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Antennas and Propagation, IEEE Transactions on

Issue 4 • Date April 1985

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Displaying Results 1 - 22 of 22
  • [Front cover and table of contents]

    Publication Year: 1985 , Page(s): 0
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    Freely Available from IEEE
  • A note on the choice weighting functions in the method of moments

    Publication Year: 1985 , Page(s): 436 - 441
    Cited by:  Papers (22)
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    The objective is to show from a mathematical standpoint that there are certain rules that must be followed in the choice of weighting functions used in the method of moments (MM). It is shown that for a particular problem it is the operator that dictates the method (Galerkin's method or another method such as the method of least squares) to be applied, and it is not computational considerations only. For example, it is shown that in solving Hallen's and Pocklington's equation by the method of moments, it is unnatural to choose the weighting functions which are zero at the ends of the domain of the solution. The deficiency of certain weighting functions is presented based on mathematical reasoning, and a numerical example is given to illustrate the effect of the choice of the weighting functions on the rate of the convergence of the solution. View full abstract»

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  • Plane wave reflection from microstrip-patch arrays--Theory and experiment

    Publication Year: 1985 , Page(s): 426 - 435
    Cited by:  Papers (13)
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    Numerical solution of plane wave reflection from an infinite, planar rectangular microstrip-patch array on a grounded dielectric substrate is presented and compared to phased array simulator measurements with a good correlation. In the theory, particular attention is paid to the edge condition and to the convergence of the matrix elements which was accelerated by the Poisson summation technique, as well as to the rate of convergence of the overall solution. The agreement of the values of the resonant frequencies, the associated Q values, and their parametric dependence on geometry and frequency, establish confidence in the application of the method used, to prediction of performance of probe-excited microstrip-patch phased arrays. View full abstract»

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  • Worst month statistics of attenuation and XPD on Earth-space path

    Publication Year: 1985 , Page(s): 390 - 396
    Cited by:  Papers (2)
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    Using the attenuation and cross-polarization discrimination (XPD) statistics measured in the CS (20/30 GHz) and BSE (12/14 GHz) centimeter wave propagation experiments performed for over four and three years, the worst month statistics of attenuation and those of XPD on earth-space path at 11.7 and 19.5 GHz are derived. The probability relation between the annual and worst month statistics is approximated by a power-law relation, and the constants for the relation are derived by a least squares procedure. It is found that the relation is independent of both frequency and polarization. The cumulative probability ratios of the worst month to annual statistics at the same attenuation or XPD values are derived as a function of annual cumulative probability. The ratios are well described by the Brussaard model of the worst month statistics. Attenuation ratio and XPD difference among the annual and worst month statistics are also derived and compared with the predicted results. View full abstract»

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  • Input impedance of annular ring microstrip antenna using circuit theory approach

    Publication Year: 1985 , Page(s): 369 - 374
    Cited by:  Papers (25)
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    Input impedance and bandwidth of an annular ring microstrip antenna have been determined by modeling the antenna as a section of radial line loaded with wall admittances. The effect of mutual coupling between the radiating apertures has been taken into account. The theoretically calculated values of input impedance for TM12-mode are compared with measurements. The agreement is good. Higher order modes have been found to be present in the vicinity of TM12-mode. The reactance due to these modes can be utilized to increase the voltage standing-wave ratio (VSWR) bandwidth of the antenna. View full abstract»

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  • Analysis of a microstrip array and feed network

    Publication Year: 1985 , Page(s): 397 - 403
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    An analysis technique for a microstrip array is presented. The array elements and mutual coupling between elements are analyzed by a method of moments (MM) solution of the exact integral equation. The combination of the microstrip array elements, plus the microstrip transmission line feed network is analyzed using a generalized Thévenin theorem. The method is applied to the specific problem of the series fed microstrip array. View full abstract»

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  • A continuation method for identification of the natural frequencies of an object using a measured response

    Publication Year: 1985 , Page(s): 445 - 450
    Cited by:  Papers (16)
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    The identification of the natural frequencies of an object using measured data is an ill-conditioned problem. A method and algorithm to solve the problem based on regularization by a continuation method is presented. The algorithm is applied to the measured response of a model aircraft, and the superiority of this method to Prony's method in the presence of noise is demonstrated. View full abstract»

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  • Characteristics of a crossed-wire scatterer without a junction point of an incident wave of circular polarization

    Publication Year: 1985 , Page(s): 409 - 415
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    A crossed-wire scatterer has the wires displaced in the backscattering direction, and is able to scatter an incident wave of circular polarization in such a way that the backscattering wave has the same rotational sense as that of the incident wave. The radiation performance of the scatterer is improved by bending the horizontal and the vertical wires. Arrays consisting of crossed-wire scatterers are constructed and the backscattering cross sections (BSCS's) are calculated. It is revealed that the increase in the current amplitude due to the mutual effects among the array elements contributes to enhancement in the BSCS. It is also shown that a maximum value of the BSCS of an array of 3 \times 3 bent crossed-wire scatterers is 1.8 times as large as that of a dihedral corner reflector which has the same aperture area. The BSCS's as a function of the angle of incidence are presented with experimental results at a frequency of 9.375 GHz. View full abstract»

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  • Arrays of horizontally polarized loop-fed slotted cylinder antennas

    Publication Year: 1985 , Page(s): 375 - 382
    Cited by:  Papers (1)  |  Patents (3)
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    Measured center element gain patterns, voltage standing-wave ratio (VSWR), and mutual coupling for passively terminated arrays of horizontally polarized loop-fed slotted cylinder antennas over a ground plane are given. A seven-element hexagonal array is investigated in detail. The element gain pattern is shown to have a null at broadside with omnidirectional coverage along a constant cone angle from broadside. Maximum gain occurs close to 50\deg from broadside which provides for wide-angle phased array scanning capability. The antennas are also configured in a linear array geometry, to investigate mutual coupling effects on the element gain pattern as the number of elements is varied. The element gain pattern is shown to converge for a relatively few number of elements and there is no indication of undesired blind spots. View full abstract»

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  • On combined source solutions for bodies with impedance boundary conditions

    Publication Year: 1985 , Page(s): 462 - 465
    Cited by:  Papers (2)
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    Numerical solutions to the impedance boundary condition (IBC) combined source integral equation (CSIE) for scattering from impedance spheres are presented. The CSIE formulation is a well-posed alternative to the IBC electric and magnetic field integral equations which can be contaminated by spurious resonant modes. Compared with the IBC combined field integral equation (CFIE), CSIE solutions have the same accuracy when the combined source coupling admittance is chosen to be the same value as the combined field coupling admittance. However, the CSIE formulation is better suited than the CFIE for creating a general purpose computer code capable of handling aperture radiation problems and/or a scatterer which has a spatially varying surface impedance. View full abstract»

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  • Boundary element method for electromagnetic scattering from cylinders

    Publication Year: 1985 , Page(s): 383 - 389
    Cited by:  Papers (23)
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    The computation of low frequency scattering of electromagnetic fields by solid/hollow dielectric or conducting cylinders using the boundary element method (BEM) is considered. A general computer program has been developed for both transverse electric and magnetic cases. Numerical examples are given for conducting circular cylinders, and solid and hollow dielectric cylinders. The computational accuracy is checked by comparing the results with the analytic solution or computing an error defined from the optical theorem. In addition some problems at an interior resonance of the scatterer are discussed. The method can be directly applied to more complicated geometries. View full abstract»

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  • Maximization of the directive gain of a parabolic reflector antenna

    Publication Year: 1985 , Page(s): 458 - 462
    Cited by:  Papers (1)
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    The directive gain of a parabolic reflector antenna is maximized by optimizing the feed aperture distribution. The feed aperture distribution is specified by a set of N basis functions weighted by coefficients to be determined. This approach is different from the conventional method where, given a particular feed, the directive gain is maximized by subjecting the reflector aperture parameters to optimization. View full abstract»

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  • Covariance of narrow-band noise in multiple beams of a phased-array system

    Publication Year: 1985 , Page(s): 455 - 458
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    Covariance of narrow-band noise among two simultaneous beams, looking toward different directions with identical power patterns, for a phased array system is formally analyzed. It is shown that the noise correlation coefficient as a function of the angle of separation between two beams is the same as the normalized beam power pattern. This result is independent of the way the beams are formed, in particular these conclusions for both the total power beam systems and the correlator beam systems are examined in detail. View full abstract»

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  • High frequency diffraction by wedges

    Publication Year: 1985 , Page(s): 357 - 368
    Cited by:  Papers (6)
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    Methods for handling high frequency fields are briefly reviewed. They are illustrated by the diffraction of a ray optical field by a curved wedge. The necessary formulas are collected or referred to for a direct application to the problem. The corresponding canonical problem, diffraction of a plane wave by a straight wedge, is presented from a point of view that shows the filiation of some diffraction factors and suggests generalization to other problems such as the diffraction by higher order wedges. View full abstract»

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  • Radiation characteristics of spherical triangular array antenna

    Publication Year: 1985 , Page(s): 472 - 476
    Cited by:  Papers (4)
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    Radiation characteristics of a type of spherical triangular array composed of turnstile elements are numerically analyzed and discussed. It is found that the spherical array proposed here is able to scan its beam up to large angle without variation of the directivity and the circular polarization property. View full abstract»

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  • The induced magnetic dipole of a polarized sphere

    Publication Year: 1985 , Page(s): 465 - 467
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    A homogeneous spherical body with a frequency dependent complex resistivity is placed in a uniform time varying magnetic field. It is shown that the induced magnetic dipole has a complex form that depends on the ratio of the diameter to the internal skin depth in a customary fashion. But the frequency dependence of the induced dipole is also influenced by the polarization properties of the material. A Cole-Cole form for the complex resistivity is employed to characterize the electrochemical polarization. View full abstract»

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  • Sunrise and sunset effects as observed on microwave propagation over a line-of-sight path

    Publication Year: 1985 , Page(s): 441 - 445
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    Microwave signal propagation provides an effective measure of studying the variable nature of the atmosphere. Sunrise and sunset periods are characterized by the dissolution and formation of nighttime temperature inversions. Signal amplitude recordings at 6.7 GHz over DumDum-Andul line-of-sight (LOS) communication link during post-sunrise period are characterized by the appearance of an enhancement in signal strength (as high as 20 dB). The sunset effect or the evening transition is observed as an enhancement in signal amplitude of about 10- 12 dB over the link. The signal characteristics observed during transition periods over the 6.7 GHz DumDum-Andul link are studied herein. View full abstract»

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  • Field singularities at metal-dielectric wedges

    Publication Year: 1985 , Page(s): 450 - 455
    Cited by:  Papers (28)
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    The wedges discussed are the dielectric wedge, the metallic 90\deg corner on a dielectric plane, and the adjacent 90\deg metallic and dielectric corners. The field components perpendicular to the edge may become infinite according to a law ( 1/r^{n} ). Numerical data are given for n , and plots of lines of force of \bar{e} (or \bar{h} ) are shown. View full abstract»

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  • Active microwave imaging of inhomogeneous bodies

    Publication Year: 1985 , Page(s): 416 - 425
    Cited by:  Papers (64)
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    A numerical method and experimental technique for microwave imaging of inhomogenous bodies is presented. This method is based on the interpretation of the diffraction phenomena and leads to tomographic reconstruction of the body under investigation. Various numerical examples are given on spatial impulse response, recognition of dielectric rods, inhomogeneous bodies, and simulated human arm. Different experimental results on dielectric rods and isolated animal organs are also given. View full abstract»

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  • Probe uncompensated near-field to far-field transformation for scanning over an arbitrary surface

    Publication Year: 1985 , Page(s): 467 - 472
    Cited by:  Papers (1)
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    A new technique of transforming the probe uncompensated near-field data to the near or far field is presented, which is useful in nearfield antenna measurements, when the probe antenna scans over an arbitrary surface enclosing the test antenna. The technique presented is analytically simple and sufficiently accurate. View full abstract»

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  • Classes of exactly reconstructable spherically distributed indices of refraction

    Publication Year: 1985 , Page(s): 476 - 478
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    Classes of exactly reconstructable spherically distributed indices of refraction are obtained by considering Bargmann potentials for the auxiliary quantum mechanical inverse scattering problems. Simple examples are given to illustrate the general procedure. View full abstract»

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  • The perfectly conducting wire grating: Computation of the diffracted field from Maxwell's equations and Hamilton's canonical system

    Publication Year: 1985 , Page(s): 404 - 408
    Cited by:  Papers (2)
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    A theoretical and numerical study of the perfectly conducting wire grating is presented. For both fundamental cases of polarization, we solve the Helmholtz equation rigorously without any physical simplifying assumption. The only approximations are due to the use of numerical techniques in the integration of a differential system. The wire cross section is to a large extent arbitrary. The interest of Hamilton's canonical equations in the numerical treatment of certain practical problems is shown. No doubt, certain ideas contained herein could be adapted for solving many other problems in electromagnetic theory. 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