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Antennas and Propagation, IRE Transactions on

Issue 6 • Date November 1962

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Displaying Results 1 - 25 of 28
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • Nonlinear signal processing in receiving arrays

    Page(s): 656 - 662
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    An analysis of the beam formation of receiving arrays employing signal limiting and sampling is performed. It is found that the effect of limiting and sampling with one signal present and the effect of limiting alone when more than one signal is present is to introduce new side lobes into the beam pattern that may be confused with signals. It is pointed out that by a suitable distribution of receiving transducers both of these effects can be reduced to a degree that becomes negligible and the performance of the array becomes similar to the one without the processing. View full abstract»

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  • Aperture fields of an array of rectangular apertures

    Page(s): 663 - 671
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    This paper presents a rigorous formulation of the boundary value problem posed by an electromagnetic wave incident upon a plane screen containing a doubly periodic array of rectangular apertures. The differential-integral equation method of Copson is employed to derive integral equations in the components of the aperture field. These are then solved approximately for normally incident plane-wave excitation. A numerical solution is obtained for square apertures which is valid over the aperture resonance region,kd approx 1.5. Values of scattering cross section and plots of the aperture field are presented for aperture sizes larger, smaller, and near resonant dimensions. The effect of singularities of the aperture field near the edges is discussed. View full abstract»

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  • Admittance of a cavity-backed annular slot antenna

    Page(s): 671 - 678
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    An annular slot antenna which is backed by a cylindrical or a coaxial cavity is excited by a current sheet in the slot plane which exhibits no azimuthal (phi) variation. The integral equation which relates the radial electric field in the slot plane to the linear source current density is solved by variational techniques. The numerical calculations emphasize narrow slots and shallow cavities. The slot antennas may resonate with cavity depthz_{0}<lambda/4. A resonant antenna exhibits nearly the same bandwidth as the slot which is backed bylambda/4deep cavity. Dielectric cavity loading decreases the size of a resonant cavity, but it also decreases the antenna bandwidth. View full abstract»

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  • The diffraction of surface waves by a terminated structure in the form of a right-angle bend

    Page(s): 679 - 686
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    A collection of numerical results have been computed from an exact solution for the diffraction of surface waves by a right-angle bend which is reactive on one surface and is perfectly conducting on the other. The power reflection coefficient and the far field pattern are presented graphically for both TM and TE cases. The truncation of the perfectly-conducting face is considered for its approximate effect on the diffraction pattern. The physical significance of these calculations is discussed in terms of its relationship to surface wave antennas. The radiation patterns are also computed by the Kirchhoff approximation and compared with those of the exact analysis. View full abstract»

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  • The crossed-spaced-loop direction-finder aerial

    Page(s): 686 - 691
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    A fixed array of four loop aerials is described which, in conjunction with a goniometer, is equivalent to a rotating spaced-loop aerial when receiving ground wave signals. 'Experimental verification of this performance is given. The theoretical performance of this system when receiving sky wave signals is developed. Under these conditions, the system offers no advantage over the simple cross-looped aerial. View full abstract»

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  • Theory of unequally-spaced arrays

    Page(s): 691 - 702
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    Although recently unequally-spaced arrays have been shown to be useful, the theory has not been fully developed, except for the use of matrices, computers, or the perturbation method. This paper presents a new approach to the unequally-spaced array problem. It is based on the use of Poisson's sum formula and the introduction of a new function, the "source position function." By appropriate transformation, the original radiation pattern is converted into a series of integrals, each of which is equivalent to the radiation from a continuous source distribution whose amplitude and phase distribution clearly exhibit the effects of the unequal spacings. By this method, it is possible to design unequally-spaced arrays which produce a desired radiation pattern. This method is effective in treating arrays of a large number of elements, and unequally-spaced arrays on a curved surface. Three examples are shown to illustrate the effectiveness of the method. The problem of sidelobe reduction for the array of uniform amplitude, which was attacked by Harrington, is treated by our method. A numerical example is shown for 25-db sidelobe level. Also, the problem of secondary beam suppression is attacked with the use of the Anger function. The interesting problem of azimuthal frequency scanning by means of an unequally-spaced circular array is also shown, using the method of stationary phase. View full abstract»

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  • The effect of an unbalance on the current along a dipole antenna

    Page(s): 702 - 707
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    The effects of an unbalanced component of current on the distribution of the current along a dipole antenna driven by a two-wire transmission line has been studied experimentally. It was found that an unbalanced component of current on the line significantly influences the measured distributions of current along antennas of shorter lengths. A quantitative study was made by decomposing the currents into symmetric and antisymmetric parts. The associated unbalance in the transverse field distribution was measured by a field probe and correlated with the ratio of the amplitudes of the symmetric to antisymmetric components of current in the transmission line and the antenna. View full abstract»

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  • Effects of random errors on the performance of a linear butler array

    Page(s): 708 - 714
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    A statistical analysis is presented which, assuming the errors in the beam forming matrix of a linear Butler array to be small independent Rayleigh-distributed random errors, indicates that the resultant power pattern has a modified Rayleigh distribution. The results of the analysis were then applied to determine the effects upon sidelobes and beam pointing yielding the following results. The allowable limits of phase and amplitude errors for a specified sidelobe deterioration are greatly reduced in comparison to the limits for an array whose elements are independently excited; furthermore, the limits are to a great extent independent of the number of elements in the array. The beam-pointing error is not severely affected and is inversely proportional to the number of elements. The nature of the results confirm what was to be expected from the periodic fashion in which errors within the matrix are distributed across the array. View full abstract»

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  • Luneberg-Kline analysis of scattering from a sinusoidal dielectric interface

    Page(s): 715 - 721
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    Application of the Luneberg-Kline asymptotic series to the solution of electromagnetic boundary value problems is extended to problems involving dielectric media. The series is employed to obtain an approximate value for the field near a sinusoidal interface between dielectric media when a perpendicularly polarized plane wave is incident. The resulting formulas are used to evaluate quantitatively the accuracy of the geometrical optics solution of the problem for a range of parameter values. It is found that for the parameter values considered, the geometrical optics solution is an excellent approximation to the exact solution. View full abstract»

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  • Statistics of phase quadrature components of microwave fields transmitted through a random medium

    Page(s): 721 - 731
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    The phase quadrature components of the total microwave field transmitted through a random volume distribution of Styrofoam spheres have been measured in the laboratory. The radii (a) of the spheres were large compared to the wavelengths (ka=2pi a/lambdasim20), and their index of refraction was close to unity (eta = 1.019). The statistical results lead in general to the bivariate normal distribution with correlation (rho) to describe the scattered incoherent field, rather than to the simpler Rayleigh distribution. The quadrature components of the incoherent field are Gaussian, but in generalsigma_{1}^{2}neqsigma_{2}^{2}andrhoneq 0. However, by rotating (in phase) the quadrature axes, two simpler situations arise: (a) at one orientation,sigma_{1}^{2}=sigma_{2}^{2}butrhoneq0; (b) at an orientation45degfrom case (a),sigma_{1}^{2}neqsigma_{2}^{2}butrhoneq0. Probability density expressions for these simpler cases exist in the literature. As the quadrature axes are rotated, the sumsigma_{1}^{2}+sigma_{2}^{2}remains equal to a constant (the incoherent power), as it should. These departures of the incoherent field from the Rayleigh distribution are a function of the sum of the reciprocal transmitter and receiver distances. This behavior suggests that the departures are related to the sphericity of the transmitting and receiving beams. View full abstract»

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  • Spectra of radio refractive index between ground level and 5000 feet above ground

    Page(s): 732 - 737
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    Atmospheric index of refraction has been measured from ground level to 5000 feet using the Deam telemetering refractometer which permitted accurate spectral analysis of these data. The results of the analysis show a wide variation in the mean slope and intensity of the spectra. Some of the spectra are presented and their characteristics discussed. View full abstract»

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  • On scattering of waves by the infinite grating of circular cylinders

    Page(s): 737 - 765
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    The boundary value problem of the infinite grating of circular cylinders is treated by specializing the new functional equation obtained previously for arbitrary elements. This specifies the problem in terms of a set of algebraic equations which involves only the known scattering coefficients of an isolated cylinder, and certain series of elementary functions. The special results for normal incidence are identically those obtained originally by Ignatowsky who worked with the separation-of-variables solution; as a check we also extend his procedure to arbitrary angles and show that the results can be transformed to those we obtain by the Green's function approach. The equations are used to construct series and closed form approximations for both polarizations, for conducting and dielectric cylinders, for arbitrary angles of incidence. The results are applied to consider multiple scattering or coupling effects for a mode near grazing (Wood anomalies), and for closely spaced scatterers (packing effects). For example, we show that to a first approximation the packing effects forEperpendicular to the axes merely increase the dipole moment of the isolated cylinder; in this range, the circular cylinder within the grating is equivalent to an isolated elliptic cylinder whose size and shape are independent of angle of incidence. We also obtain simple closed forms for low frequencies which take explicit account of coupling effects up to multipoles of order2^{5}, etc. View full abstract»

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  • On the electromagnetic resonant frequencies of the earth ionosphere cavity

    Page(s): 766 - 769
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    The earth ionosphere cavity is capable of supporting resonant electromagnetic modes (Schumann modes) at extremely low frequencies. The usual formula for the frequencies of these resonances is deduced from the waveguide mode theory in which propagation is essentially tangential to the earth's surface. Here an alternative formulation in terms of outwardly and inwardly propagating radial waves is presented and shown to result in the same formula as found from the waveguide mode theory for all reasonableD-region ionosphere parameters. View full abstract»

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  • Multiple scattering and wave propagation in periodic structures

    Page(s): 769 - 775
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    Wave propagation in periodic structures is considered from the self-consistency of multiple scattered fields. Surface waves on gratings or open structures comprising obstacles that scatter cylindrical and spherical waves are analyzed approximately by a summation technique. Finally, coupled surface waves due to interaction between adjacent structures are investigated. View full abstract»

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  • The effect of a discontinuity in curvature in high-frequency scattering

    Page(s): 775 - 780
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    A plane wave is incident upon a cylindrical surface comprised of two parabolic sections with different curvature at their junction but otherwise smoothly joined, such that the direction of their normals is continuous. The Neumann boundary condition is considered and an asymptotic expansion is obtained for the field on the surface. It is shown that the discontinuity will launch creeping waves on a curved surface, and the actual form of these waves are obtained. The special case where one of the curved surfaces degenerates into a plane is also considered. View full abstract»

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  • On VLF emissions in the exosphere

    Page(s): 785 - 787
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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