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Title: ANALYSIS OF THE FINITE ELEMENT RADIATION MODEL CODE FOR ANTENNA MODELING
Abstract: The Finite Element Radiation Model (FERM) code is applied to examine radiation patterns and input impedance of various antenna con- figurations on complex helicopters. This paper addresses the strengths and weaknesses of the FERM code when applied in antenna analysis and is compared with other national codes, such as the Numerical Electromagnetics Code (NEC). In addition, guidelines are outlined for various applications of the code. [Vol. 11, No. 2 (1996), pp 4-13]
Author(s): Marcos C. Medina, Constantine A. Balanis, Jian Peng, Panayiotis A. Tirkc Panayiotis A. Tirkc
File Type: Journal Paper
Issue:Volume: 11      Number: 2      Year: 1996
Download Link:Click here to download PDF     File Size: 702 KB

Title: ACCURACY OF THE FINITE ELEMENT METHOD WITH SECOND ORDER ABSORBING BOUNDARY CONDITIONS FOR THE SOLUTION OF APERTURE RADIATION PROBLEM
Abstract: The Finite Element Method with second order Absorbing Boundary Condition is a recently developed computational technique that finds use in antenna design and Electromagnetic Compatibility simulation. To determine the accuracy of this new procedure, the problem of aperture radiation was studied. The near zone and aperture fields of a waveguide antenna computed using the Finite Element Method are compared with published data and results found using other simulation techniques. These comparisons show that the new method is accurate even when the ABC boundary conforms to the problem geometry and is placed as near as /2pi to the aperture. [Vol. 11, No. 2 (1996), pp 14-23]
Author(s): John Silvestro, Xingchao Yuan, Zoltan Cendes
File Type: Journal Paper
Issue:Volume: 11      Number: 2      Year: 1996
Download Link:Click here to download PDF     File Size: 580 KB

Title: THE FEMAX FINITE-ELEMENT PACKAGE FOR COMPUTING THREE-DIMENSIONAL ELECTROMAGNETIC FIELDS
Abstract: The structure and the properties of the FEMAX package are discussed. The FEMAX finite-element package is an efficient and highly accurate package especially designed for computing three-dimensional transient as well as time-harmonic electromagnetic fields in arbitrarily inhomogeneous, (an)isotropic media. The most unique features of the FEMAX package are that 1) the electric field strength is computed directly, i.e. without the intermediate use of (vector) potentials, 2) when inhomogeneities are encountered in the domain of computation, the package automatically chooses edge elements to ensure that all local continuity conditions can be met, nodal elements are used elsewhere, and 3) that the electromagnetic compatibility relations are taken into account in the formulation of the finite-element method used, thus avoiding spurious solutions. These features are included in the package in such a way that optimum results are obtained both in regard to computational efficiency (storage and time) and in regard to the desired accuracy. [Vol. 11, No. 2 (1996), pp 24-31]
Author(s): Gerrit Mur
File Type: Journal Paper
Issue:Volume: 11      Number: 2      Year: 1996
Download Link:Click here to download PDF     File Size: 766 KB

Title: A MOMENT METHOD FORMULATION FOR THE ANALYSIS OF WIRE ANTENNAS ATTACHED TO ARBITRARY CONDUCTING BODIES DEFINED BY PARAMETRlC SURFACE
Abstract: A Moment Method (MM) technique for the analysis of wire antennas on board resonant-sized bodies modelled with parametric surfaces is presented. The approach may have useful applications for the study of the behaviour of wire antennas on board complex conducting structures like aircrafts. The current is represented by curved rooftop functions on the body, piecewise linear functions on the wires and a new junction function in the attachment region between the body and the antenna. The bodies are precisely defined by means of a small number of NURBS surfaces (Non Uniform Rational B-Splines) and Bezier patches (BP). In addition the new junction function that can be defined over any BP allows the antenna to be attached to any part of the body. Radiation patterns and input impedance calculations for several geometries are presented to show the accuracy of the method. The results are successfully validated when comparisons with measurements or results from other methods are carried out. [Vol. 11, No. 2 (1996), pp 32-39
Author(s): F. Rivas, L. Valle, M.F. Catedra
File Type: Journal Paper
Issue:Volume: 11      Number: 2      Year: 1996
Download Link:Click here to download PDF     File Size: 534 KB

Title: A POSTERIORI ERROR ESTIMATES FOR TWO-DIMENSIONAL ELECTROMAGNETIC FIELD COMPUTATIONS: BOUNDARY ELEMENTS AND FINITE ELEMENTS
Abstract: A brief summary of the variational boundary-value problem formulation of the 2D finite element/boundary element (FE/BE) method is presented. >From this a posteriori error estimates and error indicators for the FE/BE method are developed and applied to electromagnetic scattering and radiation problems. The results obtained indicate that these error estimates and indicators can be obtained within negligible computational times and can be used successfully to obtain valuable a posteriori accuracy and convergence information regarding the reliability of the FE/BE method solutions. [Vol. 11, No. 2 (1996), pp 40-54]
Author(s): F.J.C. Meyer, D.B. Davidson
File Type: Journal Paper
Issue:Volume: 11      Number: 2      Year: 1996
Download Link:Click here to download PDF     File Size: 1233 KB

Title: MODELLING OF AN ARBITRARILY-ORIENTED MOBILE TELEPHONE HANDSET IN THE FINITE-DIFFERENCE TIME-DOMAIN FIELD COMPUTATION METHOD
Abstract: The implementation of a generic mobile telephone handset model in the Finite Difference Time Domain (FDTD) method for computation of electromagnetic field distributions is described. The handset can be rotated about the principal FDTD axes to achieve any orientation. The 'thin wire' technique is used to model the antenna in a way that ensures that its correct electrical length is maintained despite the 'staircasing' effect of the FDTD grid. Computed predictions from the model agree with near-field measurements on a physical realisation of the handset, and accurate near and far fields are calculated for arbitrary orientations of the handset. It is concluded that this wire rotation technique has broad application to problems involving components that are required to move in relation to fixed structures. [Vol. 11, No. 2 (1996), pp 55-65]
Author(s): P.S. Excell, P. Olley, N.N. Jackson
File Type: Journal Paper
Issue:Volume: 11      Number: 2      Year: 1996
Download Link:Click here to download PDF     File Size: 886 KB

Title: A MAGNETIC FIELD ITERATIVE TECHNIQUE FOR IMPROVING HIGH FREQUENCY PREDICTION METHODS
Abstract: A Magnetic Field Iterative Technique (MFIT) is developed as a technique for improving the results from high frequency based prediction methods. The technique combines the accuracy of low frequency methods with the speed of high frequency methods to develop a contraction mapping based, iterative solver, which is directly parallelizable on current massively parallel processing machines. In this paper, the MFIT is developed from a Magnetic Field Integral Equation (MFIE) and its contraction discussed. Results obtained mapping properties are using the technique and convergence properties are three dimensional perfect illustrations of the technique's presented for both two and electrically conducting (PEC) targets. [Vol. 11, No. 2 (1996), pp 66-71]
Author(s): Daniel D. Reuster, Gary A. Thiele, Paul W. Eloe
File Type: Journal Paper
Issue:Volume: 11      Number: 2      Year: 1996
Download Link:Click here to download PDF     File Size: 1171 KB

Title: MODELING OF REMOTE FIELD EDDY CURRENT TRANSIENT PHENOMENA
Abstract: An integral formulation is presented and used for the analysis of the Remote Field Eddy Current (RFEC) transient phenomena. The model presented allows simple and accurate modeling of RFEC systems in the presence of axisymmetric defects. The method has been validated first by comparison of the computed results with results obtained with an analytical model. Then the method was used to show that the Remote Field effect is mainly due to a direct induction effect rather than propagation effects. The Remote Field effect phenomena are usually analysed using a steady state domain. However, the results obtained here have shown that detection of defects is not due to a steady state phenomenon, but depends mainly on the transient signal. [Vol. 11, No. 2 (1996), pp 72- 75]
Author(s): M. Raugi, N. Ida
File Type: Journal Paper
Issue:Volume: 11      Number: 2      Year: 1996
Download Link:Click here to download PDF     File Size: 297 KB