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Antennas and Propagation, IEEE Transactions on

Issue 11 • Date Nov. 2009

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Displaying Results 1 - 25 of 40
  • Table of contents

    Page(s): C1 - 3449
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  • IEEE Transactions on Antennas and Propagation publication information

    Page(s): C2
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  • Design, Development and Integration of Novel Antennas for Miniaturized UHF RFID Tags

    Page(s): 3450 - 3457
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1457 KB) |  | HTML iconHTML  

    An overview of design requirements and novel approaches for improved performance UHF radio frequency identification (RFID) tags is presented. Two matching techniques, an inductively coupled structure and a serial stub structure are discussed. Different miniaturized antenna topologies are proposed, focusing on low-profile, high efficiency and high directivity in very compact (less than 3 in times 3 in) configurations. View full abstract»

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  • Analysis, Design and Realization of a Novel Directive Ultrawideband Antenna

    Page(s): 3458 - 3466
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    In this paper, we present a simple log-periodic-dipole-array (LPDA) solution that allows us to achieve good ultrawideband (UWB) performances. The antenna has been manufactured and the measurements agree well with the theoretical predictions. The antenna presents an average gain of 8 dB and a return loss better than -10 dB over the band from 4.2 to 10.6 GHz. Both the measured antenna transfer function and the computed effect on pulse transmission show good performances in comparison with already known UWB antennas. View full abstract»

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  • A Planar UWB Diversity Antenna

    Page(s): 3467 - 3473
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    A planar dual-port diversity antenna, operating with broadside and/or conical radiation patterns in H-planes, is presented for ultrawideband (UWB) applications. The proposed antenna consists of a suspended square patch with a thick stem underneath. A broadband differential feeding strip is used to feed the square patch. The measured gain for the broadside mode is 8.4-10.3 dBi from 3.1 GHz to 5.2 GHz (50.6%), and the conical mode 3.2-5.1 dBi from 3.1 GHz to 4.9 GHz (45%). The measured reflection coefficients (|S 11|, |S 22|) are less than -10 dB over the frequency ranges and the isolation |21| between the two ports is greater than 13.5 dB. The operation of the differential feeding strip on the antenna is discussed. Both pattern diversity and partial polarization diversity are achieved for this antenna. View full abstract»

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  • Optimal Antenna Radiation Characteristics for Diversity and MIMO Systems

    Page(s): 3474 - 3481
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    This paper proposes a method for determining the antenna element radiation characteristics that maximize diversity gain given a specific power angular spectrum of the propagation environment. The method numerically constructs the eigenfunctions of the covariance operator for the scenario subject to constraints on the radiated power and allowable level of supergain. The discussion also focuses on how the resulting radiation characteristics approximately optimize average capacity for multiple-input multiple-output communications. Computational results reveal that optimal antenna characteristics can provide significantly more diversity gain than that offered by the characteristics of a simple design. An example computation using genetic algorithm optimization demonstrates that a numerically optimized practical design can be designed whose performance is relatively close to that of the optimal array. View full abstract»

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  • A Novel Analytical Model of Resonance Effects of Log-Periodic Planar Antennas

    Page(s): 3482 - 3488
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (668 KB) |  | HTML iconHTML  

    In this paper a new analytical model about the calculation of resonance frequencies and bandwidth of log-periodic planar antennas is proposed. The two previous known models and our novel model are compared to numerical simulations and experimental measurements. In the theoretical part analytical calculations are opposed to the results of reflection parameter simulations. Our model shows a very good coincidence according to the number and position of resonance frequencies. We show that this is not the case for the previous models. For the experimental validation of the novel model several devices with different geometries were fabricated and characterized in the 1-8 GHz frequency range. All considered antenna structures exhibit an excellent coincidence between calculations, simulations and measurements. View full abstract»

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  • Iterative Solutions for Electromagnetic Fields at Perfectly Reflective and Transmissive Interfaces Using Clifford Algebra and the Multidimensional Cauchy Integral

    Page(s): 3489 - 3499
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (435 KB) |  | HTML iconHTML  

    A technique is presented for calculating the solution of Maxwell's equations using a CFIE based on the Cauchy integral and formulated in the guise of Clifford algebra. This formulation has a geometric interpretation leading to an iterative method of solution which is easily proven as convergent and correct for both perfectly reflective and perfectly transmissive interfaces. Simple test cases involving a cubic boundary and plane wave and dipole sources are used to investigate the numerical performance of the method. View full abstract»

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  • Diffraction From A Material Loaded Tandem Slit

    Page(s): 3500 - 3511
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (538 KB) |  | HTML iconHTML  

    In this paper, we consider plane wave diffraction by a tandem slit loaded with a homogenous material. The boundary value problem is formulated into a pair of simultaneous Wiener-Hopf equations via Fourier transformation. After decoupling these equations by elementary transformation, each modified Wiener-Hopf equation is reduced to a Fredholm integral equation of the second kind. The integral equations are then solved approximately to yield the Fourier transform of the diffracted fields. The inverse transform is evaluated asymptotically to obtain the far field expressions. Measurements and numerical simulations are also performed for several different geometry and material configurations. The analytic solutions compare well with measured and simulated results. The possibility of reducing beamwidth and increasing power coupled through the loaded tandem slit is explored. View full abstract»

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  • EM-Wave Scattering by an Axial Slot on a Circular PEC Cylinder With an Eccentrically Layered Inner Coating: A Dual-Series Solution for TE Polarization

    Page(s): 3512 - 3519
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    A dual-series approach is used to formulate scattering of a TE-polarized plane wave by a circular, PEC cylinder, having a longitudinal slot and enclosing two, eccentric, cylindrical dielectric layers. The dual-series equations are analytically regularized to a matrix Fredholm equation of the second kind by use of the Abel integral-transform method. The resulting infinite set of linear algebraic equations (i.s.l.a.e.) is truncated and solved numerically. The aforementioned analytical-numerical solution intrinsically takes into consideration the correct edge behavior of the field. Furthermore, the addition theorem of cylindrical wave functions is used to match the field components on any cylindrical interface. The numerical application manifests how the structure of the inner loading of this cylindrical cavity is imprinted on backscattering. Moreover, it is shown how the location of the innermost dielectric cylinder may contribute to the suppression or enhancement of resonances. View full abstract»

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  • High-Resolution 3-D Imaging Algorithm With an Envelope of Modified Spheres for UWB Through-the-Wall Radars

    Page(s): 3520 - 3529
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1669 KB) |  | HTML iconHTML  

    Through-the-wall imaging techniques with ultrawideband (UWB) radars are promising candidates for non-destructive testing and reliable human detection, especially in disaster areas, where victims are buried under collapsed walls. These applications require high-resolution target imaging to identify the object shape, such as a human body. We have already proposed a high-quality 3-dimensional (3-D) imaging algorithm in the form of envelope that is aimed at near field sensing for non-contact measurement or target identification for robots. Envelope achieves real-time accurate 3-D imaging with group mapping from multiple observed ranges to target points, and offers a reliable image even in noisy situations. However, this method does not maintain its quality for through-the-wall imaging because an observed range shift due to wall penetration causes a serious distortion in the image. This paper presents a high-resolution 3-D imaging algorithm by modifying the original envelope, and which gives a more accurate object shape behind a wall. Furthermore, to enhance the resolution of the estimated images, this method is combined with a direct waveform compensation method, known as spectrum offset correction. Numerical simulations and an experiment verify that our proposed method achieves high-resolution 3-D imaging for through-the-wall radar applications. View full abstract»

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  • Estimating Moving Targets Behind Reinforced Walls Using Radar

    Page(s): 3530 - 3538
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3408 KB) |  | HTML iconHTML  

    We consider the estimation of moving targets located behind concrete walls reinforced with metallic bars, using radar measurements. The periodic structure of the rebar severely attenuates and distorts transmitted waveforms, which produces defocused images with ghost target estimates. We apply beamforming to estimate permittivity and thickness of the wall and number and position of the targets. The proposed solution is based on accurate physical models calculated using the method of moments. We show that the estimation is significantly improved by modeling the waveform distortion due to the bars. The resulting images are focused and clearly represent the contours of the targets. The algorithm is robust to the ambiguities in bar parameter values. In addition, the minimal necessary SNR is lower compared with the case in which the influence of the bars on the signal shape is ignored. View full abstract»

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  • Effects of Non-Uniform Motion in Through-the-Wall SAR Imaging

    Page(s): 3539 - 3548
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (863 KB) |  | HTML iconHTML  

    Synthetic aperture radar (SAR) provides high resolution images that are well suited for through-the-wall target detection and recognition. As targets behind-the-wall undergo non-uniform motions, such as vibration, rotation and acceleration, their patterns can be recognized. To understand these signatures in through-the-wall SAR, we model and analyze the non-uniform motion-induced Doppler effect as well as the focused target SAR image. In particular, the wall effects on the focused SAR image and the micro-Doppler are formulated and analyzed. These analyses facilitate improving the target recognition performance by quantitatively estimating the parameters of the micro-Doppler signatures as well as the SAR imaging. We further analyze the detection performance of the non-uniform motion-induced target based on the generalized likelihood ratio test (GLRT) technique. The relationship between motion parameters and the detection performance allows us to evaluate the performance bound and the minimum detectable parameters. View full abstract»

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  • Performance of Time Domain Migration Influenced by Non-Ideal UWB Antennas

    Page(s): 3549 - 3557
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2185 KB) |  | HTML iconHTML  

    The antennas in ultrawideband (UWB) systems act as filters in both frequency domain and the spatial domain. This means that the antenna influence on a received signal varies with the wave incidence angle. This is particulary important for imaging systems, which make use of the time information of the received signals. However, since the incidence angles of the signals are not a priori known it is difficult to remove this effect from the measured data. To assess the antenna impact on the performance of the imaging system, in this work, simulated scattered signals are used as input for time domain migration algorithm. Then the image features like position errors, shape of the target image, resolution and coverage of an imaging system are extracted and compared for different real UWB antennas. View full abstract»

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  • Combining the Higher Order Method of Moments With Geometric Modeling by NURBS Surfaces

    Page(s): 3558 - 3563
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (751 KB) |  | HTML iconHTML  

    This paper introduces the nonuniform rational B-spline (NURBS) surfaces to improve the geometric modeling of the higher order method of moments (MoM). The electric field integral equation (EFIE) is discretized by the hierarchical higher order basis functions and converted to a matrix equation. Then the elements of the impedance matrix are efficiently evaluated by a new set of formulas. The bistatic radar cross sections (RCS) obtained by this new technique are compared with those obtained by the commonly used higher order MoM. The example of a cylinder and a missile shows excellent accuracy of the NURBS surfaces and that of the resultant RCS. Moreover, this new technique can fully exploit the flexibility of the higher order basis functions when the surface is highly curved, whereas the commonly used higher order MoM can not. View full abstract»

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  • Automatic Loop-Tree Scheme for Arbitrary Conducting Wire-Surface Structures

    Page(s): 3564 - 3574
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    At very low frequencies, the electric field integral equation discretization requires the extraction of the solenoidal part of the current to circumvent problems resulting from the severe poor conditioning of the method of moments matrix. Here we describe how the solenoidal or loop bases can be generated on bodies composed of arbitrarily shaped surfaces connected to wires. Moreover we present an automatic, low-complexity algorithm to extract the closed paths from the underlying mesh for complex wire-surface structures, either free-standing or connected to an infinite ground plane. The performance of the proposed basis is confirmed by the reported numerical examples. View full abstract»

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  • An Eigencurrent Approach to the Analysis of Electrically Large 3-D Structures Using Linear Embedding via Green's Operators

    Page(s): 3575 - 3585
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1303 KB) |  | HTML iconHTML  

    We present an extension of the linear embedding via Green's operators (LEGO) procedure for efficiently dealing with 3-D electromagnetic composite structures. In LEGO's notion, we enclose the objects forming a structure within arbitrarily shaped domains (bricks), which (by invoking the equivalence principle) we characterize through scattering operators. In the 2-D instance, we then combined the bricks numerically, in a cascade of successive embedding steps, to build increasingly larger domains and obtain the scattering operator of the whole aggregate of objects. In the 3-D case, however, this process becomes quite soon impracticable, in that the resulting scattering matrices are too big to be stored and handled on most computers. To circumvent this hurdle, we propose a novel formulation of the electromagnetic problem based on an integral equation involving the total inverse scattering operator of the structure, which can be written analytically in terms of scattering operators of the bricks and transfer operators among them. We then solve this equation by the method of moments combined with the eigencurrent expansion method, which allows for a considerable reduction in size of the system matrix and thereby enables us to study very large structures. View full abstract»

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  • An Efficient Surface Integral Equation Solution to EM Scattering by Chiral Objects Above a Lossy Half Space

    Page(s): 3586 - 3593
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (635 KB) |  | HTML iconHTML  

    In this paper, an extension of the electric-magnetic current combined-field integral equation (JMCFIE) is presented for the efficient analysis of EM scattering by an arbitrary shaped homogenous chiral object located above a lossy half space. This formulation can lead to a well tested equation system using the method of moments (MoM) solution with the vector triangular basis functions and Galerkin's method. The multilevel fast multipole algorithm (MLFMA) is then employed to reduce the memory requirement and computational complexity of the MoM solution. The inner-outer flexible generalized minimal residual (FGMRES) method is used to further speed up the convergence. The accuracy and efficiency are confirmed with a couple of numerical examples. View full abstract»

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  • Fast Full-Wave Surface Integral Equation Solver for Multiscale Structure Modeling

    Page(s): 3594 - 3601
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (802 KB) |  | HTML iconHTML  

    We describe a full-wave solver to model large-scale and complex multiscale structures. It uses the augmented electric field integral equation (A-EFIE), which includes both the charge and the current as unknowns to avoid the imbalance between the vector potential and the scalar potential in the conventional EFIE. The formulation proves to be stable in the low-frequency regime with the appropriate frequency scaling and the enforcement of charge neutrality. To conquer large-scale and complex problems, we solve the equation using iterative methods, design an efficient constraint preconditioning, and employ the mixed-form fast multipole algorithm (FMA) to accelerate the matrix-vector product. Numerical tests on various examples show high accuracy and fast convergence. At last, complex interconnect and packaging problems with over one million integral equation unknowns can be solved without the help of a parallel computer. View full abstract»

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  • A Relationship Between Phase Delay and Attenuation Due to Rain and Its Applications to Satellite and Deep-Space Tracking

    Page(s): 3602 - 3611
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (497 KB) |  | HTML iconHTML  

    We present and discuss two main results concerning the relationship between phase delay due to rain and rain attenuation, useful in calculations concerning high precision tracking of satellites and deep-space spacecrafts using interferometry techniques. We have found these two results with the Synthetic Storm Technique [SST] applied to a large data bank of rain rate time series collected at three sites in Italy. The first result concerns a formula that provides the extra signal phase delay tau (picoseconds) due to rain as a function of rain attenuation A (dB), frequency f (GHz) and slant path elevation angle thetas (degrees), given by tau = (860.4 4.82 thetas)f-1.71A0.73, for 20deg les thetas les 44deg, and by tau = 648.3 f1.71 A0.73,for 44deg les thetas les 90deg. The formula allows estimating the phase delay due to rain attenuation, with overall average (normalized) error -3%, standard deviation 11.1%, rootmean square 11.5 % for 20deg slant paths. The second result concerns a method to predict phase delay from the probability distribution of rain rate (SST probability model), very useful when only the probability distribution of rain rate is known. View full abstract»

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  • Propagation of Large Bandwidth Microwave Signals in Water

    Page(s): 3612 - 3618
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (728 KB) |  | HTML iconHTML  

    Large bandwidth microwave signals propagating in dispersive media can result in pulses decaying according to a non-exponential law. In particular, large bandwidth signals in the microwave band, propagating in media that can be described by the Debye model (for example fresh water), decays as the square root of the inverse of the propagation distance, instead of exponentially. Although it is a direct consequence of well-known theory of propagation in dispersive media, this result is a bit surprising and its experimental evidence has required a careful set-up. View full abstract»

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  • Propagation Between On-Body Antennas

    Page(s): 3619 - 3627
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    The theory of propagating waves near a surface is reviewed with an eye to gain insight into the mechanisms involved, and to provide analytical-based models, for power-efficient on-body propagation. The Zenneck wave, and in particular the Norton wave, are appraised as candidate mechanisms for the propagation. For flush-mounted (ldquoband aidrdquo) antennas, desired for on-body sensors, the Norton wave is the only direct propagation mechanism between the sensors. The Norton wave fits very well to simulation results presented here, and comparisons are also made with available published physical experiments, although these measurements typically feature the optical paths of elevated, or non-flush, antennas. View full abstract»

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  • Non-Destructive Evaluation of Elastic Targets Using Acousto-Electromagnetic Wave Interaction and Time Reversal Focusing

    Page(s): 3628 - 3637
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    The objective of this research is to demonstrate the efficacy of using acoustic and electromagnetic (acousto-EM) wave interaction and time-reversal focusing in the non-destructive evaluation of an object. Acousto-EM wave interaction occurs when an electromagnetic wave scatters from an object under seismic or acoustic illumination; the acoustic vibration of the object gives rise to a frequency modulated scattered electromagnetic field which is a function of the object and both the electromagnetic and acoustic source parameters. A recently developed model, which is capable of predicting the first Doppler component of the frequency modulated scattered field for arbitrary two-dimensional objects over a wide bandwidth, is used in the analysis. Time reversal focusing is also used to improve sensitivity and obtain information about the location of flaws within the target. Both the unshifted electromagnetic fields scattered from the stationary target and the Doppler component are analyzed. The sensitivity of the Doppler component to the presence of flaws, which perturb the mechanical mode shape and resonance frequency, is demonstrated for application in non-destructive evaluation. View full abstract»

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  • Two-Dimensional Scattering by a Conducting Elliptic Cylinder Coated With a Homogeneous Anisotropic Shell

    Page(s): 3638 - 3645
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (351 KB) |  | HTML iconHTML  

    A solution to the two-dimensional scattering properties of a conducting elliptic cylinder coated with a confocal homogeneous anisotropic elliptical shell is obtained. The transmitted field of the anisotropic shell is expressed as an integral equation based on waves with different wave numbers and different directions of propagation. The waves in all directions are represented as the eigenfunction expansion in elliptic coordinates in terms of Mathieu functions. In order to solve the nonorthogonality properties of Mathieu functions, Galerkin's method is applied and a matrix is required for the computation of unknown expansion coefficients of the scattered and transmitted fields. Only the transverse magnetic (TM) polarization is presented, while the transverse electric (TE) polarization can be obtained in the same way. Some numerical results are presented in graphical forms. The result is in agreement with that available as expected when a coated elliptic cylinder degenerates to the coated circular one. View full abstract»

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  • Some Issues With Using Radiative Transfer Approach to Scattering From Layered Random Media With Rough Interfaces

    Page(s): 3646 - 3654
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    The radiative transfer (RT) approach is widely used in applications involving scattering from layered random media with rough interfaces. Although it has been successful in several disciplines it is well known that this approach involves certain approximations. In this paper these assumptions and approximations are reexamined. To enable this a statistical wave approach is employed to this problem and the governing equations for the first and second moments of the wave functions are derived. A transition is hence made to arrive at a system of equations corresponding to that of the RT approach. It is hence found that more conditions are implicitly involved in the RT approach than generally believed to be sufficient. View full abstract»

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

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Meet Our Editors

Editor-in-Chief                                                 Kwok W. Leung