at higher frequencies since it is proportional to the electrical size of scatterer. In order to suppress this load, a variety of techniques, such as the asymptotic evaluation by the stationary phase method (SP), the equivalent edge currents (EECs), the low-order polynomial expansion method and the fast physical optics (FPO), have been proposed and developed. The adaptive sampling method (ASM) proposed by Burkholder is also one of the techniques where the sampling points in radiation integral should be adaptively determined based upon the phase change of integrand. We proposed a quite different approach named “Localization of the radiation integrals.” This localization method suggests that only the small portions of the integration with a slow phase change contribute to the scattering field. In this paper, we newly introduce the ASM in the localization method and applied the proposed method into the radar cross section (RCS) analysis of 2-dimensional strip and cylinder. We have confirmed that the proposed method provides the frequency-independent number of division in the radiation integrals and computational time and accuracy. As the starting point for extension to 3-D case, the application of the proposed method for a reflection from an infinite PEC plane and a part of sphere was also examined.