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Antennas and Propagation Society International Symposium, 1990. AP-S. Merging Technologies for the 90's. Digest.

7-11 May 1990

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Displaying Results 1 - 25 of 477
  • Application of absorbing boundary conditions to TLM simulations

    Publication Year: 1990, Page(s):2 - 5 vol.1
    Cited by:  Papers (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (167 KB)

    It is demonstrated that the traditional method of match terminating the TLM (transmission line matrix) mesh does not accurately model a free space boundary. It is found that the match termination of the TLM mesh is accurate only if waves strike the boundary with normal incidence. A successful implementation of one type of FD-TD (finite-difference time-domain) absorbing boundary condition in TLM si... View full abstract»

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  • Application of time domain diakoptics to 3-D TLM method with symmetrical condensed nodes

    Publication Year: 1990, Page(s):6 - 9 vol.1
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (167 KB)

    The diakoptics (segmentation) technique is applied to TLM (transmission-line matrix) analysis of microwave circuits using Johns's (1987) 3-D symmetrical condensed node. It is shown how a microwave structure can be partitioned into substructures which are solved independently and later reassembled (all in the time domain). Diakoptics leads to considerable reduction in memory and CPU requirements fo... View full abstract»

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  • On a correction to the voltage/field relationship used in the condensed node TLM method

    Publication Year: 1990, Page(s):10 - 13 vol.1
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (156 KB)

    A new relationship, based in part on Maxwell's equations, between the voltages pulses used in the condensed node TLM (transmission line matrix) method and the electromagnetic fields is given. A numerical comparison between the old relationships given by Johns (1987) is made using the impulse response of a perfect electric conductor (PEC) cavity. It is found that the formulas of Johns yield time-do... View full abstract»

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  • Finite-difference time-domain technique for antenna radiation

    Publication Year: 1990, Page(s):14 - 17 vol.1
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (111 KB)

    The finite-difference time-domain (FD-TD) technique is used to predict the radiation pattern of antennas mounted on ground planes, either perfectly conducting or of composite material, and other complex structures. The results obtained using the FD-TD technique are compared with results using the geometrical theory of diffraction (GTD) and measurements. The normalized power pattern of a quarter-wa... View full abstract»

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  • Time domain finite element analysis of 2-D shields

    Publication Year: 1990, Page(s):18 - 21 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (147 KB)

    A two-dimensional time-domain application of a general finite-element mathematical package, IMSL:PDE/PROTRAN, is considered for two-dimensional shielding problems. The software runs on the IBM 3090 mainframe computer. The shielding problem is formulated via the magnetic vector potential and the Coulomb gauge. Validation of the program is performed via a simple test problem (plane wave incident on ... View full abstract»

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  • Time-domain scattering in 2 1/2 dimensions

    Publication Year: 1990, Page(s):22 - 25 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (107 KB)

    A finite-difference time-domain (FDTD) method is used to solve the problem of the response of an arbitrary source, in particular, an impulsive point source, in a two-dimensional isotropic inhomogeneous medium. The field is three-dimensional, whereas the inhomogeneity is two-dimensional; hence, this is called a 2-1/2-dimensional problem. Taking advantage of the invariance of the geometry in one dim... View full abstract»

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  • Time-domain physical-optics analysis of large reflector antennas

    Publication Year: 1990, Page(s):26 - 29 vol.1
    Cited by:  Papers (11)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (108 KB)

    The time-domain analysis of large reflector antennas is presented. Physical-optics time-domain analysis is used to determine the antenna characteristics under pulse-modulated RF excitation. The resulting far fields for a front-fed paraboloid are shown. The waveforms of the incident wave and scattered field are plotted. From these patterns one can determine buildup and decay transient time as a fun... View full abstract»

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  • Time domain scattering from curved surfaces

    Publication Year: 1990, Page(s):30 - 33 vol.1
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (154 KB)

    The time-dependent form of the electric field integral equation (EFIE) is used to solve transient scattering problems for perfectly conducting surfaces. The basis functions of Rao et al. (1982) and a time marching method-of-moments technique are used to solve the time-dependent EFIE. A special testing procedure and an averaging technique are used to overcome solution stability problems at late tim... View full abstract»

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  • Transient electromagnetic wave scattering by a dissipative dielectric sphere

    Publication Year: 1990, Page(s):34 - 37 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (110 KB)

    The scattered field from a step-excited dielectric sphere is evaluated by the numerical Bromwich integration and a recently developed asymptotically compensated singularity expansion method. Both lossless and dissipative cases are considered. Excellent agreement is observed between the numerical results obtained using the two techniques. An interpretation of the various features in the return sign... View full abstract»

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  • Application of the finite-difference time-domain method to electromagnetic scattering from 3-D chiral objects

    Publication Year: 1990, Page(s):38 - 41 vol.1
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (68 KB)

    It is shown how the finite-difference time-domain (FDTD) method has been adapted to handle electromagnetic wave propagation through chiral media. Two solutions to this problem are presented, enabling the FDTD method to handle propagation through chiral, as well as achiral, media. One solution is exact, involving the recursive (but still parallel) solution of the field update equations. This method... View full abstract»

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  • Solving the Helmholtz equation using multiply-propagated waves

    Publication Year: 1990, Page(s):44 - 47 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (185 KB)

    The Helmholtz equation multiple propagator (HEMP) for solving system matrices from partial differential equation (PDE) models is described. It will be of order N/sup 1/2/ and N/sup 2/3/ faster than banded techniques commonly used for two-dimensional and three-dimensional problems having N unknowns. It is pointed out that HEMP could improve the efficiency of the only modeling technique suitable for... View full abstract»

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  • A recursive algorithm for reducing algorithmic complexity of scattering problems

    Publication Year: 1990, Page(s):52 - 55 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (111 KB)

    A recursive algorithm for calculating the exact solution of field scattering from a dielectric object is proposed. As in the method of moments, the object is first divided into N subobjects. Then, every subject is treated as a single scatterer in an N-scatterer problem. The recursive algorithm is then employed to calculate the (n+1)-scatterer tensor-T matrix from the n-scatterer tensor-T matrix. W... View full abstract»

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  • On the scattering matrix formalism for electromagnetic modelling

    Publication Year: 1990, Page(s):56 - 59 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (121 KB)

    The use of a collection of scattering matrices coupled with addition theorems as a framework for general electromagnetic problems is discussed. The author presents the basic machinery, illustrates some assumptions necessary to make this approach viable, and presents some directions for further research. This work began as an investigation of the effect of mutual coupling and was motivated by the d... View full abstract»

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  • Impedance matrix localization produces a sparse moment method matrix

    Publication Year: 1990, Page(s):60 - 63 vol.1
    Cited by:  Papers (11)  |  Patents (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (143 KB)

    Basis and testing functions for moment-method calculations that make the resulting matrix sparse are discussed. Recent numerical results have verified theoretical predictions that a moment-method matrix with N/sup 2/ elements can be replaced by one with 100N nonzero elements. This technique is unlike some other techniques (e.g. k-space, differential equation, etc.) in that this is done without inc... View full abstract»

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  • Convergence acceleration techniques in the iterative solution of integral equation problems

    Publication Year: 1990, Page(s):64 - 67 vol.1
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (109 KB)

    The authors present some techniques that, when applied judiciously, can speed up convergence rates considerably or make convergence possible in otherwise impossible cases in connection with the iterative solution of integral equation problems. Particular attention is given to automatic renumbering (matrix, method), extrapolation schemes, and a multilevel approach. It is noted that the combined eff... View full abstract»

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  • Iteration, multiple scattering and the sphere of influence technique

    Publication Year: 1990, Page(s):68 - 71 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (145 KB)

    An iterative scheme, the sphere of influence (SOI) technique, specifically designed around the electromagnetic (EM) scattering problem is described. This method presents an alternative to other classical iterative methods as well as to newer schemes e.g., small domains coupled by Schelkunoff-type sources. The SOI technique is based on an iterative interpretation of multiple scattering first descri... View full abstract»

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  • Diakoptic theory and the moment method

    Publication Year: 1990, Page(s):72 - 75 vol.1
    Cited by:  Papers (7)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (150 KB)

    The modified diakoptic theory is described, and its relationship to the method of moments is explained. Utilization of the theory is illustrated by an example application of the simple curved-wire antenna. A numerically efficient iteration method for computing open-port currents on a structure is outlined, as is the use of these currents to obtain open-port impedance elements characteristic of the... View full abstract»

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  • Application of integral equation and method of moments for electrically very large scatterers using spatial decomposition technique

    Publication Year: 1990, Page(s):76 - 79 vol.1
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (153 KB)

    The spatial decomposition technique is successfully implemented to analyze electromagnetic scattering by both two-dimensional and three-dimensional perfectly conducting and dielectric scatterers. Two canonical scattering cases are reported. Electromagnetic scattering by electrically large two-dimensional perfectly conducting thin strip scatterers is illustrated. The distribution of the bistatic ra... View full abstract»

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  • Rapid solution of integral equations fast numerical algorithms

    Publication Year: 1990, Page(s):80 - 81 vol.1
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (58 KB)

    Summary form only given. The author discusses an algorithm for the rapid solution of boundary value problems for the Helmholtz equation in two dimensions based on iteratively solving integral equations of scattering theory. The algorithm requires an amount of work proportional to n/sup 4/3/, where n is the number of nodes in the discretization of the boundary of the scatterer, and, when it is comb... View full abstract»

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  • Frequency selective scattering properties of dielectric gratings

    Publication Year: 1990, Page(s):84 - 87 vol.1
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (114 KB)

    The extension of the optoacoustic scattering phenomenon to microwave and millimeter-wave applications has been investigated by many researchers using various approaches, including the coupled-wave, leaky-wave theories among the analytic methods and the unimoment, finite-difference formulations among the numerical techniques. The present study indicates that most of these methods are very time-cons... View full abstract»

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  • Design of a cascaded frequency selective surface as a dichroic subreflector

    Publication Year: 1990, Page(s):88 - 91 vol.1
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (111 KB)

    The frequency selective surface (FSS) is often used as a filter for electromagnetic radiation to separate the S- and K-band feed in a communication satellite. The problem of synthesizing such a multifrequency-band FSS as a subreflector in a communication satellite antenna system that covers the frequency range of 2-30 GHz is considered. The reflection and transmission properties of FSS screens are... View full abstract»

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  • A generalized scattering matrix analysis for cascading FSS of different periodicities

    Publication Year: 1990, Page(s):92 - 95 vol.1
    Cited by:  Papers (7)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (124 KB)

    A generalized scattering matrix for cascading frequency-selective surfaces (FSSs) of different periodicities is developed by studying the interaction of the harmonics when scattered between two screens of different periods. It is noted that the new system, formed by stacking two (or more) screens of different periods, will have a scattered spectrum which is, in general, more densely packed than th... View full abstract»

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  • A frequency selective surface using aperture coupled microstrip patches

    Publication Year: 1990, Page(s):96 - 99 vol.1
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (106 KB)

    A new type of frequency-selective surface (FSS) that uses two back-to-back arrays of aperture coupled microstrip antennas is described. The resulting bandpass response is relatively narrowband, which may be an advantage in applications where frequency-selective surfaces are used as radomes, as dichroic surfaces, or for antenna radar cross section (RCS) reduction. The frequency response can be cont... View full abstract»

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  • A simple circular polarization selective surface (CPSS)

    Publication Year: 1990, Page(s):100 - 103 vol.1
    Cited by:  Papers (15)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (80 KB)

    A new circular polarization selective surface (CPSS) (a surface that reflects one sense of circular polarization but transmits the other) is described. It is easy to fabricate and has excellent electrical characteristics. This CPSS element is made of a single piece of wire bent in three sections. The two end sections are on the faces of a dielectric slab and the middle section goes through it. Thi... View full abstract»

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  • Frequency selective surfaces with time-varying nonlinear loads

    Publication Year: 1990, Page(s):104 - 107 vol.1
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (130 KB)

    An approach to a periodic surface loaded with nonlinear devices is presented which uses an equivalent circuit representation at the load location. This method is applicable to all angles of incidence, and it takes into account the effect of dielectric substrate and superstrate layers. It is also applicable to periodic surfaces with arbitrarily placed loading and arbitrarily shaped array elements. ... View full abstract»

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