Induced Surface Current Density Research Articles

Analysis and Reduction of Mutual Coupling in a Microstrip Array With a Magneto-Electric Structure

This article provided a detailed analysis of the mutual coupling phenomena in the microstrip patch array and introduced a novel compact magnetoelectric structure as a planar decoupling element. The proposed decoupling structure, termed as the interconnected array of semicircularly slotted structure, was formed as a combination of the electric dipole, magnetic dipoles, and circular patches. This compact magnetoelectric structure improves the isolation between two patches by around 9 dB at the resonating frequency of the radiating antennas with the edge-to-edge spacing of only 0.057 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _0$</tex-math></inline-formula> . This planar design is spatially compact and can maintain the broadside radiation characteristics. The decoupling mechanisms were analyzed in terms the equivalent port transmission coefficients and the parasitically induced surface current density vector. A design method had been proposed along with an equivalent circuit representation of the of the band-notch structure. The fabricated structure was found to show good matching between the measured and simulated results.

Large-signal field analysis of a linear beam travelling wave tube amplifier for the anisotropically conducting tape helix slow-wave structure supported by dielectric rods

The large-signal behavior of traveling wave tube amplifier for a linear beam dielectric loaded anisotropically conducting tape helix slow wave structure (SWS) is realized through a swift and reliable field analysis. Using Green’s function sequence, the field components in the SWS are designated as nonlinear functionals of electron arrival time. The electron arrival time in the beam region is formulated into a nonlinear operator in the Banach space mapping form by substituting the axial electric field component into the electron ballistic equation. The nonlinear beam–wave interaction is then obtained by determining the electron arrival time through extensive successive approximations, and thus exact electric and magnetic field components in the tape helix SWS are attained. The numerical computation of the proposed model yields definitive analytical results for the electron exit velocity, induced surface current density, power gain, conversion efficiency, and optimum interaction length.

Broadband Reflectarray Antenna on a Periodically Perforated Substrate

We propose a broadband single-layer reflectarray antenna constituted of a double-screen metallic grating on a periodically perforated low-cost substrate. The reflection characteristics of this structure are computed with a full-wave computational technique that utilizes the dyadic Green’s function evaluated by an equivalent transmission line modeling in the spectral domain. The obtained dyadic Green’s function is then used in an integral equation for the induced surface current densities on the metallic gratings. The resulting integral equation is solved by the Galerkin’s method of moments with subdomain basis functions. With the help of this semianalytical method, the phase diagram of the reflectarray unit cell is computed. Using the calculated phase diagram, a center-fed reflectarray is designed at a center frequency of 10.5 GHz. To validate the numerical results, the designed reflectarray for the $X$ -band (8.95–12.1 GHz) is fabricated and measured. The measurements on a 270 mm $\times \,\, 270$ mm and F/D = 0.95 reflectarray show a maximum gain of 26.57 dBi with a 1-dB gain bandwidth of 29.5% and an efficiency of 41% at 10.5 GHz. It is shown that the fabricated reflectarray exhibits a reduced radar cross-section outside its operating bandwidth.

Spectral Solution for Scattering Analysis of Periodic Plasmonic Nano-antennas on Iso/Anisotropic Substrate

A fast solution for the scattering analysis of periodic plasmonic nano-antennas (PPNAs) on iso/anisotropic substrates is presented. This method is based on derivation of the spectral dyadic Green's function with taking into account the plasmonic effects. The obtained dyadic Green's function is then used in an integral equation formulated for computing the induced surface current densities on the PPNAs. The resultant integral equation is solved by means of Galerkin's Method of Moments with entire-domain basis and test functions. With the help of this computational technique, the scattering characteristics of several examples are analyzed. The computed results are validated by means of a full-wave EM solver based on finite element method. For showing the efficiency of this method, the convergence rate and computation time in terms of space harmonic orders are calculated. It is shown that the developed method is an efficient and speedy technique for the analysis of such periodic plasmonic structures. In addition, we study an array of PPNAs on a uniaxial anisotropic substrate where the scattering characteristics are calculated as a function of the optic-axis direction. It is found that using anisotropic materials as the substrate of PPNAs allows additional degrees of freedom for controlling the scattering information.

유전체층 위의 완전도체띠 격자구조에 의한 TE 산란에 관한 연구

In this paper, the solutions of TE(transverse electric) scattering problems by a condutive strip grating over a dielectric layer are analyzed by using the FGMM(fourier galerkin moment method) and PMM(point matching method) known as a numerical method of electromagnetic fileld. The scattered electromagnetic fields are expanded in a series of floguet mode functions, the boundary conditions are applied to obtain the unknown field coefficients, and the conductive boundary condition is used for the relationship between the tangential electric field and the induced surface current density on the strip. The numerical results for the reflected and transmitted power of zeroth mode analyzed by according as the width and spacing of conductive strip, the relative permittivity and thickness of dielectric layer, and incident angles. Generally, according to the relative permittivity of dielectric layer increased, also the normalized reflected power of zeroth mode increased. To examine the accruacy of this paper, the numerical results of FGMM shown in good agreement compared to those of PMM.

Point Matching Method를 이용한 접지된 유전체층 위의 저항띠 격자구조에 의한 TE 산란 해석

[Abstract] In this paper, the solutions of TE(transverse electric) scattering problems by a resistive strip grating over a grounded dielectric layer are analyzed by applying the PMM(point matching method) known as a numerical method of electromagnetic fileld. The boundary conditions are applied to obtain the unknown field coefficients and the resistive boundary condition is used for the relationship between the tangential magnetic field and the induced surface current density on the resistive strip. The induced surface current density of resistive strip is obtained by difference of the up and down of the magnetic field in two boundary areas of the resistive strip. The numerical results for reflected power of zeroth order mode analyzed by according as the resistivity, the width and spacing of resistive strip, the relative permittivity and thickness of dielectric layer, and incident angles. The numerical results shown in good agreement compared to those of the existing papers using FGMM(fourier galerkin moment method). Key word : TE scattering, Resistive boundary condition, Point matching method, Fourier Galerkin moment method.

2개 유전체층 위의 완전도체띠 격자구조에 의한 TM 산란의 급속한 수렴 해

본 논문에서는 2개 유전체층 위의 완전도체띠 격자구조에 의한 TM (transverse magnetic)산란의 급속한 수렴 해에 대한 문제를 수치해석 방법인 FGMM (Fourier Galerkin moment method)를 이용하여 해석하였다. TM 산란에 대하여 유도되는 표면 전류밀도는 스트립 양 끝에서 매우 큰 값이 예측되므로, 이때 스트립에 유도되는 전류밀도는 적절한 모서리 경계조건을 만족하는 함수와 1종 Chebyshev 다항식의 곱의 급수로 전개하였다. 도체띠에 유도되는 전류밀도, 정규화된 반사전력 및 투과전력을 계산하였다. 제안된 함수를 사용한 수치결과는 기존의 지수함수를 사용했을 때 보다 빠르게 수렴도가 향상되었으며, 수치결과들은 기존 논문들의 결과들과 비교하여 거의 일치하였다. In this paper, the solutions of TM (transverse magnetic) scattering problems by perfectly conducting strip grating on two dielectric layers are analyzed by applying the FGMM (Fourier Galerkin moment method) as a numerical method. For the TM scattering problem, the induced surface current density is expected to the very high value at both edges of the strip, then the induced surface current density on the strip is expanded in a series of the multiplication of the functions of appropriate edge boundary condition and the Chebyshev polynomials of the first kind. The numerical results are obtained for the magnitude of induced current density, the normalized reflected power and transmitted power. The numerical results using proposed functions were improved the convergence faster than existing exponential functions, and the numerical results shown the good agreement compared to those of the existing papers.

모서리 경계조건을 만족하는 접지된 2개의 유전체층 위의 도체띠 격자구조에 의한 TM 산란의 해

본 논문에서는 모서리 경계조건을 만족하는 접지된 2개의 유전체층 위의 완전도체띠 격자구조에 의한 TM(Transverse Magnetic) 산란 문제를 수치해석 방법인 FGMM (Fourier Galerkin Moment Method)를 이용하여 해석하였다. TM 산란에 대하여 도체띠에 유도되는 표면 전류밀도는 스트립 양 끝에서 매우 큰 값이 예측되므로, 이때 도체띠에 유도되는 표면 전류밀도는 1종 Chebyshev 다항식과 적절한 모서리 경계조건을 만족하는 함수의 곱의 급수로 전개하였다. 전반적으로, 접지평면 위에 유전체층의 비유전율의 값이 증가하면, 반사전력의 급변점에 대한 스트립 폭은 더 큰 값으로 이동하였다. 수치결과들은 기존 논문들과 비교하여 급속한 수렴해와 좋은 일치를 보였다. In this paper, the TM (Transverse Magnetic) scattering problems by a perfectly conducting strip grating over a grounded two dielectric layers with edge boundary condition are analyzed by applying the FGMM (Fourier Galerkin Moment Method). For the TM scattering problem, the induced surface current density is expected to the very high value at both edges of the strip, then the induced surface current density on the conductive strip is expanded in a series of the multiplication of the Chebyshev polynomials of the first kind and the functions of appropriate edge boundary condition. Generally, when the value of the relative permittivity of dielectric layers over the ground plane increased, the strip width according to the sharp variation points of the reflected power is shifted to a higher value. The numerical results shown the fast convergent solution and good agreement compared to those of the existing papers.

모서리 경계조건을 만족하는 접지된 2개 유전체층 위의 도체띠 격자구조에 의한 TE 산란의 해

본 논문에서는 모서리 경계조건을 만족하는 접지된 2개의 유전체층 위의 완전도체띠 격자구조에 의한 TE (Transverse Electric)산란 문제를 수치해석 방법인 FGMM (Fourier Galerkin Moment Method)를 이용하여 해석하였다. TE 산란에 대하여 유도되는 표면 전류밀도는 스트립 양 끝에서 0의 값이 기대되며, 이때 도체띠에 유도되는 표면 전류밀도는 2종 Chebyshev 다항식과 적절한 모서리 경계조건을 만족하는 함수의 곱의 급수로 전개하였다. 수치결과들은 기존 논문들과 비교하여 급속한 수렴해와 좋은 일치를 보였다. In this paper, the TE (Transverse Electric) scattering problems by a perfectly conducting strip grating over a grounded two dielectric layers with edge boundary condition are analyzed by applying the FGMM (Fourier Galerkin Moment Method). For the TE scattering problem, the induced surface current density is expected to the zero value at both edges of the strip, then the induced surface current density on the strip is expanded in a series of the multiplication of the Chebyshev polynomials of the second kind and the functions of appropriate edge boundary condition. The numerical results shown the fast convergent solution and good agreement compared to those of the existing papers.

Fourier-Galerkin Moment Method를 이용한 접지된 2개 유전체층 위의 완전도체띠 격자구조에 의한 TE 산란의 해

In this paper, The TE (Transverse Electric) scattering problems by a perfectly conducting strip grating over a grounded two dielectric layers are analyzed by applying the conductive boundary condition and the FGMM (Fourier-Galerkin Moment Method) known as a numerical procedure, then the induced surface current density is expanded in a series of the multiplication of the unknown coefficient and the exponential function as a simple function. Generally, the reflected power gets increased according as the relative permittivity and the thickness of dielectric layer of the region-2 in the presented structure gets increased, respectively. The sharp variations of the reflected power are due to resonance effects were previously called wood`s anomaly, the numerical results show in good agreement with those of the existing papers.

Generalized surface current method in the macroscopic theory of diffraction radiation

The surface current method known in the theory of electromagnetic waves diffraction has been generalized to be applied to the problems of diffraction radiation generated by a charged particle moving nearby an ideally-conducting screen in vacuum. An expression for induced surface current density leading to the exact results in the theory of transition radiation has been derived, and by using this expression several exact solutions of diffraction radiation problems are found. Limits of applicability for the earlier known models based on the surface current conception are indicated. Properties of radiation from a semi-plane and from a slit in cylinder are investigated at the various distances to observer.

접지된 2중 유전체 사이의 저항 띠 격자 구조에 의한 E-분극 전자파 산란 해석

본 논문은 접지된 2중의 유전체 평면 사이에 변화하는 저항율을 갖는 저항 띠 격자 구조로 임의의 각도로 입사되는 E-분극 전자파 산란 문제를 모멘트 법으로 해석하였다. E-분극 산란에서는 저항 띠의 모서리 양끝에서 유도되는 전류 밀도가 매우 높을 것으로 예측되므로, 이 특성과 일치하는 기저 함수를 직교 다항식 일종인 2종 Chebyshev 다항식의 급수로 전개하여 수치 해석하였다. 산란 전자계는 주기적인 구조에 대응시킬 수 있는 Floquet 모드 함수의 급수로 전개하였고, 미지의 계수를 구하기 위하여 경계 조건을 적용하였다 또한, Fourier-Galerkin 모멘트 법을 적용함으로써 접지된 2중의 유전체 사이에 다양한 저항율을 갖는 저항 띠에 대해 기하광학적인 정규화 된 반사 전력에 관한 스트립 폭과 주기, 입사각의 영향 등을 수치 해석하였다. In this paper, when a E-polarized plane wave is incident on the grating consisting of tapered resistive strips, electromagnetic scattering is analyzed using the method of moments(MoM). The induced current density of each resistive strip in a grounded double dielectric layer is expected to blow up at both edges. To satisfy this, the induced surface current density is expanded in a series of Chebyshev polynomials of the second kind. The scattered electromagnetic fields are expanded in a series of Floquet mode functions. The boundary conditions are applied to obtain the unknown current coefficients. According to the variation of the involving parameters such as strip width and spacing and angle of the incident field, numerical simulations are performed by applying the Fourier-Galerkin moment method. The numerical results of the normalized reflected power for resistive strips case for several resistivities are obtained.

Diffraction of obliquely incident waves by a strip in a bianisotropic medium

Diffraction of obliquely incident waves by a perfectly conducting strip of infinite length immersed in either 1) an unbounded bianisotropic medium or 2) a bianisotropic cylinder is investigated. Systems of singular integral-integrodifferential equations having the induced surface current densities as the unknowns are derived by following several independent formulation techniques. Discretization is carried out using moment-method-oriented techniques applied to singular integral equations. The matrix elements are given either in closed form or by exponentially convergent series which require no numerical integration. Moreover, the algorithms are found to converge exponentially versus matrix size. Numerical results are presented which show the effect of changing either the degree of bianisotropy or the strip width and orientation on the scattering characteristics.

Modeling for RF noise suppressor using a magnetic film on coplanar transmission line

A finite-element method is applied to analyze the electromagnetic field and loss generation of a soft magnetic thin film on a coplanar transmission line for which the dimension of the magnetic film is designed to control the center frequency and bandwidth of the radio-frequency (RF) electromagnetic noise attenuation in the gigahertz range without external applied magnetic fields. The coplanar transmission line with characteristic impedance of 50 /spl Omega/ has total width, width of signal line, and thickness of 400, 50, and 3 /spl mu/m, respectively. The change of the magnetic field distribution, the induced surface current density on the coplanar transmission line, and hence the RF noise suppression by soft magnetic films are significant as a function of the width (50-2000 /spl mu/m) and thickness (0.1, 0.3, 0.5, and 1 /spl mu/m) of the magnetic film.

FEM analysis on the effects of soft magnetic film as a noise suppressor at GHz range

To investigate the rf electromagnetic noise attenuation properties by soft magnetic films, the finite element method is applied to analyze electromagnetic field and loss generation in a coplanar transmission line with soft magnetic thin film at GHz range. The coplanar transmission line is with the total width of 400 μm and 50 μm width of signal line, 3 μm thickness, respectively, and has 50 Ω characteristic impedance. The change of the magnetic field distribution, the induced surface current density on the coplanar transmission line and hence the rf noise suppression by magnetic films are significant as a function of the magnetic film width/slit width (10/3, 20/3, and 50/3 μm) and magnetic film thickness (0.1, 0.3, 0.5, and 1 μm).

Scattering from frequency selective surfaces: an efficient set of v-dipole basis functions

In this paper, a novel set of V-dipole basis functions is introduced. These basis functions are used to approximate the induced surface current density on an infinite, plane frequency selective surface (FSS). The elements of the FSS are supposed to consist of straight sections and bends. Two groups of elements which the present V-dipole basis functions can be applied to are identified, namely, the center connected elements and the loop-type elements. Using the established spectral Galerkin method, where the method of moment (MoM) procedure is carried out in the spectral domain, we determine the reflection and transmission coefficients of the FSS. The convergence of the solution is demonstrated both for existing bases and the present V-dipole basis functions. It is found that the double infinite Floquet sum diverges when existing, discontinuous, basis functions are used, but that convergence is obtained for the present basis functions. Therefore, care needs to be exercised, and it would seem discontinuous bases should be avoided.

Imaging perfectly conducting objects as support of induced currents: Kirchhoff approximation and frequency diversity.

The problem of determining the shape of perfectly conducting objects from knowledge of the scattered electric field is considered. The formulation of the problem accommodates the nature of the distribution of the induced surface current density. Thus, as the unknown representing the object's contour, a single layer distribution is chosen so that the contour of the scatterer is described by its support. The nonlinear unknown-data mapping is then linearized by means of the Kirchhoff approximation, and the problem is recast as the inversion of a linear operator acting on a distribution space. An extension of the singular value decomposition approach to solve the linearized problem is provided and numerical results are presented.

Plane-wave scattering by strip-loaded circular dielectric cylinders in the case of oblique incidence and arbitrary polarization

Plane-wave scattering by strip-loaded circular, multilayered dielectric cylinders is investigated in the most general case of oblique incidence and arbitrary polarization. The problem is formulated via systems of singular integral-integrodifferential equations of the first kind which are most efficiently discretized on the basis of previously developed analytical algorithms. Several internal tests along with extended comparisons with available results have been completed to validate the numerical codes. Plotted results for both the induced surface current densities and the total radar cross section reveal how the scattering properties may be controlled by changing several physical and geometrical parameters of the structure.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Synthesis of tapered resistive strips

A technique for synthesizing a resistive taper that generates desired bistatic scattering and backscattering patterns from a strip is outlined. Antenna synthesis techniques relate the scattered field to the induced surface current density. Physical optics approximations then relate the induced current to the resistivity. The taper is checked by computing the surface current density and scattered fields of the tapered resistive strip using the integral equation formulation and comparing with the physical optics results.

Numerical analysis of surface current distribution on an infinite plane grating

A spectral domain method combined with the sampling theorem is described for evaluation of induced surface current densities concerning an infinite plane metallic grating loaded with a dielectric layer. Two different polarizations, TM and TE excitations, are treated here. Edge condition is analytically considered, and final results show a good convergence.