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| Title: | HYBRID MULTIPOLE-BEAM APPROACH TO ELECTROMAGNETIC SCATTERING PROBLEMS |
| Abstract: | A hybrid technique combining the Complex Multipole Beam Approach (CMBA) with the Method of Moments (MoM) for the solution of the problems of electromagnetic scattering is presented in this paper. In this technique the CMBA provides for a substantial reduction in the matrix size by taking advantage of the essentially band-limited spatial spectrum of the scattered field in the vicinity of smooth surfaces, while the MoM is employed for the modeling of non-smooth or inhomogeneous regions within the problem geometry. The key step in the CMBA is to represent the scattered field in terms of a series of beams produced by multipole sources located in a complex space. The CMBA not only reduces the number of unknowns, but also generates a generalized impedance matrix with a banded structure and a low condition number. In the present hybrid technique, the scattering properties of each complex region, requiring a relatively large number of unknowns per unit volume, are described in terms of a Beam-matrix, which is constructed numerically to relate the amplitudes of outgoing beams to those of incoming ones. The proposed direct solution scheme takes into account the interactions between all of the complex regions and the smooth portions of the scatterer geometry using an algorithm similar to the recursive T-matrix approach. This hybrid technique, that combines the CMBA with other conventional methods, is a versatile tool, and is expected to enhance the scope of application of the CMBA to a much wider class of problems. (Vol. 9, No. 3 (1994), Special Issue on Generalized Multipole Technique (GMT), pp 7- 17] |
| Author(s): | A. Boag, E. Michielssen, R. Mittra, A. Boag, E. Michielssen, R. Mittra |
| File Type: | Journal Paper |
| Issue: | Volume: 9 Number: 3 Year: 1994 |
| Download Link: | Click here to download PDF File Size: 2475 KB |
| Title: | ON THE COMBINATION OF MMP WITH MOM |
| Abstract: | The Multiple Multipole Program (MMP) [1] is based on the Generalized Multipole Technique (GMT) [2]. This method lies between a purely analytic solution and the well-known Method of Moments (MoM) [3]. The goal of this paper is to demonstrate how a combination of MMP with MoM can be achieved for obtaining more powerful codes. The combination presented here is based on an implementation of rooftop functions as a new type of basis function in 3D MMP. Since users of this code are often interested in the close near-field, a special implementation of rooftop functions is presented and tested. (Vol. 9, No. 3 (1994), Special Issue on Generalized Multipole Technique (GMT), pp 18-27] |
| Author(s): | Ch. Hafner, J. Waldvogel, J. Mosig, J. Zheng, Y. Brand, Ch. Hafner, J. Waldvogel, J. Mosig, J. Zheng, Y. Brand |
| File Type: | Journal Paper |
| Issue: | Volume: 9 Number: 3 Year: 1994 |
| Download Link: | Click here to download PDF File Size: 6282 KB |
| Title: | MMP-CG-PET: THE PARAMETER ESTIMATION TECHNIQUE APPLIED TO THE MMP CODE WITH THE METHOD OF CONJUGATE GRADIENTS |
| Abstract: | The Parameter Estimation Technique (PET) is presented as a new technique that can be applied to numerical codes based on dense matrices as a power booster for the computation of frequency plots, etc. In this paper it is applied to the Multiple Multipole Program (MMP) in conjunction with the method of Conjugate Gradients (CG) for iteratively and efficiently solving the rectangular MMP matrix. The PET takes advantage of the a priori knowledge obtained from previous computations and allows to a dramatic reduction of the computation time in various situations. It is demonstrated that one of the most important drawbacks in the use of frequency domain methods based on dense matrices as opposed to time domain methods based on iterative techniques can be eliminated using PET. [Vol. 9, No. 3 (1994), Special Issue on Generalized Multipole Technique (GMT), pp 28-38] |
| Author(s): | Ch. Hafner, Ch. Hafner |
| File Type: | Journal Paper |
| Issue: | Volume: 9 Number: 3 Year: 1994 |
| Download Link: | Click here to download PDF File Size: 5704 KB |
| Title: | COMPARISON OF DIFFERENT GMT-BASED APPROACHES TO CALCULATE THE FIELD DISTRIBUTION IN RECTANGULAR CAVITIES |
| Abstract: | Different GMT based approaches are applied to the problem of field distributions inside shielded rooms. These approaches are discussed and compared by means of modelling, computation time and accuracy of the results compared to a reference solution. The aim is to find a calculation procedure which allows one to compute the frequency behaviour of different test setups and different environment parameters. The usual MMP approach with a special placement of the expansion functions turns out to be the most efficient and accurate way to solve this kind of problem. [Vol. 9, No. 3 (1994), Special Issue on Generalized Multipole Technique (GMT), pp 39-45] |
| Author(s): | J. Froehlich, G. Klaus, J. Froehlich, G. Klaus |
| File Type: | Journal Paper |
| Issue: | Volume: 9 Number: 3 Year: 1994 |
| Download Link: | Click here to download PDF File Size: 5495 KB |
| Title: | ELECTROMAGNETIC SCATTERING ANALYSIS BASED ON DISCRETE SOURCES METHOD |
| Abstract: | In this paper we examine theoretical and computational aspects of Discrete Sources Method applied to the solution of time-harmonic electromagnetic scattering problems. [Vol. 9, No. 3 (1994), Special Issue on Generalized Multipole Technique (GMT), pp 46-56] |
| Author(s): | Yu.A. Eremin, N.V. Orlov, A.G. Sveshnikov, Yu.A. Eremin, N.V. Orlov, A.G. Sveshnikov |
| File Type: | Journal Paper |
| Issue: | Volume: 9 Number: 3 Year: 1994 |
| Download Link: | Click here to download PDF File Size: 786 KB |
| Title: | MODIFIED REFLECTIVE SYMMETRIES FOR IMPROVING THE EFFICIENCY OF THE MMP CODES |
| Abstract: | A more general concept for the treatment of symmetry in the 3D MMP codes allows considerable gains in usability. Up to now, symmetry decomposition of functions has been made with functions that are continuous across the symmetry plane. Now discontinuous symmetrizations are added. Possible continuity conditions in the symmetry plane can be enforced explicitly with matching points. Not only are problem sizes reduced, but the creation of good models in the MMP sense is considerably simplified in some common applications. The improved approach also illustrates some of the "classical" methods for calculating obstacles in waveguides. [Vol. 9, No. 3 (1994), Special Issue on Generalized Multipole Technique (GMT), pp 57-62] |
| Author(s): | Fin O. Bomholt, Lars H. Bomholt, Fin O. Bomholt, Lars H. Bomholt |
| File Type: | Journal Paper |
| Issue: | Volume: 9 Number: 3 Year: 1994 |
| Download Link: | Click here to download PDF File Size: 483 KB |
| Title: | COUPLING OF THE GENERALIZED MULTIPOLE TECHNIQUE AND THE FINITE ELEMENT METHOD |
| Abstract: | This paper presents a coupling of two different methods for electromagnetic scattering problems, the 3D MMP (Multiple MultiPole), code, an implementation of the Generalized Multipole Technique (GMT) and the finite element (FE) method. The coupling is performed using iterative methods. The procedure is illustrated with the solution of a benchmark problem for scattering from a three-dimensional lossy dielectric cylinder. [Vol. 9, No. 3 (1994), Special Issue on Generalized Multipole Technique (GMT), pp 63-68] |
| Author(s): | Lars H. Bomholt, Lars H. Bomholt |
| File Type: | Journal Paper |
| Issue: | Volume: 9 Number: 3 Year: 1994 |
| Download Link: | Click here to download PDF File Size: 3747 KB |
| Title: | MMP MODELING TECHNIQUES WITH CURVED LINE MULTIPOLES |
| Abstract: | The MMP modeling of different scattering structures is discussed. It is shown that highly accurate near and farfield simulations are possible, not only for simple academic structures such as spheres or cubes, but also for a multiturn helical wire of finite thickness and an absorbing ferrite cylinder placed on a cable. Some typical problem classifying figures (symmetry, error, number of equations, matching points etc.) are defined in order to classify and compare different problems. MMP's symmetry exploitation concept (reducing both memory and cpu time) is explained. Although the amount of calculation increases when edges or tips are present, rather small radii of curvature may be treated using (curved or straight) line multipoles. [Vol. 9, No. 3 (1994), Special Issue on Generalized Multipole Technique (GMT), pp 69-78] |
| Author(s): | P. Leuchtmann, P. Leuchtmann |
| File Type: | Journal Paper |
| Issue: | Volume: 9 Number: 3 Year: 1994 |
| Download Link: | Click here to download PDF File Size: 7421 KB |
| Title: | PERFORMANCE OF THE GENERALIZED MULTIPOLE TECHNIQUE (GMT/MMP) IN ANTENNA DESIGN AND OPTIMIZATION |
| Abstract: | During the last decade, the generalized multipole technique (GMT) has been extensively studied, improved and applied to many electromagnetics problems such as bioelectromagnetics, optics, waveguides and electromagnetic compatibility (EMC), but little has been reported towards utilizing this method for antenna design and optimization. On the other hand, the few published examples of simple dipoles and helices in the close vicinity of lossy scatterers have suggested the potential significance of GMT for antenna design purposes. In this paper, the applicability of the GMT based 3D multiple multipole (3D MMP) code for simulation of wire antenna has been investigated. To evaluate the advantages and limitations of 3D MMP, several basic types of wire antenna configurations were simulated. These were linear and linear array, helical, and physically constrained low profile antennas. To validate the method's performance, we calculated radiation patterns, impedance, return loss, reflection coefficient, VSWR, and compared them to available results from experiments and/or results published by others using different techniques. This investigation showed several conceptual advantages of this technique for antenna simulations. Furthermore, the thin-wire expansion in combination with multipoles and roof top functions provides a great degree of flexibility in modeling. The most recently implemented expansion, "line multipoles," extends the code's efficiency to non-thin-wire configurations (e.g., helix with small ratio of pitch to wire diameter). Critical issues of modeling are the feedpoint and wire tip area, matching point locations and segment length-to- diameter ratio. Symmetries are used where possible to minimize computation time without loss of generality as any antenna element may easily be assembled in non- symmetrical configurations with the block-iterative solver. In order to achieve better confidence on more complex configurations, extensive studies were performed to increase efficiency and stability of modeling and will be discussed. In addition, the numerical validation techniques were extended to satisfy the special requirements of antenna simulations. These studies demonstrate the potential of GMT/MMP for use in analysis, synthesis and optimization of antennas. [Vol. 9, No. 3 (1994), Special Issue on Generalized Multipole Technique (GMT), pp 79-89] |
| Author(s): | Roger Yew-Siow Tay, Niels Kuster, Roger Yew-Siow Tay, Niels Kuster |
| File Type: | Journal Paper |
| Issue: | Volume: 9 Number: 3 Year: 1994 |
| Download Link: | Click here to download PDF File Size: 3160 KB |
| Title: | THE METHOD OF FICTITIOUS SOURCES APPLIED TO DIFFRACTION GRATINGS |
| Abstract: | This paper deals with grating diffraction in electromagnetic theory, using the method of fictitious sources. We present a detailed description of the method, and we lay stress on its numerical implementation. Numerical examples are given for various grating profiles, and compared to those obtained with other methods. An efficient method for the computation of the Green's function for gratings and its derivatives is given. [Vol. 9, No. 3 (1994), Special Issue on Generalized Multipole Technique (GMT), pp 90-100] |
| Author(s): | G. Tayeb, G. Tayeb |
| File Type: | Journal Paper |
| Issue: | Volume: 9 Number: 3 Year: 1994 |
| Download Link: | Click here to download PDF File Size: 1097 KB |
| Title: | THE METHODS FOR SOLVING THE PROBLEMS OF THE DIFFRACTION OF ELECTROMAGNETIC AND ACOUSTIC WAVES USING THE INFORMATION ON ANALYTICAL PROPERTIES OF THE SCATTERED FIELDS |
| Abstract: | In spite of impressive achievements in computing technology, the study of numerical-analytical methods for solving boundary value problems in physical diffraction theory continues to be of paramount importance. This is a consequence of the fact that using such methods, we obtain a significant portion of information on solution properties at the stage of analytical investigation of the problem. This information is introduced in the problem algorithm, thus ensuring its adequacy to the problem and, consequently, its effectiveness, stability, high-performance capability etc. Conversely, ignoring the analytical solution properties results, at best, in low speed of convergence and may involve the complete loss of stability, i.e. "computation catastrophe". In this study we examine some approaches to solving boundary problems in electrodynamics and acoustics using a-priory information on analytical solution properties. [Vol. 9, No. 3 (1994), Special Issue on Generalized Multipole Technique (GMT), pp 101-111] |
| Author(s): | A.G. Kyurkchan, A.I. Sukov, A.I. Kleev, A.G. Kyurkchan, A.I. Sukov, A.I. Kleev |
| File Type: | Journal Paper |
| Issue: | Volume: 9 Number: 3 Year: 1994 |
| Download Link: | Click here to download PDF File Size: 961 KB |