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Antennas and Propagation, IEEE Transactions on

Issue 1 • Date January 1968

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Displaying Results 1 - 25 of 38
  • [Front cover and table of contents]

    Publication Year: 1968 , Page(s): 0
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  • On the electrically thick monopole - Part II - Experimental study

    Publication Year: 1968 , Page(s): 64 - 71
    Cited by:  Papers (2)
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  • Correction to "The whispering gallery nature of the earth-ionosphere waveguide at VLF"

    Publication Year: 1968 , Page(s): 147
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  • Contributors and back cover

    Publication Year: 1968 , Page(s): c4
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  • The effects of electron collisions on electric dipole radiation through a conical plasma sheath

    Publication Year: 1968 , Page(s): 118 - 123
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    The radiated power of an electric dipole antenna in a thin, dissipative, infinite conical plasma sheath is analyzed. The electromagnetic fields are represented by contour integrals, and the radiated power is calculated according to the method of Baños et al. The sheath is characterized by a single parameter, which is proportional to the integrated electron density and depends inversely on the electron collision frequency. The radiation pattern is distorted from the form of the free-space dipole pattern because of the interaction between the primary dipole fields and the fields induced on the surface of the plasma sheath. In most cases it is found that for small electron densities, electron collisions attenuate the induced surface fields so that the patterns approach their free-space form. For larger electron densities, the pattern has a characteristic heart shape for zero collision frequency. The pattern increases in magnitude, while retaining the same form, as the collision frequency increases from zero. As the collision frequency is further increased, the pattern approaches the free-space pattern in magnitude and form. View full abstract»

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  • Theory of conical equiangular-spiral antennas: Part 2--Current distributions and input impedances

    Publication Year: 1968 , Page(s): 14 - 21
    Cited by:  Papers (15)
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    According to the behavior of the current, an equiangular-spiral antenna may be divided into three distinct regions. Since the positions of these regions are frequency independent, it is possible to obtain a complete description of the current distribution on almost all practical equiangular-spiral antennas by a set of carves, which is given in this paper. It is also found that for rapidly expanding antennas there are, in general, two or more active regions that are characterized by differences in rate of attenuation. Such a phenomenon is interpreted in terms of the Brillouin diagram. A variational formulation of the input impedance of the antenna is also presented. The variation method using the approximate current provided by the set of curves gives a quick, direct means of finding the input impedances. View full abstract»

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  • Match optimization of a two-port phased array antenna element

    Publication Year: 1968 , Page(s): 47 - 57
    Cited by:  Papers (6)
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    A systematic method for designing a phased array element that is matched over a wide scan region is presented. Measured coupling coefficients from a small array of trial elements, combined with computer simulation, yield the design parameters of an individual element matching obstacle. These obstacles will optimize the match versus scan characteristics when properly inserted within the element channels. The method presented has been used to optimize the match versus scan characteristic of a circularly polarized coaxial horn type of element over a 15 percent bandwidth. A close agreement between the predicted and measured returned powers has been observed over the frequency band for a broad scan region. View full abstract»

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  • Electronic scanning of linear slot arrays using diode irises

    Publication Year: 1968 , Page(s): 8 - 14
    Cited by:  Papers (1)
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    Semiconductor diodes were employed as electronic iris control elements to scan linear slot arrays at X -band. An iris cluster of four varactor diodes mounted inside the waveguide around each slot provided 360\deg of phase control for slot coupling levels up to -15 dB and a reduced range of phase control for couplings up to -8 dB. Two linear arrays were fabricated with different iris cluster configurations: 1) A ten-slot array, with vertically mounted diodes, electronically scanned sum and difference patterns up to 90\deg ; 2) a five-slot array, with horizontally mounted diodes, scanned sum patterns up to 120\deg . Both iris configurations had an RF power handling capability of about 0.1 mW. View full abstract»

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  • The admittance of the infinite cylindrical antenna immersed in a lossy, compressible plasma

    Publication Year: 1968 , Page(s): 111 - 117
    Cited by:  Papers (6)
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    Some numerical results obtained from an analysis of the admittance of an infinite cylindrical antenna excited at a circumferential gap of finite thickness and immersed in a lossy, compressible (warm) plasma are given. The linearized hydrodynamic equations are used for the electrons (ion motion is neglected). A free-space layer, or vacuum sheath, is used to approximate the ion sheath which forms about an object at floating potential in a nonzero temperature plasma. Values for the antenna admittance are obtained by a direct numerical integration of the Fourier integral for the current, and are presented as a function of frequency for plasma parameter values typical of the E region of the ionosphere. The admittance exhibits a maximum below the plasma frequency unless the electron temperature and sheath thickness are both zero; however, above the plasma frequency, the sheath and electron temperature have relatively little effect on the antenna admittance. The nonzero plasma temperature considerably enhances the antenna conductance below the plasma frequency compared with the zero-temperature case while at the same time reducing the dependence of the conductance on the electron collision frequency. A susceptance zero the location of which is not sensitive to the vacuum sheath thickness occurs near the plasma frequency. View full abstract»

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  • An approximate formula for the admittance of a long, thin antenna

    Publication Year: 1968 , Page(s): 127 - 128
    Cited by:  Papers (4)
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    An approximate formula is presented for the admittance of a cylindricul antenna where the length is large and the diameter is small compared with the excited wavelength. A comparison of admittance results obtained from this formula is made with the more accurate results of Hurd and Wu. View full abstract»

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  • Design of corrugated plates for phased array matching

    Publication Year: 1968 , Page(s): 37 - 46
    Cited by:  Papers (8)
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    The reflection coefficient for an array of identical nonuniformly corrugated plates phased to launch a plane wave in any direction is calculated exactly. The plate spacing is limited only by the grating lobe condition, and the corrugations in each plate may be of arbitrary depth, or the bottom of each corrugation may be terminated in an arbitrary admittance. The conditions for the occurrence of a surface wave effect, corresponding to a total array mismatch or a null in the element pattern, are derived in general for arrays having an adjustable short-circuited parasitic element (such as a corrugation) with each driven element. It is shown that the existence of such a surface wave effect often can be predicted solely from the symmetry of the array in question. The optimum position of the short circuit for the best match also is discussed. Although corrugated plate arrays can be deliberately adjusted to exhibit a surface wave phenomenon in the H plane, the effect is easily avoided for the most practical ranges of scan. Design data are given for an array with one corrugation per plate for varying amounts of E -plane and H -plane scan, and for scanning within an octant of a sphere. View full abstract»

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  • In defense of dipole Van Atta arrays

    Publication Year: 1968 , Page(s): 124 - 125
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  • Construction and operating characteristics of a large-volume mercury arc plasma tube

    Publication Year: 1968 , Page(s): 144 - 146
    Cited by:  Papers (2)
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    The purpose of this communication is to describe the construction and operating characteristics of a mercury arc discharge tube which allows the generation of a large volume of stable, high-intensity plasma for use in experimental work with plasma-clad antennas operating at a frequency of a few GHz. View full abstract»

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  • An investigation of the mechanism of total internal reflection in tropospheric microwave propagation

    Publication Year: 1968 , Page(s): 71 - 77
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    Some calculations are performed concerning the amplitude and phase fluctuations of a totally reflected monochromatic and homogeneous radio beam from a monotonically stratified tropospheric layer. In a first approximation the incident beam is considered to be collimated; the reflected beam is then also collimated but inhomngeneous along a cross section parallel to the interface. Next, a more realistic case is considered in which the incident beam is given by an angular bundle of rays corresponding to a certain radiation polar diagram of the transmitting source. Under this condition the totally reflected field presents a more complicated structure in space, since it manifests focusing or defocusing effects not only along the boundary of the layer but also with height from this interface. A numerical evaluation of these fluctuations with height is of special interest; in principle they may justify vertical space diversity efficiency in a number of typical cases concerning more especially obstructed microwave paths. View full abstract»

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  • A double-slot radar fence for increased clutter suppression

    Publication Year: 1968 , Page(s): 103 - 108
    Cited by:  Papers (3)  |  Patents (2)
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    A technique of edge treatment for radar fences has been developed to provide greater suppression of radar clutter return than can be obtained with a simple straight-edge blocking fence. The technique incorporates two slots in proximity to, and parallel with, the upper edge of the fence. This configuration reduces the amplitude of the diffracted fields incident on the antenna aperture, and also provides an optimum distribution of these fields so as to result in minimum reception of the diffracted signal. Calculations show that a significant improvement is obtained over the performance of a straight-edge fence of the same maximum height as a double-slot fence. A program of measurements of the double-slot fence has been conducted at millimeter wavelengths, and the results have shown excellent agreement with the calculations. For a single elevation angle of clutter return, the double-slot fence has a measured two-way suppression of 64 dB, compared with 28 dB for the straight-edge fence. View full abstract»

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  • Backscatter from spheres: A short pulse view

    Publication Year: 1968 , Page(s): 89 - 97
    Cited by:  Papers (23)
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    The backscatter from conducting and from dielectric spheres is considered in the time domain. Utilizing rigorously computed values of the amplitude and phase of the continuous wave backscatter, short pulses of electromagnetic waves are synthesized by Fourier series. The resultant response is examined as a function of time, and the individually resolvable returns are compared with some approximate theories. View full abstract»

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  • A simple waveguide system for radiating elliptically polarized waves

    Publication Year: 1968 , Page(s): 134 - 135
    Cited by:  Papers (1)
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    It is sometimes convenient to have available a source of arbitrarily polarized waves. A simple source for this purpose is described here. Two angles of rotation or one angle of rotation and a variable phase shift in a waveguide system establish any desired polarization on the axis of a circularly symmetric radiator. View full abstract»

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  • Beam tilt-angle compensation for a rotatable flush-mounted surface-wave antenna on an asymmetrical ground plane

    Publication Year: 1968 , Page(s): 135 - 136
    Cited by:  Papers (1)
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    The beam tilt angle of a rotatable flush-mounted surface-wave antenna mounted on the underside skin of an aircraft varies as the antenna is mechanically scanned in azimuth. This beam tilt-angle variation results because the antenna is presented with a finite asymmetrical ground plane, which introduces a wide range of ground-plane conditions to the antenna as a function of azimuth angle. A method that can compensate partially for these beam tilt variations for low beam tilt angles is described. View full abstract»

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  • The transmission coefficient of elliptical and rectangular apertures for electromagnetic waves

    Publication Year: 1968 , Page(s): 78 - 83
    Cited by:  Papers (6)
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    A simple scalar method using Kirchhoff's boundary values is applied to the diffraction problems of circular, elliptical, and rectangular apertures for normally incident electromagnetic waves. As far as circular apertures are concerned, a simple formula can be derived not only for the diffraction pattern but also for the transmission coefficient. This formula yields good results for apertures greater than 0.8\lambda . Even in the ease of elliptical apertures a simple formula can he derived for the diffraction pattern. For the elliptical aperture, as well as the rectangular one, the transmission coefficient was found in the form of an integral. Relief models and diagrams are given for the transmission coefficients of the elliptical and the rectangular apertures as a function of the two aperture parameters. Diagrams are given which explain the dependence of the transmission coefficient on the aperture parameters. A comparison with other more complicated methods of approximation and with measurements shows both good agreement and the great practical value of the simple method of approximation used. View full abstract»

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  • Note on integral equations and variational expressions for arbitrary scanning of regular infinite arrays

    Publication Year: 1968 , Page(s): 136 - 138
    Cited by:  Papers (1)
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  • Effects of coupling accumulation in antenna arrays

    Publication Year: 1968 , Page(s): 31 - 37
    Cited by:  Papers (17)
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    Mutual coupling between antenna elements in a phased array causes array performance to vary with scan angle. Large impedance mismatch and radiation loss can occur in certain critical directions for which the steering phase advances match the antenna coupling delays. At these critical scan angles, many coupling contributions add inphase to produce a large impedance mismatch and minimum radiation from the array. Several different phased arrays have exhibited scanning "blind" regions that appear to be a consequence of coupling accumulation. A large, flat, homogeneous antenna array is analyzed, and a relationship is found between the critical scan angles and phase of the mutual coupling coefficients. Extensive measurements on arrays of horn antennas have shown radiation minima that correlate with coupling phase measurements and with theory. View full abstract»

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  • High-frequency backscattering from the inverse-square-power dielectric lens

    Publication Year: 1968 , Page(s): 140 - 141
    Cited by:  Papers (3)
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    The high-frequency backscattered field produced by a plane electromagnetic wave incident on an inverse-square-power dielectric lens is determined in terms of reflected field, creeping wave, and evanescent wave contributions. View full abstract»

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  • Line source feed for a spherical reflector

    Publication Year: 1968 , Page(s): 132 - 134
    Cited by:  Papers (8)
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  • Distortion of an electromagnetic pulse carrier propagating in an anisotropic homogeneous plasma

    Publication Year: 1968 , Page(s): 146 - 147
    Cited by:  Papers (3)
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    Transient signal propagation in anisotropic, homogeneous cold plasmas is considered. The anisotropy is caused by an external longitudinal magnetic field. Using the saddlepoint method of integration, an approximate expression for the electric field is obtained. The envelope of a distorted rectangular pulse carrier is plotted for various magnetic fields, including the isotropic case. View full abstract»

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  • Short-pulse scattering by a cone--Direct and inverse

    Publication Year: 1968 , Page(s): 98 - 102
    Cited by:  Papers (5)
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    Experimental measurements of short-pulse scattering by a slightly blunted, flat-back cone are described; the separation of tip and base returns is clearly indicated. An analysis of the data provides descriptions of the dependence of each scattering center on aspect angle and polarization. Comparison of the measured values with theoretical calculations generally shows good agreement. In addition, the results of an inverse-scattering analysis to determine target shape and size are presented. 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