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Principles Of Optics Electromagnetic Theory Of Propagation Interference And Diffraction Of Light

Dyadic Green Functions in Electromagnetic Theory by Chen-To-Tai.Book review.

An accurate and efficient physical-optics (PO) near-field integral representation is proposed and introduced into shooting and bouncing ray (SBR) to evaluate the electric and magnetic near-fields scattered from electrically large complex objects illuminated by dipole sources. The PO near-field integral expressions can be reduced to closed-form expressions by applying locally expanded phase approximations and surface partitioning. By introducing the proposed PO near-field integral expressions, SBR can be used to solve near-field scattering problems from electrically large complex objects. Simple and complex numerical examples are presented to demonstrate the efficiency and accuracy of the proposed method.

SBR Method for Near-Field Scattering of an Electrically Large Complex Target Illuminated by Dipole Sources

A time-domain (TD) line-integral (LI) representation of the physical-optics (PO) radiation integral is developed for the scattering from a perfectly conducting surface illuminated by an electric Hertzian dipole. The proposed LI representation, which is valid and singularity-free for all near-field observers, is derived directly in the TD by introducing dyad potentials. This TD representation can be further expressed in terms of geometric-optics and boundary-wave components of the scattering mechanisms, as in the conventional frequency-domain LI representations. Using the proposed LI representation, the computational complexity is reduced by an order of the scatterer’s linear electric size, compared with the straightforward numerical quadrature of the PO surface integral. Simple and complicated numerical examples are presented to demonstrate the efficiency and accuracy of the proposed TD-LI algorithm.

Time-Domain Line-Integral Representations of Physical-Optics Scattered Fields

An efficient time domain shooting and bouncing ray (TDSBR) method is proposed to analyze the transient near-field scattering from an electrically large complex object illuminated by a far-field antenna source. The time-domain far-field incident sources can be derived by a convolution of pulsed excitation with the inverse Fourier transform of frequency domain (FD) far-fields radiated from an antenna. In order to obtain accurate near-field scattering results, time domain physical optics (TDPO) near-field integral representations are proposed and reduced to closed-form expressions to improve computing efficiency by applying locally expanded Green function approximation. Different from the plane wave incident situation, in the case of antenna radiation, the incident fields of each individual facet in the ray path are represented by the radiation fields from the equivalent mirror antenna derived in this paper. Since the radiation fields naturally contains the time delay term, the complicated processing of the time delay problem can be avoided by solving the equivalent mirror antenna radiation fields. It is simpler and more accurate than the traditional time domain geometrical optics (TDGO) method. Numerical examples are presented to demonstrate the efficiency and accuracy of the proposed method.

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The Study on Near-Field Scattering of a Target Under Antenna Irradiation by TDSBR Method

Near-field backscattering problems are often encountered in computational electromagnetics. In this paper, contour-integral representations have been presented to evaluate the physical-optics backscattered electric and magnetic fields from a perfectly conducting object illuminated by a dipole source. The advantage of the proposed representations is that the integrands in the contour integrals along the rim of the scatterer are free from singularities for all the source/observer positions. In addition, the proposed algorithm is easily extensible to analyze the scattering from complex objects. Such a liberty is achieved by deriving the novel representations using vector-algebra theorems in global coordinates, instead of existing scalar theorems in a particular angular coordinate. Numerical examples are presented to illustrate the efficiency and accuracy of the proposed contour-integral representations.

Singularity-Free Contour-Integral Representations for Physical-Optics Near-Field Backscattering Problem

This paper presents a novel line-integral representation of the physical-optics radiation integral from a perfectly conducting surface illuminated by a finite number of electric Hertzian dipoles. By introducing a new dyad potential, this novel representation guarantees the integrand free from singularities along the computational path. As such, it can be easily integrated for arbitrary positions of the source and observation points. Conversely, for certain situations of the Hertzian dipole being on the cone connecting the observation point to the scattering rim, the existing formulations exhibit a nonremovable singularity in their integrands. This will lead to invalid or inaccurate results. Meanwhile, for near-singular integration region, time-consuming computations need to be performed by utilizing a variable mesh integration. The efficiency in numerical calculation is the main objective of this kind of approach, and the time reduction performance would be improved by our singularity-free formula. The line-integral representation offers an alternative method to rapidly solve the scattering problem as it is usually more efficient than producing the same result in conventional surface-integral. Simple and complicated numerical examples are included to demonstrate the beneficial effect of the proposed expressions in terms of efficiency and accuracy.

Numerically Efficient Line-Integral Representation of Physical-Optics Scattered Field: The Case of Perfectly Conducting Surface Illuminated by Electric Hertzian Dipoles

Antennas radiation on electrically large objects is often encountered in computational electromagnetics. In this paper, we present an approximation strategy for the line integral reduction of arbitrary far-field source excitation. By approximating the arbitrary far-field source as different vector point sources for each sub-segment on the contour of the PO integral surface, the PO scattered field is cast in a line integral format. This algorithm permits a fast and accurate evaluation of the PO integral for arbitrary far-field source excitation. Compared with traditional line integral approach by expressing the incident wave as angular spectrum of plane waves, our method is simpler and more explicit. Numerical examples are presented to illustrate the exactness of the line integral representation.

http://ieeexplore.ieee.org/iel7/7504047/7510252/07510437.pdf

Tian Tian Fan

Papers

Singularity-Free Contour-Integral Representations for Physical-Optics Near-Field Backscattering Problem

Time-Domain Line-Integral Representations of Physical-Optics Scattered Fields

Numerically Efficient Line-Integral Representation of Physical-Optics Scattered Field: The Case of Perfectly Conducting Surface Illuminated by Electric Hertzian Dipoles

Efficient evaluation of near-field PO scattering from PEC objects illuminated by arbitrary far-field sources