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Antennas and Propagation, IEEE Transactions on

Issue 1 • Date January 1982

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Displaying Results 1 - 25 of 27
  • [Front cover and table of contents]

    Page(s): 0
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  • A discussion of various approaches to the identification/approximation problem

    Page(s): 89 - 98
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    The identification/approximation of a linear system by poles and residues from a measured finite length input-output record of the system is discussed. The objective of this paper is to illustrate that several different formulations for characterizing the impulse response of a system yield the same set of poles. View full abstract»

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  • [Back cover]

    Page(s): c4
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  • Unified theory of near-field analysis and measurement: Nonmathematical discussion

    Page(s): 99 - 107
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    A new unified theory of near-field analysis and measurement emphasizes highly accurate, extremely efficient data processing to yield, e.g., radiation, receiving, and scattering patterns, and absolute gain values. The theory includes 17 types of plane rectangular and plane radial scanning, a more accurate and efficient plane polar scanning, spherical scanning, various types of circular cylindrical scanning, many procedures for determining complex dyadic scattering patterns, the extrapolation method for gain and effective area, and application of symmetry analysis to scattering and inverse scattering analysis. High accuracy is obtained by expressing the fields as linear combination of exact solutions of the differential equations involved (Maxwell's in the electromagnetic (EM) cases) and by using exact expressions for their transformations under coordinate changes. High efficiency is obtained with natural orthogonalities of both the solutions and transformation coefficients with respect to integration, especially summation, and implemented with the fast Fourier transform (FFT) as an approximation-free symmetry decomposition. The unified theory is based upon relativistic and gauge invariances, symmetry analysis, and the scattering matrix theory; it yields all the preceding facets and systems, both electromagnetic and scalar, and the single unified notation, general equations, and explicit expressions for the quantities which vary with the physical or scanning system. A nonmathematical discussion of other papers on the theory is provided. Many of the conceptual errors of the literature are corrected. The advantages and limitations of near-field measurements are described, and scanning systems are compared. View full abstract»

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  • An alternative approach to linearly constrained adaptive beamforming

    Page(s): 27 - 34
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    A beamforming structure is presented which can be used to implement a wide variety of linearly constrained adaptive array processors. The structure is designed for use with arrays which have been time-delay steered such that the desired signal of interest appears approximately in phase at the steered outputs. One major advantage of the new structure is the constraints can be implemented using simple hardware differencing amplifiers. The structure is shown to incorporate algorithms which have been suggested previously for use in adaptive beamforming as well as to include new approaches. It is also particularly useful for studying the effects of steering errors on array performance. Numerical examples illustrating the performance of the structure are presented. View full abstract»

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  • Scattering of a dipole field by a moving plasma column

    Page(s): 76 - 82
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    The problem of scattering of a dipole field by a plasma column moving uniformly in the axial direction is treated. In order to know the effect of the motion of the plasma on the scattering pattern, first the scattering properties of the dipole field by a stationary plasma with the aid of numerical examples are discussed. In this case two kinds of scattering patterns are illustrated: one in a cross section of the column and the other in the longitudinal section of the column. Then the scattering pattern of the dipole field by the moving plasma is investigated. From the numerical examples for the stationary plasma it is found that the scattering patterns are well-classified into three typical patterns by investigating the ratio of the backward scattering to the forward scattering with respect to the parameters which govern the scattering properties. In the case of moving plasma, it is shown that the scattering pattern in the longitudinal section will have a characteristic directional pattern, which does not appear in the case of stationary plasma, at a frequency lower than the plasma frequency. View full abstract»

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  • Exact gain measurement of large aperture antennas using celestial radio sources

    Page(s): 157 - 161
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    The correction factors for angular extension of celestial radio sources, Cassiopeia A (Cas A), Taurus A (Tau A), and Cygnus A (Cyg A) were calculated based on the detailed contour maps of brightness temperature. Examinations of the flux densities of those radio sources were made using the published data. The gain of antennas of several sizes measured by using the three radio sources was determined by applying the newly obtained parameters. It was found that the gain of large aperture antennas at 4- and 6-GHz bands could be determined to the accuracy of better thanpm0.45 dB (3sigma)by use of the three radio sources. View full abstract»

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  • Adaptive arrays: A new approach to the steady-state analysis

    Page(s): 128 - 138
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    Our main goal is a closed-form expression for the steady-state output signal-to-noise ratio (SNR) of ann-element adaptive array excited by one desired narrow-band signal andK - 1narrowband jammers. This is facilitated by representing each excitation by a complexn-dimensional vector-the excitation vector. We show that the important system parameters are functions of scalar products of pairs of these exctiation vectors. In particular, the normalized output SNR of the array is shown to be the ratio of determinants whose elements involve these scaler products. Such determinants are also shown to be involved in the expressions for the optimal array weights. View full abstract»

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  • On the integral representation of electromagnetic field vectors

    Page(s): 148 - 153
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    Integral representations of the electromagnetic field vectors are derived by the systematic use of a free-space Green's function and file appropriate Green's theorem. The resulting integrals are in terms of the tangential components of the field vectors at the boundary surface. These representations satisfy Maxwell's equations even for open surfaces, thus additional Kottler's boundary-line charges are not required. Several alternative representations are derived and related to previously known formulas. Some of the computational aspects of these alternatives are pointed out. View full abstract»

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  • Folded and T-matched dipole transformation ratio

    Page(s): 161 - 162
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    Accurate curves of impedance transformation ratio for folded dipoles orT-match dipoles with conductors of unequal radii are presented. View full abstract»

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  • Feed region modes in dipole phased arrays

    Page(s): 66 - 75
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    Feed region modes are derived for a class of dipole phased arrays. The dipole and its balun are a linearly polarized version of the perimeter array radar (PAR) antenna element, and are modeled in strip-line geometry. Knowledge of the feed region modes is essential in determining the influence of supports on the element scan performance, and should shed light on the formation of blind spots in dipole arrays. It is shown that for practical spacings, the balanced strip-line feed structure supports a propagating transverse magnetic (TM) mode in addition to two transverse electromagnetic (TEM) modes. The propagation constant of this mode is scan dependent, and under inappropriate conditions its cutoff occurs before the onset of the grating lobe. Pending further analysis, it is conjectured that this mode cutoff may cause blind spots which limit the array scan coverage. View full abstract»

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  • Radiation from flanged waveguide: Comparison of solutions

    Page(s): 147 - 148
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    The reflection coefficient of the transverse electric (TE1) mode in a flanged parallel-plate waveguide is considered, its solutions derived by the four different methods are numerically compared. View full abstract»

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  • Radiation from an open-ended waveguide with beam equalizer--A spectral domain analysis

    Page(s): 44 - 53
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    A septum and an impedance matching post are used as a beam equalizer in an open-ended waveguide feed for reflectors used in satellite communications systems. The performance of this design over a frequency band is evaluated using a spectral domain approach. The computed radiation patterns in theE- andH-planes, as well as the results for the impedance match are presented. View full abstract»

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  • Ground wave propagation over a mixed path with an elevation change

    Page(s): 139 - 141
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    Calculations have been performed for high frequency (HF) ground wave transmission over a mixed path with an abrupt elevation change. The effect of the elevation change is to decrease the field strength at large distances. View full abstract»

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  • Dielectric tapered rod antennas for millimeter-wave applications

    Page(s): 54 - 58
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    Tapered dielectric rod antennas of rectangular cross section are developed for possible application in millimeter-wave dielectric integrated circuits. Design principles for a maximum gain design are described, and an example is given. Experimental results for antennas designed for low sidelobes and for maximum gain are presented. View full abstract»

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  • Efficient computation of antenna coupling and fields within the near-field region

    Page(s): 113 - 128
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    The theory, techniques, details of the important equations, and description of two computer programs are presented for calculating efficiently the mutual coupling at a single frequency between any two antennas arbitrarily oriented and separated in free space. Both programs emphasize efficiency and generality, and require, basically, the complex electric far field of each antenna, and the Eulerian angles designating the relative orientation of each antenna. Multiple reflections between the antennas are neglected but no other restrictive assumptions are involved. If an electric field component is desired instead of coupling, the receiving antenna is replaced by a virtual antenna with uniform far field. The first computer program computes coupling (or fields) versus transverse displacement of the antennas in a plane normal to their axis of separation. An efficient fast Fourier transform (FFT) program was made possible by "collapsing" the far-field input data and showing that inmost cases the spectrum integration need cover only the solid angle mutually subtended by the smallest spheres circumscribing the antennas. Limiting the integration to this solid angle artifically band limits the coupling function, thereby allowing much larger integration increments and reducing run times and storage requirements to a feasible amount for electrically large antennas. The second program is based on a spherical wave representation of the coupling function and rapidly computes coupling (or fields) versus separation distance between the antennas. The spherical wave representation emerged naturally from an intriguing characteristic proven for the mutual coupling function; it, like each rectangular component of electric and magnetic field in free space, satisfies the homogeneous wave equation. View full abstract»

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  • Precision experimental characterization of the scattering and radiation properties of antennas

    Page(s): 108 - 112
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    An accurate and simple experimental technique to characterize the scattering and radiation properties of antennas has been developed. The structural scattering constant is determined by the relative amplitude and phase of the radar cross section (RCS) of the antenna. The antenna gain can also be readily obtained from this information and from an absolute calibration for the echo amplitude. In comparison with other methods this phase-distinction technique is considered more convenient to use and is more accurate for antennas with a structural constant approaching unity. View full abstract»

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  • Boresight-gain loss and gore-related sidelobes of an umbrella reflector

    Page(s): 153 - 157
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    It is shown that energy in the gore-related sidelobes of an umbrella reflector comes from energy lost from the main beam. Both boresight gore-loss and sidelobe level correlate directly with cyclic aperture phase error caused by the geometry. The gore-sidelobe peak is located neartheta_{p}, wheresin theta_{p} = 1.2N_{G} (pi/Dlambda)whereN_{G}is the number of gores andDis the reflector diameter. An expression is also derived for the amplitude of the gore-related sidelobe. View full abstract»

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  • Surface-curvature-induced microwave shadows

    Page(s): 83 - 88
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    Ray behavior and the corresponding fields in the vicinity of surface-curvature-induced reflection boundaries are examined and compared with edge-induced reflection boundaries. The slopes of the reflection boundaries vary, respectively, as(lambda)^{-5/6}and(lambda)^{-1/2}. Asymptotic evaluation of the physical optics scattering integrals leads to the definition of equivalent "diffrhction" coefficients involving the Airy function. View full abstract»

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  • A low elevation angle propagation measurement of 1.5-GHz satellite signals in the Gulf of Mexico

    Page(s): 10 - 15
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    The current maritime L-band (1.5-GHz) mobile satellite communications service (MARISAT) is not available for communications paths below10degelevation angles because fading and scintillation at low elevation angles introduce signal degradations. These are attributable to scattering, diffraction, and multipath effects arising from ionospheric, tropospheric, and/or sea surface irregularities. To obtain a better understanding of the above-mentioned signal degradations, propagation measurements were made in the Gulf of Mexico with a MARISAT terminal on board the SS Mobil Aero for elevation angles from ship to satellite in the15degto0degrange. Results indicated that mean signal strength was severely attenuated with remarkably increased fluctuations at elevation angles below5deg. Characterizations of signal strength and peak-to-peak fluctuations of the L-band signal as a function of elevation angles are presented. View full abstract»

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  • Transmission into staggered parallel-plate waveguides

    Page(s): 35 - 43
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    The modal field transmitted into a staggered parallel-plate waveguide when illuminated by a line source is studied. To widen the limited applicability of existing ray methods, an aperture field integration (AFI) method is developed, in which the field in the waveguide aperture is first calculated by high-frequency techniques (uniform asymptotic theory (UAT) and spectral theory of diffraction (STD)) and then decomposed into modal fields via the Fourier analysis. For problems in which the exact Wiener-Hopf and/or the ray solutions are available, AFI gives excellent numerical results. New results are staggered waveguides which find application in the analysis of a waveguide lens. View full abstract»

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  • A statistical raindrop canting angle model

    Page(s): 141 - 147
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    A mathematical model to predict accurately the mean and standard deviation of each drop-size canting angle, assuming Gaussian canting angle distributions, is presented. The model utilizes the one-dimensional energy spectrum of horizontal turbulence given by Davenport. By using the differential equation for the horizontal-drop movement, the mean and standard deviation of each drop-size canting angle are calculated. Comparison with Saunders's work shows good agreement. View full abstract»

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  • Diakoptic theory for multielement antennas

    Page(s): 15 - 26
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    A theory is presented for the analysis of multielement antennas which consist of interconnected, conductive structure elements of electrically small dimensions. The theory is based on the retarded electromagnetic potentials which permit a diakoptic approach to the problem. The antenna is broken up into its individual structure elements. Each element is assumed to be excited by currents which are impressed at its terminals, i.e., junctions with adjacent elements (current coupling) and by the electric fields of the currents and charges on all the other elements (fieid coupling). Both excitations are treated independently. Each impressed current produces a "dominant" current distribution, a characteristic of the element, which can be readily computed. Current coupling is formulated by "intrinsic" impedance matrices which relate the scaler potentials at the terminals of an element, caused by its dominant current distributions, to the impressed currents of the element. Field coupling produces "scatter" currents on all the elements and is formulated by a "fieid-coupling" matrix which relates the scalar potentials at the terminals, caused by field coupling, to the impressed currents at all the terminals. Intrinsic and "field-coupling" matrices are combined to form the "complete" impedance matrix of the diakopted antenna. Enforcing continuity of the currents and equality of the scalar potentials at all the interconnections between the elements yields a system of linear equations for the junction currents and the input impedance of the antenna. Current coupling dominates field coupling. Fieid coupling is primarily affected by the dominant current distributions of the elements, and in general the scatter currents have negligible effect on it. Although detailed numerical investigations will be presented in another paper, a simple example is included here to demonstrate that the diakoptic theory yields very good results even if greatly simplified assumptions are made. 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