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Amir Boag - One of the best experts on this subject based on the ideXlab platform.

  • shadow radiation iterative Physical Optics method for high frequency scattering
    2018
    Co-Authors: Igor Gershenzon, Yaniv Brick, Amir Boag
    Abstract:

    A shadow-radiation-based fast iterative Physical Optics (IPO) scheme, for the analysis of the scattering from large complex geometries involving multiple reflection and occlusion effects, is proposed. By employing a “shadow-radiation” mechanism, the scheme alleviates the need for expensive computation and storage of a geometric visibility function. In a nested fashion, shadow radiation iterations are performed for each “bounce” in the conventional multiple reflection IPO scheme. The resulting method makes use of simple field integrals which are all accelerable using a multilevel nonuniform grid-based field evaluation algorithm, with a modification tailored to the scheme’s integral kernels. The proposed scheme is also shown analytically to be a more stable (faster converging) equivalent of existing IPO schemes. The method is studied in terms of accuracy and performance for representative examples and compared with alternative Physical Optics and numerically exact solution techniques.

  • fast iterative Physical Optics with shadowing
    2016
    Co-Authors: Igor Gershenzon, Amir Boag, Yaniv Brick
    Abstract:

    A fast iterative Physical Optics (IPO) algorithm for the analysis of scattering from large complex geometries involving multiple scattering and self-shadowing effects is presented. The algorithm comprises two types of nested iterations: reflection ("bounce") iterations and self-shadowing iterations. Both types of iterations involve time consuming surface integrations carrying an O (N2) computational cost (N being the number of quadrature points). The nested iterative formulation is accelerated by using the multilevel non-uniform grid algorithm reducing the computational complexity to O(NlogN). The procedure's applicability to complex geometries and numerical efficiency are demonstrated by comparison to a numerically exact method and to the conventional Physical Optics.

  • multilevel Physical Optics algorithm for near field double bounce scattering
    2015
    Co-Authors: Moty Roudstein, Yaniv Brick, Amir Boag
    Abstract:

    A fast algorithm for the evaluation of the double-bounce (DB) contributions to the Physical Optics scattering integrals, over a range of aspect angles and frequencies, is presented. The work extends the preceding far-field algorithm, to encompass three-dimensional and near-field scenarios. The algorithm relies on multilevel sampling and interpolation of phase- and amplitude-compensated contributions of subdomain pairs. A particular design of the phase- and amplitude-compensation functions and sampling grids, tailored to the DB near-field case, is presented. The improved performance and error controllability are demonstrated via representative examples.

  • multilevel Physical Optics algorithm for near field scattering
    2014
    Co-Authors: Alex Gendelman, Yaniv Brick, Amir Boag
    Abstract:

    An algorithm for the fast computation of the Physical Optics (PO) integral describing single bounce back scattering in near-field scenarios is presented. The algorithm is based on a multilevel computation of partial contributions to the PO integral by hierarchically ordered subdomains. Phase- and amplitude-compensation of the partial contributions allows for their coarse sampling over non-uniform spherical grids. The solution is obtained by gradual aggregation of such partial contributions via interpolation on progressively denser grids. The computational complexity is further reduced by representation of small subdomains' contributions via their far-field patterns and transition to the near-field representations only at a higher level. Speed-up, accuracy, and error controllability are demonstrated.

  • Generalized multilevel Physical Optics (MLPO) for comprehensive analysis of reflector antennas
    2012
    Co-Authors: Christine Letrou, Amir Boag
    Abstract:

    Recent developments of the multilevel Physical Optics (MLPO) algorithm aiming at the comprehensive analysis of complex reflector antenna systems are presented. The Physical theory of diffraction (PTD) line integral along the rim of a reflector is combined with the Physical Optics (PO) surface integral within the multilevel algorithm. The multilevel scheme is also generalized to combine fields radiated by various components of different sizes, as encountered in complex antenna systems with multiple feeds and/or reflectors. Comparison with published results demonstrates the ability of the MLPO algorithm to cope accurately and efficiently with realistic reflector antenna problems.

Yusuf Ziya Umul - One of the best experts on this subject based on the ideXlab platform.

  • wave diffraction by a soft hard strip modified theory of Physical Optics solution
    2018
    Co-Authors: Yusuf Ziya Umul
    Abstract:

    Abstract The scattering problem of waves by a strip, the faces of which are composed of soft and hard surfaces, is investigated by the method of modified theory of Physical Optics. The scattering integral is divided into two parts according to the single effects of the faces. The boundary conditions are integrated into the integrals and the resultant field expressions are obtained by the asymptotic evaluation methods. The scattered waves are examined numerically.

  • diffraction of cylindrical waves by a perfectly conducting half screen a modified theory of Physical Optics solution
    2016
    Co-Authors: Yusuf Ziya Umul
    Abstract:

    The scattering problem of waves, radiated by a line source, is investigated by the method of modified theory of Physical Optics. The solution is obtained for both of the Dirichlet and Neumann boundary conditions. Two dimensional modified theory of Physical Optics integral is considered, since the problem is symmetric according to one of the spatial coordinates. The scattering integral is directly evaluated and a new function is defined for the scattered fields. The mathematical properties of the function are studied. The total, geometrical Optics and diffracted waves are analyzed numerically. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1996–2001, 2016

  • three dimensional modified theory of Physical Optics
    2016
    Co-Authors: Yusuf Ziya Umul
    Abstract:

    Abstract The three dimensional version of the modified theory of Physical Optics is introduced with the aid of a Green's function that satisfies the Helmholtz equation in local spherical coordinates. The algorithm which leads to the construction of the scattering integral is given. The method is applied to the three dimensional diffraction problem of plane waves by a perfectly conducting half-plane. The comparison of the resulting field expressions with the literature shows that the modified theory of Physical Optics leads to the exact solution.

  • Physical Optics theory for the scattering of waves by an impedance strip
    2011
    Co-Authors: Yusuf Ziya Umul
    Abstract:

    Abstract The Physical Optics integral of the scattered waves by an impedance strip is derived by using the modified theory of Physical Optics. The surface currents of the Physical Optics integral, which was introduced for the scattered waves by an impedance half-plane, are taken into account. The uniform diffracted fields of the impedance strip are evaluated asymptotically. The second order diffraction terms are also obtained. The total scattered field and its subcomponents are plotted and the effect of the second order diffraction and strip width to the scattering is investigated numerically.

  • the relation between the boundary diffraction wave theory and Physical Optics
    2008
    Co-Authors: Yusuf Ziya Umul
    Abstract:

    The Physical Optics surface integral is asymptotically reduced to a line integral along the contour of the diffracting edge. It is shown that the resultant integral can be separated into two sub-integrals which represent the reflected and transmitted diffracted fields. The integrands are transformed into the same forms with the potential function of the boundary diffraction wave theory.

Lixin Guo - One of the best experts on this subject based on the ideXlab platform.

  • hybrid time domain ptd and Physical Optics contour integral representations for the near field backscattering problem
    2019
    Co-Authors: Guangbin Guo, Lixin Guo
    Abstract:

    Time-domain Physical Optics (TDPO) contour integral representations are developed for backscattered near fields from a perfectly conducting surface illuminated by a dipole source. The proposed representations are derived from the TDPO surface integral representations by introducing two theorems: surface gradient and surface divergence theorems. The proposed representations are free from singularities for all the source/observer positions in which the dipole antenna is located. In addition, the time-domain Physical theory of diffraction is introduced to modify the Physical optical field considering the effect of the edge diffraction. Numerical examples are presented to demonstrate the efficiency and accuracy of the proposed method.

  • Scattering From Contaminated Rough Sea Surface by Iterative Physical Optics Model
    2016
    Co-Authors: Rui Wang, Lixin Guo, Zhibin Zhang
    Abstract:

    This letter focuses on scattering from rough sea surface covered by insoluble oil. Oil film damps the capillary wave of the rough sea surface, which leads to a smooth profile of the contaminated sea. We investigate this phenomenon using a highly efficient iterative model based on Physical Optics (PO) and Huygens' equivalence principle. PO is used to calculate the scattering from the oil film and underlying rough sea surface. The Huygens equivalence principle and iterative strategy are employed to evaluate the coupled scattering between the oil film and rough sea surface. The scattering of contaminated rough sea surface based on the iterative model is compared with those using the method of moments as well as computational time and memory requirements. Then, the influence of some important parameters, such as wind speed, oil thickness, incident wave frequency, and oil coverage, on scattering is investigated and discussed in detail.

Tie Jun Cui - One of the best experts on this subject based on the ideXlab platform.

  • singularity free contour integral representations for Physical Optics near field backscattering problem
    2017
    Co-Authors: Tian Tian Fan, Xiao Zhou, Tie Jun Cui
    Abstract:

    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.

  • an alternative treatment of saddle stationary phase points in Physical Optics for smooth surfaces
    2014
    Co-Authors: Jun Zhang, Tie Jun Cui
    Abstract:

    In a recent paper on computing the Physical Optics (PO) integral with a saddle stationary phase point (SPP) by numerical steepest descend method (NSDM) (F. Vico-Bondia, “A new fast Physical Optics for smooth surfaces by means of a numerical theory of diffraction,” IEEE Trans. Antennas Propag., vol. 58, no. 3, pp. 773-789, Mar. 2010), a one dimensional integral was obtained, on the path of which there existed higher-order (up to third) poles. To avoid tackling the singular integral, the Abel's summation technique was used to solve the problem ingeniously. However, it has been shown in some literatures that the integral would be divergent if there were even-order poles on the path of integral. Superficially, the integral in F. Vico-Bondia, 's paper, does not obey this law and the main aim of the communication is to clear this contradiction. We show rigorously that higher-order poles have no contributions to the final result. To acquire a general law, we further consider arbitrary polynomials of higher degrees for the PO integral, in which the orders of poles can be arbitrary number. In such a general case, we still show that all higher-order poles have no contributions and thus solve the contradiction satisfactorily. Numerical examples are presented to validate the new derivations and illustrate the accuracy and efficiency of NSDM.

P Ufimtsev - One of the best experts on this subject based on the ideXlab platform.

  • comments on wave diffraction by a soft hard strip modified theory of Physical Optics solution
    2018
    Co-Authors: Gokhan Apaydin, Levent Sevgi, P Ufimtsev
    Abstract:

    Abstract Modified theory of Physical Optics (MTPO) solution for a soft/hard strip is analyzed. It is shown that this solution is incorrect because the MTPO Green function does not satisfy boundary conditions. Defects of MTPO in calculations of fringe waves are also noticed.

  • On the Modified Theory of Physical Optics
    2013
    Co-Authors: Feray Hacivelioglu, Levent Sevgi, P Ufimtsev
    Abstract:

    Basic features of the modified theory of Physical Optics (MTPO) are discussed on the example of scattering at perfectly reflecting half-planes and wedges. It is shown that violations of the geometrical Optics (GO), introduced in this technique, result in the MTPO solutions which do not satisfy the Helmholtz equation. They are incorrect at a finite distance from a scattering object; however it can be considered as sort of approximations for the field at a large distance from an edge and away from the GO boundaries.

  • new insight into the classical macdonald Physical Optics approximation
    2008
    Co-Authors: P Ufimtsev
    Abstract:

    The Physical Optics approximation is widely used in analysis of antennas and scattering problems for electromagnetic and acoustic waves. The present paper investigates the nature of this classical approximation. It is shown that the scattered field in this approximation can be separated into two parts: the reflected field, containing all reflected rays and beams, and the shadow radiation, responsible for the Fresnel diffraction and the forward scattering. This observation elucidates the physics behind the fundamental diffraction law related to the total power scattered by large reflecting objects. It also clarifies the diffraction limit for reduction of scattering by absorbing materials.