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Antennas and Propagation, IEEE Transactions on

Issue 9 • Date Sept. 2005

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Displaying Results 1 - 25 of 50
  • Table of contents

    Publication Year: 2005 , Page(s): c1 - 2781
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  • IEEE Transactions on Antennas and Propagation publication information

    Publication Year: 2005 , Page(s): c2
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  • Characterization of effects of periodic and aperiodic surface distortions on membrane reflector antennas

    Publication Year: 2005 , Page(s): 2782 - 2791
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1640 KB) |  | HTML iconHTML  

    The focus of this paper is to characterize the effects of periodic and aperiodic surface distortions on the performance of membrane reflector antennas. Since the surface of this class of reflector antennas is very thin, it is susceptible to various types of periodic and aperiodic distortions. The particular antenna dimensions used for this study are similar to the specifications for the JPL/UCLA half scale model of second generation precipitation radar (PR-2) mission reflector. Analytical expressions are introduced to model periodic and aperiodic surfaces and based on these models the effects of distortions on the radiation performance of the antenna are simulated. Aperiodic distortions are more realistic cases of distortions due to the fact that the period of the distortions is not constant through out the reflector surface. For each case, far-field patterns of the reflector are simulated and it is shown that closed-form expressions can then be derived which result in a very efficient computational method to predict some of the unique features of these patterns including location and level of observed grating lobes. Furthermore, based on spatial Fourier analysis of the surface distortion, it is shown that deviation from periodicity in the distortions of reflector surface results in lowering these grating lobes. Parametric studies have been performed to provide design guidelines for acceptable surface behavior for large deployable membrane reflector antennas for future space borne missions. View full abstract»

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  • A high efficiency offset-fed X/ka-dual-band reflectarray using thin membranes

    Publication Year: 2005 , Page(s): 2792 - 2798
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (936 KB) |  | HTML iconHTML  

    Modern space-borne applications require large-aperture antennas having capabilities of low mass and high packaging efficiency to overcome the launch vehicle size and weight restrictions. This paper presents a dual-band reflectarray antenna developed for future space inflatable structures with thin membranes. To offset the effects of the thin-membrane substrates required in the inflatable structure, foam layers are inserted below the X and Ka band membranes, allowing broadband CP performance at both bands. More than 50% efficiencies are achieved at both frequency bands, showing potential for even larger high-gain inflatable antennas for future space applications. View full abstract»

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  • Classical axis-displaced dual-reflector antennas for omnidirectional coverage

    Publication Year: 2005 , Page(s): 2799 - 2808
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1072 KB) |  | HTML iconHTML  

    The aim of this work is to discuss the synthesis and performance of classical dual-reflector antennas suited for an omnidirectional coverage. The reflector arrangements are axially symmetric with surfaces of revolution generated by axis-displaced conic sections, established from geometrical-optics (GO) standpoints to achieve omnidirectional radiation characteristics. Closed-form equations are derived for the design of all possible reflector configurations. The vector GO aperture field is also obtained, yielding an approximate analysis by the aperture method. Some pertinent geometrical characteristics and efficiency curves are then presented and discussed for several antenna configurations fed by transverse electromagnetic coaxial horns (for vertical polarization). A practical antenna design is conducted and analyzed by the method-of-moments technique, demonstrating the accuracy of the efficiency analysis yield by the aperture method for moderately large antenna apertures. View full abstract»

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  • Microstrip-fed slot antennas with suppressed harmonics

    Publication Year: 2005 , Page(s): 2809 - 2817
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (768 KB) |  | HTML iconHTML  

    In this paper, microstrip-fed slot antennas with suppressed harmonics are proposed. To obtain this operation, conductor lines connected with ground plane are inserted in slot antennas. To verify the validation of the proposed antennas, the equivalent circuit analysis is presented. Also, the miniaturization and bandwidth enhancement of the antenna for various applications are achieved and analyzed through parameter study. From the measured return losses, input impedances, and radiation patterns, it is shown that the proposed antennas offer excellent harmonic suppression characteristic in harmonic bandwidth including the second and third harmonic frequencies. View full abstract»

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  • A new aperture coupled microstrip slot antenna

    Publication Year: 2005 , Page(s): 2818 - 2826
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (864 KB) |  | HTML iconHTML  

    A new aperture coupled design is proposed for microstrip slot antennas to improve their radiation performance. The proposed design is based on a new aperture coupling technique in which the slot is fed by a microstrip line and coupled to several parasitic patch radiators etched on the opposite side from the slot. In contrast to the combination of a slot and a microstrip patch in conventional aperture coupled microstrip antennas, the patches here are employed to reduce the radiation into the half-space that they occupy and increase the radiation in the other half-space. Therefore, the slot antenna can produce radiation patterns with a high front-back ratio. The above objective is achieved by optimizing standing wave distributions of the aperture electric field in the slot through the adjustment of the position of the patches along the axis of the slot. In this paper, design considerations are given, and the results are validated by numerical simulations and experimental measurements. View full abstract»

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  • Linearly and curvilinearly tapered cylindrical- dielectric-rod antennas

    Publication Year: 2005 , Page(s): 2827 - 2833
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB) |  | HTML iconHTML  

    The body-of-revolution finite-difference time-domain (BOR-FDTD) method is applied to the analysis of a tapered cylindrical-dielectric-rod fed by a metallic waveguide with a launching horn. Before evaluating the wave propagating along the tapered rod, we design the launching horn to efficiently excite the fundamental guided-mode of a uniform rod. After confirming the effectiveness of the launching horn, guided-mode conversion properties are evaluated in linearly and curvilinearly tapered rods. As a result, the guided mode excited at the feed end is smoothly converted into that at the free end in a curvilinearly tapered rod. It is numerically revealed that the smooth guided-mode conversion leads to the expansion of the equiphase field region in a terminal aperture with a subsequent increase in the gain. The calculated radiation patterns are in good agreement with experimental data. View full abstract»

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  • Analysis and design of periodic leaky-wave antennas for the millimeter waveband in hybrid waveguide-planar technology

    Publication Year: 2005 , Page(s): 2834 - 2842
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1376 KB) |  | HTML iconHTML  

    This work presents a full-wave integral equation approach specifically conceived for the analysis and design of laterally-shielded rectangular dielectric waveguides, periodically loaded with planar perturbations of rectangular shape. This type of open periodic waveguide supports the propagation of leaky-wave modes, which can be used to build leaky-wave antennas which exhibit many desirable features for millimeter waveband applications. The particularities of the leaky-mode analysis theory are described in this paper, and comparisons with other methods are presented for validation purposes. Using this leaky-mode analysis method, a novel periodic leaky-wave antenna is presented and designed. This novel antenna shows some important improvements with respect to the features of previously proposed antennas. The results of the designed radiation patterns are validated with three-dimensional electromagnetic analysis using commercial software. View full abstract»

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  • Absorption efficiency of receiving antennas

    Publication Year: 2005 , Page(s): 2843 - 289
    Cited by:  Papers (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB) |  | HTML iconHTML  

    A receiving antenna with a matched load will always scatter some power. This paper sets an upper and a lower bound on the absorption efficiency (absorbed power over sum of absorbed and scattered powers), which lies between 0 and 100% depending on the directivities of the antenna and scatter patterns. It can approach 100% as closely as desired, although in practice this may not be an attractive solution. An example with a small endfire array of dipoles shows an efficiency of 93%. Several examples of small conical horn antennas are also given, and they all have absorption efficiencies less than 50%. View full abstract»

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  • Superdirectivity in MIMO systems

    Publication Year: 2005 , Page(s): 2850 - 2857
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB) |  | HTML iconHTML  

    Multiantenna systems such as devices for multiple-input-multiple-output (MIMO) communication can theoretically use array superdirectivity to optimally exploit the propagation channel. In traditional analyses of MIMO systems, such superdirectivity is not observed due to the commonly applied constraint that limits the excitation current magnitudes. However, when an electromagnetically appropriate constraint on the power radiated by the array is applied, the computed capacity can include effects of transmit superdirectivity. A similar result occurs at the receiver for spatially colored noise. This paper formulates the MIMO system capacity under these circumstances and provides a framework for computing this capacity when the level of tolerable superdirectivity (as measured by the superdirectivity Q factor) is constrained. Example computations using the framework illustrate the impact that superdirectivity can have on achievable MIMO system performance. View full abstract»

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  • Interleaved thinned linear arrays

    Publication Year: 2005 , Page(s): 2858 - 2864
    Cited by:  Papers (27)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB) |  | HTML iconHTML  

    This paper presents three approaches to improving the efficiency of an array aperture by interleaving two arrays in the same aperture area. The interleaved arrays have aperiodic spacings that are integer multiples of a set minimum spacing and are optimized to reduce the maximum sidelobe level. Fully and partially interleaved sum arrays operating at the same frequencies are demonstrated as well as interleaved sum and difference arrays for a monopulse system. A genetic algorithm is used to optimize arrays of isotropic point sources as well as arrays of dipoles modeled using the method of moments. Narrow beamwidths are possible while avoiding high sidelobes. The available aperture area is efficiently used. View full abstract»

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  • A slotted post-wall waveguide array with interdigital structure for 45° linear and dual polarization

    Publication Year: 2005 , Page(s): 2865 - 2871
    Cited by:  Papers (39)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1064 KB) |  | HTML iconHTML  

    This work proposes a dual-polarized planar antenna; two post-wall slotted waveguide arrays with orthogonal 45° linearly-polarized waves interdigitally share the aperture on a single layer substrate. Uniform excitation of the two-dimensional slot array is confirmed by experiment in the 25 GHz band. The isolation between two slot arrays is also investigated in terms of the relative displacement along the radiation waveguide axis in the interdigital structure. The isolation is 33.0 dB when the relative shift of slot position between the two arrays is -0.5λg, while it is only 12.8 dB when there is no shift. The cross-polarization level in the far field is -25.2 dB for a -0.5λg shift, which is almost equal to that of the isolated single polarization array. It is degraded down to -9.6 dB when there is no shift. View full abstract»

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  • Artificially integrated synthetic rectangular waveguide

    Publication Year: 2005 , Page(s): 2872 - 2881
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1472 KB) |  | HTML iconHTML  

    A synthetic rectangular waveguide (SRW), which consists of two electrical sidewalls and two parallel periodical structures placed at the top and bottom surfaces of the waveguide, is presented. The SRW is made by multilayered integrated circuit processes, which typically have large ratios of SRW lateral dimensions to substrate thickness. Two theoretical methods, finite-element method and deembedding of composite structure consisting of SRW and mode converters, are applied to investigate the propagation characteristics of the SRW. Application of the dispersion characteristics of the two-dimensional periodical structures coupled with appropriate mode converter designs leads to results in SRW designs supporting TE10, TM00, and TM10 modes. Measurements and the two theoretical approaches indicate that the slow-wave factor is 4.9 and Q-factor is 260 at 6.85 GHz for the TE10 mode propagation with a cutoff frequency of 4.10 GHz (0.348 factor of cutoff frequency of conventional rectangular waveguide using the same material and dimensions). The theoretical data show the TM00 mode to have a slow-wave factor of 1.8, Q-factor of 187.6 at 11.4 GHz, and cutoff frequency of 10.2 GHz. The TM10 mode has a slow-wave factor of 1.98, Q-factor of 187.6 at 12.5 GHz, and cutoff frequency of 10.4 GHz. View full abstract»

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  • Unified frequency and time-domain antenna modeling and characterization

    Publication Year: 2005 , Page(s): 2882 - 2888
    Cited by:  Papers (44)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1264 KB) |  | HTML iconHTML  

    A new methodology is presented for characterizing an antenna system in both the time and frequency domains with one set of parameters using a singularity expansion method representation. A minimal parameter set for modeling antenna systems has been demonstrated using the matrix-pencil method. It has been shown that it is possible to obtain frequency-domain patterns from pole/residue models of antenna realized effective length. Thus, a pole/residue model of the antenna realized effective length presents a complete description in both the time and frequency domains. Once such a model is available, one can obtain the antenna pattern, directivity, and gain in the frequency domain and the radiated transient waveform for an arbitrary excitation waveform and an arbitrary antenna orientation. View full abstract»

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  • High spatial order finite element method to solve Maxwell's equations in time domain

    Publication Year: 2005 , Page(s): 2889 - 2899
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    This paper presents a finite element method with high spatial order for solving the Maxwell equations in the time domain. In the first part, we provide the mathematical background of the method. Then, we discuss the advantages of the new scheme compared to a classical finite-difference time-domain (FDTD) method. Several examples show the advantages of using the new method for different kinds of problems. Comparisons in terms of accuracy and CPU time between this method, the FDTD and the finite-volume time-domain methods are given as well. View full abstract»

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  • A generalized mass lumping technique for vector finite-element solutions of the time-dependent Maxwell equations

    Publication Year: 2005 , Page(s): 2900 - 2910
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (720 KB) |  | HTML iconHTML  

    Time-domain finite-element solutions of Maxwell's equations require the solution of a sparse linear system involving the mass matrix at every time step. This process represents the bulk of the computational effort in time-dependent simulations. As such, mass lumping techniques in which the mass matrix is reduced to a diagonal or block-diagonal matrix are very desirable. In this paper, we present a special set of high order 1-form (also known as curl-conforming) basis functions and reduced order integration rules that, together, allow for a dramatic reduction in the number of nonzero entries in a vector finite element mass matrix. The method is derived from the Nedelec curl-conforming polynomial spaces and is valid for arbitrary order hexahedral basis functions for finite-element solutions to the second-order wave equation for the electric (or magnetic) field intensity. We present a numerical eigenvalue convergence analysis of the method and quantify its accuracy and performance via a series of computational experiments. View full abstract»

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  • A fast solver for the Helmholtz equation on long, thin structures

    Publication Year: 2005 , Page(s): 2911 - 2919
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    We present a fast solver for the Helmholtz equation on long, thin structures. It operates on an integral equation formulation of the problem, in which the solution is represented as a superposition of fields generated by sources on the structure (usually on the boundary or boundaries of the structure). It uses a standard iterative solver for linear equations, in conjunction with a novel method for applying the forward matrix, whose computational complexity is O(N), where N is the number of points on which the integral equation is solved. The algorithm is suitable for structures in either two dimensions (2-D) or three dimensions. It does not depend in any great detail on the specifics of the Helmholtz equation, and, thus, is also suitable for similar equations. We demonstrate the algorithm by using it to simulate scattering in 2-D from dielectric structures, using an integral equation formulation constructed using a combination of single-layer and double-layer potentials, yielding a second-kind integral equation. Numerical results show the algorithm to be efficient and accurate. View full abstract»

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  • Numerical artifacts in finite-difference time- domain algorithms analyzed by means of principal components

    Publication Year: 2005 , Page(s): 2920 - 2927
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1368 KB)  

    Finite-difference time-domain (FDTD) algorithms are affected by numerical artifacts and noise. In order to obtain better results we propose the use of the principal component analysis based on multivariate statistical techniques. It allows a straightforward discrimination between the numerical noise and the actual electromagnetic field distributions, and the quantitative estimation of their respective contributions. Besides, the FDTD results can be filtered to clean the effect of the noise. The method has been applied successfully to two dimensional simulations: propagation of a pulse in vacuum using total field-scattered field techniques, and mode computation in a two-dimensional photonic crystal. In this last case, PCA has revealed hidden electromagnetic structures related to actual modes of the photonic crystal. View full abstract»

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  • Finite-difference time-domain modeling of frequency selective surfaces using impedance sheet conditions

    Publication Year: 2005 , Page(s): 2928 - 2937
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB) |  | HTML iconHTML  

    Novel finite-difference time-domain (FDTD) models of frequency-selective surfaces (FSS) based on impedance sheet conditions are developed. The analytical basis of the models lies in impedance sheet conditions with general reactive grid impedances applying to a great variety of grid realizations. New models for periodic arrays of metal particles and for the complementary structures of slots in metal screen are formulated for FDTD in the case of normal incidence. The properties of the FSS are included in the grid impedance, which is implemented into FDTD, considerably simplifying the otherwise extremely cumbersome modeling task. The convergence and the accuracy of the models are assessed with numerical simulations by comparing with analytical and measured reference results. View full abstract»

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  • Improved FDTD subgridding algorithms via digital filtering and domain overriding

    Publication Year: 2005 , Page(s): 2938 - 2951
    Cited by:  Papers (21)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2016 KB) |  | HTML iconHTML  

    In numerical simulations of Maxwell's equations for problems with disparate geometric scales, it is often advantageous to use grids of varying densities over different portions of the computational domain. In simulations involving structured finite-difference time-domain (FDTD) grids, this strategy is often referred as subgridding (SG). Although SG can lead to major computational savings, it is known to cause instabilities, spurious reflections, and other accuracy problems. In this paper, we introduce two strategies to combat these problems. First, we present an overlapped SG (OSG) approach combined with digital filters (in space). OSG can recover standard SG (SSG) schemes but it is based upon a more general, explicit separation between interpolation/decimation operations and the FDTD field update itself. This allows for a better classification of errors associated with the subgrid interface. More importantly, digital filters and phase matching techniques can be then employed to combat those errors. Second, we introduce SG with a domain overriding (SG-DO) strategy, consisting of overlapped (sub)grid regions that contain auxiliary (buffer) subdomains with perfectly matched layers (PML) to allow explicit control on the reflection and transmission properties at SG interfaces. We provide two-dimensional (2-D) numerical examples showing that residual errors from 2-D SG-DO FDTD simulations can be significantly reduced when compared to SSG schemes. View full abstract»

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  • Development of higher order FDTD schemes with controllable dispersion error

    Publication Year: 2005 , Page(s): 2952 - 2960
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    A new methodology that facilitates the control of the inherent dispersion error in the case of higher order finite-difference time-domain (FDTD) schemes is presented in this paper. The basic idea is to define suitable algebraic expressions that reflect numerical inaccuracies reliably. Then, finite-difference operators are determined via the minimization of the error estimators at selected frequencies. In order to apply this procedure, an error expansion in terms of cylindrical harmonic functions is performed, which also enables accuracy enhancement for all propagation angles. The design process produces a set of two-dimensional (2-D) FDTD algorithms with optimized frequency response. Contrary to conventional methodologies, the proposed techniques adjust their reliability range according to the requirements of the examined problem and can be, therefore, more efficient in computationally demanding simulations. View full abstract»

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  • Entire-domain MoM analysis of an array of arbitrarily oriented circular loop antennas: a general formulation

    Publication Year: 2005 , Page(s): 2961 - 2968
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB) |  | HTML iconHTML  

    This paper presents a general formulation for the entire-domain method of moments analysis of an N-element array of arbitrarily oriented coupled circular loop antennas. The orientations of the loops with respect to each other are defined through the use of Eulerian angles. The positions of the loops in space are defined by translation vectors from the center of a loop to another. By making use of coordinate transformations and vector algebra, a concise set of linear equations for solving the currents on the loops is obtained. The formulation is sufficiently general to be used for all the previously reported coupled loop orientations. It is also ideal for the study of skewed circular loops which may be oriented in innumerable ways and in turn demand a general formulation for their analysis. The use of the general formulation is illustrated by analyzing the coupling currents between collocated skewed loops. The formulation is also applied to study the effects on the transfer impedance between a pair of noncollocated skewed loops as one of the loops is rotated about various axes. View full abstract»

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  • An improved MoM model for line-fed patch antennas and printed circuits

    Publication Year: 2005 , Page(s): 2969 - 2976
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB) |  | HTML iconHTML  

    In this paper, an improved model is proposed to analyze the edge-connected line-fed patch antennas and printed circuits based on the method of moments (MoM), where the number of unknowns can be significantly reduced using simplified meshes. In the presented model, three types of basis functions are used to describe the currents on the antenna patch and circuit, the feedline and the feedline-patch junction. A new feedline-patch junction basis function is proposed based on the conventional wire-surface junction basis function. Numerical results are given to illustrate the accuracy and efficiency of the improved MoM model. View full abstract»

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  • Efficient computation of the 2-D Green's function for 1-D periodic structures using the Ewald method

    Publication Year: 2005 , Page(s): 2977 - 2984
    Cited by:  Papers (56)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB) |  | HTML iconHTML  

    The Ewald method is applied to accelerate the evaluation of the Green's function of an infinite periodic phased array of line sources. The Ewald representation for a cylindrical wave is obtained from the known representation for the spherical wave, and a systematic general procedure is applied to extend previous results. Only a few terms are needed to evaluate Ewald sums, which are cast in terms of error functions and exponential integrals, to high accuracy. Singularities and convergence rates are analyzed, and a recipe for selecting the Ewald splitting parameter ε is given to handle both low and high frequency ranges. Indeed, it is shown analytically that the choice of the standard optimal splitting parameter ε0 will cause overflow errors at high frequencies. Numerical examples illustrate the results and the sensitivity of the Ewald representation to the splitting parameter ε. View full abstract»

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IEEE Transactions on Antennas and Propagation includes theoretical and experimental advances in antennas.

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Editor-in-Chief                                                 Kwok W. Leung