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Antennas and Propagation, IEEE Transactions on

Issue 11 • Date November 1985

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Displaying Results 1 - 18 of 18
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • Introduction

    Page(s): 1161 - 1162
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    Freely Available from IEEE
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  • Monopulse printed circuit dipole array

    Page(s): 1280 - 1283
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    The design and performance of a monopulse Ku-band planar array is described. The antenna is designed to provide 20 dB sidelobes sum pattern in the azimuth plane and an operating bandwidth of 1 GHz (16.25-17.25 GHz). The voltage standing-wave ratio (VSWR) of this array at the input is less than 2:1 over the bandwidth. View full abstract»

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  • Resonant length of longitudinal slots and validity of circuit representation: Theory and experiment

    Page(s): 1264 - 1271
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    Pertinent theory for the design of longitudinal slot arrays is reviewed and its dependence on the dominant mode scattering off a single slot is pinpointed. The critical need to know resonant length versus slot offset is emphasized and the desirability of determining this information theoretically rather than experimentally is argued. Then method of moments solutions are used to calculate resonant length versus slot offset for given waveguide dimensions and frequency. These theoretical results are compared to new, carefully obtained experimental data. Agreement is found to be so good, it is concluded that one can dispense with the costly gathering of experimental input data when designing longitudinal slot arrays fed by standard rectangular waveguide. A critical look is taken at the validity of representing the longitudinal slot as a shunt element on an equivalent transmission line. This assumption is found to be more and more questionable as the b dimension is reduced. For quarter-height guide, an alternate design procedure is suggested as being more accurate. View full abstract»

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  • An iterative method for solving scattering problems

    Page(s): 1272 - 1279
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    An iterative method is developed for computing the current induced by plane wave excitation on conducting bodies of arbitrary shape. In this method, the scattering body is divided into lit- and shadow-side regions separated by the geometric optics boundary. The induced current at any point on the surface of the scatterer is expressed as the sum of an approximate optics current and a correction current. Both of these currents are computed by iteration for the lit and shadow regions separately. The general theory is presented and applied to the problems of scattering from a two-dimensional cylinder of circular and square cross sections. The results are compared with the method of moments and good agreement is obtained. This method does not give erroneous results at internal resonances of the scatterer, does not suffer from computer storage problems and can be extended to nonperfect conductors as well as to three-dimensional bodies. View full abstract»

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  • The receiving antenna as a linear differential operator: Application to spherical near-field scanning

    Page(s): 1175 - 1185
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    The general receiving antenna is represented as a linear differential operator converting the incident field and its spatial derivatives at a single point in space to an output voltage. The differential operator is specified explicitly in terms of the multipole coefficients of the antenna's complex receiving pattern. When the linear operator representation is applied to the special probes used in spherical near-field measurements, a probe-corrected spherical transmission formula is revealed that retains the form, applicability, and simplicity of the nonprobe-corrected equations. The new spherical transmission formula is shown to be consistent with the previous transmission formula derived from the rotational and translational addition theorems for spherical waves. View full abstract»

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  • Resolving uncorrelated and correlated sources by linear prediction

    Page(s): 1221 - 1227
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    The resolution and the estimation error are investigated for two linear prediction (LP) algorithms for bearing estimation with uniform linear array of sensors, in the presence of incoherent and coherent sources: the Burg algorithm (BA) and the generalized Burg algorithm (GBA). The superresolution is easily achieved with both algorithms when the sources are incoherent. For coherent sources, however, the BA estimate is somewhat more sensitive to the magnitude and the phase of the intersignal correlation than the GBA, thereby resulting in the increased error in the bearing estimates. View full abstract»

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  • Electromagnetic surface waves: New formulas and applications

    Page(s): 1204 - 1212
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    Relatively simple and accurate formulas are now available for the complete electromagnetic field generated by vertical and horizontal dipoles located on or near the boundary between two electrically different half-spaces such as air and water or rock and sea water. The principal part of the field is an outward-traveling lateral wave with useful properties. The formulas are given and their application to a variety of problems reviewed briefly. These include: radio communication over the surface of the earth or sea, the wave antenna, communication with submarines using vertical dipoles in air and horizontal dipoles in the sea, the location of buried objects using horizontal dipoles on the surface of the earth, and the measurement of the conductivity of the sea floor. View full abstract»

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  • Synthesis of spacecraft array antennas for intelsat frequency reuse multiple contoured beams

    Page(s): 1186 - 1193
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    A method is described for synthesis of planar array antennas where both the amplitude and phase of each radiating element is a design variable. The method improves the computational efficiency of conventional optimization procedures based upon, for example, minimax or least square algorithms. Application of the proposed method demon-strafes the feasibility of spacecraft frequency reuse array antennas with multiple contoured beams for typical Intelsat sixfold frequency reuse requirements. It is demonstrated that repetitive optimization will reduce the number of array elements required. Shifting the array aperture normal toward a beam center will dramatically improve the frequency sensitivity of the beam coverage. View full abstract»

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  • Directivity optimization of a reflector antenna with cluster feeds: A closed-form solution

    Page(s): 1163 - 1174
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    The directivity of a reflector antenna deteriorates as the feed moves away from the focal point for beam scanning. This deterioration can be substantially reduced if a cluster feed instead of a single feed is used to control a beam. A closed-form solution is presented for the cluster excitation to achieve the optimum directivity. For an offset 108 \lambda parabolic reflector scanning 10 beamwidths, the optimum-directivity achieved by a 19-element (seven-element) cluster is 12 dB (8 dB) higher than that of a single element. Comparison of the optimum-directivity design and the popular conjugate field matching design is made. When the cluster spacing d is greater than 1 \lambda , it is found that the optimum directivity is higher than that of conjugate field matching (CFM) scheme by an insignificant amount, although the excitations of two designs can be quite different. For d < 0.5 \lambda , the optimum design may exhibit the supergain phenomenon, namely, extremely high directivities achieved by an oscillatory cluster excitation. View full abstract»

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  • Finite periodic structure approach to large scanning array problems

    Page(s): 1213 - 1220
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    There are two conventional techniques dealing with mutual coupling problems for antenna arrays. The "element-by-element" method is useful for small to moderate size arrays. The "infinite periodic structure" method deals with one cell of infinite periodic structures, including all the mutual coupling effects. It cannot, however, include edge effects, current tapers, and nonuniform spacings. A new technique called the "finite periodic structure" method, is presented and applied to represent the active impedance of an array, it involves two operations. The first is to convert the discrete array problem into a series of continuous aperture problems by the use of Poisson's sum formula. The second is to use spatial Fourier transforms to represent the impedance in a form similar to the infinite periodic structure approach. The active impedance is then given by a convolution integral involving the infinite periodic structure solution and the Fourier transform of the equivalent aperture distribution of the current over the entire area of the array. The formulation is particularly useful for large finite arrays, and edge effects, current tapers, and nonuniform spacings can also be included in the general formulation. Although the general formulation is valid for both the free and forced modes of excitation, the forced excitation problem is discussed to illustrate the method. View full abstract»

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  • Optimized three-dimensional lenses for wide-angle scanning

    Page(s): 1227 - 1236
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    Three-dimensional bootlace lens antennas with two and four focal points can be optimized to produce high-quality scanned beams over a wide field of view. For two-dimensional scanning, the planar feed locus is replaced by a curved feed locus designed to minimize path length errors. Comparisons with previous bootlace lens designs demonstrate the advantages of this focal distribution. The bifocal lens shows good scanning performance in both principal and orthogonal planes. The quadrufocal lens performs better in its principal plane than in its orthogonal plane. It is also shown that the quadrufocal lens can be realized with a planar outer surface and a circular focal arc, and improved scanning performance is still achievable. Further optimization of the focal arc and/or relaxation of the planar outer surface condition results in quadrufocal lenses with negligible phase errors in the principal plane. View full abstract»

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  • An aperture-matched compact range feed horn design

    Page(s): 1249 - 1255
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    The moment method and the uniform geometrical theory of diffraction are used to obtain two separate solutions for the E -plane far field pattern of an aperture-matched horn antenna. This particular horn antenna consists of a standard pyramidal horn with the following modifications: a rolled edge section attached to the aperture edges and a curved throat section. The resulting geometry provides significantly better performance in terms of the pattern, impedance, and frequency characteristics than normally obtainable. The moment method is used to calculate the E -plane pattern and voltage standing-wave ratio (VSWR) of the antenna. However, at higher frequencies, the moment method requires large amounts of computation time. On the other hand, the uniform geometrical theory of diffraction provides a quick and efficient high frequency solution for the E -plane field pattern. In fact, the uniform geometrical theory of diffraction may be used to initially design the antenna; then the moment method may be applied to "fine tune" it. In both methods, a two-dimensional E -plane model of the antenna is used, but these two-dimensional solutions yield excellent agreement with measured data of the actual three-dimensional antenna. This procedure has been successfully applied to design a compact range feed horn. View full abstract»

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  • Microwave holography of large reflector antennas--Simulation algorithms

    Page(s): 1194 - 1203
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    The performance of large reflector antennas can be improved by identifying the location and amount of their surface distortions and then by correcting them. Microwave holography techniques are finding considerable applications as viable tools for performing this task. In these techniques, the complex (amplitude and phase) far-field pattern of the antenna is measured, using a reference antenna. Then, the Fourier transform relationship, which exists between the far field and a function related to the induced current, is invoked to result in the identification of the surface distortions. To critically examine the accuracy of the constructed surface profiles, simulation studies are required to incorporate both the effects of systematic and random distortions, particularly the effects of the displaced surface panels. In this paper, different simulation models are investigated with emphasis given to a model based on the vector diffraction analysis of a curved reflector with displaced panels. The simulated far-field patterns are then used to reconstruct the location and amount of displacement of the surface panels by employing a fast Fourier transform (FFT)/iterative procedure. The sensitivity of the microwave holography technique based on the number of far-field sampled points, level of distortions, polarizations, illumination tapers, etc., is also examined. In addition, the relationships between Az-El and u-v spaces are addressed in the Appendix. Most of the data are tailored to the dimensions of the NASA/JPL Deep Space Network (DSN) 64-m reflector antennas for which the result of a recent measurement is also presented. View full abstract»

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  • Mutual admittance characteristics for two-element parallel prolate spheroidal antenna systems

    Page(s): 1255 - 1263
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    Spheroidal dipole antenna systems consisting of two thin center-fed parallel prolate spheroids in various configurations (side-by-side and collinear) are considered, The resultant EM fields are represented as modal expansions in terms of spheroidal vector eigenfunctions. The translational addition theorems for spheroidal functions developed by the authors in a previous paper play the central role in the formulation of a system matrix [ G ] which transforms the primary. EM excitations of the fed dipoles into their scattered responses. From the knowledge of the [ G ] matrix, the mutual admittances of the dipole system are obtained and plotted against center-to-center separation of the dipoles for side-by-side and collinear dipole configurations. The major to minor axial ratios of 10:1 and 100:1 of the prolate spheroidal dipoles are considered for presenting various curves. However, for the side-by-side configuration, due to a radius of convergence of the translational relation for outgoing wave to incoming wave transformation, the separation d of the spheroids is restricted to d > {a_{1}, a_{2}}_{\max } , whose a_{1} and a_{2} are the semimajor axial lengths of the two spheroids. View full abstract»

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  • Phase-space asymptotic analysis of wave propagation in homogeneous dispersive and dissipative media

    Page(s): 1237 - 1248
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    Arising naturally in the study of one-dimensional pulse propagation in homogeneous dispersive and/or dissipative media are certain classes of oscillatory and/or diffusion integrals which encompass the canonical diffraction catastrophe integrals due originally to Thorn and Arnold. This is especially evident within the framework of a phase-space asymptotic analysis. Depending on the order of approximation of the exact solution beyond the Liouville or "first-order quasiparticle" limit, one recognizes caustic-like structures smoothed over by hyperdiffusion. Asymptotic series for these structures, which essentially define new basic functions, have been derived, but will not be presented here. Only the salient features of these structures will be reviewed briefly, and they will be illustrated by means of several simple canonical problems. Also, their applicability to other physical areas (e.g., wave propagation in deterministically and/or randomly varying channels, diffraction, etc.) will be pointed out. View full abstract»

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Aims & Scope

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

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Editor-in-Chief                                                 Kwok W. Leung