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1.
A stable solution of time domain electric field Integral equation for thin-wire antennas using the Laguerre polynomials 总被引:5,自引:0,他引:5
Zhong Ji Sarkar T.K. Baek Ho Jung Young-Seek Chung Salazar-Palma M. Mengtao Yuan 《Antennas and Propagation, IEEE Transactions on》2004,52(10):2641-2649
In this paper, a numerical method to obtain an unconditionally stable solution of the time domain electric field integral equation for arbitrary conducting thin wires is presented. The time-domain electric field integral equation (TD-EFIE) technique has been employed to analyze electromagnetic scattering and radiation problems from thin wire structures. However, the most popular method to solve the TD-EFIE is typically the marching-on in time (MOT) method, which sometimes may suffer from its late-time instability. Instead, we solve the time-domain integral equation by expressing the transient behaviors in terms of weighted Laguerre polynomials. By using these orthonormal basis functions for the temporal variation, the time derivatives can be handled analytically and stable results can be obtained even for late-time. Furthermore, the excitation source in most scattering and radiation analysis of electromagnetic systems is typically done using a Gaussian shaped pulse. In this paper, both a Gaussian pulse and other waveshapes like a rectangular pulse or a ramp like function have been used as excitations for the scattering and radiation of thin-wire antennas with and without junctions. The time-domain results are compared with the inverse discrete Fourier transform (IDFT) of a frequency domain analysis. 相似文献
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Baek Ho Jung Sarkar T.K. Young-Seek Chung Salazar-Palma M. Zhong Ji Seongman Jang Kyungjung Kim 《Antennas and Propagation, IEEE Transactions on》2004,52(9):2329-2340
In this paper, we propose a time-domain electric field integral equation (TD-EFIE) formulation for analyzing the transient electromagnetic response from three-dimensional (3-D) dielectric bodies. The solution method in this paper is based on the Galerkin's method that involves separate spatial and temporal testing procedures. Triangular patch basis functions are used for spatial expansion and testing functions for arbitrarily shaped 3-D dielectric structures. The time-domain unknown coefficients of the equivalent electric and magnetic currents are approximated using a set of orthonormal basis function that is derived from the Laguerre functions. These basis functions are also used as the temporal testing functions. Use of the Laguerre polynomials as expansion functions for the transient portion of response enables one not only to handle the time derivative terms in the integral equation in an analytic fashion but also completely separates the space and the time variables. Thus, the time variable along with the Courant condition can be eliminated in a Galerkin formulation using this procedure. We also propose an alternative formulation using a different expansion of the magnetic current. The total computational cost for this new method is similar to that of an implicit marching-on in time (MOT)-EFIE scheme, even though at each step this procedure requires more computations. Numerical results involving equivalent currents and far fields computed by the two proposed methods are presented and compared. 相似文献
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Young-Seek Chung Sarkar T.K. Baek Ho Jung Salazar-Palma M. 《Microwave Theory and Techniques》2003,51(3):697-704
In this work, we propose a numerical method to obtain an unconditionally stable solution for the finite-difference time-domain (FDTD) method for the TE/sub z/ case. This new method does not utilize the customary explicit leapfrog time scheme of the conventional FDTD method. Instead we solve the time-domain Maxwell's equations by expressing the transient behaviors in terms of weighted Laguerre polynomials. By using these orthonormal basis functions for the temporal variation, the time derivatives can be handled analytically, which results in an implicit relation. In this way, the time variable is eliminated from the computations. By introducing the Galerkin temporal testing procedure, the marching-on in time method is replaced by a recursive relation between the different orders of the weighted Laguerre polynomials if the input waveform is of arbitrary shape. Since the weighted Laguerre polynomials converge to zero as time progresses, the electric and magnetic fields when expanded in a series of weighted Laguerre polynomials also converge to zero. The other novelty of this approach is that, through the use of the entire domain-weighted Laguerre polynomials for the expansion of the temporal variation of the fields, the spatial and the temporal variables can be separated. 相似文献
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Young‐Hwan Lee Baek Ho Jung Tapan K. Sarkar Mengtao Yuan Zhong Ji Seong‐Ook Park 《ETRI Journal》2007,29(1):8-17
In this paper, we present a time domain combined field integral equation formulation (TD‐CFIE) to analyze the transient electromagnetic response from dielectric objects. The solution method is based on the method of moments which involves separate spatial and temporal testing procedures. A set of the RWG functions is used for spatial expansion of the equivalent electric and magnetic current densities, and a combination of RWG and its orthogonal component is used for spatial testing. The time domain unknowns are approximated by a set of orthonormal basis functions derived from the Laguerre polynomials. These basis functions are also used for temporal testing. Use of this temporal expansion function characterizing the time variable makes it possible to handle the time derivative terms in the integral equation and decouples the space‐time continuum in an analytic fashion. Numerical results computed by the proposed formulation are compared with the solutions of the frequency domain combined field integral equation. 相似文献
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Wenming Yu Dagang Fang Chen Zhou 《Microwave and Wireless Components Letters, IEEE》2007,17(12):813-815
A marching-on-in-degree (MOD) based time-domain magnetic field integral equation method for bodies of revolution (BOR) is proposed and applied to obtain the induced currents on perfectly electric conducting BOR. Before this work, the time-domain integral equation method for BOR based on a marching-on-in-time procedure cannot really reduce the computational cost, since the number of unknowns cannot really be reduced. But it is the unknown reduction that serves as the key point of cost saving in BOR-problems. The method implemented in this letter can really utilize the symmetric property of BOR by applying two sets of entire domain basis functions. One is a set of scaled Laguerre polynomials inherited from common MOD method and used as temporal basis functions. The other is a Fourier series which comes from frequency domain method for solving BOR-problems. The validity, efficiency, and stability of the method are verified by several numerical examples. 相似文献
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Jiang G. X. Zhu H. B. Ji G. Q. Cao W. 《Microwave and Wireless Components Letters, IEEE》2007,17(1):1-3
A novel technique for improving the stability of time domain electric field integral equation (TD-EFIE) method is presented. The method involving the introduction of a new class of temporal basis functions employs a modified form of TD-EFIE to generate stable transient responses from arbitrarily shaped conducting objects, which possesses the advantage of simplicity in implementation. Numerical examples are given to demonstrate the accuracy and the efficiency of the proposed method 相似文献
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Wei Shao Bing-Zhong Wang Huilai Liu 《Journal of Infrared, Millimeter and Terahertz Waves》2006,27(9):1217-1225
In this paper, the application of the order-marching time-domain (OMTD) method to the solution of the cutoff frequencies of TE and TM modes in millimeter-wave waveguides is described. Starting from Maxwell’s two-dimensional (2-D) differential equations for TE or TM case, the OMTD method uses the orthonormality of weighted Laguerre polynomials and Galerkin’s testing procedure to eliminate the temporal variables and results in an order-marching scheme. To verify it’s accuracy and efficiency, the numerical results for millimeter-wave guided systems are compared with those of finite-difference time-domain (FDTD) method and analytical solutions. The OMTD method improves computational efficiency notably, especially for fine grid division problems restricted by stability constraints in the FDTD method. 相似文献
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A comparison of performance of three orthogonal polynomials in extraction of wide-band response using early time and low frequency data 总被引:1,自引:0,他引:1
Mengtao Yuan Jinhwan Koh Sarkar T.K. Wonwoo Lee Salazar-Palma M. 《Antennas and Propagation, IEEE Transactions on》2005,53(2):785-792
The objective of this paper is to generate a wideband and temporal response of three-dimensional composite structures by using a hybrid method that involves generation of early time and low-frequency information. The data in these two separate time and frequency domains are mutually complementary and contain all the necessary information for a sufficient record length. Utilizing a set of orthogonal polynomials, the time domain signal (be it the electric or the magnetic currents or the near/far scattered electromagnetic field) could be expressed in an efficient way as well as the corresponding frequency domain responses. The available data is simultaneously extrapolated in both domains. Computational load for electromagnetic analysis in either domain, time or frequency, can be thus significantly reduced. Three orthogonal polynomial representations including Hermite polynomial, Laguerre function and Bessel function are used in this approach. However, the performance of this new method is sensitive to two important parameters-the scaling factor l/sub 1/ and the expansion order N. It is therefore important to find the optimal parameters to achieve the best performance. A comparison is presented to illustrate that for the classes of problems dealt with, the choice of the Laguerre polynomials has the best performance as illustrated by a typical scattering example from a dielectric hemisphere. 相似文献
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Wei Shao Bing-Zhong Wang Xiao-Hua Wang Xiao-Fei Liu 《Electromagnetic Compatibility, IEEE Transactions on》2006,48(3):442-448
An efficient time-domain method based on a compact two-dimensional (2-D) finite-difference time-domain (FDTD) method combined with weighted Laguerre polynomials has been proposed to analyze the propagation properties of uniform transmission lines. Starting from Maxwell's differential equations corresponding to the compact 2-D FDTD method, we use the orthonormality of weighted Laguerre polynomials and Galerkin's testing procedure to eliminate the time variable. Thus, an implicit relation, which results in a marching-on-in-degree scheme, can be obtained. To verify the accuracy and efficiency of the hybrid method, we compare the results with those from the conventional compact 2-D FDTD and compact 2-D alternating-direction-implicit (ADI) FDTD methods. The hybrid method improves the computational efficiency notably, especially for complex problems with fine structure details that are restricted by stability constrains in the FDTD method. 相似文献
15.
To analyze a wire antenna excited by a time varying voltage source or a wire scatterer excitated by transient electromagnetic incident wave, the problem is formulated in terms of a time-domain integral equation for the induced current. To solve the integral equation, we reduce it to matrix equation via the method of moments using the known-to-be-stable implicit scheme. However, rather than directly constructing and solving the relatively large matrix equation, we propose an iterative procedure which allows us to gradually obtain a solution of refined accuracy both everywhere and simultaneously at any time instance. To render this procedure rapidly converging, we use a basis of spatio-temporal wavelet functions. This basis facilitates a good approximation of the induced current using far less basis functions than would be needed if other expansions, such as standard-pulse or Fourier basis functions were chosen. The use of this basis further enables the iterative procedure to increase the temporal and spatial resolutions where required without unnecessarily affecting their levels elsewhere. 相似文献
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The application of the finite-difference time-domain (FDTD) technique to problems in ionospheric radio wave propagation is complicated by the dispersive nature of the ionospheric plasma. In the time domain, the electric displacement is the convolution of the dielectric tensor with the electric field, and thus requires information from the entire signal history. It is shown that this difficulty can be avoided by returning to the dynamical equations from which the dielectric tensor is derived. By integrating these differential equations simultaneously with the Maxwell equations, temporal dispersion is fully incorporated. An FDTD approach utilizing the vector wave equation is also presented. The accuracy of the method is shown by comparison for a special case for which an analytic solution is available. The method is demonstrated with examples of pulse propagation in one and two dimensions. The computational limitations of present-generation computers are discussed. The application of this approach to the study of wave propagation in randomly structured ionization is addressed 相似文献
17.
Cerri G. de Leo R. de Rentiis R. Primiani V.M. 《Electromagnetic Compatibility, IEEE Transactions on》1997,39(4):377-386
This paper presents a time domain approach for the analysis of the coupling between an electrostatic discharge (ESD) current and the internal region of a shielded enclosure with a slot. The application of the equivalence principle allows us to obtain an integro-differential equation for the unknown distribution of the aperture electric field. The numerical solution is obtained by an iterative procedure developed by the method of moments (MoM) in the time domain. The approach is also applied at the case of a transient incident field of a plane wave impinging on the enclosure. The use of proper impulse responses for the space and cavity regions make the model efficient from a computational point of view, without loss in accuracy. Theoretical results are validated by measurements 相似文献
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Shyh-Kang Jeng 《Antennas and Propagation, IEEE Transactions on》1990,38(10):1523-1529
Two-dimensional transverse electric wave scattering from a cavity-backed slit in a ground plane is analyzed by R.F. Harrington and J.R. Mautz's (1976) generalized network formulation. The admittance matrix of the cavity or arbitrary shape and medium is obtained by the finite-element method. A variational equation for the cavity problem is established and then discretized to a matrix equation. An efficient algorithm using the modified frontal-solution algorithm is developed to solve the matrix equation. The solution is manipulated to get the admittance matrix of the cavity. The computed admittance matrix is added to the radiation admittance matrix of the equivalent magnetic current on a ground plane and is used to solve for the equivalent magnetic current on the slit. Numerical results for trapezoidal and coated rectangular cavities are included 相似文献
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Presented here is a method for computing near- and far-field patterns of an antenna from its near-field measurements taken over an arbitrarily shaped geometry. This method utilizes near-field data to determine an equivalent electric current source over a fictitious surface which encompasses the antenna. This electric current, once determined, can be used to ascertain the near and the far field. This method demonstrates the concept of analytic continuity, i.e., once the value of the electric field is known for one region in space, from a theoretical perspective, its value for any other region can be extrapolated. It is shown that the equivalent electric current produces the correct fields in the regions in front of the antenna regardless of the geometry over which the near-field measurements are made. In this approach, the measured data need not satisfy the Nyquist sampling criteria. An electric field integral equation is developed to relate the near field to the equivalent electric current. A moment method procedure is employed to solve the integral equation by transforming it into a matrix equation. A least-squares solution via singular value decomposition is used to solve the matrix equation. Computations with both synthetic and experimental data, where the near field of several antenna configurations are measured over various geometrical surfaces, illustrate the accuracy of this method 相似文献