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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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  • 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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  • 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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  • Sidelobe reduction of modulated surface wave structures

    Publication Year: 1964 , Page(s): 503 - 505
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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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  • Minimization of sidelobes in space tapered linear arrays

    Publication Year: 1964 , Page(s): 497 - 498
    Cited by:  Papers (3)
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  • Solutions to spherical anisotropic antennas

    Publication Year: 1964 , Page(s): 459 - 463
    Cited by:  Papers (4)
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    An exact solution is found for the fields of a spherical antenna with an anisotropic surface. The surface, for which a rather simple solution is found, conducts perfectly only along spiral lines which go from pole to pole, and is otherwise nonconducting. The antenna is either excited by fields at a gap around the equator or at low frequencies between adjacent spirals. The method of solution is described, and results of several representative cases are presented. 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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  • Propagation through an elevated duct: Tradewinds III

    Publication Year: 1964 , Page(s): 479 - 490
    Cited by:  Papers (2)
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    In July and August of 1960, a joint Naval Research Laboratory-Naval Electronics Laboratory radio-meteorological program (Project Tradewinds III) was carried out between San Diego, Calif., and Opana, Hawaii. The purpose of this project was to evaluate the propagation characteristics of the duct formed by the tradewinds inversion which is generally found in this region. Two frequencies, 220 Mc and 445 Mc, were used and data concerning signal strength vs range from each terminal, height gain data at several points in the path, as well as the gross meteorological conditions which prevailed over the path were taken. This report attempts both to correlate the radio propagation data with the observed meteorology and to formulate a mechanism to explain the presence in the duct of signal power transmitted from a point well below the duct. In general, cloud heights and types serve as indicators of the stability of the tradewinds inversion and can be correlated with the altitude and strength of the inversion and consequently of the duct. By using both ray and scatter theories, a relation is developed which may be used to determine the signal losses expected in transmission through an elevated duct in which either or both terminals are well below the duct. 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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  • 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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  • 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 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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  • Excitation of surface waves on a unidirectionally conducting screen by a phased line source

    Publication Year: 1964 , Page(s): 470 - 478
    Cited by:  Papers (9)
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    The excitation of surface waves on a unidirectionally conducting screen produced by a phased line source located above the screen and perpendicular to the wire elements is considered. The screen consists of an infinite number of straight, perfectly conducting, parallel wires and conducts only in the direction of the wire elements. The phased line source consists of a periodic line current with an electric charge distributed along its length. The complete electromagnetic field is determined exactly and simple expressions are given for the scattered far field. It is shown that surface waves exist and simple expressions for the amplitudes are given. Another principal result is the determination of the magnitude of the complex Poynting vector for the radiated power. It is found that the pattern function lies on a cone independent of the presence of the screen and that the cone angle depends only on the phasing of the source. The pattern function at points below the screen is independent of the location of the source above the screen. Furthermore, the pattern function vanishes in the direction of the screen and this seems concomittant to the existence of surface waves. Two pattern functions are drawn for typical cases of interest. The power propagated by the surface waves is also determined. The method employed to solve the problem is based on the deduction that the scattered magnetic field component in the direction of the wire elements is zero. A consequence of this deduction is that the electromagnetic field can be derived from a single scalar wave function that satisfies a partial differential equation in the plane of the screen and a jump condition across the screen. This method is quite general and can be applied to a large class of interesting propagation problems arising from different types of excitation. The scattered far field is obtained using another method that is algebraic in character and does not require a complete solution of the problem. View full abstract»

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  • A multi-layer microwave absorber

    Publication Year: 1964 , Page(s): 508 - 509
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  • Self-gyro demodulation

    Publication Year: 1964 , Page(s): 510 - 511
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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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  • Influence of the refractive index profile in VHF reflection from a tropospheric layer

    Publication Year: 1964 , Page(s): 512 - 513
    Cited by:  Papers (2)
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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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  • 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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  • Antenna pattern perturbations for a quadratic phase error

    Publication Year: 1964 , Page(s): 506 - 507
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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