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Antennas and Propagation, IEEE Transactions on

Issue 12 • Date Dec. 2003

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Displaying Results 1 - 25 of 25
  • A matrix decomposition technique based on the concept of measure and its application to planar phased dipole arrays

    Page(s): 3276 - 3279
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (394 KB) |  | HTML iconHTML  

    Full impedance matrices of the method of moments (MoM) type have been decomposed into sparse matrices in the application of on-surface measured equation of invariance (OSMEI) (Rius et al. (1996, 1997)). The objectives in Rius are to find continuous current distributions on scatterers. Thus, the concept of metron and measure is justified under the postulate that the local relation between fields and current densities is an invariant of the excitation. In this paper, we have extended the concept to dipole arrays, where the objective is to find the discrete driving point currents. Numerical results show that using the windowed metrons presented in this paper, the sparsity rate of the sparse matrices can be kept within 1%, while the E- and H-plane patterns are still in good agreement with the MoM results except for the farthest side lobes of the H-plane patterns. View full abstract»

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  • Root-mean-square measure of nonlinear effects to the transient response of thin wires

    Page(s): 3280 - 3283
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (281 KB) |  | HTML iconHTML  

    A root-mean-square (rms) measure of effect of nonlinear loading on the transient response of thin wires is proposed. The transient behavior of nonlinearly loaded wires is analyzed directly in the time domain. The problem is formulated via the space-time Hallen integral equation. The equation is solved by the space-time Galerkin Bubnov boundary element procedure. Numerical results for the transient response of a thin wire computed by a time domain code based on this method are compared with results obtained from a frequency domain code. Some illustrative numerical results for the spatial distribution of the rms values of time varying currents are also presented. View full abstract»

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  • Robust design of absorbers using genetic algorithms and the finite element-boundary integral method

    Page(s): 3249 - 3258
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (491 KB) |  | HTML iconHTML  

    A new method for the genetic algorithm (GA) based design of broadband, high-performance electromagnetic absorbers is discussed. The method gives rise to novel absorber designs with a geometrical complexity greater than that of absorbers typically in use today. The finite element-boundary integral method is applied to efficiently analyze the scattering from complex geometries occupied by given lossy material, and genetic algorithms are adopted to optimize the geometry parameters to minimize the overall reflection coefficients. In addition, a method is proposed for accelerating the convergence of the GA. Numerical results for absorbers are presented for wide-angle incidence over a broad frequency range considering both polarizations, and demonstrate the new technique's power and robustness. View full abstract»

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  • Efficient computation of the time-domain TE plane-wave reflection coefficient

    Page(s): 3283 - 3285
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB) |  | HTML iconHTML  

    An efficient method for the calculation of the transient reflection coefficient for TE plane wave reflection from a conducting half space is given. The series form is shown to converge within a few terms for typical values of material parameters. View full abstract»

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  • Natural frequency extraction using late-time evolutionary programming-based CLEAN

    Page(s): 3285 - 3292
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (475 KB) |  | HTML iconHTML  

    In this paper, we present a novel method for natural frequency extraction. Our algorithm is called late-time evolutionary programming (EP)-based CLEAN, and has many advantages compared to conventional methods. The accuracy of our algorithm is not affected by the false estimation of the number of natural resonance modes. Furthermore, our method is insensitive to random noise. Insensitivity is a very important characteristic in the resonance extraction algorithm since the late-time response usually has small energy. Using synthetic data, we show these characteristics by comparing them to Prony's method and the E-pulse technique. We also applied our method to the numerical data and B-52 measured data which is obtained at Michigan State University (MSU) arch range. View full abstract»

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  • Observed frequency scaling of amplitude scintillation at 20, 40, and 50 GHz

    Page(s): 3259 - 3267
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB) |  | HTML iconHTML  

    This paper presents an analysis of instantaneous frequency scaling of scintillation using propagation data recorded during a three month period (May-July 1997) at Sparsholt UK from the ITALSAT satellite beacons at frequencies 18.7, 39.6, and 49.5 GHz. Variations in the height of turbulence within reasonable limits were found to have a negligible effect on the scaling ratios. Furthermore, the exponent in the power law dependence of scintillation intensity on signal frequency was found to be on average 27% smaller than the theoretical value of 7/12 and to exhibit a slight diurnal effect. It is shown that this behavior can be partly accounted for by receiver thermal noise contribution to the measured signal variance. Ascribing the minimum observed short-term variance in each beacon to thermal noise and excluding this contribution yielded a higher exponent, which was nevertheless 15% below the theoretical value. View full abstract»

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  • Power-azimuth-spectrum modeling for antenna array systems: a geometric-based approach

    Page(s): 3292 - 3294
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (262 KB) |  | HTML iconHTML  

    In this paper, we propose the geometric-based channel modeling technique as a means to establish innovative models for the power azimuth spectrum (PAS). When the geometry of the environment is matched to that of the TSUNAMI II project, the PAS model we achieve (referred to as the secant-square model) may be compared to the Laplacian model introduced previously in the literature. In this case, we observe that our model is a better fit to the TSUNAMI II project measurements. Specifically, our model has a simple mathematical representation and demonstrates a lower squared error when compared to measurement data, and considers effects ignored in the earlier modeling (e.g., the nonzero values at the edge of the PAS). Moreover, the proposed geometric-based channel modeling technique extends to other environments with different topologies, whereas the earlier Laplacian model is limited to the TSUNAMI II measurement environment. View full abstract»

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  • Green's functions in lossy layered media: integration along the imaginary axis and asymptotic behavior

    Page(s): 3200 - 3208
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (542 KB) |  | HTML iconHTML  

    This paper presents an efficient technique for evaluating Green's functions associated to layered media, when formulated as Sommerfeld integrals in the space domain. The key step in the formulation is that Sommerfeld integrals are computed choosing a suitable integration path which is closed through the imaginary axis of the complex spectral plane. It is shown that with this original choice of the integration contour, the numerical effort usually involved in the evaluation of Sommerfeld integrals can be greatly reduced, specially when large source-observer distances are involved. One asset of this technique is that it can be easily incorporated into integral equation based CAD packages for the efficient analysis of complex printed microwave circuit and antennas. In addition, the theoretical developments needed to set up the numerical algorithm throw a new light on the asymptotic behavior of the layered media Green's functions for large source-observer distances. View full abstract»

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  • An absorbing boundary condition for FDTD truncation using multiple absorbing surfaces

    Page(s): 3268 - 3275
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (581 KB)  

    An absorbing boundary condition (ABC) is developed using multiple absorbing surfaces. This ABC is stable and efficient. It can be easily added in the finite-difference time-domain computer program. It also produces the same reflection as a higher order Higdon ABC and it is therefore comparable to the perfectly matched layer method. View full abstract»

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  • A systematic design method to obtain broadband characteristics for singly-fed electromagnetically coupled patch antennas for circular polarization

    Page(s): 3239 - 3248
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    We present a systematic, empirical design technique to obtain optimum broadband impedance, axial-ratio (AR) and gain bandwidths for a singly-fed electromagnetically coupled patch antenna for circular polarization. Our investigation has also revealed tradeoffs amongst obtainable AR, impedance bandwidth and AR bandwidth. Using two design examples at different frequency bands and for different senses of circular polarization, we have demonstrated the effectiveness of the proposed knowledge-based tuning method. We have obtained at C-band measured values of impedance bandwidth (VSWR≤2) equal to 43%, 3-dB AR bandwidth of 8%, AR of less than 0.3 dB and a mean gain level of 7 dB. For the Ku-band element, a 40% impedance bandwidth and a 17.3% of 3-dB AR bandwidth have been obtained with a peak gain of 7.2 dBic. View full abstract»

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  • Efficient calculation of the electromagnetic dyadic Green's function in spherical layered media

    Page(s): 3209 - 3220
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (816 KB) |  | HTML iconHTML  

    A numerical methodology is proposed for the evaluation of the electromagnetic fields of an electric or magnetic dipole of arbitrary orientation in spherical stratified media. The proposed methodology is based on the numerical solution of the differential equation in the radial coordinate that is satisfied by each coefficient in the spherical harmonics expansion of the governing Helmholtz equation. More specifically, the finite-difference solution of this equation may be cast in a pole-residue form that allows the analytic evaluation of the spherical harmonics series by means of the Watson transformation. Thus, a closed-form expression is obtained for the electromagnetic fields in terms of a short series of associated Legendre functions Pmν(cos(θ)) of integer order m and complex degree ν. The number of terms in the series is strongly dependent on the angle θ, and decreases very fast when the point of observation moves away from the source. The method allows for arbitrary variation in the permittivity and permeability profiles in the radial directions. View full abstract»

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  • A Taylor series expansion method for calculation of the radiation integral for a circular aperture

    Page(s): 3298 - 3302
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (302 KB) |  | HTML iconHTML  

    The Taylor series expansion method developed in this paper is an efficient algorithm for performing the popular Jacobi series expansion for the radiation integral describing the operation of reflector and other circular aperture antennas. This approach results in a Bessel series expansion for the radiation integral. The method is then applied for simplicity to different examples of a source function with rotational symmetry. View full abstract»

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  • Novel modal properties and relevant scanning behaviors of phased arrays of microstrip leaky-wave antennas

    Page(s): 3228 - 3238
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (747 KB) |  | HTML iconHTML  

    In this work, different previously unexplored features are investigated for the radiation performance of linear phased arrays based on printed-circuit leaky-wave antennas for microwave and millimeter-wave applications. By means of a rigorous modal analysis in the unit cell based on the spectral-domain approach, we have considered the beam-scanning properties of microstrip leaky-wave arrays in terms of spatial harmonics, as a function of both the phase shift and the spacing between the radiating microstrip lines. We have thus found and interpreted in a consistent way various original characteristics, such as transition regions between leaky-wave and surface-wave regimes, and the occurrence of spurious radiation (grating lobes) in largely spaced arrays related to the presence of new, additional complex improper modes. Numerical full-wave simulations of the radiation patterns for realistic configurations of microstrip arrays confirm the theoretical predictions made on the basis of the modal properties of the involved leaky waves. View full abstract»

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  • E-pulse diagnostics of simple layered materials

    Page(s): 3221 - 3227
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (465 KB) |  | HTML iconHTML  

    The feasibility of using the E-pulse technique to diagnose changes in the properties of simple layered materials is undertaken. Numerical results for a conductor-backed lossy slab and a Salisbury screen show that changes in permittivity, conductivity and thickness can be diagnosed in the presence of white Gaussian noise. View full abstract»

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  • A dual polarized aperture coupled circular patch antenna using a C-shaped coupling slot

    Page(s): 3295 - 3298
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (387 KB) |  | HTML iconHTML  

    The design and development of a dual linearly polarized aperture coupled circular microstrip patch antenna at C-band are presented. The antenna uses a novel configuration of symmetric and asymmetric coupling slots. Variations in isolation between orthogonal feedlines and antenna axial ratio with the position of coupling slots are studied and broadband isolation and axial ratio are achieved. The prototype antenna yields 7.6 dBi peak gain, 70° 3-dB beam width, 25 dB cross-polarization levels and an isolation better than 28 dB between the two ports. With an external quadrature hybrid coupler connected to the two orthogonal feedlines, the antenna yields 3-dB axial ratio bandwidth of more than 30% at 5.8 GHz. View full abstract»

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  • 2003 Institute-wide awards electromagnetics award

    Page(s): 3190
    Save to Project icon | Request Permissions | PDF file iconPDF (165 KB)  
    Freely Available from IEEE
  • 2003 antennas and propagation society awards distinguished achievement award recipient

    Page(s): 3191
    Save to Project icon | Request Permissions | PDF file iconPDF (162 KB)  
    Freely Available from IEEE
  • 2003 Chen-to Tai distinguished educator award

    Page(s): 3192
    Save to Project icon | Request Permissions | PDF file iconPDF (159 KB)  
    Freely Available from IEEE
  • 2003 outstanding service award

    Page(s): 3193
    Save to Project icon | Request Permissions | PDF file iconPDF (165 KB)  
    Freely Available from IEEE
  • 2003 IEEE fellow awards from the antennas and propagation society

    Page(s): 3194
    Save to Project icon | Request Permissions | PDF file iconPDF (137 KB)  
    Freely Available from IEEE
  • S.A. Schelkunoff transactions prize paper award

    Page(s): 3195 - 3197
    Save to Project icon | Request Permissions | PDF file iconPDF (193 KB)  
    Freely Available from IEEE
  • H.A. Wheeler Applications Prize Paper Award

    Page(s): 3198
    Save to Project icon | Request Permissions | PDF file iconPDF (181 KB)  
    Freely Available from IEEE
  • R.W.P. King Award

    Page(s): 3199
    Save to Project icon | Request Permissions | PDF file iconPDF (157 KB)  
    Freely Available from IEEE
  • Author index

    Page(s): 3303 - 3315
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    Freely Available from IEEE
  • Subject index

    Page(s): 3315 - 3347
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    Freely Available from IEEE

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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