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Antennas and Propagation, IEEE Transactions on

Issue 4 • Date July 1964

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Displaying Results 1 - 25 of 35
  • [Front cover and table of contents]

    Publication Year: 1964 , Page(s): 0
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  • Compensation of tropospheric effects on Doppler tracking

    Publication Year: 1964 , Page(s): 513 - 514
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  • Correction to "On the radar cross section of a coated plate"

    Publication Year: 1964 , Page(s): 516
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  • [Back cover]

    Publication Year: 1964 , Page(s): c4
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  • Radar cross section of a corrugated metallic pipe

    Publication Year: 1964 , Page(s): 507 - 508
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  • Sidelobe reduction of modulated surface wave structures

    Publication Year: 1964 , Page(s): 503 - 505
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  • Fresnel zones for ground-based antennas

    Publication Year: 1964 , Page(s): 417 - 422
    Cited by:  Papers (1)
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    The ordinary Fresnel zone concept is modified to include the influence of finite ground conductivity. This is important for ground-based antennas because the influence on the radiation pattern of irregularities near the antenna is determined by the amplitude and phase of the groundwave. A new definition of Fresnel zones which takes into account the phase shift of groundwave propagation is given and it is shown that these new zones are zones of greatest influence, at least when discontinuities of the electrical parameters of the ground are considered. Numerical results for the first Fresnel zone are given, and it is shown that the zone is much smaller for a finite conductivity than for an infinity conductivity, especially for small angles of elevation. View full abstract»

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  • Transient and steady-state antenna pattern characteristics for arbitrary time signals

    Publication Year: 1964 , Page(s): 492 - 493
    Cited by:  Papers (3)
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  • The admittance of bare circular loop antennas in a dissipative medium

    Publication Year: 1964 , Page(s): 434 - 438
    Cited by:  Papers (17)
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    The normalized input admittance of thin bare circular loop antennas has been evaluated from the theory of T. T. Wu. Computations have been made for loops in air and in an infinite homogeneous isotropic dissipative medium. A comparison is also made with Storer's theory of the loop. Numerical results are given in the form of graphs for several wire sizes and for loops up to two and one-half wavelengths in circumference. The properties of the medium are represented by the ratio \alpha /\beta in the range from zero (perfect dielectric) to one (good conductor); \alpha and \beta are the imaginary and real parts of the complex propagation constant k=\beta -j\alpha = \omega \sqrt {\mu(\epsilon-j\sigma /\omega )} where \mu is the permeability, \epsilon the dielectric constant, and \sigma the conductivity of the medium. View full abstract»

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  • Self-gyro demodulation

    Publication Year: 1964 , Page(s): 510 - 511
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  • Design of dual-reflector antennas with arbitrary phase and amplitude distributions

    Publication Year: 1964 , Page(s): 403 - 408
    Cited by:  Papers (81)  |  Patents (1)
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    A synthesis method based on geometrical optics for designing a dual-reflector antenna system with an arbitrary phase and amplitude distribution in the aperture of the second reflector is presented. The first reflector may be illuminated by a pattern with an arbitrarily curved phase front. A pair of first-order ordinary nonlinear differential equations of the form dy/dx=f(x, y) are developed for the system. Questions concerning uniqueness, existence and bounds for the solutions can be answered. Calculations and numerical results for the design of a uniform amplitude and phase dual-reflector system are presented. View full abstract»

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  • Statistically designed density-tapered arrays

    Publication Year: 1964 , Page(s): 408 - 417
    Cited by:  Papers (41)  |  Patents (2)
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    The design of "thinned" planar array antennas is considered in which the density of elements located within the aperture is made proportional to the amplitude of the aperture illumination of a conventional "filled" array. Density tapering permits good sidelobe performance from arrays of equally radiating elements. The selection of the element locations is performed statistically by utilizing the amplitude taper as the probability density function for specifying the location of elements. The statistical design procedures and the theoretical prediction of performance are given. Application to a 50 wavelength diameter planar aperture is discussed and the results compared to conventional amplitude-taper designs. Examples of computed patterns are shown for density tapers modeled after 25, 30, 35, and 40 db circular Taylor distributions. The properties of a planar array of 10,000 elements are examined for "natural" thinning and for 70 per cent and 90 per cent of the elements removed. The sidelobes are determined more by the number of remaining elements than by the model amplitude taper. Statistically designed density-tapered arrays are useful when the number of elements is large and when it is not practical to employ an amplitude taper to achieve low sidelobes. View full abstract»

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  • Minimization of sidelobes in space tapered linear arrays

    Publication Year: 1964 , Page(s): 497 - 498
    Cited by:  Papers (3)
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  • Annular slot monopulse antenna arrays

    Publication Year: 1964 , Page(s): 391 - 403
    Cited by:  Papers (9)
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    This paper describes the design and performance of annular slot planar arrays which generate pencil beams and monopulse tracking beams in both principal planes. These planar arrays consist of a transmission line in the form of a radial waveguide whose upper plate contains annular groups of linear slots. Monopulse operation is obtained by dividing the transmission line into four independently excited quadrants, each of which is propagating a field configuration identical to the dominant H_{01} radial waveguide mode. The antennas radiate linear polarization. In contrast with many other types of two-dimensional waveguide slot arrays, these antennas can be fabricated inexpensively. Small diameter versions possess the following electrical and mechanical advantages when compared to a dish antenna of comparable size: 1) comparable gain, 2) improved backlobe suppression, and 3) more compact size and lower weight. Designs have been developed at X band. View full abstract»

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  • The element-gain paradox for a phased-array antenna

    Publication Year: 1964 , Page(s): 423 - 433
    Cited by:  Papers (76)
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    In a phased-array antenna with a very large number of regularly-spaced radiating elements, the gain realized at the beam peak is equal to the number of elements times the gain realized in the same direction when only one typical element is excited. The ideal radiation pattern of one such element in a large planar array has a cosine variation of gain with angle when the elements are closely spaced, and has a peak value of gain equal to 4\pi A/\lambda ^{2} where A is the area allotted to each element. The active impedance of each element in a practical phased array varies with scan angle, because of mutual coupling between the elements. The associated mismatch causes power to be returned to the generators, thereby reducing the gain realized by the array and by the element. The element pattern, measured in the proper environment of surrounding elements, deviates from the ideal pattern in proportion to this effect. Mutual coupling is inherently unavoidable in a closely-spaced infinite array of elements; for example, in a square array with less than \lambda /\sqrt {2} spacing. There is a loss of element efficiency caused by the coupling, and since coupling increases with closer spacing, this accounts for the lower gain expected from ideal elements with reduced allotted area. Grating lobes can exist when the elements are not closely spaced; for example, in a square array with more than \lambda /2 spacing. In this case, the ideal pattern is truncated to discriminate against grating lobes; this gives the higher gain expected from ideal elements with larger allotted area. It is concluded that in a phased-array antenna having a very large number of regularly-spaced radiating elements, perfect impedance match for all scan angles can be postulated for every typical element without encountering any real discrepancy in the determination of element gain. In the absence of grating lobes, such an antenna would realize the greatest possible gain for all scan angles. View full abstract»

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  • Pattern synthesis with nonseparable aperture fields

    Publication Year: 1964 , Page(s): 502 - 503
    Cited by:  Papers (2)
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  • A field equivalence theorem for linear magnetoionic media

    Publication Year: 1964 , Page(s): 511 - 512
    Cited by:  Papers (1)
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  • Pulsed electromagnetic wave propagation in dispersive media

    Publication Year: 1964 , Page(s): 494 - 496
    Cited by:  Papers (28)
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  • The effect of a conducting half-plane sheet on the radiation patterns of dolph-chebyshev arrays

    Publication Year: 1964 , Page(s): 455 - 458
    Cited by:  Papers (1)
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    The radiation patterns of end-fire and broadside Dolph-Chebyshev arrays radiating in the presence of a conducting half-plane sheet have been calculated. Several values of the angle of incidence of these arrays with respect to the conducting half-plane sheet have been considered. These results are presented graphically and it can be seen that there is considerable distortion of the original pattern caused by the half-plane sheet. In general, when the main beam is directed toward the edge of the haft-plane sheet it is either partially reflected or split into several lobes. View full abstract»

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  • An accurate absolute gain calibration of an antenna for radio astronomy

    Publication Year: 1964 , Page(s): 439 - 447
    Cited by:  Papers (7)
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    The methods used to determine the absolute gain of an 80-square foot aperture horn-reflector antenna over a frequency range from 2.8 to 14.0 Gc, and in the absence of a high-level test range, are described. A "mirror" range, in which the size of the smooth reflecting surface required was relatively small, was used and the measurements were performed in the Fresnel zone of the antenna with corrections applied for the resulting gain reduction. These and other provisions reduced the probable error in the final values to about one per cent. View full abstract»

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  • Air to undersea communication with magnetic dipoles

    Publication Year: 1964 , Page(s): 464 - 470
    Cited by:  Papers (6)
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    Simplified expressions are derived for the electromagnetic fields produced by a vertical or horizontal magnetic dipole (loop antenna) located in air above the sea. The expressions hold over the quasi-near range in both media subject to certain mild restrictions. The solutions are obtained by first applying the boundary conditions to determine the magnetic Hertz potential \bar{\pi}^{\ast } in the form of Sommerfeld integrals, and then relating these to two auxiliary integrals U, V and their derivatives, asymptotic series for which are obtained by extending the work of Baños and Wesley. The horizontal magnetic dipole (loop in the vertical plane) is found to be superior to the vertically-oriented dipole of the same size and excitation from the point of view of field strength induced in the sea at large distances from the source. A comparison with previously published results for the electric dipole shows the magnetic dipole to be better, provided the number of turns in the loop exceeds a certain minimum. An approximate analysis on the basis of equal powers also shows the magnetic dipole to be better except for points near the outer rim of the quasi-near range, where the two types of dipoles are equivalent. View full abstract»

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  • The optimum directivity of uniformly spaced broadside arrays of dipoles

    Publication Year: 1964 , Page(s): 447 - 454
    Cited by:  Papers (35)
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    The optimum directivity of various types of uniformly spaced broadside arrays of dipoles is investigated theoretically in this paper. The formulation is processed with the aid of an array matrix. The expression for the optimum directivity and the corresponding excitation are expressed directly in terms of the elements of the array matrix. The computed values are assembled in several sets of curves, and the results are compared with the directivity of uniformly excited arrays. View full abstract»

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  • Equatorial patterns of an axially-slotted cylinder coated with a critically dense plasma

    Publication Year: 1964 , Page(s): 498 - 502
    Cited by:  Papers (2)
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  • The radiation pattern of an array of dipoles in a dielectric slab

    Publication Year: 1964 , Page(s): 384 - 391
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    By using the reciprocity theorem, simple expressions are derived for the far-field patterns of normal and parallel dipoles in a plane dielectric slab. The dielectric slab may have a conducting ground plane on one surface. Numerical results are presented in a graphical form to show the effects of the dielectric on the antenna pattern. A dipole array embedded in a radome occupies less space than a conventional parabolic antenna, and the ground plane offers structural support for the radome. View full abstract»

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  • The gain-beamwidth product of an antenna

    Publication Year: 1964 , Page(s): 505 - 506
    Cited by:  Papers (14)
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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