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Antennas and Propagation, IEEE Transactions on

Issue 6 • Date June 1986

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Displaying Results 1 - 19 of 19
  • [Front cover and table of contents]

    Publication Year: 1986 , Page(s): 0
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    Freely Available from IEEE
  • Correction to "Microwave holography of large reflector antennas--Simulation algorithms"

    Publication Year: 1986 , Page(s): 853
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    First Page of the Article
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  • Cross polarization in dual reflector antennas--A PO and PTD analysis

    Publication Year: 1986 , Page(s): 849 - 853
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    A physical optics (PO) and physical theory of diffraction (PTD) analysis of symmetric and offset dual reflector antennas is performed. It is shown that in most cases PO gives sufficient accuracy, but the PTD correction can be of importance to determine the depolarization, especially if the subreflector edge taper is low. View full abstract»

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  • Interferometric measurement of tropospheric phase fluctuations at 22 GHz on antenna spacings of 27 to 540 m

    Publication Year: 1986 , Page(s): 797 - 803
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    Phase fluctuations at 22 GHz introduced by tropospheric events were measured by observing cosmic compact radio sources with the Nobeyama millimeter-wave array on antenna spacings of 27 to 540 m. The observed interferometer phases were used to derive Allan standard deviations \sigma _{A} of phase fluctuations. The standard deviations \sigma _{A} had good relations to antenna spacing L as a function, \sigma _{A} =A \times L^{N} + B . The exponent N derived from the observations in February distributed around 5/6 as expected from the Kolmogorov turbulence model, but was smaller than 5/6 from the observations in May. Time domain spectra of \sigma _{A} also imply that atmospheric structures (such as moist air, clouds, precipitation, etc.) have seasonal variations. Meteorological parameters monitored at the height of 20 m did not show good correlations to \sigma _{A} . View full abstract»

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  • Some design parameters for point-source compact ranges

    Publication Year: 1986 , Page(s): 845 - 847
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    Current development efforts with compact ranges are concerned primarily with optimizing the performance of compact ranges. The relationship of the diameter of the test zone to the beamwidth of the feed pattern and to the focal point of a point-source compact range is addressed. Parametric design information is presented in graphical form. View full abstract»

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  • Modified GTD for generating complex resonances for flat strips and disks

    Publication Year: 1986 , Page(s): 779 - 790
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1144 KB)  

    The complex resonance frequencies of a scatterer are important elements in target classification and identification. In the singularity expansion method (SEM), the resonances are defined by a homogeneous integral equation whose numerical solution is feasible in the low, but not in the high, frequency range. At high frequencies, the geometrical theory of diffraction (GTD) provides an attractive numerical alternative and, furthermore, incorporates an interpretation of the resonance generation process in terms of multiple wavefront (ray) traversals. Except for extremely simple scatterer configurations, the (damped) complex resonances are known to occupy an entire half of the complex frequency plane. Dominant and higher order creeping wave GTD applied to cylinders and spheres does indeed yield resonances arranged along a sequence of "layers" in that entire half-plane, but multiple edge diffracted GTD applied to flat strips and disks furnishes only a single (dominant) layer. By drawing analogies with higher order creeping waves on a smooth object, the conventional edge diffracted GTD field is here augmented by higher order ray fields undergoing higher order "slope diffraction." Each of these higher order ray fields can be made to satisfy its own resonance equation, which is now found to provide the missing layers, with remarkably accurate values for the resonances when compared, where available, with those calculated numerically by the moment and T-matrix methods. The success of higher order ray diffraction in predicting the complex resonance structure suggests that this mechanism may play a corrective role also in other edge dominated scattering phenomena. View full abstract»

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  • Angularly propagating waves in a radially inhomogeneous, lossy dielectric cylinder and their connection with the natural modes

    Publication Year: 1986 , Page(s): 813 - 824
    Cited by:  Papers (1)
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    A physical interpretation is proposed for the natural modes of a radially inhomogeneous, lossy dielectric circular cylinder embedded in a homogeneous, lossless dielectric. These modes are either of the creeping-wave or of the whispering-gallery type. With the aid of a generalized Wentzel-Kramer-Brillouin (WKB) asymptotics, an asymptotic characteristic equation is derived for each type, which can be explained physically. Numerical results obtained from the exact characteristic equation and both approximate equations are presented and discussed. View full abstract»

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  • An extension to GTD for an edge on a curved perfectly conducting surface

    Publication Year: 1986 , Page(s): 837 - 841
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    The construction of a high-frequency solution for the generation of edge-diffracted space rays and edge-excited surface rays by an electromagnetic wave normally incident on the edge of a curved perfectly conducting surface surrounded by an homogeneous medium is considered. The solution is a collection of the results of second degree canonical problems considered by Idemen et al. which will be cast into forms appropriate to numerical applications. View full abstract»

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  • Electromagnetic scattering by arbitrary shaped three-dimensional homogeneous lossy dielectric objects

    Publication Year: 1986 , Page(s): 758 - 766
    Cited by:  Papers (115)
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    The recent development and extension of the method of moments technique for analyzing electromagnetic scattering by arbitrary shaped three-dimensional homogeneous lossy dielectric objects is presented based on the combined field integral equations. The surfaces of the homogeneous three-dimensional arbitrary geometrical shapes are modeled using surface triangular patches, similar to the case of arbitrary shaped conducting objects. Further, the development and extensions required to treat efficiently three-dimensional lossy dielectric objects are reported. Numerical results and their comparisons are also presented for two canonical dielectric scatterers-a sphere and a finite circular cylinder. View full abstract»

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  • Electromagnetic reflection from a curved dielectric interface

    Publication Year: 1986 , Page(s): 842 - 845
    Cited by:  Papers (1)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    The reflection of a high-frequency electromagnetic field from an arbitrarily curved dielectric interface is considered. The fields are expanded in asymptotic series of k^{-1} , known as Luneburg-Kline expansions. Based on a ray method the zero- and first-order terms of k^{-1} of the reflected and transmitted field are evaluated at the interface. Associated with the fields at the interface, effective surface current densities can be used to determine the reflected and transmitted field at points away from the interface, which is done analytically for the reflected far field in the case of plane wave incidence. The result consists of a frequency-independent term, which is related to geometrical optics solution, and a term of k^{-1} , which is a useful extension of geometrical optics solution in some cases. View full abstract»

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  • An experimental investigation of electrically thick rectangular microstrip antennas

    Publication Year: 1986 , Page(s): 767 - 772
    Cited by:  Papers (83)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    The electromagnetic properties of electrically thick rectangular microstrip antennas were investigated experimentally. Antennas were fabricated with different patch sizes and with electrical thicknesses ranging from 0.03 to 0.23 wavelengths in the dielectric substrate. The resonant frequencies were measured and compared to existing formulas. The bandwidth was calculated as a function of electrical thickness and the antenna radiation patterns were measured. View full abstract»

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  • Diffraction by a dielectric half-plane

    Publication Year: 1986 , Page(s): 830 - 833
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    The problem of diffraction of a plane electromagnetic wave by a dielectric half-plane is reconsidered for solution by utilizing a set of recently developed approximate boundary conditions and the Wiener-Hopf technique. It is observed from the present solution of the problem that reflected waves cease to exist if the angle of incidence takes up the value \tan^{-1}(1/n) where n represents the refractive index of the material of the half-plane under consideration. Expression for the diffracted far field is obtained by using a modification of the saddle point method, and numerical values of the diffraction coefficients are presented in the form of a table for a special value of the refractive index n and for different values of the parameter kh, h representing the (small) thickness of the half-plane and k the wavenumber. View full abstract»

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  • A spiral antenna backed by a conducting plane reflector

    Publication Year: 1986 , Page(s): 791 - 796
    Cited by:  Papers (90)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    An Archimedean planar spiral antenna is numerically analyzed in the presence of a conducting plane reflector. The analysis shows that the spiral antenna backed by the plane reflector has two distinct regions in the current distribution, which explain the radiation of a circularly polarized wave for the outer circumference C ranging over about 1.3 \lambda < C < 1.5 \lambda and C > 2.9 \lambda , where \lambda is a free-space wavelength. Further consideration is given to a truncated spiral antenna whose outer circumference is on the order of 1.4 \lambda . The truncated spiral antenna maintains a decaying current distribution and radiates a circularly polarized wave over a 1:1.2 frequency bandwidth. It is also demonstrated that a power gain on the order of 8.5 dB is realized over the same frequency range. View full abstract»

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  • TM and TE scattering by a dielectric/ferrite cylinder in the presence of a half-plane

    Publication Year: 1986 , Page(s): 804 - 813
    Cited by:  Papers (16)
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    An integral equation solution to the problem of transverse magnetic (TM) or transverse electric (TE) scattering by an isotropic dielectric/ferrite material cylinder in the presence of a perfectly conducting half-plane is presented. The technique is termed a method of moments (MM)/Green's function solution since the method of moments is used to determine the electric and magnetic polarization currents representing the material cylinder, while the presence of the half-plane is accounted for by including the half-plane Green's function in the kernel of the integral equations. Numerical results are presented for the echo width, material cylinder interior fields, and the surface impedance of a material slab on the surface of a half-plane. View full abstract»

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  • On the far-field approximation for scattering from randomly rough surfaces

    Publication Year: 1986 , Page(s): 847 - 849
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    Various authors have justified the far-fields approximation for rough surface scattering using one of the classical approximations for the scattered fields, usually considering either the coherent scattered field or the incoherent scattered intensity. An exact expression for the field scattered from a perfectly conducting rough surface is considered. The expression for the incoherent scattered intensity is formally derived, and a condition under which the far-field approximation is valid is found, independent of specific approximations for the surface or scattered fields or for the surface height statistics. The condition so derived is, under many circumstances, substantially less restrictive than that derived before in the general case. Furthermore, the previous results may be easily recovered by further specialization of our result. View full abstract»

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  • An algorithm for pattern synthesis improvement

    Publication Year: 1986 , Page(s): 825 - 829
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    When shaped beams are synthesized using array antennas with a limited number of elements, insufficient degrees of freedom sometimes result in practically unsatisfactory patterns. In such cases, it is very convenient if the unsatisfactory patterns can be improved to satisfactory ones using some techniques. An example is presented of such pattern improvement techniques. First, an algorithm necessary for the improvement technique is derived by modifying an algorithm commonly used for adaptive array antennas into a form not requiring real time information of receiving signals. Then, three application examples of this technique are presented. In the example of a shaped beam array antenna of which two elements are removed out of ten elements, measured results are compared to the calculated pattern to show the validity and usefulness of this technique. View full abstract»

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  • A new technique of synthesis of the near- or far-field patterns of arrays

    Publication Year: 1986 , Page(s): 773 - 778
    Cited by:  Papers (4)
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    A unified approach for synthesizing the near- or far-field radiation patterns of an array of uniformly or nonuniformly spaced point sources or directive elements located on a planar contour of arbitrary shape is presented. The synthesis problem is formulated employing the free-space Green's dyadic as well as the translational and rotational addition theorems for spherical vector wave functions. A similar unified approach for synthesizing the near- or far-field radiation patterns of a uniformly or nonuniformly spaced linear array of point dipoles is also presented. The validity of the technique presented is established with several typical numerical illustrations. View full abstract»

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  • Diffraction of a TM whispering gallery mode by the edge of a nonperfectly conducting spherically curved sheet

    Publication Year: 1986 , Page(s): 833 - 837
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    Electromagnetic scattering is a function of the scatterer's material properties as well as its geometry. Therefore, it is necessary to examine the effect of the physical properties of a body on diffraction phenomena besides the geometrical properties. The aim here is to give a rigorous asymptotic solution for the diffraction of high-frequency electromagnetic fields by an edge on a spherically curved sheet having a particular impedance property. The solution is interpreted with the terminology of the geometrical theory of diffraction (GTD). View full abstract»

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  • Design of wide-band corrugated conical horns for Cassegrain antennas

    Publication Year: 1986 , Page(s): 750 - 757
    Cited by:  Papers (30)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB)  

    Design procedures based on extensive theoretical and experimental investigations are given for hybrid-mode corrugated conical horns having near-constant beamwidth, low cross-polarized sidelobes and low reflection for continuous bandwidths up to 2.1:1. The design techniques are applicable for horn flare semi-angles to about 30\deg , which includes most feed horns in dual-reflector antennas. View full abstract»

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Aims & Scope

IEEE Transactions on Antennas and Propagation includes theoretical and experimental advances in antennas.

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Meet Our Editors

Editor-in-Chief                                                 Kwok W. Leung