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Antennas and Propagation, IEEE Transactions on

Issue 5 • Date May 1989

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Displaying Results 1 - 18 of 18
  • RCS of two-dimensional structures consisting of both dielectrics and conductors of arbitrary cross section

    Publication Year: 1989 , Page(s): 546 - 554
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (478 KB)  

    The problem of determining the electromagnetic field scattered by two-dimensional structures consisting of both dielectric and conducting cylinders of arbitrary cross section is considered. The conductors may be in the form of strips and the dielectrics may be in the form of shells. The conductors may be partially or fully covered by dielectric layers, while the dielectrics may be partially covered by conductors. Only homogeneous dielectrics are studied. Both the transverse electric (TE) and the transverse magnetic (TM) cases are considered. The problem is formulated in terms of a set of coupled integral equations involving equivalent electric and magnetic surface currents radiating in unbounded media. The method of moments is used to solve the integral equations. Simple expansion and testing procedures are used. Numerical results for scattering cross sections are given for various structures.<> View full abstract»

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  • Electromagnetic scattering from dielectric bodies

    Publication Year: 1989 , Page(s): 673 - 676
    Cited by:  Papers (42)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (267 KB)  

    Far-field results obtained by two different methods are compared for the problem of electromagnetic scattering from dielectric objects. The two methods are the surface integral formulation, utilizing equivalent electric and magnetic surface currents, and the volume formulation, utilizing the equivalent electric polarization current. Triangular patches are used in the surface formulation and cubical cells are used in the volume formulation. The far-scattered fields obtained by the two methods are in good agreement, thereby validating both the approaches for the analysis of scattering problems. Numerical problems associated with the fields in the source region are also addressed.<> View full abstract»

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  • A numerical scheme to obtain the RCS of three-dimensional bodies of resonant size using the conjugate gradient method and the fast Fourier transform

    Publication Year: 1989 , Page(s): 528 - 537
    Cited by:  Papers (49)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    A numerical scheme to obtain radar cross section (RCS) of three-dimensional bodies of resonant size (BRS) with arbitrary geometry and material composition is described. The RCS is obtained by solving the electric-field integral equation (EFIE) using the conjugate gradient-fast Fourier transform method (CG-FFT). The choice of a suitable set of basis and testing functions to discretize the EFIE leads to a very accurate and computationaly efficient CG-FFT procedure. This accuracy is checked by comparison with RCS measurements or predictions by other methods. As compared to the moment method, this CG-FFT scheme avoids the storage of large matrices and reduces the computer time by orders of magnitude View full abstract»

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  • Electromagnetic wave scattering by a system of two spheroids of arbitrary orientation

    Publication Year: 1989 , Page(s): 608 - 618
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (636 KB)  

    An exact solution to the problem of the scattering of a plane electromagnetic wave by two perfectly conducting arbitrarily oriented prolate spheroids is obtained by expanding the incident and scattered electric fields in terms of an appropriate set of vector spheroidal eigenfunctions. The incident wave is considered to be a monochromatic, uniform plane electromagnetic wave of arbitrary polarization and angle of incidence. To impose the boundary conditions, the field scattered by one spheroid is expressed in terms of its spheroidal coordinates, using rotational-translational addition theorems for vector spheroidal wave functions. The column matrix of the scattered field expansion coefficients is equal to the product of a square matrix which is independent of the direction and polarization of the incident wave, and the column matrix of the known incident-field expansion coefficients. The unknown scattered-field expansion coefficients are obtained by solving the associated set of simultaneous linear equations. Numerical results for the bistatic and backscattering cross sections for prolate spheroids with various axial ratios and orientations are presented View full abstract»

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  • Near-field scattering measurements for determining complex target RCS

    Publication Year: 1989 , Page(s): 576 - 585
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (920 KB)  

    The application of near-field scattering measurements for determining the near-zone and far-zone radar cross section (RCS) of complex targets that are both physically and electrically large is reviewed and examined in the light of recent advances in near-field measurement technology and data processing capabilities View full abstract»

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  • Electromagnetic scattering from a flat plate with rim loading and RAM saving

    Publication Year: 1989 , Page(s): 659 - 663
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (324 KB)  

    The problem of electromagnetic scattering from a plate with a rim loading for transverse electric (TE) and transverse magnetic (TM) polarizations is investigated. The analysis is based on the work of R. Tiberio et al. (ibid., vol.AP-33, no.8, p.867-73, 1985) on the uniform geometrical theory of diffraction analysis of a wedge with two face impedances. The two-dimensional field is converted into three-dimensional field using Siegel's 2-D to 3-D conversion formula. The corner effects are neglected. The width of the coating around the edges which gives the same result as a uniformly coated plate of the same size is estimated. Hence, the percentage of saving of radar-absorbing material (RAM) can also be estimated for practical application in radar cross-section (RCS) reduction problems View full abstract»

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  • High-frequency RCS of open cavities with rectangular and circular cross sections

    Publication Year: 1989 , Page(s): 648 - 654
    Cited by:  Papers (33)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    The radar cross-section (RCS) analysis of open-ended cavities with rectangular and circular cross sections is carried out using the waveguide modal approach and the shooting-and-bouncing ray (SBR) approach. For a cavity opening on the order of ten wavelengths or larger, the comparison between the two approaches is excellent. It is also observed that at lower frequencies the SBR results deviate from the more accurate modal results. On the other hand, the SBR approach allows for greater flexibility in geometrical modeling, and can be applied to problems where waveguide modes cannot be easily found. SBR results for an offset rectangular cavity and a circular cavity with rounded endplate are presented View full abstract»

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  • Radar scattering from bodies of revolution using an efficient partial differential equation algorithm

    Publication Year: 1989 , Page(s): 538 - 545
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB)  

    A technique is presented for solving the problem of scattering by a three-dimensional body of revolution using a partial differential equation (PDE) technique in conjunction with a radiation boundary condition applied in the Fresnel region of the scatterer. The radiation boundary condition, which is used to truncate the PDE mesh, is based on an asymptotic expansion derived by Wilcox (1956). Numerical results illustrating the procedure and verifying the accuracy of the results are included View full abstract»

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  • Scattering by an arbitrary cylinder at a plane interface: broadside incidence

    Publication Year: 1989 , Page(s): 619 - 628
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (668 KB)  

    The problem of the determination of the fields scattered by an infinite dielectric cylinder of arbitrary cross section located at the interface between two semi-finite dielectric media is reduced to the solution of integral equations for unknown functions defined on the boundaries. These boundary functions are chosen so as to minimize their number. The incident field is that of a plane monochromatic wave. The derivation of the integral equations is given for the transverse electric (TE) mode for a dielectric cylinder and for a perfectly conducting cylinder. The exact electromagnetic fields are obtained from the solutions of the integral equations by integration, and the radar cross section can be computed from the far-field approximation. Sample outputs of the computer programs that implement this solution are shown View full abstract»

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  • Scattering from three-dimensional cracks

    Publication Year: 1989 , Page(s): 586 - 591
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (636 KB)  

    Scattering from three-dimensional cracks is analyzed and measured. The crack geometry is modeled as a rectangular groove in a perfectly conducting surface. The groove forming the crack may be terminated with an open aperture creating a slit in the conducting surface or with an impedance boundary creating a trough. The scattered fields from a crack are analyzed with two types of scattering mechanisms: a component directly related to the scattered fields from a two-dimensional crack, and a traveling-wave component View full abstract»

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  • Modal, ray, and beam techniques for analyzing the EM scattering by open-ended waveguide cavities

    Publication Year: 1989 , Page(s): 635 - 647
    Cited by:  Papers (42)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1052 KB)  

    The problem of high-frequency electromagnetic scattering by open-ended waveguide cavities with an interior termination is analyzed via three different approaches. When cavities can be adequately modeled by joining together piecewise separable waveguide sections, a hybrid combination of asymptotic high-frequency and modal techniques is employed. In the case of more arbitrarily shaped waveguide cavities for which modes cannot even be defined in the conventional sense, the geometrical optics ray approach proves to be highly useful. However, at sufficiently high frequencies, both of these approaches tend to become inefficient; hence, a paraxial Gaussian beam technique, which retains much of the simplicity of the ray approximation but is potentially more efficient, is investigated. Typical numerical results based on the different approaches are discussed View full abstract»

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  • A lower bound to the broad-band power scattered from an electrically linear antenna with a general lumped load

    Publication Year: 1989 , Page(s): 555 - 563
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (644 KB)  

    A mode analysis that is independent of detailed field expression is made of the total power Psc(ω) scattered from an electrically linear body of arbitrary size and shape, excited by a single-frequency incident field and loaded at a reference port. This load may be linear, nonlinear, and passive, or nonlinear and active at a given frequency ω. Psc(ω) is the sum of a scatter mode power that is proportional to the scatter-mode radiation resistance, a transmitter mode power that is proportional to the port radiation resistance, and their cross power. The form of this expression for Psc yields criteria for determining whether an antenna could be a minimum-scattering (MS) Dicke antenna, an MS antenna as defined by W.K. Kahn and H. Kurss (1965), or a CMS antenna of the type of W.K. Kahn and W. Wasylkiwskyj (1966). The general expression for Psc(ω) yields a load-independent lower bound. An expression analogous to Psc for the bistatic power Psc(ω) scattered into a specified solid angle is presented. A lower bound to Psc(ω) is obtained. Its integral frequency yields the broadband lower bound View full abstract»

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  • Diffraction of high-frequency electromagnetic waves by curved strips

    Publication Year: 1989 , Page(s): 592 - 600
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB)  

    The authors describe the construction of a high-frequency solution in the geometrical theory of diffraction (GTD) format for the generation of edge-diffracted space rays and edge-excited surface waves by an electromagnetic wave normally incident on the edge of a curved impedance strip. The transformation coefficients necessary for the analysis of the diffraction on curved surfaces with equal vanishing face impedances are tabulated in a form appropriate for numerical applications. The procedure for evaluating the diffracted field excited by the edge of a cylindrically curved strip, which can be associated with a reflector antenna or an aperture on a curved surface, is presented for both perfectly and nonperfectly conducting cases View full abstract»

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  • Multiple diffractions among polygonal impedance cylinders

    Publication Year: 1989 , Page(s): 664 - 672
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    Rigorous diffraction coefficients are derived for the doubly and triply diffracted fields among impedance wedges of arbitrary orientation not sharing a common surface. The analysis is an extension of previous work applicable to impedance wedges on a common surface. The derived diffraction coefficients are shown to remain valid at the transition regions. Similar diffraction coefficients are also given for all triply diffracted fields between two polygonal impedance cylinders; these contain the necessary surface-wave contributions in a uniform manner. When these coefficient are coupled with those already derived for the multiply diffracted fields on a single cylinder, the complete analysis of the doubly and triply diffracted fields among two or more polygonal cylinders is possible. To verify the uniformity and validity of the total field at the transition regions, some scattering patterns for certain simple geometries are presented View full abstract»

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  • A frequency-domain differential equation formulation for electromagnetic scattering from inhomogeneous cylinders

    Publication Year: 1989 , Page(s): 601 - 607
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    A procedure is described for calculating scattering cross-section data based on the numerical solution of differential equations in the frequency domain. The scatterers considered are two-dimensional and consist of lossy, inhomogeneous dielectric, magnetic, and perfectly conducting material. The appropriate wave equation is combined with an approximate local absorbing boundary condition and discretized with the finite-element method. Results for conducting and dielectric scatterers are presented to illustrate the accuracy and generality of the approach View full abstract»

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  • A method for calculating eigenfrequencies of arbitrarily shaped convex targets: eigenfrequencies of conducting spheroids and their relation to helicoidal surface wave paths

    Publication Year: 1989 , Page(s): 629 - 634
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    In a previous study by the authors (1986) the phase matching of surface waves on prolate, perfectly conducting spheroids generated, for example, by the scattering of an incident plane electromagnetic wave was investigated. Now, the considerably more complex spheroidal case with an obliquely incident primary wave, whose scattering will give rise to helicoidally (i.e. quasihelically) propagating surface waves is treated. The conditions under which phase matching of such types of surface waves, which propagate along helicoidal geodesics, can occur are investigated. It is found that only a discrete set of the required closed propagation paths exists, corresponding to a discrete set of allowed angled of incidence. These angles can be associated with different azimuthal quantum numbers m of the azimuthal propagation component around the symmetry axis, where mn and n is the mode number which corresponds to the number of standing wavelengths at resonance View full abstract»

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  • Radar backscattering from partially coated targets with axial symmetry

    Publication Year: 1989 , Page(s): 564 - 575
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    An experimental and theoretical study is reported on the polarization scattering properties of various radar targets with sizes in the resonance region. The targets have totally dielectric, totally conducting, or a combination of dielectric and metallic surfaces. A formulation of the scattering problem in terms of the equivalent currents on the surface of the scatterer is used, leading to surface integral equations which are solved using method of moments. This numerical approach is flexible, as it can be used to handle targets of various sizes and shapes that cannot be treated easily using other methods. Measurements of the backscattering polarization matrix on the same targets are performed at circular polarization. Both amplitude and relative phase measurements are performed. Reasonably good agreement between the numerical calculations and the experimental data is obtained. The numerical and experimental procedures are described. Results on the polarization scattering properties of selected targets are shown and discussed View full abstract»

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  • Scattering cross section of a small radome of arbitrary shape

    Publication Year: 1989 , Page(s): 655 - 658
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    A simple moment procedure is used to compute the scattering cross section of a small radome of arbitrary shape. Numerical results are presented for a radome with Von Karmon shape and a spherical shell. The computed and exact results for the spherical shell are in good agreement. Data for the Von Karmon shape are presented but not yet assessed. The method presented is found to be mainly limited to radomes in the resonance region since as the size of radome increases, the number of unknowns required for reasonable convergence drastically increases 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