Scheduled System Maintenance:
On Monday, April 27th, IEEE Xplore will undergo scheduled maintenance from 1:00 PM - 3:00 PM ET (17:00 - 19:00 UTC). No interruption in service is anticipated.
By Topic

Antennas and Propagation, IEEE Transactions on

Issue 12 • Date Dec. 2000

Filter Results

Displaying Results 1 - 12 of 12
  • A fast high-order solver for EM scattering from complex penetrable bodies: TE case

    Publication Year: 2000 , Page(s): 1862 - 1864
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (133 KB)  

    We present a new high-order integral algorithm for the solution of scattering problems by heterogeneous bodies under TE radiation. Here, a scatterer is represented by a (continuously or discontinuously) varying refractive index n(x) within a two-dimensional (2-D) bounded region. Solutions of the associated Helmholtz equation under given incident fields are then obtained by high-order inversion of the Lippmann-Schwinger integral equation. The algorithm runs in O(N log(N)) operations, where N is the number of discretization points. Our method provides highly accurate solutions in short computing times, even for problems in which the scattering bodies contain complex geometric singularities. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Extraction of power line maps from millimeter-wave polarimetric SAR images

    Publication Year: 2000 , Page(s): 1802 - 1809
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    Radar backscatter of power lines has lower values than those of the surrounding ground clutter when the power line is oriented at an off-normal direction with respect to the radar line of sight. For power lines, the traditional detection algorithms that are commonly based on the statistics of the backscatter power of the clutter and target result in excessive false-alarm rates due to very low signal-to-clutter ratio. The application of a statistical polarimetric detection algorithm that significantly improves the signal-to-clutter ratio is demonstrated. The coherence between the co- and cross-polarized backscatter components is used as the detection parameter. This statistical detection parameter can be applied to any extended targets such as a suspended cable in clutter background. Detection criteria based on clutter backscattering coefficients, power line size, and aspect angle, as well as the number of independent samples are obtained. The performance of the algorithm for mapping power lines in SAR images is demonstrated using a number of low-grazing incidence polarimetric SAR images at 35 GHz View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A low-profile conical beam loop antenna with an electromagnetically coupled feed system

    Publication Year: 2000 , Page(s): 1864 - 1866
    Cited by:  Papers (9)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (120 KB)  

    The radiation characteristics of a low-profile loop antenna are evaluated using the method of moments (MoM). The loop having a circumference of approximately two wavelengths is electromagnetically coupled to a bent Feed line and radiates a circularly polarized conical beam. The frequency bandwidth for a 3-dB axial ratio criterion is calculated to be approximately 0.5% for an antenna height of h=0.064 wavelengths. Over the same bandwidth, the input impedance is approximately 50 ohms and the gain is approximately 7 dB View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the solution of a class of large body problems with full or partial circular symmetry by using the finite-difference time-domain (FDTD) method

    Publication Year: 2000 , Page(s): 1810 - 1817
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB)  

    This paper presents an efficient method to accurately solve large body scattering problems with partial circular symmetry. The method effectively reduces the computational domain from three to two dimensions by using the reciprocity theorem. It does so by dividing the problem into two parts: a larger 3-D region with circular symmetry, and a smaller 2-D region without circular symmetry. An finite-difference time-domain (FDTD) algorithm is used to analyze the circularly symmetric 3-D case, while a method of moments (MoM) code is employed for the nonsymmetric part of the structure. The results of these simulations are combined via the reciprocity theorem to yield the radiation pattern of the composite system. The advantage of this method is that it achieves significant savings in computer storage and run time in performing an equivalent 2-D as opposed to a full 3-D FDTD simulation. In addition to enhancing computational efficiency, the FDTD algorithm used in this paper also features one improvement over conventional FDTD methods: a conformal approach for improved accuracy in modeling curved dielectric and conductive surfaces. The accuracy of the method is validated via a comparison of simulated and measured results View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A mixed FDTD-integral equation approach for on-site safety assessment in complex electromagnetic environments

    Publication Year: 2000 , Page(s): 1830 - 1836
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    A mixed finite-difference time-domain (FDTD)-integral equation approach for the evaluation of the power deposition in the human body model immersed in a complex electromagnetic environment is proposed. The advantage of the proposed approach is that safety assessment for exposure to generic sources may be performed on-site, in a few minutes, with high accuracy and without the need of a high-power workstation. The method uses previously stored FDTD-computed impulse responses (Green's functions) of the human body model by integrating them with the complex incident electromagnetic field distribution that can be measured on site. The application of this method to the dosimetry of cellular telephone base station antennas is presented to show its versatility and ease of use View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Single-feed circularly polarized equilateral-triangular microstrip antenna with a tuning stub

    Publication Year: 2000 , Page(s): 1869 - 1872
    Cited by:  Papers (14)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    Novel circular polarization (CP) designs of single-feed equilateral-triangular microstrip antennas are proposed and experimentally studied. The proposed CP designs can easily be achieved by loading a narrow tuning stub at the triangle tip or at the center of the bottom edge of the triangular patch. Moreover, by embedding a cross-slot of equal slot lengths in the triangular patch, a compact CP operation can easily be obtained, with an antenna size reduction up to about 22%, as compared to the CP design of a regular triangular microstrip antenna without cross-slot at a fixed frequency View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An ultrawide-bandwidth tapered resistive TEM horn antenna

    Publication Year: 2000 , Page(s): 1848 - 1857
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    A novel stable beamwidth, ultrawide-bandwidth low-scattering antenna is presented. This antenna is a modified version of the conducting slotline bowtie hybrid (SBH) antenna with resistive sheets (Rcards) introduced into the guiding structure design. Since the resistive sheets can attenuate creeping wave fields, much smaller rolled edges are needed in the Rcard SBH antenna. Moreover, due to the Rcard's partially transparent nature with respect to electromagnetic fields, the radar cross section (RCS) associated with this new antenna is smaller than the original conducting rolled edge one. By employing an optimization process based on the concept of the genetic algorithm, one can easily design the Rcard SBH antenna to obtain a very stable antenna beamwidth and phase center in both the E- and H-planes across the entire operating frequency bandwidth. Because of its constant beamwidth, low RCS, and broad-band features, the Rcard SBH antenna is an ideal antenna for many applications such as a compact range feed. Calculated and measured results are presented to demonstrate the performance of this new antenna View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Gain and G/T of multielement receive antennas with active beamforming networks

    Publication Year: 2000 , Page(s): 1818 - 1829
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB)  

    A basic system-level model for the gain and G/T of active multielement receive antennas is presented that covers arbitrary beamforming networks and direct radiating arrays, as well as array-fed systems with one or more focusing elements (reflectors or lenses). Since the model is based on measurable parameters and uses definitions, which are consistent with conventional communication system analysis terms, it can be applied directly to the analysis and design of systems using such antennas and can be used to support the specification, design, and test of such antennas as well, measurement possibilities for the basic parameters are discussed and the characteristic parameters of generic active beamforming networks are derived and compared. Finally, the impact of the different parameters on the overall antenna gain and G/T is illustrated by one application example that covers a reconfigurable multifeed reflector antenna with selectable beamwidth. The presented theory has been verified successfully in the frame of a classified EHF antenna development whose details cannot be reported here View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A coupled surface-volume integral equation approach for the calculation of electromagnetic scattering from composite metallic and material targets

    Publication Year: 2000 , Page(s): 1866 - 1868
    Cited by:  Papers (62)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (92 KB)  

    A coupled surface-volume integral equation approach is presented fur the calculation of electromagnetic scattering from conducting objects coated with materials. Free-space Green's function is used in the formulation of both integral equations. In the method of moments (MoM) solution to the integral equations, the target is discretized using triangular patches for conducting surfaces and tetrahedral cells for dielectric volume. General roof-top basis functions are used to expand the surface and volume currents, respectively. This approach is applicable to inhomogeneous material coating, and, because of the use of free-space Green's function, it can be easily accelerated using fast solvers such as the multilevel fast multipole algorithm View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An effective approach for the optimal focusing of array fields subject to arbitrary upper bounds

    Publication Year: 2000 , Page(s): 1837 - 1847
    Cited by:  Papers (34)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    A new approach to the optimal focusing of array fields subject to arbitrary upper bounds is presented. The approach formulates the problem as the minimization of a linear function in a convex set. Unlike other approaches, this one guarantees the achievement of the global optimum by using local optimization techniques and can, moreover, deal with any convex constraint on the unknowns, such as near field constraints. Optimization is performed by two ad hoc developed solution algorithms, which exploit the geometrical characteristics of the problem at hand, thus leading to extremely effective and computationally efficient numerical codes. An extensive numerical analysis has been performed in all cases of linear, planar, and circular arc arrays. The enhanced performance of the proposed technique with respect to the solution algorithms available in the literature fully confirms the effectiveness of the approach View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Efficient radar target classification using adaptive joint time-frequency processing

    Publication Year: 2000 , Page(s): 1789 - 1801
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB)  

    This paper presents a new target recognition scheme via adaptive Gaussian representation, which uses adaptive joint time-frequency processing techniques. The feature extraction stage of the proposed scheme utilizes the geometrical moments of the adaptivity spectrogram. For this purpose, we have derived exact and closed form expressions of geometrical moments of the adaptive spectrogram in the time, frequency, and joint time-frequency domains. Features obtained by this method can provide substantial savings of computational resources, preserving as much essential information for classifying targets as possible. Next, a principal component analysis is used to further reduce the dimension of feature space, and the resulting feature vectors are passed to the classifier stage based on the multilayer perceptron neural network. To demonstrate the performance of the proposed scheme, various thin-wire targets are identified. The results show that the proposed technique has a significant potential for use in target recognition View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the homogenization of thin isotropic layers

    Publication Year: 2000 , Page(s): 1858 - 1861
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (80 KB)  

    Homogenization of extremely thin dielectric or composite layers is considered. Special attention is focused on the fact that the permittivity near the surface of the slab is affected by the presence of the boundary. This makes the effective permittivity inhomogeneous, and the slab becomes effectively anisotropic. The anisotropy effect cannot he neglected for slabs whose thickness is on the order of the depth of one molecular or inclusion layer. The analysis results in approximate second-order boundary conditions, which describe the electromagnetic properties of the layer. Numerical examples show that the effect in reflection coefficient cannot be neglected if the depth of the boundary layer is a quarter of the slab thickness. Also, the magnitude of the boundary effect increases for higher slab permittivities View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

IEEE Transactions on Antennas and Propagation includes theoretical and experimental advances in antennas.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief                                                 Kwok W. Leung