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Antennas and Propagation, IEEE Transactions on

Issue 3 • Date May 1976

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Displaying Results 1 - 25 of 28
  • [Front cover and table of contents]

    Publication Year: 1976 , Page(s): 0
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    Freely Available from IEEE
  • Corrections to "Electronic lobe switching by 90° corner reflector antenna with ferrite cylinders"

    Publication Year: 1976 , Page(s): 394
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    First Page of the Article
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  • [Back cover]

    Publication Year: 1976 , Page(s): c4
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    Freely Available from IEEE
  • The design of correcting secondary reflectors

    Publication Year: 1976 , Page(s): 336 - 340
    Cited by:  Papers (15)
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    A computer program called DERIVE is described for the design of the reflecting surfaces of two-mirror radio telescopes. It calculates the shape of a secondary reflector to any given primary by use of geometrical optics, yielding zero path length errors for all paraxial rays. The only condition to be fulfilled is (for Cassegrain types) that incoming rays, after reflection at the primary, do not cross each other before reaching the secondary. Equations for this condition are given. This method can be used to improve existing telescopes at short wavelengths by correcting for the surface deviations of the primary reflector with a specially shaped secondary. The results of 17 calculated examples are described, for various types of deviations View full abstract»

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  • 90° rotation of a line source by reflection

    Publication Year: 1976 , Page(s): 384 - 387
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    A new reflecting surface that re-orients a line-source through an angle of 90\deg is discussed. Several curves on the surface are simple parabolas and ellipses, but the expression for an arbitrary curve on the surface is a fourth-order equation. The curves are derived by preserving phase relationship between the line source and the rotated line using geometrical optics. The intensity distribution on the rotated line is found by numerical integration. View full abstract»

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  • The insulated conductor as a scattering antenna in a relatively dense medium

    Publication Year: 1976 , Page(s): 327 - 330
    Cited by:  Papers (6)
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    A simple formula is derived for the current induced in an insulated conducting cylinder when embedded in an isotropic homogeneous dissipative medium and excited by a periodic electric field with uniform amplitude and phase along its axis. The currents on electrically short, resonant, and terminated insulated conductors are discussed. View full abstract»

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  • Study by conformal mapping of TE and TM waves in open dielectric waveguides

    Publication Year: 1976 , Page(s): 353 - 356
    Cited by:  Papers (1)
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    We show by suitable conformal mapping and appropriate boundary conditions that the H guide permits study on the Goubau line, the O guide, and the dielectric rod. By this method, we confirm a well-known result [10] and generalize about some new waveguides. View full abstract»

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  • Dipole group delay time

    Publication Year: 1976 , Page(s): 388 - 389
    Cited by:  Papers (2)
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    For wideband communication systems, the differential group delay time may be a critical parameter. Dipole type elements are frequently used in arrays at the low end of the microwave band; the group delay of a dipole is calculated for frequencies in the vicinity of a half wavelength. The calculation is based on the zero order impedance and a formula developed previously for computer use. View full abstract»

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  • A note on SAR imagery of the ocean

    Publication Year: 1976 , Page(s): 393 - 394
    Cited by:  Papers (16)
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    An example of SAR imagery of the ocean surface including the Gulf Stream Boundary reported by Moskowitz [1] is used to discuss potential mechanisms of SAR image formation of the ocean. It is pointed out that images in addition to those due to modulation of surface scatterer strength may result from organized scatterer motions such as those due to currents or wave orbital velocities. The modulation of scattering cross section by large waves is expected to depend on the magnitude and direction of the wind, making the relationship between image strengths and wave amplitudes rather complicated. It is suggested that the effect of wave orbital accelerations upon azimuthal focus might provide a more direct measure of wave amplitude. View full abstract»

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  • Terrain modeling using the half-plane geometry with applications to ILS glide slope antennas

    Publication Year: 1976 , Page(s): 370 - 378
    Cited by:  Papers (4)
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    A technique for modeling ground terrain is presented. The analysis is based on resolution of the ground in question into semi-infinite planes or strips. Using the half-plane solutions for diffracted radiation developed by Senior, Woods, and Bromwich it is shown that with slight modification, the effects of arbitrarily oriented dipole and ground planes can be considered. Application of the modeling is presented for instrument landing system (ILS) glide slope arrays. The results show close correlation between the theoretical and experimental DDM and signal patterns. For transverse half-planes the capture effect and sideband reference systems out-perform the null reference, whereas for lateral edges close to the antenna the reverse is shown to be true. This is in agreement with the relative ground currents characteristic of each antenna. View full abstract»

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  • Design of line source antennas for difference patterns with sidelobes of individually arbitrary heights

    Publication Year: 1976 , Page(s): 310 - 316
    Cited by:  Papers (6)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    A design method previously developed to give a sum pattern with arbitrary sidelobe topography is shown to be applicable to difference patterns as well. The basis is Bayliss patterns (Taylor-type patterns for the difference mode) which are transformed through an iterative procedure to the desired result. For practical cases the convergence is rapid and a previously developed do-loop computer program has been modified to facilitate the computations and provide final patterns and aperture distributions. View full abstract»

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  • On the optimum directivity of antenna consisting of arbitrarily oriented dipoles

    Publication Year: 1976 , Page(s): 322 - 327
    Cited by:  Papers (4)
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    The optimum directivity of antennas consisting of arbitrarily oriented dipoles is examined. This is done with the help of formulas found by the Gram-Schmit method of orthonormalization of the base, which includes the intensity of the electric field. Some examples follow. View full abstract»

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  • Synthesis of equiripple sector antenna patterns

    Publication Year: 1976 , Page(s): 347 - 353
    Cited by:  Papers (6)  |  Patents (1)
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    A tutorial description is given of a procedure for synthesizing equiripple approximations to a sector pattern which is constant over the coverage region and zero elsewhere. This procedure, which represents a generalization of Dolph-Chebyshev synthesis, can be used to synthesize both zero phase and minimum phase approximations (with the latter yielding a better approximation to the desired magnitude function). Theoretical considerations and comparisons of recently constructed arrays suggest that the synthesized patterns have maximum rolloff at the coverage region boundary given constraints on the maximum allowable deviations from the desired pattern and the number of array elements. Extension to synthesis of more complex desired functions is discussed. View full abstract»

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  • Effects of random phase errors at Kaband resulting from a composite material radome

    Publication Year: 1976 , Page(s): 356 - 365
    Cited by:  Papers (2)
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    The effects of random phase errors introduced by way of a composite material radome on the sidelobes of a low-sidelobe transmitting antenna are investigated. The nominal sidelobe level of interest is - 40 dB below maximum directive gain outside a minimum conical angle about boresight. The radome used was constructed using strips of fiberglass cloth pre-impregnated with epoxy resin with each strip overlapping adjacent strips. The overlapping is staggered so that the final thickness contains roughtly the same number of layers. The shape of the radome is cylindrical on the side, capped by a hemispherical sector. The radome curvature is large with respect to wavelength, and is several wavelengths thick at K_{a} band (37 GHz). Measurements made on the radiation patterns of a large aperture low-sidelobe lens antenna enclosed by the radome indicate that the sidelobe degradation introduced by the radome can be directly related to the construction technique and materials used. Subsequent measurements on the insertion phase versus position on the radome support these conclusions. In particular, the correlation length of the random insertion phase introduced upon transmission through the radome was determined to be essentially that of the overlapping width used in the fiberglass layup. Furthermore, periodicities in insertion phase having the basic period of the overlap width cause grating lobes to occur in the radiation pattern, further degrading the sidelobes. View full abstract»

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  • A new method of estimating microwave attenuation over a slant propagation path based on rain gauge data

    Publication Year: 1976 , Page(s): 381 - 384
    Cited by:  Papers (3)
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    A basic problem in estimating the microwave attenuation over a satellite-earth propagation path on the basis of rain gauge data is that, for a given precipitation event, the attenuation and the rainfall records very often do not have consistent detailed correlation. Such inconsistencies can be greatly reduced if the falling speed of the rain drops, i.e., 2 to 9 m/s for drop sizes of 0.05 to 0.7 cm, is taken into account. Adjustments in time and drop size spectrum are needed for data collected from field rain gauges to realize the actual rainfall along the slant path for correlating rain gauge data with measured satellite signals. View full abstract»

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  • Radar return from a continuous vegetation canopy

    Publication Year: 1976 , Page(s): 269 - 276
    Cited by:  Papers (9)
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    The radar backscatter coefficient \sigma \deg of alfalfa was investigated as a function of both radar parameters and the physical characteristics of the alfalfa canopy. Measurements were acquired with an 8-18 GHz FM-CW mobile radar over an angular range of 0\deg -70\deg as measured from nadir. The experimental data indicate that the excursions of \sigma \deg at nadir cover a range of nearly 18 dB during one complete growing cycle. An empirical model for \sigma \deg was developed, which accounts for its variability in terms of soil moisture, plant moisture, and plant height. View full abstract»

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  • Simplified matrix inversion for optimization of antenna arrays

    Publication Year: 1976 , Page(s): 387 - 388
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    A special form of complex matrix called a "phase-difference matrix" that arises in the optimization of antenna arrays is discussed. It is shown that the inverse of such a matrix can be obtained by inverting an associated real matrix without having to perform any arithmetic operations with complex numbers. View full abstract»

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  • The electromagnetic theory of three-dimensional inhomogeneous lenses

    Publication Year: 1976 , Page(s): 365 - 370
    Cited by:  Papers (9)
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    The characteristics of some inhomogeneous lenses are investigated. The lenses covered are the Luneburg, the Eaton-Lippmann, and the Eaton. Radiation patterns and the bistatic scattering cross sections for the small-diameter lenses as well as the directivity and the distribution of the energy around the geometrical focus of the Luneburg lenses are numerically computed and examined in detail. View full abstract»

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  • Insertion loss due to a spherical shell in low frequency zone

    Publication Year: 1976 , Page(s): 389 - 393
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    Electromagnetic scattering due to a spherical conductor in presence of a slightly conducting dielectric cover has been studied. Numerical results have been presented for a three-layer model, excited by a uniform time harmonic magnetic field, where the intermediate layer accounts for the spacing between the core and the shield. Scattering coefficients for the covered and uncovered situations are compared in terms of an insertion loss parameter. The resulting curves provide information about the interesting frequency bands of supertransmission of energy between the source and the core-conductor. The results may find application in electromagnetic probing of some terrestrial and lunar situations. View full abstract»

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  • Microwave holographic metrology of large reflector antennas

    Publication Year: 1976 , Page(s): 295 - 303
    Cited by:  Papers (52)  |  Patents (1)
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    A microwave holographic technique for the determination of amplitude and phase of the principal and cross-polarized aperture fields of large reflector antennas is described. The hologram formation process utilizes the elevation over azimuth scanning system normally associated with these antennas, and, in this respect, appears to be unique among other proposed methods of field probing. The present work describes the means used to obtain vital information on the antenna structure such as E - and H -plane phase centers of the feed, and rms values of the reflector surface profile errors. Accurate prediction of E - and H -plane radiation patterns in the near- and far-field is also demonstrated. View full abstract»

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  • A broadband antenna array for sea scatter measurements

    Publication Year: 1976 , Page(s): 340 - 347
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    A nonuniformly spaced array of 25 side-terminated vertical half rhombics is synthesized for the entire high-frequency band. The array is to be used for both transmitting and receiving, as a sky-wave Doppler radar for sea scatter measurements. The array has the capability for providing a maximum transmitting-receiving product gain in the order of 60 dB at low take-off angles, a product azimuth pattern with a nominal beamwidth of 2\deg , a 40\deg sectoral coverage, a final product sidelobe level of -38 dB, and a grating-lobe level of -30 dB. View full abstract»

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  • Induced current in and scattered field from a finite cylinder with arbitrary conductivity and permittivity

    Publication Year: 1976 , Page(s): 330 - 336
    Cited by:  Papers (6)
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    A finite cylinder with arbitrary conductivity and permittivity is illuminated by an EM wave. The induced current in and the scattered field by the cylinder are determined based on the numerical solution of a tensor integral equation. An experiment has been conducted to verify the theory. Biological and metallic cylinders are emphasized in the study. View full abstract»

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  • Analysis of the symmetric center-fed V-dipole antenna

    Publication Year: 1976 , Page(s): 316 - 322
    Cited by:  Papers (5)
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    A wire antenna moment method using piecewise sinusoidal expansion and testing functions is used to obtain properties of a symmetric center-fed V -dipole antenna driven by a slice generator. The impedance, admittance, current distribution, radiation patterns in the dipole plane, and other properties are computed as functions of the parameters 0 < h/\lambda \leq 0.60 , 100 \leq h/a \leq 20 000 , and 30\deg \leq \psi \leq 180\deg , where h = arm length, \lambda = free space wavelength, a = wire radius, and \psi = apex angle. The results are checked with experiment and compared with similar results previously reported for the linear dipole. It is shown that 1) omnidirectional patterns over a wide bandwidth are achieved for \psi \leq 90\deg , but at the expense of reduced resonant radiation resistance and reduced bandwidth, insofar as the impedance is concerned, 2) for \psi less than about 75\deg -80\deg , lowest resonant length \geq \lambda /4 and increases as h/a decreases, and 3) lowest antiresonant length for \psi > 30\deg is within 0.01\lambda of that for a linear dipole with the same h/a . View full abstract»

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  • On the optimization of the aspect angle windows for the Doppler analysis of the radar return of rotating targets

    Publication Year: 1976 , Page(s): 378 - 381
    Cited by:  Papers (3)
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    Optimum resolution in the Doppler spectra of rotating targets is obtained by using an optimum aspect angle window from which the data for the Fourier transforms are taken. The width of the optimum aspect angle window depends on the location, relative to the axis of rotation, of the scattering center to be resolved, so that for optimum resolution a sort of focusing by choosing the appropriate aspect angle window is necessary. Formulae and graphs for optimum width of aspect angle windows and the obtainable resolutions are given. Typical applications of the scheme presented are in the experimental determination of the location, the strength, and the interaction of the scattering centers on a target. These in turn are of major interest, e.g., for the analysis and synthesis of radar cross sections, in glint investigations, and in target imaging. View full abstract»

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  • Radar imaging from ramp response signatures

    Publication Year: 1976 , Page(s): 276 - 282
    Cited by:  Papers (41)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    A new approach to synthetic image generation of radar targets from electromagnetic scattering measurements is described and illustrated. Complex harmonic samples of the backscattered response at ten frequencies lying in the low resonance range of the target response spectrum are used as input data for this approach. A periodic ramp response waveform synthesized from these data is shown to be correlated to the cross-sectional area versus distance along the line-of-sight, or profile function, of the targets measured. A technique using profile function data at three orthogonal target look angles for the mathematical specification of a three-dimensional "approximate limiting surface" is described. Visual images simulating an isometric view of the surface are then constructed. Images produced from model measurements of several target shapes are presented to illustrate some characteristics of this imaging process. 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