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Antennas and Propagation, IEEE Transactions on

Issue 1 • Date Jan. 2000

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Displaying Results 1 - 20 of 20
  • Comments on "On the formulation of hybrid finite-element and boundary-integral methods for 3-D scattering" [with reply]

    Publication Year: 2000 , Page(s): 129 - 130
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (26 KB)  

    For original article by X. Q. Sheng et al. see ibid., vol.46, no.3, p.303-11 (Mar. 1998). View full abstract»

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  • Authors' reply

    Publication Year: 2000 , Page(s): 130
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (9 KB)  

    First Page of the Article
    View full abstract»

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  • Frequency-domain Green's function for a planar periodic semi-infinite phased array. II. Diffracted wave phenomenology

    Publication Year: 2000 , Page(s): 75 - 85
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    For pt.I see ibid., vol.48, no.1, p.67-74, 2000. This second part of a two-paper sequence deals with the physical interpretation of the rigorously derived high-frequency asymptotic wave-field solution in part I, pertaining to a semi-infinite phased array of parallel dipole radiators. The asymptotic solution contains two parts that represent contributions due to truncated Floquet waves (FWs) and to the corresponding edge diffractions, respectively. The phenomenology of the FW-excited diffracted fields is discussed in detail. All possible combinations of propagating (radiating) and evanescent (nonradiating) FW and diffracted contributions are considered. The format is a generalization of the conventional geometrical theory of diffraction (GTD) for smooth truncated aperture distributions to the truncated periodicity-induced FW distributions with their corresponding FW-modulated edge diffractions. Ray paths for propagating diffracted waves are defined according to a generalized Fermat principle, which is also valid by analytic continuation for evanescent diffracted ray fields. The mechanism of uniform compensation for the FW-field discontinuities (across their truncation shadow boundaries) by the diffracted waves is explored for propagating ad evanescent FWs, including the cutoff transition from the propagating to the evanescent regime for both the FW and diffracted constituents. Illustrative examples demonstrate: (1) the accuracy and efficiency of the high-frequency algorithm under conditions that involve the various wave processes outlined above and (2) the cogent interpretation of the results in terms of the uniform FW-modulated GTD View full abstract»

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  • Compensation for the effects of mutual coupling on direct data domain adaptive algorithms

    Publication Year: 2000 , Page(s): 86 - 94
    Cited by:  Papers (106)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    This paper investigates the effects of mutual coupling between the elements of an array on direct data domain algorithms. Mutual coupling severely undermines the interference suppression capabilities of direct data domain algorithms. The method of moments (MoM) is used to evaluate the mutual coupling between the elements of a given array. The MoM admittance matrix is then used to eliminate the effects of mutual coupling View full abstract»

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  • Theory of miniaturized shorting-post microstrip antennas

    Publication Year: 2000 , Page(s): 41 - 47
    Cited by:  Papers (33)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    An analytical theory for the eigenfrequencies and eigenmodes of shorting-post microstrip antennas (MPA's) is presented. These antennas are seen as promising candidates for miniaturized mobile telecommunication handsets. In particular, it is shown that the zero mode of the unloaded MPA plays a central role for reducing the lowest operation frequency of the loaded MPA. The theory allows a complete calculation of all relevant antenna parameters and can easily be extended to the case of multiple shorting posts. Applications to the examples of rectangular and circular shorting post MPA's are illustrated View full abstract»

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  • Artificial versus natural crystals: effective wave impedance of printed photonic bandgap materials

    Publication Year: 2000 , Page(s): 95 - 106
    Cited by:  Papers (20)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    Printed metallo-dielectric photonic bandgap (PBG) materials are analyzed using an analytical approach based on multipole expansions for the scattered fields of individual scatterers and a transfer-matrix method for reconstructing the total scattered fields created by successive lattice planes of the artificial crystal. An effective description of the PBG medium is derived and its correspondence with natural crystals is further advanced through an analysis based on Lorentzian response functions, which characterize natural crystals. The effective wave impedance and bulk reflection coefficient of the medium are provided and their properties inside and outside the bandgaps are examined. The presented treatment for these effective response functions extends far beyond the traditional effective medium theory (EMT) limits View full abstract»

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  • Bistatic scattering and emissivities of random rough dielectric lossy surfaces with the physics-based two-grid method in conjunction with the sparse-matrix canonical grid method

    Publication Year: 2000 , Page(s): 1 - 11
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    Bistatic EM wave scattering from 2-D lossy dielectric random rough surfaces (3-D scattering problem) with large permittivity is studied. For media with large permittivities, the fields can vary rapidly on the surface. Thus, a dense discretization of the surface is required to implement the method of moments (MoM) for the surface integral equations. Such a dense discretization is also required to ensure that the emissivity can be calculated to the required accuracy of 0.01 for passive remote sensing applications. We have developed a physics-based two-grid method (PBTG) that can give the accurate results of the surface fields on the dense grid and also the emissivities. The PBTG consists of using two grids on the surface, the coarse grid and the required dense grid. The PBTG only requires moderate increase in central processing unit (CPU) and memory. In this paper, the numerical results are calculated by using the PBTG in conjunction with the sparse-matrix canonical grid (SMCG) method. The computational complexity and memory requirement for the present algorithm are O(Nscglog(Nscg )) and O(Nscg), respectively, where Nscg is the number of grid points on the coarse grid. Numerical simulations are illustrated for root mean square (rms) height of 0.3 wavelengths and correlation length of 1.0 wavelength. The relative permittivity used is as high as (17+2i). The numerical results are compared with that of the second-order small perturbation method (SPM). The comparisons show that a large difference in brightness temperature exists between the SPM and numerical simulation results for cases with moderate rms slope View full abstract»

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  • Formulation of spatial correlation statistics in Nakagami-Rice fading environments

    Publication Year: 2000 , Page(s): 12 - 18
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    Propagation environments in line-of-sight (LOS) communications, such as mobile-satellite communications and indoor radio communications, can be expressed by a Nakagami-Rice (or Rician) fading model. Since the Nakagami-Rice fading model also covers the Rayleigh fading model as an extreme case, it seems a very widely applicable model. This paper gives a theoretical formulation of spatial correlation characteristics in the Nakagami-Rice fading environment. Based on this theoretical model, spatial correlation characteristics of Nakagami-Rice fading are clarified comparing with those of Rayleigh fading. Moreover, the difference in spatial correlation characteristics between wide-band signals and narrow-band signals is discussed View full abstract»

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  • Diffraction from a truncated grounded dielectric slab: a comparative full-wave/physical-optics analysis

    Publication Year: 2000 , Page(s): 48 - 57
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    The problem of diffraction at the edge of a semi-infinite grounded dielectric slab excited by a line source is investigated. This canonical problem may be used as a reference solution in the high-frequency regime for patch antennas radiating from a finite grounded slab. Both physical optics (PO) and integral equation (IE) approaches are used and compared. The PO formulation is cast in a convenient asymptotic form that neatly describes the diffraction processes associated with the various wave species. The IE, solved by the method of moments, is formulated by enforcing the continuity of the electric field on an infinite aperture orthogonal to the slab. This allows a drastic reduction of unknowns, provided that appropriate entire domain basis functions are used that are shaped to match the asymptotic behavior of the aperture field. Comparison between the PO and IE solutions is presented to determine the range of validity of PO View full abstract»

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  • Use of minimum phase signals to establish the time reference in transient radar target identification schemes

    Publication Year: 2000 , Page(s): 124 - 125
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (48 KB)  

    The minimum phase representation of the transient scattered field response of aircraft targets is used to establish the time origin of a measured signal in reference to a stored target library. This allows time-shift-sensitive schemes such as the E-pulse method and neural networks to be used effectively. An example in which the wavelet spectra of unknown and library target responses are correlated demonstrates the viability of the technique View full abstract»

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  • Novel material with narrow-band transparency window in the bulk

    Publication Year: 2000 , Page(s): 107 - 116
    Cited by:  Papers (5)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    This paper presents the theoretical design of an artificial dielectric exhibiting narrowband frequency selective properties in the bulk without relying on periodic placement of elements. In this manner, it initiates a novel approach that bypasses the drawbacks of the traditional frequency selective surfaces (FSS), namely, unwanted passbands, dependence on excitation angle and polarization, and difficulties in conversion from planar to curved geometries. The key design elements are the concentric geometry of the inclusions and the use of Lorentzian resonant media. A discussion of physical resonant materials is presented, substantiating the credibility of the theoretical design. To illustrate the approach, a novel complex medium is synthesized as an ensemble of spherical particles composed of a lossy core coated with a highly resonant dielectric layer and embedded into a dielectric host. The resulting structure is an amorphous substance, lossy over its entire spectrum except for two narrow-band transparency windows, where it may become as lossless as desired. The parameter space of the system is thoroughly analyzed which determines the type of constitutive materials and geometries for tailor-designing the windows according to specifications (shape, positioning and overall normalization). In this sense, the lossy concentric structure forms an ideal candidate for thin absorbing films (TAFs) with extensive applications in antenna systems, RF absorbers, and anechoic chambers View full abstract»

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  • Active metallic photonic band-gap materials (MPBG): experimental results on beam shaper

    Publication Year: 2000 , Page(s): 117 - 119
    Cited by:  Papers (22)  |  Patents (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (72 KB)  

    We focus our attention on the possibilities to control the beam radiated by antennas, which are initially omnidirectional using active metallic photonic band-gap materials (AMPBG). In fact, MPBG composed of continuous or discontinuous wires present different and interesting characteristics when they are used as an antenna reflector or a radome. Adding active components on wires allows one to switch from continuous to discontinuous structures. Wires with active elements on can then be placed inside a structure, which shapes the beam radiated by a dipole antenna. Experimental results show that it allows one to switch on/off the beam or to change its shape View full abstract»

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  • Frequency-domain Green's function for a planar periodic semi-infinite phased array .I. Truncated floquet wave formulation

    Publication Year: 2000 , Page(s): 67 - 74
    Cited by:  Papers (42)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    This two-part sequence deals with the derivation and physical interpretation of a uniform high-frequency solution for the field radiated at finite distance by a planar semi-infinite phased array of parallel elementary electric dipoles. The field obtained by direct summation over the contributions from the individual radiators is restructured into a double series of wavenumber spectral integrals whose asymptotic reduction yields a series encompassing propagating and evanescent Floquet waves (FWs) together with corresponding diffracted rays, which arise from scattering of the FW at the edge of the array. The formal aspects of the solution are treated in the present paper. They involve a sequence of manipulations in the complex spectral wavenumber planes that prepare the integrands for subsequent efficient and physically incisive asymptotics based on the method of steepest descent. Different species of spectral poles define the various species of propagating and evanescent FW. Their interception by the steepest descent path (SDP) determines the variety of shadow boundaries for the edge truncated FW. The uniform asymptotic reduction of the SDP integrals, performed by the Van der Waerden (1951) procedure and yielding a variety of edge-diffracted fields, completes the formal treatment View full abstract»

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  • Copolar and cross-polar radiation of Vivaldi antenna on dielectric substrate

    Publication Year: 2000 , Page(s): 19 - 25
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (168 KB)  

    The copolar and cross-polar radiation patterns of the Vivaldi antenna on a dielectric substrate are calculated and validated by measurements. The method involves a two-step procedure. The electric field distribution across the antenna slot aperture is calculated first. The radiated fields are then calculated, using Green's functions. The continuous exponential tapered shape is approximated by annular linearly tapered sections. The conical transmission-line theory and a variational method yield the electric field in each section. The radiation calculation is based on closed-form expressions for the dyadic Green's function of an elementary electric field source in a conducting half sheet. Both copolar and cross-polar radiation patterns of the Vivaldi antenna are calculated by integrating the Green's functions weighted by the electric field distribution over the antenna aperture. The effect of lateral truncation is taken into account by defining weighting patterns. The method is validated by original measurements and limitations of the model are discussed. Antenna directivity and sensitivity are calculated View full abstract»

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  • Circularly polarized circular sector dielectric resonator antenna

    Publication Year: 2000 , Page(s): 126 - 128
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (116 KB)  

    A circular sector dielectric resonator antenna (DRA) with circular polarization and a single feed is investigated and demonstrated. The design utilizes the radius to height ratio and feed position of the circular sector DRA to excite two resonant modes that are spatially orthogonal in polarization and in phase quadrature. Experimental results are provided for the design and these demonstrate that the circular sector DRA produces circular polarized radiation with axial ratio less than 3 dB over a 10% bandwidth View full abstract»

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  • Elimination of impedance anomalies in single- and dual-polarized endfire tapered slot phased arrays

    Publication Year: 2000 , Page(s): 122 - 124
    Cited by:  Papers (36)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (120 KB)  

    A method to eliminate bandwidth-limiting impedance anomalies or resonances in stripline-fed single- and dual-polarized tapered slot phased arrays is presented. For dual-polarized arrays, others have shown that the resonance with the lowest frequency is related to a cavity constituted by the dielectric region of the tapered slot element. Simulations have been performed to test if this cavity model also predicts the remaining resonances. It was found that the cavity model predicts some but not all of the resonances. However, it was found that all resonances in both single- and dual-polarized arrays have some dependence on the dielectric region. The resonances are effectively suppressed by introducing plated through vias in the element. The vias are positioned along the edges of the slotline, slotline cavity, stripline, and stripline stub. The analysis is performed with the finite-difference time-domain method by considering a unit cell in an infinite array View full abstract»

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  • Dual-band dual-polarized perforated microstrip antennas for SAR applications

    Publication Year: 2000 , Page(s): 58 - 66
    Cited by:  Papers (35)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    For dual-band dual-polarized synthetic aperture radar (SAR) applications a compact low-profile design is investigated. The operating frequencies are in the L and C-bands, centered about 1.275 and 5.3 GHz, respectively. Since the C-band frequency is larger by a factor of four, its array elements and inter-element separations are smaller by the same ratio. Thus, to allow similar scan ranges for both bands, the L-band elements are selected as perforated patches to enable the placement of C-band elements within them. Stacked-patch configurations were used to meet the bandwidth requirements, especially in the L-band. The C-band element was designed numerically, but the perforated L-band one required final experimental optimization. Also, in the latter case of L-band, a balanced transmission line feed was used to minimize cross polarization. For the C-band elements, slot coupling was used and, to simplify the feed, symmetric parasitic slots were incorporated to minimize cross polarization. No vertical connections were utilized, and electromagnetic couplings resulted in a compact low-profile design, with an electrically and thermally symmetric geometry View full abstract»

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  • Problem-matched basis functions for moment method analysis-an application to reflection gratings

    Publication Year: 2000 , Page(s): 35 - 40
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB)  

    In the evaluation of the frequency response of a scattering object by the integral equation technique, generally a large linear system of equations has to be solved for each frequency point. This paper deals with a technique that drastically reduces the size of the linear system without loss of accuracy, The key point is the definition of a set of problem-matched basis functions. These basis functions are extremely efficient in the representation of the unknown in the parameter range of interest. In this way, the central processing unit (CPU) time required in the response evaluation is drastically reduced. Examples of application concerning reflection gratings are reported View full abstract»

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  • An experimental technique used to measure the unloaded Q of microstrip antennas

    Publication Year: 2000 , Page(s): 119 - 122
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (148 KB)  

    This paper presents a scattering method for measuring the unloaded Q of a prototype microstrip (patch) antenna structure without the need to implement connecting circuitry View full abstract»

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  • Analysis of multilayer printed arrays by a modular approach based on the generalized scattering matrix

    Publication Year: 2000 , Page(s): 26 - 34
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    In this paper, a modular technique is used to treat infinite multilayer printed arrays with apertures and patches of irregular shapes. Each array layer is characterized by a generalized scattering matrix (GSM) from which the overall GSM of the multilayer structure is computed. The excitation of each element is modeled as a transition from the microstrip line to an aperture in the ground plane. The GSM of this transition is computed using the reciprocity theorem and spectral domain moment method. Several arrays have been analyzed by the proposed technique and the numerical results are in good agreement with other theoretical and experimental data 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