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Antennas and Propagation, IEEE Transactions on

Issue 5 • Date May 1992

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Displaying Results 1 - 16 of 16
  • Two-dimensional angle and polarization estimation using the ESPRIT algorithm

    Publication Year: 1992 , Page(s): 550 - 555
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    It is shown how the ESPRIT (estimation of signal parameters via rotational invariance techniques) algorithm may be used with a square array of crossed dipoles to estimate both the two-dimensional arrival angles and the polarization of incoming narrowband signals. The ESPRIT algorithm exploits the invariance properties of such an array so that both angle and polarization estimates may be computed. Some typical examples showing the use of this approach are presented View full abstract»

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  • Millimeter wave propagation in arid land-a field study in Riyadh

    Publication Year: 1992 , Page(s): 492 - 499
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (620 KB)  

    A field study on wave propagation has been actively running for four years in Riyadh, Saudi Arabia. The study involves the operation and monitoring of two links at a frequency of 40 GHz, and an infrared link at 0.88-μm wavelength. A meteorological station is also operated and monitored. The effect of sand storms on propagation is studied by measuring storm parameters, namely, visibility, particle size and size distribution, and induced attenuation. The results are compared with long-term visibility data for Riyadh, and a complete statistical analysis is given. The effect of rain is studied by measuring both rain rate and rain attenuation. Long-term rain data are utilized to derive long-term rain statistics. It is shown that the measured attenuation due to sand storms is about four times larger than the calculated attenuation at 40 GHz. The measured rain attenuation at infrared is found to be smaller by a factor of 0.3 than theoretically predicted attenuation View full abstract»

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  • Multiport scattering analysis of general multilayered printed antennas fed by multiple feed ports. I. Theory

    Publication Year: 1992 , Page(s): 469 - 481
    Cited by:  Papers (31)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1092 KB)  

    A general solution is given for a class of printed antenna geometries composed of multiple dielectric layers or ground planes, radiating patches, dipoles, or slots, and an arbitrary configuration of multiple transmission lines proximity-coupled or aperture-coupled to the radiating elements. The solution uses a full-wave spectral-domain moment method approach, and a new generalized multiport scattering formulation to model the excitation from the multiple feed lines. This method treats infinite phased arrays as well as isolated elements. The general theory using the new multiport scattering formulation is elaborated, with details of the key analytical and numerical aspects. Considering the unified nature of the multiport scattering analysis, and its simplicity, this analysis is appropriate for computer simulation of a large variety of multilayered microstrip antennas involving radome layers, dual polarized feeds, proximity-coupled or aperture-coupled elements, multifeed stacked or parasitic patches, and several related configurations for integrated phased array applications View full abstract»

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  • Leaky and surface waves in anisotropic printed antenna structures

    Publication Year: 1992 , Page(s): 566 - 569
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    The behavior of the leaky- and surface-wave modes supported by single- and double-layered grounded anisotropic dielectric structures is investigated. Simple low-frequency and high-frequency asymptotic formulas are derived for the wavenumbers. The effects of dielectric anisotropy and losses on the cutoff frequency of the TM and TE surface waves and on the H-plane radiation pattern of a leaky-wave antenna are examined View full abstract»

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  • Accurate characterization of planar printed antennas using finite-difference time-domain method

    Publication Year: 1992 , Page(s): 526 - 534
    Cited by:  Papers (39)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (840 KB)  

    The finite-difference-time-domain method (FD-TD) is used to characterize complex planar printed antennas with various feed structures, which include coaxial probe feed, microstrip line feed, and aperture coupled feed structures. A coaxial probe model is developed by using a three-dimensional FD-TD technique. This model is shown to be an efficient and accurate tool for modeling coaxial line fed structures. A novel use of a dispersive absorbing boundary condition is presented for a printed antenna with a high dielectric constant. All the numerical results obtained by the FD-TD method are compared with experimental results, and the comparison shows excellent agreement over a wide frequency band View full abstract»

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  • Multiport scattering analysis of general multilayered printed antennas fed by multiple feed ports. II. Applications

    Publication Year: 1992 , Page(s): 482 - 491
    Cited by:  Patents (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (792 KB)  

    For Part I, see ibid., vol.40, no.5, p.469-481 (1992). The general analysis of part I is applied to several practical geometries of multilayer/multifeed printed antennas. These examples include a dual-feed circularly polarized geometry; a stacked patch geometry; a stripline-aperture coupled geometry with a radome; an open-end proximity-coupled patch; and dipole and slot geometries inclined or perpendicularly coupled to different feedlines. Features of the selected geometries cover many practical aspects of multilayer integrated phased arrays. Experimental results for several geometries are compared with the analytical results to demonstrate the accuracy and versatility of the analysis used. Various design considerations for the use of these multilayered printed antenna geometries in integrated phase array applications are discussed View full abstract»

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  • Evaluation of Hankel functions with complex argument and complex order

    Publication Year: 1992 , Page(s): 569 - 578
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (596 KB)  

    The use of F.W.J. Olver's (1974) uniform asymptotic expansions to compute Hankel functions (of interest in EM scattering) of complex argument z and complex order v is examined. Emphasis is placed on how to choose the proper branches in evaluation of the complex functions in the asymptotic representations. Comparison is made with the nonuniform formulas of Debye and Watson. The Debye formulas are valid when z and v are far apart, and the Watson formulas are valid when z and v are close together. The fact that the Olver formulas are uniform is important from a numerical viewpoint, because a satisfactory criterion for deciding when to switch between the Debye and Watson (1958) formulas is not available. Validation by comparison with two nonasymptotic methods verifies that the Olver formulas are considerably more accurate than the Debye or Watson formulas View full abstract»

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  • A systematic treatment of conducting and dielectric bodies with arbitrarily thick or thin features using the method of moments

    Publication Year: 1992 , Page(s): 555 - 559
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    A systematic procedure for modeling electromagnetic scattering problems involving bodies with electrically thin features is discussed. The scattering bodies are represented using standard surface integral equation formulations and solutions are obtained via the method of moments (MOM). It is demonstrated that accurate evaluation of the moment matrix elements is critical for obtaining accurate solutions for scatterers having thin features. It is also shown (by numerical example) that some of the various surface integral formulations remain valid and can be used to obtain accurate scattering results for arbitrarily thin dielectric and conducting features. The use of the systematic approach for such problems is illustrated by incorporating the procedures into a two-dimensional (MOM) program. Sample results illustrating the technique's utility and validity are provided View full abstract»

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  • Mutual coupling effects on phase-only direction finding

    Publication Year: 1992 , Page(s): 535 - 541
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    Most direction finding systems currently in use are based on phase-only measurements. The performance of these systems in the presence of mutual coupling is examined. It is shown that phase-only direction finding systems are statistically efficient in the absence of mutual coupling, but they lose this property when mutual coupling is present. Included here are a description of a phase-only algorithm, an analysis of its performance, derivation of the Cramer-Rao bounds for the direction estimates, and some numerical examples View full abstract»

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  • Specification of polarization parameters for optimal-performance in rain of dual circularly polarized radio links

    Publication Year: 1992 , Page(s): 510 - 516
    Cited by:  Papers (3)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (584 KB)  

    Rain depolarization of nominally circularly polarized waves alters the polarization state of the wave to produce a polarization ellipse in which the major axis is tilted with respect to the horizontal. Tilt angles for right-hand and left-hand polarization are opposite in sign. It is shown that these tilt angles are almost independent of rain rate and only slightly dependent on frequency. At 62 GHz the magnitude of tilt is close to 60°C. The suggestion is made that the antenna system be deliberately designed to match, as closely as possible, the polarization state of the incoming wave when the expected rain attenuation is at the design maximum (rain margin) for a given communications link. This strategy assures that the crosstalk between polarizations will be minimized when the signal-to-thermal noise ratio (SNR) is at its lowest value. In clear weather, the SNR will be larger, and a greater degree of polarization crosstalk can be tolerated. Finding an optimal match involves selection of the correct rotational orientation of at least one of the antennas as well as specification of its axial ratio to lie between minimum and maximum limits View full abstract»

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  • Exterior moment method analysis of conducting scatterers by using the interior Green's function and the method of least square

    Publication Year: 1992 , Page(s): 563 - 565
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    A method previously proposed by the authors in 1988 for obtaining the mutual admittance matrix in the moment method analysis by using the interior Green's function is improved by introducing the method of least square (MLS). A numerical example of a two-dimensional problem shows that accurate results can be obtained by introducing the MLS even when arbitrary sources are assumed for numerical experiments in the interior region View full abstract»

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  • Electromagnetic scattering from an inhomogeneous object by ray tracing

    Publication Year: 1992 , Page(s): 517 - 525
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (660 KB)  

    A shooting and bouncing ray (SBR) formulation is presented for treating the electromagnetic scattering from electrically large, inhomogeneous objects. A dense grid of rays representing the incident plane wave is shot toward the inhomogeneous objects. At the scatterer boundary, reflected rays and refracted rays are generated due to the discontinuity of the medium parameters. The trajectory, amplitude, phase and polarization of the rays inside the inhomogeneous object are traced based on geometrical optics. Whenever the rays cross the scatterer surface, additional reflected/refracted rays are generated and are tracked. This is repeated until the intensities of the refracted/reflected rays become negligible. The contributions of the existing rays to the total scattered field are calculated using the equivalence principle in conjunction with a ray-tube integration scheme. The ray formulation is applied to calculate the backscattering from cylinders and spheres and good agreement with the exact series solutions is observed in the high-frequency range. In addition, the backscattering mechanisms in penetrable objects are interpreted in terms of simple ray pictures View full abstract»

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  • Superresolution of multipath delay profiles measured by PN correlation method

    Publication Year: 1992 , Page(s): 500 - 509
    Cited by:  Papers (23)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (724 KB)  

    Time resolution of multipath delay profiles measured by using the autocorrelation of a pseudonoise (PN) code sequence is generally limited by the chip interval of the PN code sequence. A superresolution PN correlation method (SPM) is proposed which improves the time resolution of delay profiles measured by the conventional PN correlation method. The SPM is based on a decomposition of the eigenvector space of the correlation matrix of the delay profile data vector and gives the number of paths and their delay times with higher resolution. It is verified by computer simulations and experiments using coaxial delay lines that the SPM can resolve two paths with a delay difference of a few tenths of the chip interval. The applicability of the SPM to the analysis of an indoor multipath environment in which many delayed waves arrive with short delay differences is demonstrated by an indoor radio propagation experiment at 2.3 GHz View full abstract»

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  • A note on the use of the Neumann expansion in calculating the scatter from rough surfaces

    Publication Year: 1992 , Page(s): 560 - 563
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    The Neumann expansion has been used to compute the solutions of the magnetic-field integral equation (MFIE) for two-dimensional, perfectly conducting, Gaussian, rough surfaces. For surfaces whose roughness is of a similar order to the incident wavelength, it is shown that the expansion may diverge rapidly. The rate of convergence is compared with the conjugate-gradient (CG) method, whose convergence is sure. When it converges, the Neumann expansion convergence is more rapid. It is concluded that the Neumann expansion is not suitable without qualification as a numerical solution to the rough surface MFIE. Moreover, the failure of the Neumann expansion of the solution of the discrete representation of the MFIE provides strong evidence that the use of the Neumann expansion as a formal solution to the MFIE is open to doubt View full abstract»

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  • Finite phased array of microstrip patch antennas: the infinite array approach

    Publication Year: 1992 , Page(s): 579 - 582
    Cited by:  Papers (41)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    An efficient method of analysis of large infinite arrays based on a convolution technique that allows one to obtain the finite array characteristics from the infinite array results is presented. The edge effects are taken into account by convoluting the infinite array results with the proper current amplitude window on the array. The method is based on the use of Poisson's sum formula in the case of finite arrays applied here to microstrip antennas. It is an approximate technique that can be assimilated into a perturbation method View full abstract»

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  • A study of discretization error in the finite element approximation of wave solutions

    Publication Year: 1992 , Page(s): 542 - 549
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (672 KB)  

    A dispersion analysis is used to study the errors caused by the spatial discretization of the finite-element method for the two-dimensional scalar Helmholtz equation. It is shown that the error can be determined analytically for a uniform mesh of infinite extent. Numerical results are presented to show the effects of several parameters on the error. These parameters are the nodal density, the electrical size of the mesh, the direction of propagation of the incident wave, the type of element, and the type of boundary condition 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