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Antennas and Propagation, IEEE Transactions on

Issue 2 • Date March 1974

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Displaying Results 1 - 25 of 46
  • [Front cover and table of contents]

    Publication Year: 1974 , Page(s): 0
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  • Comments on the solutions of dipoles in semi-infinite media

    Publication Year: 1974 , Page(s): 339 - 340
    Cited by:  Papers (2)
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    It is pointed out that Baños's formulas of the contribution from the pole in the evaluation of the Hertz vector for the radiation field of a dipole cannot be applied even when both the dipole and the observing point are in the lossy half-space due to the approximate method for the integration. View full abstract»

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  • Corrections to "Radiation characteristics of corrugated E-plane sectoral horns"

    Publication Year: 1974 , Page(s): 366
    Cited by:  Papers (2)
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  • Correction to "Scale model development of a high efficiency dual polarized line feed for the arecibo spherical reflector"

    Publication Year: 1974 , Page(s): 366
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  • Correction to "Meander-line polarizer"

    Publication Year: 1974 , Page(s): 366
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  • [Back cover]

    Publication Year: 1974 , Page(s): c4
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  • Arbitrarily polarized slot radiators in bifurcated waveguide arrays

    Publication Year: 1974 , Page(s): 196 - 200
    Cited by:  Papers (5)  |  Patents (3)
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    The feasibility of obtaining arbitrary polarization in both one- and two-dimensional arrays of slots in dual mode bifurcated Waveguides has been demonstrated. The radiating element consists of a pair of crossed slots in the sidewall of a bifurcated rectangular waveguide that couple to even and odd waveguide modes. One linear polarization is excited by the even or "sum" mode and the orthogonal linear polarization is excited by the odd or "difference" mode. By superposing the sum and difference modes in the proper amplitude and phase, any arbitrary polarization can be realized. A two-dimensional array consisting of eight waveguide linear arrays, ferrite phase shifters for scanning in the plane normal to the linear arrays, and a feed network for power distribution and polarization control was constructed. Good radiation performance for various polarizations was obtained. In the case of linear polarization, the cross polarization component was on the order of -25 dB and in the case of circular polarization, the axial ratio was on the order of 1 dB. The polarization was controlled with a ferrite phase shifter. Close-in sidelobes of better than 20 dB were obtained for all polarizations. The preceding performance characteristics were obtained over a scan range of \pm20\deg and over a 6 percent frequency band. View full abstract»

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  • Effects of the element pattern on the directive properties of a scanning planar array

    Publication Year: 1974 , Page(s): 169 - 172
    Cited by:  Papers (2)
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    An approximate expression is derived for a shift of a main-beam direction due to its element pattern in a uniformly illuminated, scanning planar array for a \sin^{p} \theta \cdotp \sin^{q} \phi element pattern. Furthermore, the integral of the radiation power pattern of the array is approximately evaluated, and discussions are given about the effect of the element pattern on the scanned directivity of the array. Numerical results are presented for several cases. View full abstract»

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  • Mutual coupling in a finite planar array of circular apertures

    Publication Year: 1974 , Page(s): 178 - 184
    Cited by:  Papers (15)
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    Equations are presented for the calculation of the interelement mutual coupling in a finite size planar array of waveguide-fed apertures in an infinite flat conductor. The general mutual admittance expression is evaluated for circular apertures and the mutual coupling calculations are verified experimentally for two TE_{11} mode excited apertures. Qualitative agreement between calculations for a 183 element array and an infinite array establishes the validity of the finite array theoretical model. View full abstract»

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  • On the refractive properties of media with poles or zeros in the index of refraction

    Publication Year: 1974 , Page(s): 242 - 251
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    The refractive properties of inhomogeneous fibers are examined with emphasis being placed on the limiting situation where the index of refraction possesses poles or zeros. If, e.g., the index of refraction is n(\xi) = \xi^{m}, \xi = r/a , where a is the radius of the fiber and m an arbitrary constant, it is found that energy integrability is satisfied if m > -1 . When m \leq -1 energy infinities occur. The ray behavior of such media is examined in terms of geometrical optics, and corrections to geometrical optics are obtained by an asymptotic analysis of the exact solution. For m > 0 , the lens is of the diverging type, and when the angle of incidence is \alpha = 0 , geometrical optics predicts that rays "reflect" at various angles from the origin (depending on the value of m ). When m < 0 , rays "wrap" around the origin several times with a zero radius of curvature before they leave the lens ( \alpha = 0 ). For -1 < m < -frac{1}{2} , it is found that when \alpha = [(2m + 1)/2m] \pi caustics occur ( \alpha = 0, \pi/2 excluded). Pictorial diagrams show the behavior of these caustics and the correction coefficients to geometrical optics are obtained. View full abstract»

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  • Gain of a E-plane sectoral horn--A failure of the Kirchhoff theory and a new proposal

    Publication Year: 1974 , Page(s): 221 - 226
    Cited by:  Papers (10)
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    Accurate absolute gain measurements on a typical 10-cm band E -plane sectoral horn are described which demonstrate the conventional gain expression underestimates by 20 percent or more. More refined Kirchhoff expressions give little improvement. A new gain formula, incorporating the exact on-axis TE_{10} mode field of an open-ended parallel-plate waveguide and yielding much closer agreement with experiment, is proposed. View full abstract»

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  • The quadrifilar helix antenna

    Publication Year: 1974 , Page(s): 173 - 178
    Cited by:  Papers (18)  |  Patents (5)
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    The characteristics of the quadrifilar helix antenna [1] and [2], a broad-band high-gain device, are described in detail. Experimental data on beam patterns, impedance, and axial ratio are given for both the circularly polarized quadrifilar helix antenna (QHA) and the linearly polarized counterwound quadrifilar helix antenna (CQHA). Bandwidths in excess of 5:1 are obtained. The low frequency behavior is discussed. Computation of the QHA characteristics by moment methods [3] is described and computed data on beam patterns and current distributions are given. View full abstract»

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  • Natural-mode representation of transient scattering from rotationally symmetric bodies

    Publication Year: 1974 , Page(s): 266 - 274
    Cited by:  Papers (26)
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    A procedure for calculating the natural frequencies and the current distribution of the natural modes of a perfectly conducting body of revolution is presented. The analysis is based on the magnetic-field integral equation simplified to account for rotational symmetry. A technique is developed for the numerical evaluation of the natural frequencies and modes of a perfectly conducting rotationally symmetric body. The technique is used in a numerical sample calculation of natural frequencies and modes of a prolate spheroid. The general method of treating transient electromagnetic scattering problems developed previously is specialized to perfectly conducting bodies of revolution. In particular, scattering of a step-function plane wave from a prolate spheroid is treated numerically. The time response of the induced surface current is constructed from the natural modes in the same way as in network theory. The convergence of the solution, as the number of modes is increased, is also considered. View full abstract»

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  • Circular waveguide method for measuring reflection properties of absorber panels

    Publication Year: 1974 , Page(s): 251 - 256
    Cited by:  Papers (2)
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    A technique is developed for direct determination of the plane wave reflection properties of plane layered media. The approach is applicable for media containing a high-index absorber layer. A circular waveguide aperture is used to measure the near field scattering from the external medium. The analytical development results in a set of Smith chart contours from which the reflection properties of the medium can be determined from the measured waveguide reflection coefficient. The approach is demonstrated with measurements of a ferrite absorber panel. View full abstract»

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  • Mutual coupling between antennas for emission or reception--Application to passive and active dipoles

    Publication Year: 1974 , Page(s): 347 - 349
    Cited by:  Papers (14)
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    Two different definitions of coupling between antennas are given, for emission or reception. Using these definitions, computations have been made for two passive dipoles and two active dipoles (passive dipoles fed with a transistor). It appears that reduction of coupling is obtained only with an emissive active dipole array. View full abstract»

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  • Near electric and magnetic fields of wire antennas

    Publication Year: 1974 , Page(s): 364
    Cited by:  Papers (10)
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  • Fock currents for concave surfaces

    Publication Year: 1974 , Page(s): 357 - 360
    Cited by:  Papers (1)
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    The concept of a negative radius of curvature is used to show that the Fock currents can be extended to cover the case of a concave parabola, as well as a convex one. A simple analytic continuation of a parameter in the expression for the Fock currents leads to a residue series representation. The residue series is compared with an integral equation solution for a specific parabola. View full abstract»

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  • On the maximum backscattering cross section of passive linear arrays

    Publication Year: 1974 , Page(s): 360 - 361
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    The maximum backscattering cross section of an equispaced linear array connected to a reactive network and consisting of isotropic radiators is calculated for n = 2, 3 , and 4 elements as a function of the incident angle and of the distance between the elements. On the basis of the results obtained, some conjectures pertaining to the general n -element array are presented. View full abstract»

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  • Radiation efficiency of an X band waveguide array

    Publication Year: 1974 , Page(s): 355 - 357
    Cited by:  Papers (1)
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    This paper investigates the radiation efficiency of an X band waveguide array as the number of elements is varied for Uniform, Chebyshev, and Taylor aperture distributions. The radiating elements consist of edge slots machined in the narrow wall of an RG/52U waveguide terminated with a matched load. Efficiency calculations are made for a frequency of 9 GHz and a slot spacing of 0.8 in. Finally, theoretical and experimental radiation efficiencies are compared for a 20-dB Chebyshev array operating at maximum efficiency. View full abstract»

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  • Notes on duct influences on line-of-sight propagation

    Publication Year: 1974 , Page(s): 295 - 302
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    Microwave propagation over the sea within the horizon may be treated by ray tracing. Because of the maritime evaporation duct at sea, the receiving field may vanish at a certain antenna height. With increasing duct thickness, this special receiving point is shifted upwards. Vertical polarization puts this point on a lower level than horizontal polarization. Moreover, with increasing duct thickness it is shifted upwards more slowly for vertical polarization than for horizontal polarization. The resultant phase of the receiving field depends on the magnitude of the refractivity on a fixed but arbitrary reference level and on the thickness of the evaporation duct. Between the phase and the refractivity there exists a linear relation. As a function of duct thickness, however, the phase reveals a discontinuity amounting to integer multiples of 2\pi . In geodesy, where a modified kind of phase measurement is used for telemetry (Tellurometer), the evaporation duct may cause considerable errors. View full abstract»

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  • Element patterns and active reflection coefficient in uniform phased arrays

    Publication Year: 1974 , Page(s): 207 - 212
    Cited by:  Papers (12)
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    Several fundamental element pattern-active reflection coefficient interrelationships in uniform phased arrays are summarized, extended, and integrated. For central elements of sufficiently large arrays the results provide the basis for attractive measurement schemes of array parameters. View full abstract»

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  • Propagation in statistically irregular waveguides--Part II: Second order statistical moments

    Publication Year: 1974 , Page(s): 288 - 295
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    The correlation function of a point-source field is shown to be governed by the Bethe-Salpeter equation which reduces to the transfer equations for the eigenwave intensities. Because of the boundary irregularities the initial energy distribution among the modes undergoes substantial changes at great distances. In the case of a multimode waveguide the radiation transfer equation takes the form of the diffusion equation in the mode number domain, with the role of time played by the distance along the waveguide. In the framework of the multiple scattering theory developed, the propagation of a time-dependent quasi-monochromatic signal is also discussed. The wall roughness manifests in distortions of the signal shape. In a number of cases explicit expressions have been obtained for the pulse shape as a function of time and coordinates. Typical distances are estimated at which an amplitude modulation is effectively "washed away" by the influence of the multiple scattering. View full abstract»

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  • Instabilities and resonances of actively and passively loaded antennas

    Publication Year: 1974 , Page(s): 344 - 347
    Cited by:  Papers (1)
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    A theory on the phenomena of resonances and instabilities of passively and actively loaded antennas is presented. The general conditions for resonances for loaded radiating and receiving antennas are given. The conditions and types of instabilities encountered by actively loaded radiating and receiving antennas are analyzed. The instability of a conventional receiving antenna is discussed. View full abstract»

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  • TE radiation and scattering from infinitely-long noncircular conducting cylinders

    Publication Year: 1974 , Page(s): 365
    Cited by:  Papers (5)
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  • Bistatic scatter from rain

    Publication Year: 1974 , Page(s): 312 - 320
    Cited by:  Papers (21)  |  Patents (5)
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    An experimental investigation of bistatic scatter from rain was conducted using a 143 km scatter path at frequencies of 4.5 and 7.7 GHz. The ratio of transmitted to received power (transmission loss) was measured for scattering angles ranging from 6\deg to 130\deg . Simultaneous weather radar observations were made at a frequency of 1.3 GHz. Transmission loss estimates for the bistatic scatter path were computed using the weather radar data, the bistatic radar equation, and a model for the scattering cross section per unit volume of rain based upon Rayleigh scattering by an ensemble of water spheres. The measured and estimated transmission loss values were compared to test the use of the scattering model for the estimation of interference. The averaged ratio of measured-to-calculated transmission loss for the 4.5 GHz data is 1.2 \pm 0.4 dB. The averaged ratio for the 7.7 GHz data is -1.6 \pm 0.5 dB. Both these values are within the combined calibration uncertainties of each measurement system. The results show that the use of the simplified Rayleigh scattering cross section model for an ensemble of water spheres adequately describes bistatic scatter for a wide range of scattering angles and frequencies below 7.7 GHz for the hydrometeor types (rain, snow, and mixed rain and snow) encountered in New England. 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