scholarly journals Electrodynamic analysis of mirror antennas in the approximation of the barycentric method

2021 ◽  
Vol 23 (4) ◽  
pp. 36-47
Author(s):  
Ivan S. Polyansky ◽  
Dmitry E. Stepanov ◽  
Dmitry K. Ketoh ◽  
Vyacheslav A. Shevchenko
Keyword(s):  
Arbitrary Shape ◽  
Surface Current ◽  
Basis Functions ◽  
Classical Representation ◽  
Surface Current Density ◽  
Electrodynamic Analysis ◽  
Internal Problem ◽  
Basic Functions ◽  
Mirror Antenna ◽  
The Galerkin Method

In the article, the features of using the barycentric method in solving problems of electrodynamic analysis of mirror antennas are considered. The solution of the internal problem of electrodynamics is the basis of the study. The problem of electrodynamic analysis of a mirror antenna is formulated in the classical representation of the problem of diffraction of an electromagnetic wave on a system of infinitely thin perfectly conducting screens of arbitrary shape and reduced to a system of integro-differential equations. The solution of the latter is performed numerically in the projection formulation of the Galerkin method when determining the approximation of the desired surface current density function in the system of global basis functions formed in the approximation of the barycentric method for the analyzed screen. The integral representation of the electromagnetic field of the mirror antenna, taking into account the properties of the introduced basic functions, is given. Thefeatures of the algorithmic implementation of the developed solutions are clarified. The efficiency and comparative preference of the use of the barycentric method in the problems of electrodynamic analysis of mirror antennas are tested on test examples.

A numerical solution for conducting bodies of arbitrary shape

1990 ◽  
Vol 68 (6) ◽  
pp. 459-468 ◽  
Author(s):  
H. Moheb ◽  
L. Shafai
Keyword(s):  
Electromagnetic Scattering ◽  
Arbitrary Shape ◽  
Numerical Technique ◽  
Three Dimensional ◽  
Surface Current ◽  
Basis Functions ◽  
The Other ◽  
Current Component ◽  
Discrete Surfaces ◽  
Conducting Bodies

An efficient numerical technique based on a Fourier expansion of the surface current is developed to study the electromagnetic scattering from three-dimensional geometries of arbitrary shape. In this method, the discrete domain representing the structure surface is geometrically represented by two orthogonal contours. One is selected along the intersection of the x–z plane with the object's surface, and the other along the corresponding one in the x–y plane. Entire domain basis functions are selected for the current component in the x–y plane, and subdomain linear basis functions are used to represent the other current component. The method of moments is used to solve the problem numerically. The technique is then applied to study the scattering from discrete surfaces such as squares and rectangles, to compare them with those of the coordinate-transformation technique developed earlier. The behavior of the solutions with the number of modes is investigated to determine their coupling.

Single-peak-regulation and wide-angle dual-band metamaterial absorber based on hollow-cross and solid-cross resonators

2020 ◽  
Vol 91 (3) ◽  
pp. 30901
Author(s):  
Yibo Tang ◽  
Longhui He ◽  
Jianming Xu ◽  
Hailang He ◽  
Yuhan Li ◽  
...  
Keyword(s):  
Transverse Electric ◽  
Surface Current ◽  
Dielectric Substrate ◽  
Transverse Magnetic ◽  
Metamaterial Absorber ◽  
Absorption Peak ◽  
Dual Band ◽  
Single Peak ◽  
Wide Angle ◽  
Surface Current Density

A dual-band microwave metamaterial absorber with single-peak regulation and wide-angle absorption has been proposed and illustrated. The designed metamaterial absorber is consisted of hollow-cross resonators, solid-cross resonators, dielectric substrate and metallic background plane. Strong absorption peak coefficients of 99.92% and 99.55% are achieved at 8.42 and 11.31 GHz, respectively, which is basically consistent with the experimental results. Surface current density and changing material properties are employed to illustrate the absorptive mechanism. More importantly, the proposed dual-band metamaterial absorber has the adjustable property of single absorption peak and could operate well at wide incidence angles for both transverse electric (TE) and transverse magnetic (TM) waves. Research results could provide and enrich instructive guidances for realizing a single-peak-regulation and wide-angle dual-band metamaterial absorber.

scholarly journals Radar Cross-Section Formulation of a Shell-Shaped Projectile Using Modified PO Analysis

2012 ◽  
Vol 2012 ◽  
pp. 1-9
Author(s):  
Mohammad Asif Zaman ◽  
Md. Abdul Matin
Keyword(s):  
Differential Geometry ◽  
Cross Section ◽  
Current Density ◽  
Surface Current ◽  
Radar Cross Section ◽  
Analysis Procedure ◽  
Physical Optics ◽  
Surface Current Density ◽  
Filtering Method ◽  
Good Agreement

A physical optics based method is presented for calculation of monostatic Radar Cross-Section (RCS) of a shell-shaped projectile. The projectile is modeled using differential geometry. The paper presents a detailed analysis procedure for RCS formulation using physical optics (PO) method. The shortcomings of the PO method in predicting accurate surface current density near the shadow boundaries are highlighted. A Fourier transform-based filtering method is proposed to remove the discontinuities in the approximated surface current density. The modified current density is used to formulate the scattered field and RCS. Numerical results are presented comparing the proposed method with conventional PO method. The results are also compared with published results of similar objects and found to be in good agreement.

Application of a modified variational formulation of the vector finite element method for modelling a harmonic electric field in areas with curved shields

2021 ◽  
pp. 26-41
Author(s):  
Дарья Владимировна Добролюбова ◽  
Элла Петровна Шурина
Keyword(s):  
Electric Field ◽  
Variational Formulation ◽  
Computational Cost ◽  
Surface Current ◽  
Local Source ◽  
Current Loop ◽  
Surface Current Density ◽  
Field Source ◽  
The Media ◽  
Cylindrical Shield

Рассматриваются особенности применения модифицированной вариационной постановки векторного метода конечных элементов (ВМКЭ), основанной на замене тонких сильнопроводящих объектов токонесущими поверхностями, для моделирования гармонического электрического поля в областях с криволинейными экранами при различном типе возбуждения поля. Исследуется применимость модифицированной вариационной постановки в широком диапазоне частот Purpose. The paper addresses applicability of the modified variational formulation of vector FEM for the harmonic electric field to the media with cylindrical shields. Thin highly conductive objects are treated as surfaces with the equivalent surface current density. We consider the excitation of the field by a local source (current loop) located either inside or outside the cylindrical shield. Methodology. The simulations are carried out on unstructured tetrahedral meshes. Since the modified variational formulation treats thin highly conductive objects as surfaces, only the surface of a cylinder is discretized. The results yielded by the modified variational formulation are compared with the results of the classic vector FEM. Findings. For the frequency range between 100 KHz and 100 MHz, the modified variational formulation provides correct results when the field source is located outside the cylindrical shield. The modified variational formulation reduces computational cost, since the volume of the thin shield is not discretized. When the field source is located inside the shield, the modified variational formulation gives valid results only in the proximity of the source. Originality/value. The limitations for the application of the reduced variational formulation for the modelling of harmonic electric field in the media with hollow cylindrical shields are investigated

A reduced formulation for modelling time-harmonic electromagnetic field in the media with thin highly conductive inclusions

2018 ◽  
Author(s):  
Э.П. Шурина ◽  
Д.В. Добролюбова ◽  
Е.И. Штанько
Keyword(s):  
Electric Field ◽  
Variational Formulation ◽  
Computational Cost ◽  
Surface Current ◽  
Wide Frequency Range ◽  
Geometrical Shape ◽  
Frequency Range ◽  
Surface Current Density ◽  
Time Harmonic ◽  
The Media

При решении задач электромагнетизма в широком частотном диапазоне в областях с тонкими пластинами, оболочками и экранами численными методами возникает проблема резкого роста сеточной дискретизации вблизи внутренних структур с разномасштабными габаритными размерами. В работе предложена модификация вариационной постановки векторного метода конечных элементов, основанная на снижении размерности модели в окрестности тонких включений, которая позволяет преодолеть эту проблему за счет специфического учета таких структур на уровне вариационной постановки. Так как редуцирование модели обычно приводит к появлению ограничений на область ее применимости, выполнено исследование диапазона допустимых частот, контрастности электрофизических характеристик матрицы и включений, геометрических особенностей внутренней структуры, для которых предложенная модель позволяет получить корректные с точки зрения физики результаты. Purpose. In this paper, we propose a reduced variational formulation for the Helmholtz equation for the electric field, in which thin highly conductive objects are approximated by surfaces with the equivalent surface current density. We conduct a study aimed at defining the range of application for the reduced variational formulation, focusing on highly contrasting thin objects of various geometrical shape and arrangement in a wide frequency range. Methodology. The modelling is performed on unstructured tetrahedral meshes. Since the reduced variational formulation treats thin highly conductive objects as surfaces, no volume mesh is constructed inside of them.We compare the results obtained by the vector FEM using the proposed variational formulation with the results obtained using standard formulation. Findings. Due to the fact that the proposed variational formulation does not require volume meshing of the thin objects, its computational cost is significantly lower. However, the reduced formulation yields correct results in a restricted frequency range. It also imposes some limitations on the minimal contrast and maximal thickness of the thin highly conductive objects. Originality/value. The proposed reduced variational formulation can be applied to simulate the time-harmonic electric field in the media with thin highly conductive inclusions of either regular or chaotic arrangement, as well as thin shielding plates or casings of various geometrical forms.

scholarly journals Convergence of approximate solution of mixed Hammerstein type integral equations

2018 ◽  
Vol 38 (2) ◽  
pp. 61-74
Author(s):  
Monireh Nosrati Sahlan
Keyword(s):  
Galerkin Method ◽  
Integral Equations ◽  
Basis Functions ◽  
Computational Method ◽  
Operational Matrices ◽  
B Spline ◽  
Spline Wavelets ◽  
Type Integral ◽  
The Galerkin Method ◽  
Dual Functions

In the present paper, a computational method for solving nonlinear Volterra-Fredholm Hammerestein integral equations is proposed by using compactly supported semiorthogonal cubic B-spline wavelets as basis functions. Dual functions and Operational matrices of B-spline wavelets via Galerkin method are utilized to reduce the computation of integral equations to some algebraic system, where in the Galerkin method dual of B-spline wavelets are applied as weighting functions. The method is computationally attractive, and applications are demonstrated through illustrative examples.

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