Antennas and Propagation Society Symposium 1991 Digest

24-28 June 1991

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Displaying Results 1 - 25 of 464
  • A UTD solution for the EM diffraction by a corner in a plane angular sector

    Publication Year: 1991, Page(s):2 - 5 vol.1
    Cited by:  Papers (5)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (109 KB)

    A new approximate uniform geometrical theory of diffraction (UTD) solution is obtained for describing the field diffracted by a corner (vertex) in a perfectly conducting plane angular sector which is illuminated by a high-frequency electromagnetic plane wave. This corner diffraction solution is found by a uniform asymptotic reduction of the plane wave spectral integral formulation for the field sc... View full abstract»

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  • Equivalent edge currents of physical optics components for flat plate

    Publication Year: 1991, Page(s):6 - 9 vol.1
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (150 KB)

    The authors propose a novel and heuristic concept for surface to edge integral reduction of physical optics currents in order to obtain PO-EECs (physical-optics equivalent edge currents) without false singularities. Firstly, the edge of the scatterer is divided into segments, each of which is replaced with a fictitious one satisfying the diffraction law at each point. Secondly, classical PO diffra... View full abstract»

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  • Radiation pattern analysis of major angle corner reflector antenna by GTD including corner diffraction

    Publication Year: 1991, Page(s):10 - 13 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (140 KB)

    An approximate formula for the hollow corner diffraction is derived from the asymptotic evaluation of UTD (uniform-theory of diffraction)-combined equivalent current integration along the finite wedge edge. The radiation patterns of a major angle corner reflector antenna are computed with this hollow corner diffraction formula, and it is verified that the present GTD (geometrical theory of diffrac... View full abstract»

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  • A UTD description of surface and space wave excitation at the edge of an impedance wedge

    Publication Year: 1991, Page(s):14 - 17 vol.1
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (159 KB)

    The canonical problem of evaluating the field scattered at a finite distance from the edge of an impedance wedge which is illuminated by a line source is analyzed. Emphasis is placed on an analysis of surface wave excitation mechanisms. In particular, high-frequency expressions for the coupled surface wave-space wave contributions are presented. Also, suitable high-frequency diffracted field contr... View full abstract»

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  • Uniform theory of diffraction analysis of conductive strips with constant and tapered resistive loads

    Publication Year: 1991, Page(s):18 - 21 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (94 KB)

    The authors explore the use of a uniform theory of diffraction (UTD) approach to the analysis of conductive strips with constant and tapered resistive loads. UTD diffraction coefficients are found for resistive edges and junctions using the geometrical-optics reflection and transmission coefficients of resistive strips. The UTD radar echo-length predictions for edge-loaded strips agree well with m... View full abstract»

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  • High frequency electromagnetic scattering from an inhomogeneous dielectric body by ray tracing

    Publication Year: 1991, Page(s):22 - 25 vol.1
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (150 KB)

    The authors present the use of a ray tracing/surface integration technique to treat the scattering from electrically large, inhomogeneous objects. They attempt to extend the 'shooting and bouncing ray' scheme to handle inhomogeneous objects, with the addition of ray tracing in inhomogeneous media. In two-dimensional examples, the ray formulation was applied to radially inhomogeneous circular cylin... View full abstract»

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  • Some results of the scattering of simple conducting bodies in the vicinity of a cloud of dipoles

    Publication Year: 1991, Page(s):26 - 29 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (114 KB)

    A method-of-moments wire model is employed to obtain the variation of the radar cross section of a perfectly conducting plate when it is placed near a cloud of resonant dipoles. The effect of the relative position between the plate and the cloud is studied. Different cases of coupling between the dipoles are also analyzed in order to study their influence on the interaction between the plate and t... View full abstract»

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  • Iterative technique for scattering by a linear array of spheres

    Publication Year: 1991, Page(s):30 - 33 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (127 KB)

    A novel iterative procedure is proposed for the solution to the scattering by a system of conducting spheres. This approach requires the solution of the field scattered by each sphere assumed to be alone in the incident field, which acts as an incident field on the other spheres. Therefore, the first-order scattered field results from the excitation of each sphere by the incident field only, while... View full abstract»

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  • Analysis of electromagnetic scattering from three-dimensional dielectric objects by field iteration method

    Publication Year: 1991, Page(s):34 - 37 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (115 KB)

    An iteration method is presented for solving electromagnetic scattering of 3D dielectric objects. The convergence, stability, effectiveness, and accuracy of the solution obtained by the method are proved. Radar cross section versus incident angle is plotted for a dielectric plate with 0.813 lambda square by 0.051 lambda thick and epsilon /sub r/=4. The numerical results calculated by using the pro... View full abstract»

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  • RCS of resonant scatterers with attached wires

    Publication Year: 1991, Page(s):38 - 41 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (187 KB)

    It is demonstrated that a wire antenna has a dominant effect on the RCS (radar cross section) of a strip scatterer or a cylinder scatterer for end-on incidence. The wire introduces resonance peaks into the RCS at frequencies making the wire length odd multiples of the quarter-wavelength. The wire dominates the RCS for end-on incidence. For broadside incidence the wire has a major effect on the RCS... View full abstract»

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  • Analysis of a microstrip patch antenna using the method of moments

    Publication Year: 1991, Page(s):44 - 47 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (72 KB)

    An analysis of a microstrip patch antenna on a finite dielectric substrate is presented. The antenna is excited by the feedline passing below the dielectric bed. For analysis purposes, the patch, the feedline, and the dielectric substrate are modeled by triangular patches. A set of coupled integral equations, in terms of equivalent currents, is obtained by using the equivalence principle and assoc... View full abstract»

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  • The development of an active integrated microstrip antenna

    Publication Year: 1991, Page(s):48 - 51 vol.1
    Cited by:  Papers (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (162 KB)

    The development of an active integrated antenna utilizing MMIC (monolithic microwave integrated circuit) amplifiers and microstrip transmission lines is presented. The design procedure is described and the antenna performance is discussed. An active integrated antenna has been verified experimentally. This active antenna configuration has several advantages over the passive configuration in terms ... View full abstract»

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  • The sinuous microstrip antenna

    Publication Year: 1991, Page(s):52 - 55 vol.1
    Cited by:  Papers (3)  |  Patents (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (115 KB)

    Multioctave microstrip antennas recently developed by the authors (1990) for a spiral geometry have been extended to a sinuous geometry with good performance over a 5:1 bandwidth. The motivation for using the sinuous configuration is to achieve polarization diversity. Dual linear polarizations or dual circular polarizations can be obtained from a single sinuous antenna. Other desirable performance... View full abstract»

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  • The boundary-integral method as applied to coupled cavity-backed slot antennas

    Publication Year: 1991, Page(s):56 - 59 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (109 KB)

    The boundary-integral method (BIM) has been successfully demonstrated to predict the input impedance for coupled thin cavity-backed slot antennas which have appreciable coupling. The BIM models the antenna as a 'thin' structure; the fields are invariant in one direction. Characteristics of the antenna can therefore be found in terms of the interactions among sources that exist only along the bound... View full abstract»

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  • On the use of metallized cavities backing microstrip antennas

    Publication Year: 1991, Page(s):60 - 63 vol.1
    Cited by:  Papers (17)  |  Patents (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (140 KB)

    A cavity-backed patch phased array is proposed. The antenna configuration has some extra degrees of freedom not found in conventional microstrip patch antennas. These include the cavity dimensions and the slot size. It may be possible to exploit these features in order to further increase the bandwidth (e.g. by double-tuning) or to decrease the antenna mode scattering. The integral equation approa... View full abstract»

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  • Multiport network model for two-port gap-coupled rectangular microstrip patches

    Publication Year: 1991, Page(s):64 - 67 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (105 KB)

    A multiport network modeling (MNM) approach is developed for the analysis and design of a gap-coupled two-port rectangular microstrip patch. The case when the radiating edge is along the gap is considered. A good agreement between moment-method results and the results based on the MNM approach has been obtained verifying the accuracy of the MNM approach developed for gap-coupled patch.<> View full abstract»

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  • Microstrip patch designs which do not excite surface waves

    Publication Year: 1991, Page(s):68 - 71 vol.1
    Cited by:  Papers (1)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (136 KB)

    Two types of microstrip antennas are presented which do not excite the dominant TM/sub 0/ surface wave, and thus have a radiation efficiency of 100%. The first design is a circular path antenna with a 'cored' substrate, in which a circular piece of substrate material is removed from the region directly below the patch, with the resulting hole filled by a material (such as air) which has a lower pe... View full abstract»

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  • A wide-band microstrip antenna using two triangular patches

    Publication Year: 1991, Page(s):72 - 75 vol.1
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (96 KB)

    A wideband patch antenna composed of two triangular patches is investigated using an EM simulation program. The antenna bandwidth is twice as large as that of an ordinary rectangular patch of the same size. Numerical results also shown that good radiation patterns are obtained with the cross-polarization level of -14 dB in the whole frequency range.<> View full abstract»

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  • Improved strip element for a circularly polarized printed array operating at 12 GHz band

    Publication Year: 1991, Page(s):76 - 79 vol.1
    Cited by:  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (239 KB)

    An improved strip element is described which allows CP-PASS (circularly polarized printed array antenna composed of strip dipoles and slots) to reduce the necessity of correcting the element length after placing a reflector. By using the improved strip element, a high-efficiency CP-PASS can be realized when even a thick substrate is used because all elements are placed on one side of the substrate... View full abstract»

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  • Perturbation formulation for nearly-degenerate microstrip dipole eigenmodes

    Publication Year: 1991, Page(s):80 - 83 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (106 KB)

    System eigenmodes of N-coupled, nearly degenerate microstrip dipoles are investigated through a singularity-expansion-based perturbation formulation. This method is based on integral-operator techniques employing rigorous dyadic Green's functions for the layered microstrip environment. Mutual coupling between microstrip antennas has been previously accounted for by full-wave formulations, and simi... View full abstract»

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  • Performance analysis of a concurrent adaptive least-squares sidelobe cancellation system with excess degrees of freedom

    Publication Year: 1991, Page(s):86 - 89 vol.1
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (177 KB)

    The authors present an analysis of the performance of a concurrent blocked sidelobe canceler when there are more auxiliary array elements, or degrees of freedom, than spatially coherent interferers. The existence of an excess degrees-of-freedom problem for the concurrent processor is reconsidered. The main result is the analytic determination of tight bounds for the mean square error for the concu... View full abstract»

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  • Limitations of a sidelobe canceller concept

    Publication Year: 1991, Page(s):90 - 93 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (109 KB)

    An analysis is presented which suggests that adding a sidelobe canceller to an existing antenna will not produce effective cancellation over a bandwidth. fortunately, an alternative exists which uses adaptive transversal filters to correct for antenna dispersion and a simple set of horn elements whose gain exceeds the sidelobe gain of the main reflector to avoid unnecessary increases in the system... View full abstract»

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  • Real amplitude-only nulling algorithm (RAMONA) for adaptive sum and difference patterns

    Publication Year: 1991, Page(s):94 - 97 vol.1
    Cited by:  Papers (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (87 KB)

    The authors present a real amplitude-only nulling algorithm (RAMONA) for adaptive sum and difference patterns of antenna arrays. This algorithm can simultaneously form nulls in sum and difference patterns to reject the exterior jammers. In computation, only real arithmetic operations are needed. In comparison with the corresponding algorithm which consists of complex operations, the RAMONA algorit... View full abstract»

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  • Adaptive nulling of fully coherent interferences in a nonstationary signal environment

    Publication Year: 1991, Page(s):98 - 101 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (175 KB)

    An alternative approach for finding an optimal set of weights for antenna arrays which effectively nulls out fully coherent interferences is presented. Since the proposed technique does not require the signal matrix to be positive semidefinite the matrix can be formed at every observation time with the instantaneous values. The optimal weights are iteratively computed in a minimum number of steps ... View full abstract»

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  • Rapid and stable optimization of CMA adaptive array by Marquardt method

    Publication Year: 1991, Page(s):102 - 105 vol.1
    Cited by:  Papers (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (114 KB)

    The authors present a rapidly converging and well-conditioned algorithm based on the nonlinear least squares method referred to as the Marquardt method for the CMA (constant modulus algorithm) adaptive array. Computer simulation with a pi /4-shifted QPSK (quadrature phase-shift keying) signal verified its rapid and stable convergence characteristics for any radio environment. Taking into considera... View full abstract»

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