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Antennas and Propagation, IRE Transactions on

Issue 1 • Date January 1957

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

    Page(s): 0
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    Freely Available from IEEE
  • News and views

    Page(s): 1 - 3
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  • The impedance properties of narrow radiating slots in the broad face of rectangular waveguide: Part I--Theory

    Page(s): 4 - 11
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    Theoretical results, valid at and away from resonance, for the impedance properties of the rotated series slot, the displaced series slot, and the longitudinal shunt slot have been derived by the use of variational expressions coupled with certain stored power considerations. The additional influence of finite wall thickness, an appreciable factor, is taken into account by a microwave network treatment. The results for the zero-thickness resistive elements become identical with those of Stevenson when the slot length is made equal to a half wavelength. The theoretical derivations are presented in Part I. In Part II, comparison is made with experimental data both previously available and specially taken in this connection. The effect of wall thickness and the distinction between slots of rounded and rectangular ends are also considered. The agreement between theory and measurement is reasonably good. View full abstract»

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  • A Luneberg lens scanning system

    Page(s): 21 - 25
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    A 16,000-mc scanner is described which scans a40degazimuth sector alternately with each of two beams at a rate of 17 scans per beam per second. The beams have half-power vertical and horizontal beamwidths of0.76degand1.06degrespectively and are separated vertically by an angle of1.85deg. Horizontal collimation of each beam is achieved by a geodesic analog of the two-dimensional Luneberg lens. The lenses feed a section of a semiparabolic cylinder for effecting vertical collimation. Feeding the lenses is a switching system, consisting of two four-way turnstile waveguide switches and a waveguide chopper switch, which gives a scan-time dead-time ratio of 8:1. View full abstract»

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  • A design procedure for dielectric microwave lenses of large aperture ratio and large scanning angle

    Page(s): 25 - 30
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    Methods are given for designing point-source three-dimensional aspheric rotationally-symmetric dielectric lenses and for zoning such lenses. Designs for scan angles and aperture ratios much larger than conventional may be achieved and all computations can be done on a desk calculator. The three-dimensional lens is obtained by first designing an exact two-point corrected cylindrical dielectric lens and then rotating a section of the cylindrical lens about the axis of symmetry of the section. The design procedures for the cylindrical lens are based on ray-tracing techniques. Experimental results indicate that the three-dimensional lenses possess good wide-angle scanning characteristics. View full abstract»

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  • Circularly polarized slot radiators

    Page(s): 31 - 36
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    A pair of narrow slots crossed at right angles and located at the proper point in the broad wall of a rectangular waveguide will radiate a circularly polarized wave. Some of the results of a study of the properties of such slots is presented. The study was undertaken with the aim of obtaining information useful in design of a circularly polarized linear array. Some of the properties of the slot pairs are as follows: 1) They are inherently matched, independent of the slot length. 2) When the slot arms are made resonant, approximately 75 per cent of the incident power is radiated, with a vswr of 1.12. 3) When fed from one end of the waveguide, the slots radiate right-hand circular polarization; from the other end, left-hand. In using these slots in linear arrays the power radiated is varied by changing slot length, since position and orientation are fixed by the requirements of circular polarization. The slots must be separated by a guide wavelength, so waveguide loading or other complicated schemes must be used to reduce the slot spacing. View full abstract»

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  • The effect of mutual impedance on the spacing error of an eight-element adcock

    Page(s): 36 - 39
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    An eight-element Adcock array has the advantage of reduced spacing error as compared to four element arrays of the same size. If this error is calculated when the mutual impedances between elements are neglected, spacing error curves result which are poor approximations and may not be attainable in actual measurement. New relationships are derived for the two-phase eight-element array which include the effect of mutual impedance. Curves are plotted to show that earlier published values for the angular spacing between elements are probably too high to result in the best performance. It is shown that the value ofrho=27deg15'which results when the mutual impedances are neglected may result in an appreciable spacing error. It is apparent that the selection of an antenna becomes quite important since the mutual impedance is determined thereby. Evaluation of the error in a particular case will depend on the antenna selected. It is also shown that, if the goniometer impedance is high, the spacing error will be reduced. View full abstract»

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  • On the synthesis of line-sources and infinite strip-sources

    Page(s): 40 - 46
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    In this investigation Woodward's synthesis problem for line-sources and infinite strip-sources with arbitrarily spaced sample points is discussed on the basis of the well-known sampling theorem of bandwidth limited functions. Herein is described a method of synthesis based on the migration of zeros of the integral function(sin pi u)/pi ufrom which all possible solutions of the problem can be derived. Because of the nonuniqueness of the solution, a criterion is introduced, to derive a unique distribution function so that the integrated value of its squared magnitude is a minimum. It turns out that the solution under this criterion coincides with the one obtained by Woodward and Lawson. Examples are given to illustrate the different solutions obtainable for particular problems, and the significance of the least integrated squared magnitude criterion. View full abstract»

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  • Radiation characteristics with power gain for slots on a sphere

    Page(s): 47 - 55
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    Radiation patterns, impedances, and power gains of nonsymmetrically excited narrow slots on a sphere are considered. Numerical calculations of higher orderphi-dependent modes of the radiation and admittance functions are discussed. These functions are applied to obtain the radiation characteristics of an equatorial slot backed by a radial transmission line and excited by feed points along the slot periphery. This geometry is treated directly as a boundary value problem, no assumption of aperture field distribution along the slot being made. Further application is shown for half wave slots on the sphere and for determining gains of uniformly excited zonal slots as a function of their location. Experimental results simulating the asymmetrically excited equatorial slot geometry are given. View full abstract»

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  • Cylindrical radio waves

    Page(s): 56 - 70
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    The formulas required for simple accurate numerical evaluation of the radiation patterns from slots on large circular cylinders are derived. From the usual harmonic series, integral representations are obtained. These lead to either the residue series via the Watson transformations or to the geometrical-optics representations via a saddle-point evaluation. Considerable attention is given to the calculation of the residue series constants so as to obtain sufficiently accurate numerical values for a wide range of circumference to wavelength ratios. Very good numerical agreement is shown between the representations derived here and results previously obtained from the harmonic series. The physical significance of the various representations is discussed and compared. View full abstract»

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  • A study of radar elevation-angle errors due to atmospheric refraction

    Page(s): 71 - 77
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    Refractive-index variations in the atmosphere cause errors in radar measurements. This paper presents the results of a theoretical study of the elevation-angle error due to the refraction of electromagnetic waves in the troposphere. The study is based upon ray theory, using standard meteorological data reported by the United States Weather Bureau for the surface and the standard pressure levels. Computed errors are tabulated for thirty-four monthly mean refractive-index profiles selected as being representative of various type air masses for different seasons and latitudes. In order to get an indication of the spread in propagation errors to be expected during a particular season for fixed locations, computations have been carded out based on the 0300Z soundings for the odd days of January (1950-1954) and July (1950-1953) for nine U. S. locations. The diurnal influence is investigated by analyzing the variations in surface refractive index for January and July, 1953, and also for nine U. S. locations. View full abstract»

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  • Solar flares and atmospheric noise

    Page(s): 78 - 80
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    In this paper, the effects of solar flares on low-frequency atmospheric noise are examined. Relations between the rise of noise, and the area of the flares its intensity, location on the sun, and time of day are studied. Noise levels preceding flares are also examined to determine whether there are any phenomena which may be used for the prediction of high-frequency fade-outs. View full abstract»

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  • On scattering and reflection of electromagnetic waves by rough surfaces

    Page(s): 81 - 90
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    Simple approximations for the reflection coefficients and differential scattering cross sections per unit area of a random distribution of arbitrary protuberances on a ground plane are given in terms of the scattering amplitude of an isolated protuberance, their average number in unit area, and the given incident wave. These functions take into account multiple coherent scattering, and are mutually consistent in fulfilling the energy principle. It is shown, in general, that if the horizon angle approaches zero, then the reflection coefficients approach unity linearly, and the horizontal/vertical back scattering vanishes like the fourth/second power of the angle. General results are then specialized to arbitrary hemispheres and circular semicylinders, and applied to limiting cases of perfect conductors with radii very small or very large compared to wavelength. View full abstract»

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  • Diffraction of surface waves by a semi-infinite dielectric slab

    Page(s): 100 - 109
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    The discontinuity at the end of the slab is regarded as the junction of an open dielectric-filled waveguide and a free-space waveguide. A variational expression is set up for the terminal impedance representing the effect of the discontinuity on the surface wave. Close upper and lower bounds for the impedance are obtained. A variational expression is also set up for the transfer impedance between the surface wave and one of the modes of the continuous mode spectrum associated with the free-space waveguide. The transfer impedances yield the modal amplitudes of the fields. The synthesis of all the modal components gives the electromagnetic field scattered by the end of the slab. The synthesis is carried out for the far field by the method of steepest descents. Terminal impedances and forward radiation patterns are plotted as functions of the thickness for several permittivitiesepsilon_{r}=2.49; 10; 100. The approximation obtained by the variational expression is excellent for small values ofepsilon_{r}and begins to be bad forepsilon_{r} > 10. For very large values ofepsilon_{r}it is possible to obtain a rough estimate of the impedance, immediately, from the values forepsilon_{r} = 10. View full abstract»

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  • Alternative field representations in regions bounded by spheres, cones, and planes

    Page(s): 109 - 121
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    Alternative representations are obtained directly by the method of characteristic Green's functions for the fields radiated by arbitrarily placed scalar and vector (electromagnetic) point sources in regions bounded by surfaces which are describable in terms of single coordinates in a spherical coordinate system. Such surfaces are spheres, cones, and planes, or a combination of these. The representations are distinguished from one another by different convergence properties for various ranges of values of the location of source and observation points and of the boundary surface geometry. Considered in particular are the diffraction by a sphere, a wedge, and a wedge with a spherical dome for both the scalar and vector cases. View full abstract»

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  • Plane-wave scattering by small-angle cones

    Page(s): 121 - 129
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    Rigorous expressions alternative to the familiar formulas in terms of spherical harmonic series are developed for the scattering of acoustic (and electromagnetic) waves by the tip of a perfectly rigid (or perfectly conducting) semi-infinite cone. For plane wave incidence the expressions are valid for observation points lying in a region excluding the rays which are reflected from the sides of the cone according to the laws of geometrical optics. Approximate closed-form results are obtained for on-axis or off-axis incidence and observation for cones with small apex angle for the acoustical plane wave scattering, and for electromagnetic scattering of incident waves whose electric vector is directed perpendicular to the cone axis. The results are correct to0(phi^{2}), wherephiis the cone apex angle, and agree,for the special case of plane wave back-scattering along the cone axis, with those obtained previously by a different method. The case of diffraction by a spherically tipped cone is also treated. View full abstract»

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  • Theory of the scintillation fading of microwaves

    Page(s): 130 - 136
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    A theory is presented indicating that the scintillation fading may be attributed to the incoherent scattering of microwaves by atmospheric irregularities in mass motion at an average velocity. By use of the perturbation theory, the resultant of scattered fields at the receiver is calculated which, on account of the interference with the direct wave, gives rise to the received field oscillating rapidly with small amplitudes around a mean level. Account is taken of the directivity of transmitting and receiving antennas which facilitates the calculation of received field, and also of the Doppler effect due to the translational mass motion of turbulent eddies. Agreement with experimental results is satisfactory. View full abstract»

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  • Ray theory vs normal mode theory in wave propagation problems

    Page(s): 137 - 140
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    The Euler-Maclaurin expansion, as a possible tool for summing mode series in wave propagation problems, is examined for the problem of a dipole radiating monochromatic energy between two parallel plates. When the expansion is applied to this problems it is found that the expansion formula transforms the mode series into the known ray theory solution. View full abstract»

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  • Universal Curves for the vertical polarization reflection coefficient

    Page(s): 140 - 142
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    A set of universal curves is presented by which the approximate magnitude and phase of the reflection coefficient for vertical polarization can be determined at any grazing angle with relatively little computation. The approximation, which is almost always sufficiently accurate for engineering purposes, is excellent if the relative impedance of the reflecting medium is high and still quite good even if the impedance ratio is only moderately greater than unity. View full abstract»

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  • Aircraft telemetry antenna

    Page(s): 143
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Aims & Scope

The Transactions ceased publication in 1962. The current retitled publication is IEEE Transactions on Antennas and Propagation.

Full Aims & Scope