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Antennas and Propagation, IEEE Transactions on

Issue 6 • Date June 2003

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Displaying Results 1 - 25 of 40
  • Scalar BPM analyses of TE and TM polarized fields in bent waveguides

    Page(s): 1185 - 1198
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (815 KB) |  | HTML iconHTML  

    We have applied the effective index method to reduce the two-dimensional (2-D) refractive index profile into the 1-D refractive index structure and modified the wave equations to obtain the paraxial wave equations. Then, transverse electric (TE) and transverse magnetic (TM) polarized fields in the curved single-mode planar waveguides are analyzed by using the scalar beam-propagation method (BPM) employing the finite-difference method with a slab structure. The bending loss in bent waveguides is analyzed for optical fields obtained from the BPM and comparisons are made between the loss for the waveguides with various radius of curvature and refractive index difference. The outward shift of the optical field, which is generated at the connection between a straight and a bent waveguide, is obtained from the results of calculation of location of the maximum optical intensity. The transition loss can be reduced by introducing an optimized inward offset at a straight-to-bend junction. The birefringence for TE and TM polarized fields in bent waveguides is calculated from the phase difference of the optical fields. The wavelength shift due to the birefringence of TE and TM polarized fields in bent waveguides is also calculated. View full abstract»

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  • An E-plane ferrite loaded simple waveguide radiator

    Page(s): 1315 - 1320
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (839 KB) |  | HTML iconHTML  

    Experimental investigations were conducted to examine the effect of dielectric loading on a ferrite loaded waveguide radiator (notch antenna). The antenna was made by symmetrically tapering an X-band waveguide. A cylindrical ferrite post was disposed at the apex of the notch and it was biased with a dc magnetic field. The antenna was tested for several notch angles namely 140°, 120°, 90°, 80°, 60° while ferrite was loaded with several dielectric sleeves, such as wood, polymer, pyrex. The dielectric loading with high permittivity material is found to give better radiation and scanning characteristics. The radial thickness of the dielectric ring is observed to affect the radiation. View full abstract»

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  • A new transform relationship for interpreting axial fields near a focus

    Page(s): 1230 - 1235
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (334 KB) |  | HTML iconHTML  

    A new Fourier transform relationship is shown to apply between the axial distribution of a field near a focus and the field, averaged around the axis, in the aperture of the focussing device. If phase and amplitude are measured along the axis the transform gives the radial distribution in the aperture, averaged around the axis, of the field amplitude and of any deviations in phase from an ideally focussed wavefront. The transform is, therefore, useful in diagnosing surface errors in reflector antennas. It may also be of use in determining errors in optical aspheric lenses and mirrors where radial errors are more prevalent in manufacture than are azimuthal errors. If only axial power is measured, a Wiener-Khinchine relationship gives the autocorrelation of the averaged radial field distribution in the aperture. The autocorrelation by itself contains useful phase information and, in some instances, the averaged aperture field can be recovered from the autocorrelation through a process of modeling. Symmetry relationships are discussed together with a practical example where phase and amplitude in a radio telescope aperture are estimated by modeling from the autocorrelation function. View full abstract»

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  • Radiation characteristics of corrugation loaded dielectric-coated conducting cylinder

    Page(s): 1321 - 1330
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (955 KB) |  | HTML iconHTML  

    The radiation characteristics of a corrugation loaded dielectric coated conducting cylinder are investigated theoretically for the infinite periodic and finite structures. For the infinite periodic structure, the mode matching method is applied. The integral equation is derived for the finite structure by use of the Fourier transform and mode expansion. The influences of the corrugation width, corrugation depth, dielectric thickness, cylinder radius, and finite corrugation number on the radiation characteristics (leakage constant, phase constant, and radiation pattern) are investigated. The results of the finite periodic corrugations are compared with those of the infinite extent structure and good agreement is found. To reduce the high side lobe of the uniform periodic structure, nonuniform quasiperiodic corrugation arrays are considered. The surface wave radiated by the structure having end-fire radiation pattern is also investigated. View full abstract»

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  • Electro-acoustic scattering in an atmosphere with wind

    Page(s): 1242 - 1250
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (650 KB)  

    An electromagnetic wave propagating in the atmosphere is scattered by a beam of acoustic waves. The paper studies how a wind interferes with the scattering process. The purpose is to use the results for measuring the wind velocity and the temperature of the atmosphere at varying heights. A scattering calculation is carried out by means of standard methods used in problems of wave scattering. The scattering characteristics show a pronounced resonance, due to interference between spherical, i.e, nonplanar, waves. The resonance, and particularly the width of the resonance curve, represents a possibility of measuring the temperature of the atmosphere in the scattering region. The paper points out the advantage of having the acoustic beam generated by an array of phase controlled elementary acoustic sources. This opens the possibility of counteracting the effect of the wind on the acoustic beam so that the beam is keeping its direction undisturbed by the wind. By this method the problem of measuring the horizontal wind components is converted to a measurement of phase. View full abstract»

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  • Circularly polarized single-fed wide-band microstrip patch

    Page(s): 1277 - 1280
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB) |  | HTML iconHTML  

    For more than 25 years, the circularly polarized single-fed microstrip patch was considered to be extremely narrow-band. The reported performances are almost exclusively related to single patches printed on a dielectric substrate, which partially explains the frequency characteristics. The antenna proposed is a variation of the "almost square" patch and exhibits measured axial radio of less than 2.5 dB over a 13% bandwidth. The antenna was designed for wireless applications. View full abstract»

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  • Random surface error effects on offset cylindrical reflector antennas

    Page(s): 1331 - 1337
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (542 KB)  

    The focus of this paper is to characterize the average power pattern of an offset cylindrical parabolic reflector antenna subject to random surface errors. A novel computational method is developed for studying the random surface error effects on the boresight gain loss and the sidelobe levels of the average power pattern. The particular antenna dimensions used for this study are similar to the specifications for the second generation precipitation radar (PR-2) mission. In keeping with the requirements in the PR-2 mission, both the Ku and Ka frequency bands are considered. Random surface error effects are also studied for different edge taper levels. In addition to analysis of a reflector with uniform random surface errors, a nonuniform surface error case is presented in this study. This is an important consideration for evaluating the suitability of large deployable membrane reflector antennas for the PR-2 mission. View full abstract»

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  • Electromagnetic inverse scattering of multiple two-dimensional perfectly conducting objects by the differential evolution strategy

    Page(s): 1251 - 1262
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (583 KB) |  | HTML iconHTML  

    Electromagnetic inverse scattering of multiple two-dimensional (2-D) perfectly conducting objects with transverse magnetic (TM) wave incidence by the differential evolution strategy (DES) is presented. The governing electric field integral equations for the scattering problem are expressed as surface integral over the cylinder contours. The cylinder contours are approximately represented by closed cubic B-splines local shape functions in local polar coordinate system. The inverse problem is to locate the cylinders and to reconstruct their shape with or without a priori knowledge of the number of cylinders. It is cast into an optimization problem and is solved using the DES. Both synthetic and real reconstructions are carried out. The reconstruction results agree with the true profiles very well. Comparison with the real-coded genetic algorithm has been carried out. It has been observed that the DES outperforms the real-coded genetic algorithm. View full abstract»

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  • Efficient wideband printed antennas on lithium niobate for OEICs

    Page(s): 1413 - 1415
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB) |  | HTML iconHTML  

    Printed antenna structures for integration with z-cut and x-cut LiNbO3 based optoelectronic devices are presented. The designs are based on the hi-lo stacked patch element, which yields a high efficiency broadband antenna. Experimental verification of both printed antennas is given. View full abstract»

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  • Scattering analysis of a large body with deep cavities

    Page(s): 1157 - 1167
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (764 KB) |  | HTML iconHTML  

    A numerical scheme is presented for simulating electromagnetic scattering from a large and arbitrarily shaped body, coated with inhomogeneous composite materials, with large and deep cavities. This numerical scheme employs the higher order vector finite-element method (FEM) to discretize the fields inside the cavities and coatings and the higher order boundary integral (BI) method to terminate the FEM computational domain. A highly efficient special solver is designed to eliminate the unknowns inside the cavities, which yields a computed relation (CR) matrix over the cavity's aperture between the tangential electric and magnetic fields. This CR matrix is then combined with the finite element-boundary integral (FE-BI) matrix equation to form a complete linear system for the discrete fields everywhere in the computational domain. The resulting system is solved iteratively using a novel preconditioner derived by replacing the BI with a corresponding absorbing boundary condition (ABC). View full abstract»

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  • Mutual coupling of two collocated orthogonally oriented circular thin-wire loops

    Page(s): 1307 - 1314
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (612 KB) |  | HTML iconHTML  

    Coupling between two collocated orthogonal circular thin-wire loops is analyzed in this paper. Two coupled integral equations for the loop currents are derived and their solution in general form is found in terms of Fourier series. An analytical expression for currents induced through the mutual coupling is obtained for the case when all loop current harmonics higher than first can be ignored. It is found that strong coupling can exist for all loop current harmonics, except for the fundamental. It is also found that coupling for orthogonal collocated loop antennas depends on the relative locations of the loop terminals. View full abstract»

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  • Exact solution to diffraction problem by wedges with a class of anisotropic impedance faces: oblique incidence of a plane electromagnetic wave

    Page(s): 1216 - 1220
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (438 KB) |  | HTML iconHTML  

    This paper studies diffraction of an obliquely incident, arbitrarily polarized plane electromagnetic wave by an anisotropic impedance wedge with an opening angle 2Φ between 0 and 2π, and presents a closed-form exact solution to a class of impedance wedge faces and the related uniform asymptotic solution (UAS). On use of a unitary similarity transform, the boundary conditions on the wedge faces is brought into a form, which makes the exactly soluble class of impedance faces evident. The exact solution is found with help of the Sommerfeld-Malyuzhinets (1896, 1958) technique, a generalized Malyuzhinets function χΦ and the so-called S-integrals. A standard procedure yields therefrom the UAS. The exact solution agrees with known analytical results in special cases, and the numerical results of UAS are confirmed by that of parabolic equation method (PEM). View full abstract»

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  • New results for the effective propagation constants of nonuniform plane waves at the planar interface of two lossy media

    Page(s): 1206 - 1215
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1296 KB) |  | HTML iconHTML  

    This paper presents a correction and a generalization of the solution presented previously (for original papers see R. D. Radcliff and C. A. Balams, "Modified propagation constants for nonuniform plane wave transmission through conducting media," IEEE Transactions in Geoscience Remote Sensing, vol. GE-20, no. 3, p. 408-411 (1982) and C. A. Balams, Advanced Engineering Electromagnetics, New York: Wiley (1989)) for the effective propagation constants of nonuniform plane waves at the planar interface of two isotropic homogeneous possibly lossy media of infinite transverse dimensions. View full abstract»

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  • A novel center-slot-fed suspended plate antenna

    Page(s): 1407 - 1410
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (409 KB) |  | HTML iconHTML  

    This paper describes a novel broadband suspended plate antenna with enhanced radiation performances, which is centrally fed by a balance-like feeding structure. The design consideration is discussed, and measured results are presented. The parametric studies are also included. View full abstract»

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  • An efficient algorithm for electromagnetic scattering from rough surfaces using a single integral equation and multilevel sparse-matrix canonical-grid method

    Page(s): 1142 - 1149
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    An efficient algorithm for wave scattering from two-dimensional lossy rough surfaces is proposed. It entails the use of a single magnetic field integral equation (SMFIE) in conjunction with a multilevel sparse-matrix canonical-grid (MSMCG) method. The Rao-Wilton-Glisson (RWG) triangular discretization is adopted to better model the rough surface than the pulse basis functions used in the well-established SMCG method. Using the SMFIE formulation, only one unknown per interior edge of the triangular mesh approximating the rough surface is required, and the iterative solution to the moment equation converges more rapidly than that of the conventional coupled equations for dielectric rough surfaces. The MSMCG method extends the applicability of the SMCG method to rougher surfaces. Parallel implementation of the proposed method enables us to model dielectric surfaces up to a few thousand square wavelengths. Simulation results are presented as bistatic scattering coefficients for Gaussian randomly rough surfaces. View full abstract»

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  • Truncated Floquet wave full-wave (T(FW)2) analysis of large periodic arrays of rectangular waveguides

    Page(s): 1373 - 1385
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1492 KB) |  | HTML iconHTML  

    A new hybrid technique has been recently proposed for the analysis of large periodic arrays. This method is based on a high-frequency representation of the active Green's function of a finite array, involving a Floquet wave (FW) expansion with the relevant edge and vertex diffracted ray fields originating at the array border. Using this representation, the unknown current of an appropriate fringe integral equation is expanded in terms of a few basis functions shaped as FW-induced diffracted rays. This representation drastically reduces the numerical effort and provides a physical insight into the mechanism of the array truncation. In this paper, this method is applied to the analysis of large arrays of rectangular waveguides opened on an infinite ground plane. Numerical results are shown to demonstrate the effectiveness and the numerical efficiency of the method. View full abstract»

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  • On the lower bound of the radiation Q for electrically small antennas

    Page(s): 1263 - 1269
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (363 KB)  

    The fundamental question of the lower bound on the radiation Q of an electrically small antenna is of practical importance because of its relationship to the antenna bandwidth. Previous works predict a lower bound on the radiation Q that is usually too low and, hence, a bandwidth that can be optimistically large. This paper addresses why this is so and offers a new prediction for a realizable lower bound on the radiation Q. This new prediction is based on the far-field pattern, in both the visible and invisible spatial regions, in contrast to previous works based upon a near-field modal approach. Results for a linear dipole, bow-tie, and end-loaded dipole are presented to illustrate the validity of the lower bound presented herein. Radiation Q can be related to bandwidth provided the Q is adequately large. Implicit is the presence of a matching network as a part of the antenna system. Both the losses in the antenna and the losses in the matching network have an effect on the system bandwidth, the system efficiency and the system Q, of which the radiation Q is a part. These various relationships are also discussed. View full abstract»

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  • An exact line integral representation of the magnetic physical optics scattered field

    Page(s): 1395 - 1398
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (411 KB) |  | HTML iconHTML  

    An exact line integral representation is derived for the magnetic physical optics field scattered by a perfectly electrically conducting planar plate illuminated by electric or magnetic Hertzian dipoles. The positions of source and observation points can be almost arbitrary. Numerical examples are presented to illustrate the exactness of the line integral representation. View full abstract»

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  • Comprehensive analysis and simulation of a 1-18 GHz broadband parabolic reflector horn antenna system

    Page(s): 1418 - 1422
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (553 KB)  

    A 1-18 GHz parabolic reflector horn antenna system featuring a broadband double ridged primary horn with a coaxial feed line is investigated. For the ridged horn antenna it is found that the radiation pattern, contrary to common belief, does not maintain a single main lobe in the direction of the horn axis over the whole frequency range. Instead, at frequencies above 12 GHz the main lobe in the radiation pattern starts to split into four lobes pointing in off-axis directions with a dip of up to 6 dB between them along the center axis. To investigate this phenomenon in detail, a combined method of moments and physical optics approach has been adopted to simulate the complete antenna system. View full abstract»

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  • Highly efficient C-band circularly polarized rectifying antenna array for wireless microwave power transmission

    Page(s): 1347 - 1356
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (859 KB) |  | HTML iconHTML  

    This paper reports a new circularly polarized (CP) high-gain, high-efficiency rectifying antenna (rectenna) array designed in a coplanar stripline (CPS) circuit. The array can maintain a constant dc output voltage regardless of its broadside orientation. The array is etched on Rogers Duroid 5870 substrate with εr=2.33 and 10 mil thickness. High-gain dual rhombic loop antennas and a reflecting plane are used in order to reduce the total number of rectenna elements necessary to cover a fixed area. Each antenna has a CP antenna gain of 11 dB and a better than 1 dB axial ratio fractional bandwidth of 4.7%. The single element rectenna achieves 81% RF-to-dc coversion efficiency at 5.71 GHz and uses a CPS band-reject filter (BRF) to suppress the reradiated harmonics by more than 19 dB. At 5.61 GHz, using an array loading of 150 Ω, a 3 × 3 rectenna array produces 0.86 W of dc output power with an RF-to-dc conversion efficiency of 78% and an axial ratio of 0.25 dB for an incident CP power density of 7.6 mW/cm2. View full abstract»

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  • Effects of noise and system's parameters on the tomographic image reconstruction of ground surfaces

    Page(s): 1401 - 1403
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (333 KB) |  | HTML iconHTML  

    In a recent paper by the author (for original paper see ibid., vol. 48, p. 1384-1392 (2000)) it has been shown that using the measurements of the scattered fields produced by an isolated ground surface from transmitting antennas in different azimuthal directions, the distribution of the dielectric properties of the isolated ground surface can be reconstructed using well-established ground wave propagation theory. In practice, the operation of a system using this technique is subject to measurement errors and noise, and it also depends on a number of parameters including the operating frequency, the number of antennas used, and their locations. These effects are, thus, studied and the results of the reconstruction errors are presented. View full abstract»

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  • Experimental validation of electromagnetic edge waves on a PEC wedge

    Page(s): 1236 - 1241
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    The dyadic Green's function for electric and magnetic fields of a point current source radiating in close vicinity of a perfectly electric conducting wedge (PEC) has been derived through two independent means by Pearson (1986) and by Buyukdura , Goad, and Kouyoumjian (1996). Asymptotically, a so-called the edge wave may be identified when the source and the observation points are in proximity to the edge but widely separated along the edge, and has become part of the canonical problems in asymptotic diffraction theory. Both of the formulations indicated lead to identical asymptotic results. To corroborate the existence of edge waves, a series of measurements has been performed and the measured data are fit to a model based on the asymptotic results. The fit of the data supports the asymptotic form. View full abstract»

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  • Surface-wave suppression of resonance-type periodic structures

    Page(s): 1221 - 1229
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (691 KB)  

    Periodic structures of the resonance type are investigated with a focus on the utilization of structure dispersion to achieve a wide-band operation for the surface-wave suppression. Both approximate and exact formulations are presented to illustrate wave processes involved in the resonant structure and to develop useful criteria for design purpose. In addition, experiments are performed to verify the phenomena with stopband and leakage associated with the resonance-type periodic structures. View full abstract»

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  • Reduction of backward radiation for CPW fed aperture stacked patch antennas on small ground planes

    Page(s): 1411 - 1413
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (409 KB) |  | HTML iconHTML  

    A coplanar waveguide fed aperture coupled patch antenna mounted on a finite sized ground plane that incorporates a reflector element to reduce backward radiated fields is investigated. By altering the reflector element parameters, the rear field pattern can be adjusted to provide field cancellation in arbitrary directions. View full abstract»

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  • Analysis of hard surfaces of cylindrical structures of arbitrarily shaped cross section using asymptotic boundary conditions

    Page(s): 1150 - 1156
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (471 KB) |  | HTML iconHTML  

    The surface equivalence principle is used to formulate the problem of infinitely long cylindrical structures of arbitrary cross section and loaded with metallic strips. The strips are tilted by an angle with respect to the cross section plane. Special cases are considered when the strips are directed along or transverse to the cylinder axis. The excitation is an oblique plane wave incident with arbitrary polarization. The asymptotic strip boundary condition (ASBC) is used to simplify the problem. The surface integral equations are solved using the method of moments. The numerical solution is verified with the series solutions of the circular cylinders loaded with helical strips. Several applications of hard surfaces are presented for structures loaded with tilted strips such as the struts loaded with tilted strips to reduce the equivalent blockage width of the struts and make it polarization independent. 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