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Antennas and Propagation, IEEE Transactions on

Issue 6 • Date June 2012

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  • Table of contents

    Publication Year: 2012 , Page(s): C1 - 2610
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  • IEEE Transactions on Antennas and Propagation publication information

    Publication Year: 2012 , Page(s): C2
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  • Differential Microstrip and Slot-Ring Antennas for Millimeter-Wave Silicon Systems

    Publication Year: 2012 , Page(s): 2611 - 2619
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2193 KB) |  | HTML iconHTML  

    Differential on-chip microstrip and slot-ring antennas with a quartz superstrate are presented for wafer-scale silicon systems. The antennas are fed at the nonradiating edge, which is compatible with differential coupled-lines, and are built on a 0.13-μ m CMOS process with a layout that meets all the metal density rules. A high radiation efficiency is achieved using a 100- μm quartz superstrate placed on top of the silicon chip. Both antennas have a measured gain varies from about 2 to 3 dBi at 91-94 GHz, with a - 10-dB S11 bandwidth of 7-8 GHz and a simulated radiation efficiency of >;50%. The designs are compatible with single- and multielement transceivers, and with wafer-scale imaging systems and power-combining arrays. View full abstract»

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  • Dual-Band Long-Range Passive RFID Tag Antenna Using an AMC Ground Plane

    Publication Year: 2012 , Page(s): 2620 - 2626
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1153 KB) |  | HTML iconHTML  

    A dual-band passive radio frequency identification (RFID) tag antenna applicable for a recessed cavity in metallic objects such as heavy equipment, vehicles, aircraft, and containers with long read range is proposed by using an artificial magnetic conductor (AMC) ground plane. The proposed tag antenna consists of a bowtie antenna and a recessed cavity with the AMC ground plane installed on the bottom side of the cavity. The AMC ground plane is utilized to provide dual-band operation at European (869.5 869.7 MHz) and Korean (910 914 MHz) passive UHF RFID bands by replacing the bottom side of the metallic cavity of a PEC-like behavior and, therefore, changing the reflection phase of the ground plane. It is worthwhile to mention that the European and the Korean UHF RFID bands are allocated very closely, and the frequency separation ratio between the two bands is just about 0.045, which is very small. It is demonstrated by experiment that the maximum reading distance of the proposed tag antenna with optimized dimensions can be improved more than 3.1 times at the two RFID bands compared to a commercial RFID tag. View full abstract»

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  • Frequency- and Time-Domain Performance of Four-Arm Mode-2 Spiral Antennas

    Publication Year: 2012 , Page(s): 2627 - 2634
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2619 KB) |  | HTML iconHTML  

    The performance of simply-fed four-arm Archimedean and equiangular spiral antennas operating in mode-2 (conical beam) and their suitability for pulsed communication applications are investigated. The frequency-domain transfer function of spiral antennas-based ultra-wideband (UWB) link is synthesized using complex far field information measured in a spherical near-field chamber from 2 to 12 GHz. The time-domain performance is obtained by post-processing frequency-domain data using the inverse fast Fourier transform. The synthesized approach is validated computationally and using direct link measurements. The quality of radiated pulses is evaluated in terms of the fidelity factor over the full field of view. The study demonstrates that the mode-2 spirals exhibit good time- and frequency-domain performance over a multioctave bandwidth which allows multiple communication services including UWB and time-frequency RF surveillance applications to be integrated into a single aperture system. View full abstract»

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  • Evanescently Fed Electromagnetic Band-Gap Horn Antennas and Arrays

    Publication Year: 2012 , Page(s): 2635 - 2644
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3409 KB) |  | HTML iconHTML  

    The design of a horn antenna based on electromagnetic band-gap structures (EBGs) and fed by evanescent fields in the containing periodic structure is presented. Such all-dielectric antennas can form compact arrays and provide a promising solution for millimeter, submillimeter, and terahertz (THz) devices. An evanescently fed EBG horn antenna design based on a woodpile structure and operating at frequencies around 110 GHz is presented, together with experimental and simulation results for an analogous scaled-up prototype antenna operating in the Ku-band. It exhibits a 9% bandwidth and an average level of maximum gain approximately equal to 14.6 dBi. View full abstract»

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  • Generation of Propagating Bessel Beams Using Leaky-Wave Modes: Experimental Validation

    Publication Year: 2012 , Page(s): 2645 - 2653
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2859 KB) |  | HTML iconHTML  

    We present the experimental generation of Bessel beams using a leaky radial waveguide. The radial waveguide consists of a capacitive sheet over a ground plane. The capacitive sheet is composed of patch elements printed on both sides of a dielectric substrate. The radial waveguide is coaxially fed and supports an azimuthally invariant leaky-wave mode whose normal electric-field component is a truncated, zeroth-order Bessel function. Two prototypes are presented with the same propagation constant and lateral extent, but different attenuation constants. 2D electric field measurements and their respective Fourier transforms validate the operation of the prototypes as Bessel-beam launchers at two frequency bands. Cleaner patterns are achieved by the prototype with lower attenuation constant. The dual-band capability and associated frequency dependent resolution can be useful in near-field planar focusing systems. The proposed structure can be used for generating arbitrary zeroth-order propagating Bessel beams at microwave and millimeter-wave frequencies. View full abstract»

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  • A Compact Outer-Fed Leaky-Wave Antenna Using Exponentially Tapered Slots for Broadside Circularly Polarized Radiation

    Publication Year: 2012 , Page(s): 2654 - 2661
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1691 KB) |  | HTML iconHTML  

    A novel leaky-wave slot antenna for broadside circularly polarized (CP) radiation is presented. The antenna simply consists of a slotline for the feed, an exponentially tapered slot for the radiator, and a shaped end for the terminator. Separating the feed from the curved radiating slot makes the presented antenna unique in design and compact in size. The resulting antenna yields inherent broadband characteristics of leaky-wave antennas on the input impedance, axial ratio (AR), and radiation gain. Particularly, to solve the tilt-beam problem commonly seen in leak-wave antennas, we proposed an extended dual-slot design that successfully achieved the pattern stability over a wide bandwidth. An antenna module with a reflector for unidirectional pattern applications was also developed. The measured performances of the final prototype were found to exhibit 10-dB return loss bandwidth of 40%, 3-dB AR bandwidth of 53%, and half-power gain bandwidth of 59% with CP gain level about 8 dBic. The measured and simulated results were well consistent with each other. View full abstract»

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  • Linear-/Circular-Polarization Designs of Dual-/Wide-Band Cylindrical Dielectric Resonator Antennas

    Publication Year: 2012 , Page(s): 2662 - 2671
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1814 KB) |  | HTML iconHTML  

    Linear-/circular-polarization designs of the dual-/wide-band cylindrical dielectric resonator antennas (DRAs) are presented. The HEM111 and HEM113 modes of the cylindrical DRA are utilized to design the dual-mode cylindrical DRA. A wideband antenna can be obtained by merging the two resonant modes. To facilitate the designs, new engineering formulas that determine the dimensions of the dual-mode cylindrical DRA are found for the first time. They are obtained by using the covariance matrix adaptation evolutionary strategy (CMA-ES). Design examples for the dual-/wide-band cylindrical DRAs are given for both the linearly and circularly polarized cases. Ansoft HFSS was used to simulate the DRAs and the simulations were verified with our measurements. Good agreement between the measured and simulated results is observed. View full abstract»

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  • Physical Bounds and Optimal Currents on Antennas

    Publication Year: 2012 , Page(s): 2672 - 2681
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2912 KB) |  | HTML iconHTML  

    Physical bounds on the directivity Q-factor quotient and optimal current distributions are determined for antennas of arbitrary shape and size using an optimization formulation. A variational approach offers closed form solutions for small antennas expressed in the polarizability of the antenna structure. Finite sized antennas are solved using Lagrangian parameters in a method of moments formulation. It is also shown that the optimal charge density for a small antenna can be generated by several current densities. Numerical examples for small and large antennas are used to illustrate the results. View full abstract»

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  • Optimization of a Compact Frequency- and Environment-Reconfigurable Antenna

    Publication Year: 2012 , Page(s): 2682 - 2689
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1298 KB) |  | HTML iconHTML  

    This paper presents a novel ultra-compact (0.17 × 0.17 × 0.05 wavelengths) reconfigurable antenna equipped with shunt switches at the edges of the radiating elements; in addition to wide-band frequency-reconfigurability, the antenna can also adapt to different environments. The challenging task of designing a compact antenna for multi-band and multi-environment operation is tackled by a hierarchical optimization process consisting of the genetic algorithm (GA) and local search for geometry optimization, and exhaustive search for computation of the optimum switch patterns for a fixed geometry. Both tunability and environment robustness were confirmed in simulation and measurements on a proof-of-concept prototype where switches were simulated by soldering. Numerical analysis of the impact of commercial MEMS devices is also reported, including a case study of practical interest: a compact antenna that can operate at different locations around a simplified model of a laptop PC without performance degradation. View full abstract»

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  • A Parasitic Layer-Based Reconfigurable Antenna Design by Multi-Objective Optimization

    Publication Year: 2012 , Page(s): 2690 - 2701
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2602 KB) |  | HTML iconHTML  

    A parasitic layer-based multifunctional reconfigurable antenna (MRA) design based on multi-objective genetic algorithm optimization used in conjunction with full-wave EM analysis is presented. The MRA is capable of steering its beam into three different directions (θi = -30°, 0°, 30°) simultaneously with polarization reconfigurability (Pj = Linear, Circular) having six different modes of operation. The MRA consists of a driven microstrip-fed patch element and a reconfigurable parasitic layer, and is designed to be compatible with IEEE-802.11 WLAN standards (5-6 GHz range). The parasitic layer is placed on top of the driven patch. The upper surface of the parasitic layer has a grid of 5 5 electrically small rectangular-shaped metallic pixels, i.e., reconfigurable parasitic pixel surface. The EM energy from the driven patch element couples to the reconfigurable parasitic pixel surface by mutual coupling. The adjacent pixels are connected/disconnected by means of switching, thereby changing the geometry of pixel surface, which in turn changes the current distribution over the parasitic layer, results in the desired mode of operation in beam direction and polarization. A prototype of the designed MRA has been fabricated on quartz substrate. The results from simulations and measurements agree well indicating ~8 dB gain in all modes of operation. View full abstract»

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  • A MNG-TL Loop Antenna Array With Horizontally Polarized Omnidirectional Patterns

    Publication Year: 2012 , Page(s): 2702 - 2710
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1932 KB) |  | HTML iconHTML  

    A horizontally polarized omnidirectional planar loop antenna that employs an artificial mu-negative transmission line (MNG-TL) is proposed. The MNG-TL is designed using periodically loaded parallel-plate lines. The reactive loading is inspired by the zeroth-order resonator (ZOR), which has a propagation constant of zero. Due to the unique property of an infinite wavelength, the MNG-TL loop antenna presented in this paper allows current along the loop to remain in phase so that a horizontal polarized omnidirectional pattern is generated. A series-fed array, which is composed of four MNG-TL loop antennas and operates at 2.4 GHz band, is designed, fabrication, and measured. The MNG-TL loop antenna array offers a horizontally polarized omnidirectional radiation pattern with enhanced gain of 6.5 ~ 7.9 dBi and measured radiation efficiency exceeding 85% for covering bands. The concept extends the degrees of design freedom for horizontally polarized omnidirectional antenna array. View full abstract»

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  • Planar Near-Field Measurement of Digital Phased Arrays Using Near-Field Scan Plane Reconstruction

    Publication Year: 2012 , Page(s): 2711 - 2718
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1986 KB) |  | HTML iconHTML  

    A phased array with a transmit/receive (T/R) digital beamforming (DBF) network was designed and fabricated by CEA Technologies Pty Ltd., Canberra, Australia, under the joint Australia/USA AUSPAR Program. The array was characterized through a series of antenna measurements that utilized a compact range and planar near-field scanning facility at the U.S. Naval Research Laboratory. The near-field measurements acquired element-level near-field responses that were received by the array of digital receivers present at each element in the array. This paper discusses a processing technique - referred to as near-field scan plane reconstruction - to generate any desired beam from the element-level data. The results are compared to compact range measurements of beams formed using real-time processing showing good agreement. View full abstract»

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  • A Simple Leaky-Wave Analysis of 1-D Grooved Metal Structure for Enhanced Microwave Radiation

    Publication Year: 2012 , Page(s): 2719 - 2726
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1642 KB) |  | HTML iconHTML  

    We present a simple analytical solution for a one dimensional grooved structure which, when placed concentrically around or flanking a small aperture, has been shown to enhance microwave radiation from it. We will show that the transcendental equation which describes the grooved structure reduces to a transverse resonance condition at the slot openings. For some parameters, the solution to the problem manifests as a complex wave. We demonstrate that this complex wave indeed well approximates the field distribution when a single aperture is excited for frequencies where the enhancement is most significant. In addition, we propose a simple and intuitive design procedure for the grooved structure. View full abstract»

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  • Traveling Waves on Three-Dimensional Periodic Arrays of Two Different Magnetodielectric Spheres Arbitrarily Arranged on a Simple Tetragonal Lattice

    Publication Year: 2012 , Page(s): 2727 - 2739
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    Based on Shore and Yaghjian's work (IEEE Trans. Antennas Propag., vol. 57, no. 10, pp. 3077-3091, Oct. 2009), a general theory has been developed to describe traveling waves on three-dimensional (3-D) periodic arrays of two sets of magnetodielectric spheres arbitrarily arranged on a simple tetragonal lattice. This theory is eventually in the form of k-β (dispersion) equations. To improve the computational efficiency, rapidly converging expressions and their double summation form are derived for slowly converging summations in the k-β equations. The dispersion diagrams of seven different arrangements of the spheres are analyzed for three combinations of sphere types: 1) dielectric spheres with equal permittivity but different radius; 2) dielectric spheres with equal radius but different permittivity; and 3) one set of spheres is purely dielectric while the other set is magnetic. Results show that the maximum bandwidths of the double-negative (DNG) region provided by different spheres arrangements for spheres combinations 1-3 are, respectively, 0.21%, 0.069%, and 7.403%. Compared to results reported in previous literature, analysis of these possible arrangements of the spheres shows similar narrow DNG bandwidths for spheres combinations 1 and 2, and wider DNG bandwidths for spheres combination 3. Although purely dielectric materials with relative permittivity much greater than one are readily available, the usefulness of purely dielectric DNG metamaterials still depends on whether the narrow bandwidths achievable are acceptable for the particular applications. Since purely magnetic materials with relative permeability much greater than one above 1 GHz are not currently available, the practicality of fabricating DNG metamaterials using arrays with spheres combination 3 is questionable for radio frequency (RF) applications, at least at present, despite the fact that this combination yields much wider DNG bandwidths than those of spheres c- mbinations 1 and 2. View full abstract»

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  • A Frequency Selective Radome With Wideband Absorbing Properties

    Publication Year: 2012 , Page(s): 2740 - 2747
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1894 KB) |  | HTML iconHTML  

    A frequency selective radome is presented, acting as a pass band filter at a given frequency band, while behaving as an absorber above the transmission band. The pass band behavior is obtained by a metallic FSS realized through a compact interdigitated Jerusalem cross element characterized by a very large rejection band. The metallic FSS is used as the ground plane of a thin wideband absorber based on resistive high-impedance surfaces within the total reflection band. The outer absorber reduces the signature of the antenna system when the radome is illuminated by out of band signals. The resistive FSS which comprises the absorber is designed so to minimize losses within the transmitting band of the radome. The composite structure is thoroughly analyzed by an efficient equivalent circuit approach and by full-wave numerical simulations. View full abstract»

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  • Fluidically Tunable Frequency Selective/Phase Shifting Surfaces for High-Power Microwave Applications

    Publication Year: 2012 , Page(s): 2748 - 2759
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2194 KB) |  | HTML iconHTML  

    We examine fluidically tunable periodic structures acting as highly-selective frequency selective surfaces (FSSs) or spatial phase shifters (SPSs) capable of providing phase shifts in the range of 0°-360°. These devices are multi-layer periodic structures composed of non-rePsonant unit cells. The tuning mechanism is based on integrating small, movable liquid metal droplets with the unit cells of the periodic structure. By moving these liquid metal droplets by small distances within the unit cell, the structure's frequency response can be tuned continuously. Using this technique, a fluidically tunable FSS with a fifth-order bandpass response is designed and its tuning performance is examined for various incidence angles and polarizations of the incident EM wave. Additionally, electronically tunable counterparts of the same structure are also designed and their tuning performances are examined under short-duration high-power excitation conditions. It is demonstrated that such electronically tunable FSSs/PSSs demonstrate extremely nonlinear responses. Since the fluidically tunable structure examined in this work does not use any nonlinear devices, its response is expected to remain linear for such short-duration high-power excitation conditions. The tuning performances of these fluidically tunable periodic structures are also experimentally demonstrated by fabricating three prototypes and characterizing their responses in a waveguide environment. View full abstract»

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  • Full-Wave Analysis of Periodic Dielectric Frequency-Selective Surfaces Under Plane Wave Excitation

    Publication Year: 2012 , Page(s): 2760 - 2769
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1376 KB) |  | HTML iconHTML  

    A novel full-wave method for the modal characterization of dielectric electromagnetic band-gap structures under oblique plane wave excitation is presented, showing the dielectric lattice periodicity in both the longitudinal and the transverse propagation directions. In this method, an eigenvalue problem is obtained in terms of the generalized ABCD matrix of the periodic cell, whose solution provides not only the propagation constant of the fundamental Floquet mode, but also of the higher order modes of the global periodic structure. The proposed analysis technique has been successfully validated with a commercial software based on the frequency domain finite element method. The transmittance of a finite periodic material with a finite number of unit cells has also been successfully verified through comparisons with other theoretical results reported in the technical literature. Then, our new algorithm has been used to study band-gap materials made of rectangular dielectric parallel rods, investigating the variation of the dispersion diagram and the transmission and reflection transfer functions when modifying both geometrical and electrical parameters of this structure. Finally, the response differences when a periodical defect is considered in a finite periodic arrangement have also been highlighted. View full abstract»

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  • A Versatile Design Strategy for Thin Composite Planar Double-Sided High-Impedance Surfaces

    Publication Year: 2012 , Page(s): 2770 - 2780
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2410 KB) |  | HTML iconHTML  

    A novel methodology is introduced for the design synthesis of thin planar realizations of volumetric high-impedance or artificial magnetic conducting surfaces (AMC). The design synthesis involves optimization of two different metallic frequency selective surface (FSS) type structures printed on each side of a thin dielectric substrate material. This technique eliminates the need for a complete metallic backplane common in conventional AMC designs, making use of the same dielectric substrate for two high-impedance surfaces; one on each side. Optimization of the FSS unit cell geometries is carried out with a robust genetic algorithm (GA) technique that is combined with a full-wave periodic finite element boundary integral (PFEBI) electromagnetic simulation code for fast and accurate optimization of desired AMC performance at a single frequency or over multiple frequency bands. Several examples of thin AMC ground planes are optimized for use in the X-band. Additional design examples that provide AMC behavior on one side and absorber behavior on the other are also provided. Lastly, an example illustrating the utility of the double-sided AMC separator structure is shown for a design targeting the standard Wi-Fi frequencies of 2.4 GHz and 5.2 GHz. View full abstract»

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  • Memory-Efficient Modeling of Reverberation Chambers Using Hybrid Recursive Update Discrete Singular Convolution-Method of Moments

    Publication Year: 2012 , Page(s): 2781 - 2789
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2075 KB) |  | HTML iconHTML  

    A hybrid method is proposed for memory-efficient analysis of reverberation chambers (RCs). In the hybrid method, the cavity is modeled by the recursive update discrete singular convolution (RUDSC) method, and antennas and stirrers inside the cavity are simulated using the flexible method of moments (MoM). In order to solve DSC and MoM unknowns separately, a layer-based elimination algorithm is utilized to eliminate the DSC unknowns. The MoM unknowns are then solved by a direct solver. Once the solution for the MoM model is obtained, the original RC is equivalent to a cavity excited by known current sources. The equivalent problem is finally solved using the RUDSC method. Taking advantage of the layer-based elimination algorithm and the recursive update technique, the memory requirement of the new hybrid method is much smaller than that of using a direct solver. Numerical simulations are presented to show the efficacy of the proposed method. It is shown that the the proposed method substantially reduces the memory cost of RC modeling, which extends RC analysis to higher frequencies. View full abstract»

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  • Optimal Modeling Parameters for Higher Order MoM-SIE and FEM-MoM Electromagnetic Simulations

    Publication Year: 2012 , Page(s): 2790 - 2801
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2986 KB) |  | HTML iconHTML  

    General guidelines and quantitative recipes for adoptions of optimal higher order parameters for computational electromagnetics (CEM) modeling using the method of moments and the finite element method are established and validated, based on an exhaustive series of numerical experiments and comprehensive case studies on higher order hierarchical CEM models of metallic and dielectric scatterers. The modeling parameters considered are: electrical dimensions of elements (h -refinement), polynomial orders of basis functions (p-refinement), orders of Gauss-Legendre integration formulas (integration accuracy), and geometrical (curvature) orders of elements in the model. The goal of the study, which is the first such study of higher order parameters in CEM, is to reduce the dilemmas and uncertainties associated with the great modeling flexibility of higher order elements, basis and testing functions, and integration procedures (this flexibility is the principal advantage but also the greatest shortcoming of the higher order CEM), and to ease and facilitate the decisions to be made on how to actually use them, by both CEM developers and practitioners. View full abstract»

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  • Nyström Solution to Oblique Scattering of Arbitrarily Polarized Waves by Dielectric-Filled Slotted Cylinders

    Publication Year: 2012 , Page(s): 2802 - 2813
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4041 KB) |  | HTML iconHTML  

    We investigate oblique diffraction of arbitrarily polarized waves by axially slotted, dielectric-filled, perfectly conducting circular cylinders with infinitesimally thin walls. The relevant 2 × 2 system of coupled singular integral-integrodifferential equations is solved by a highly accurate Nyström method. For enhanced efficiency, several asymptotic terms are extracted from the kernels. This helps isolate the inherent singularities and, thus, transform the initial slowly converging Green-function expansions into rapidly converging series. As a consequence, all elements of the resulting Nyström matrix take exact expressions in the form of very rapidly converging series of elementary terms. Numerical examples and case studies are presented that validate the algorithm, illustrate its rapid convergence, and bring to light the effect of changing several physical and geometrical parameters on the reflection, transmission, and absorption characteristics of the structure. View full abstract»

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  • Gradient-Singular, Hierarchical Finite Elements for Vector Electromagnetics

    Publication Year: 2012 , Page(s): 2814 - 2820
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1216 KB) |  | HTML iconHTML  

    New tetrahedral finite elements are described for the analysis of vector electromagnetic fields. They are singular elements that are more accurate than conventional, polynomial-based elements near sharp edges and corners. They are hierarchical, meaning that elements of different orders (accuracies) are available and may be placed together in the same mesh without violating continuity of the field. The elements are formed from a series of scalar singular elements by taking the gradient, and are therefore called gradient singular. Results using the new elements in p-adaptive analysis, orders 1 to 3, demonstrate that when they are used in place of conventional elements the scattering parameters are as much as 10 times more accurate for the same number of unknowns. View full abstract»

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  • Electromagnetic Analysis of Radiometer Calibration Targets Using Dispersive 3D FDTD

    Publication Year: 2012 , Page(s): 2821 - 2828
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2063 KB) |  | HTML iconHTML  

    Accurate electromagnetic and thermal analysis is essential for designing wideband radiometer calibration targets as well as for understanding the electromagnetic wave interaction with these highly absorbing structures. To serve this purpose, a three dimensional dispersive finite difference time domain (FDTD) engine has been developed. We present the various aspects associated with this FDTD formulation, including modeling of dispersive lossy media using piecewise linear recursive convolution (PLRC) and application of uniaxial perfectly matched layer (UPML) absorbing boundary condition and symmetry/periodic boundary conditions to provide high accuracy using moderate computational resources. Time domain modeling of the dispersive radar absorbent material is performed by fitting the measured complex permittivity and permeability data to a series of Debye like terms using genetic algorithm (GA) optimization. The broadband reflectivity spectrum of the calibration target is obtained by transient plane wave excitation. The reflectivity spectra of pyramidal calibration targets in the frequency range [6, 200] GHz is obtained and compared to the geometrical optics limit and a finite element solution. The spectrum depends significantly on the height to base ratio and coating thicknesses of the absorbent material. 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