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We have presented rapidly hybrid spectral-spatial techniques for the rapid calculation of 3D Green's functions of a linear periodic array residing in near a layered medium. The techniques are based on spectral field expansion over the transverse (to the array's axis) spectral parameter, extraction any singular field components, and efficient integration rules. The techniques are efficient for any...
The new algorithm developed presents an advance in the analysis of the radiation pattern of antennas on board complex targets. The results shown verify the accuracy of this method and the efficiency in terms of CPU time.
RT (ray tracing) tools are commonly used to simulate UWB-IR (ultra wideband-impulse radio) propagation channel for different applications like network optimization, interference monitoring, or localization based applications. In this paper, different methods of reconstructing received signal in RT tools are presented, concluding that they are not all equivalent from digital implementation point of...
A real-time UWB positioning system has been developed which has dynamic 3D accuracy of better than 6 mm and static 3D accuracy of 3-4 mm. This accuracy is an order of magnitude higher than currently available commercial UWB tracking systems and opens up new applications for indoor wireless positioning including robot tracking, patient monitoring, and tracking during computer assisted surgeries. 3D...
Loop-tree bases are used to model the object in the current EPA scheme. Compared to the RWG based EPA, the new method can deal with the low frequency problem more accurately. Numerical results show the validity of the proposed scheme. More realistic and complicated testing examples will be considered in the future work.
In this work, a response of a resonant structure is represented as a finite sum of weighted orthogonal polynomials and pole terms. The driving-point current of a resonant antenna is extrapolated with each pole-estimation method and accuracy is studied as a function of the amount of early-time and low-frequency data used. Computational electromagnetic (CEM) methods are often used to numerically compute...
The "Wheeler Cap" can be used to determine the radiation efficiency of electrically small antennas very accurately. The purpose of this paper is to simulate the improved Wheeler Cap measurement method with a Vivaldi antenna. The WIPL-D simulation tool is used to simulate the antenna in free space and in the Cap. This process can be used to test the accuracy of the improved Wheeler Cap method...
When the 3D building structures visualized in Google Earth are reconstructed using photogrametric method, errors or inaccuracies will occur to the building vertices and the building heights. In this paper the statistics of these errors are discussed and the effect of these errors on the propagation prediction results is examined in detail. It is found that our reconstruction method introduces distance...
This paper remarks IDR(s) method as an alternative solver for GMRES(m) method. A preconditioned IDR(s) algorithm is presented. Performance evaluations are done for the computation of the dense linear system of equations of order 105 followed by BEM analysis of EM multiple scattering. IDR(s) method with the optimal parameters (5 < s < 10) converges faster than GMRES(mmax) method, using small...
In this work, an H2 matrix was constructed to represent the dense system matrix resulting from integral-equation-based analysis of electrodynamic problems. The H- and H2-matrix framework is a general mathematical framework that enables a highly compact representation and efficient numerical computation of dense matrices. Here, fast multiple based methods, fast low-rank compression methods, and FFT-based...
Large planar microwave structures, such as frequency selective surfaces and reflectarrays, are of practical use in many applications. These structures' scattering cross sections are of great interest to the design engineer. In the work Ginste et al. (2006) a perfectly matched layer based multilevel fast multipole algorithm (PML-MLFMA) was presented to accelerate the classical method of moments (MOM)...
High-order techniques have been proposed for obtaining high accuracy and rapid convergence in numerical solutions of integral equations for electromagnetics. Results obtained for structures with smooth surfaces exhibit relatively low errors, and the rate of decrease in the error improves with reduced cell sizes as either the basis function or the representation order increases. Recent publications...
Oblique Fibonacci samplings provide a methodology to improve the accuracy of numerical calculations for various antenna performance parameters since they are not parallel to the radiation pattern similarities. Conclusions drawn from the periodic array example illustrate how this method can reduce the amount of time required to evaluate far field radiation characteristics of antennas.
The paper introduces a method to cover several wire segments with a single basis function, describes related practical algorithms, and gives some results. The process involves three steps: identifying chains of wire segments, splitting the chains into shorter sub-chains, and assigning basis functions to the resulting geometrical structures. The method may improve efficiency of computations when modeling...
Surface integral equations (SIEs) are commonly used to formulate scattering and radiation problems involving three-dimensional metallic and homogeneous dielectric objects with arbitrary shapes. For numerical solutions, equivalent electric and/or magnetic currents defined on surfaces are discretized and expanded in a series of basis functions. Then, the boundary conditions are tested on surfaces via...
The error controllability of fast algorithms, such as the fast multipole method (FMM) and the multilevel fast multipole algorithm (MLFMA), is an important issue. On the one hand, it is crucial that the error sources can be clearly identified. On the other hand, heuristics need to be implemented that allow an easy automatic error setting of the fast algorithms. An error analysis has already been conducted...
We present the solution of extremely large electromagnetics problems formulated with surface integral equations (SIEs) and discretized with hundreds of millions of unknowns. Scattering and radiation problems involving three-dimensional closed metallic objects are formulated rigorously by using the combined-field integral equation (CFIE). Surfaces are discretized with small triangles, on which the...
The goal of this paper is to investigate how accuracy and efficiency of MLFMM of a given level depends on the order of approximation. We performed this investigation using a corner scatterer of side 20 lambda as a benchmark. We chose this model because its RCS results show several distinctive lobes in specific directions and at different levels, calculation of which is challenging even for direct...
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