Scheduled System Maintenance:
On May 6th, single article purchases and IEEE account management will be unavailable from 8:00 AM - 12:00 PM ET (12:00 - 16:00 UTC). We apologize for the inconvenience.
By Topic

Antennas and Propagation, IEEE Transactions on

Issue 1 • Date Jan 1992

Filter Results

Displaying Results 1 - 18 of 18
  • Scattering from conductors coated with materials of arbitrary thickness

    Publication Year: 1992 , Page(s): 108 - 112
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    Electromagnetic scattering from axisymmetric conducting bodies coated with thin materials of arbitrary thickness is considered and numerical results are obtained. The formulation presented for the coated conductor problem is based on existing E-PMCHW formulations for coated objects. This formulation is valid both for thick coatings and as the coating thickness approaches zero. Other existing surface integral equation implementations have been observed to fail for thin coatings. Two simple modifications are suggested for existing numerical codes to make them applicable for thin coatings. Several numerical examples are presented. The numerical solution is verified by comparison with the exact solution for a coated sphere View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Characterization of quasi-optical filters with picosecond transient radiation

    Publication Year: 1992 , Page(s): 63 - 66
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    The broadband microwave transmission properties of quasi-optical components are characterized with optoelectronically generated, picosecond transient radiation. The polarization sensitivity of a lithographically fabricated wire grating, from 15-140 GHz, is presented. The complex transmission functions of two different uniform arrays of cross dipoles are measured and compared with theoretical predictions View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Synthesis of sum and difference patterns possessing common nulls for monopulse bearing estimation with line arrays

    Publication Year: 1992 , Page(s): 25 - 37
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1024 KB)  

    In conventional monopulse radar, the bearing of a single target within the main lobe of the transmitted beam is estimated via a maximum likelihood (ML) procedure based in a 2-D beamspace defined by sum and difference beams. The authors show that if the sum and difference beams have all but a few nulls in common, the ML estimate of the target bearing may be determined via a simple trigonometric expression which is exact in the case of no noise. It is shown that sum and difference beams exhibiting both the common nulls property as well as low sidelobe levels can be synthesized via linear combinations of phase-only steered beams formed in the receive mode. For proper operation in the presence of interference, a procedure is developed for synthesizing adaptive-adaptive sum and difference beams for which the set of common nulls includes nulls aligned with the bearings of strong interferences. The procedure works to maintain low sidelobe levels as best as possible under the interference null constraints. Sample patterns demonstrating the efficacy of the method are presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An improved calculation procedure for the radiation pattern of a cylindrical leaky-wave antenna of finite size

    Publication Year: 1992 , Page(s): 19 - 24
    Cited by:  Papers (4)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (500 KB)  

    A method is given for calculating the radiation pattern of a finite-size cylindrical leaky-wave antenna structure consisting of a single source near a planar surface that supports leaky-wave propagation. The method accounts for the finite radius of the planar surface by subtracting the radiation from that part of the leaky wave that lies beyond the physical surface, from the exact radiation pattern corresponding to an infinite planar surface. Experimental results obtained for a leaky-wave structure consisting of multiple dielectric layers above a ground plane confirm the improved accuracy of the method, particularly for the part of the radiation pattern away from the peak View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Finite-difference time-domain implementation of surface impedance boundary conditions

    Publication Year: 1992 , Page(s): 49 - 56
    Cited by:  Papers (67)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    Surface impedance boundary conditions can be utilized to avoid using small cells, made necessary by shorter wavelengths in conducting media throughout the solution volume. The standard approach is to approximate the surface impedance over a very small bandwidth by its value at the center frequency, and then use that result in the boundary condition. In this paper, two implementations of the surface impedance boundary condition are presented. One implementation is a constant surface impedance boundary condition and the other is a dispersive surface impedance boundary condition that is applicable over a very large frequency bandwidth and over a large range of conductivities. Frequency domain results are presented in one dimension for two conductivity values and are compared with exact results. Scattering width results from an infinite square cylinder are presented as a two dimensional demonstration View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The use of surface impedance concepts in the finite-difference time-domain method

    Publication Year: 1992 , Page(s): 38 - 48
    Cited by:  Papers (60)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    Surface impedance concepts are introduced into the finite-difference time-domain (FDTD) method. Lossy conductors are replaced by surface impedance boundary conditions (SIBC), reducing the solution space and producing significant computational savings. Specifically, a SIBC is developed to replace a lossy dielectric half-space. An efficient implementation of this FDTD-SIBC based on the recursive properties of convolution with exponentials is presented. Finally, three problems are studied to illustrate the accuracy of the FDTD-SIBC formulation: a plane wave incident on a lossy dielectric half-space, a line current over a lossy dielectric half-space, and wave propagation in a parallel-plate waveguide with lossy walls View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modeling of cylindrical objects by circular dielectric and conducting cylinders

    Publication Year: 1992 , Page(s): 96 - 99
    Cited by:  Papers (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    The scattering of an incident plane wave from an array of parallel circular dielectric and/or conducting cylinders is derived rigorously using a boundary value approach. Both transverse electric (TE) and transverse magnetic (TM) polarized incident plane waves are considered. The validity and accuracy of the method are verified by comparing the numerical results with those based on other available methods. The advantage of the proposed analysis is the simplicity and efficiency in computation. The modeling of two-dimensional objects of arbitrary cross section and composite material is outlined and sample numerical results are presented to illustrate the versatility of the method View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Scattering from dielectric structures above impedance surfaces and resistive sheets

    Publication Year: 1992 , Page(s): 67 - 78
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (672 KB)  

    Interest in understanding of electromagnetic interaction with rough surfaces has prompted the study of scattering from typical dielectric humps over impedance surfaces. It is shown that the Green's function of the problem for a resistive sheet resembles that of the impedance surface. Hence both problems are considered here. A numerical solution for the scattered field of a two-dimensional dielectric object, possibly inhomogeneous, with arbitrary cross section above the impedance surface or resistive sheet is sought. First the Green's function of the problem is derived based on the exact image theory. This form of the Green's function is amenable to numerical computation. Then the induced polarization currents are calculated by casting the integral equations into a matrix equation via the method of moments. Numerical problems in calculation of the Green's function when both source and observation points are close to the surface are discussed. Comparison of numerical results with a perturbation solution shows excellent agreement between the two methods View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Numerical modeling of impedance loaded multi-arm Archimedean spiral antennas

    Publication Year: 1992 , Page(s): 102 - 108
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (604 KB)  

    A method of moments formulation for the current on arbitrarily shaped thin wires is applied to the problem of radiation and scattering from Archimedean spiral antennas. This formulation includes impedance loading along the wires. Additional analysis is performed to take advantage of structures which exhibit discrete rotational symmetry. Numerical results for a four-arm Archimedean spiral antenna with and without impedance loading are compared, showing that the loading significantly affects the current distribution and the far-field pattern for the higher order modes View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A pattern synthesis technique for array feeds to improve radiation performance of large distorted reflector antennas

    Publication Year: 1992 , Page(s): 57 - 62
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    Technologies exist for construction of antennas with adaptive surfaces that can compensate for many of the larger distortions caused by thermal and gravitational forces. However, as the frequency and size of the reflectors increase, the subtle surface errors become significant and degrade the overall electromagnetic performance. Electronic compensation through an adaptive feed array offers a means for mitigation of surface distortion effects. A pattern synthesis approach for electromagnetic compensation of surface error is presented. The pattern synthesis approach uses a localized algorithm in which pattern corrections are directed toward specific portions of the pattern requiring improvement. The pattern synthesis techniques uses radiation pattern data to perform the compensation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High resolution radar target modeling using a modified Prony estimator

    Publication Year: 1992 , Page(s): 13 - 18
    Cited by:  Papers (59)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    A method for characterizing radar signatures using a Prony model is developed based on the concept of scattering centers. A parameterization of the Prony model specific to the radar target identification problem is chosen and several key components to the algorithm, including the use of singular value decomposition and the removal of spurious scattering centers, are presented. The resulting algorithm is tested with data taken from a compact range. These tests include comparison of different targets, different aspect angles and frequency ranges, as well as robustness tests on the algorithm and evaluation of performance in noise View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Far-field errors due to random noise in cylindrical near-field measurements

    Publication Year: 1992 , Page(s): 79 - 84
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    A full characterization of the far-field noise obtained from cylindrical near-field to far-field transformation, for a white Gaussian, space stationary, near-field noise is derived. A possible source for such noise is the receiver additive noise. The noise characterization is done by obtaining the autocorrelation of the far-field noise, which is shown to be easily computed during the transformation process. Even for this simple case, the far-field noise has complex behavior dependent on the measurement probe. Once the statistical properties of the far-field noise are determined, it is possible to compute upper and lower bounds for the antenna radiation pattern for a given probability. These bounds define a strip within the radiation pattern with the desired probability. This may be used as part of a complete near-field error analysis of a particular cylindrical near-field facility View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis of aperture blockage in reflector antennas by using obstacle-located blockage currents

    Publication Year: 1992 , Page(s): 100 - 102
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    An improved method is presented to account for blockage effects in the analysis of reflector antennas. Commonly this is done by introducing shadows on the reflector surface according to the location of the obstacles when performing the physical optics integration. By using physical optics blockage currents located at the blocking obstacle instead of at the main reflector surface, the effect of the different locations in the axial direction is accurately accounted for. This can easily be included by a single phase factor in existing computer programs based on physical optics integration View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optically fed aperture-coupled microstrip patch antennas

    Publication Year: 1992 , Page(s): 85 - 90
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    Several techniques are presented for feeding microstrip antennas with RF-modulated lightwave signals via an optical fiber. Lightwave-to-RF conversion is performed in a module containing a photodiode, RF circuitry, and a microstrip antenna element. Three different transmitting configurations at microwave frequencies were designed and tested: passive matching, matching with amplification, and an injection-locked oscillator. In each case, the only connections to the antenna modules were an optical fiber and DC bias lines View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Characteristics of the spatial statistical dependence of rainfall rate over large areas

    Publication Year: 1992 , Page(s): 8 - 12
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    The design of on-board common resources systems that are envisaged for advanced satellites operating simultaneously to a large number of widely space earth stations is discussed. Based on 50 locations and 10 yr of rain data in Italy, the design-oriented figures for the probability of joint rain attenuation outages occurring at two or more of the assisted stations are derived, and why the assumption of statistical independence cannot be made at least before about 800 km is shown. The spatial large-scale structure of the rain is also studied by means of a statistical dependence index, which allows for a general description of the meteorological mechanisms independent of the considered data View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Duality transformations for general bi-isotropic (nonreciprocal chiral) media

    Publication Year: 1992 , Page(s): 91 - 95
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    The transformation is defined to leave a given bi-isotropic medium invariant, whence it is self-dual in this transformation. It is shown that duality transformations always exist in pairs, labeled as left-hand and right-hand transformations. Self-dual fields are seen to be generalizations of the wave fields E± applied in the analysis of reciprocal chiral media. It is demonstrated that plane wave propagation and reflection problems in bi-isotropic media can be solved easily in terms of self-dual field decompositions. Nonreciprocity is seen to give rise to effects like polarization rotation in reflection, which cannot be interpreted in terms of reciprocal chiral media View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A closed form to predict outage of digital radio

    Publication Year: 1992 , Page(s): 112 - 115
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    A simplified formula for predicting the outage probability of an unprotected high capacity line-of-sight digital radio link operating under frequency-selective fading conditions is presented. First, the propagation anomaly is modeled as a linear in-band amplitude dispersion in conjunction with a transmission minimum (notch) frequency located within or outside the signal band of interest. A simplified expression for the outage probability of the radio system under these conditions is then obtained. This expression is based on the fade occurrence factor in the climatic region of interest, the bandwidth of the transmitted signal, the carrier frequency of operation, the modulation scheme employed and the length of the link under consideration. The formula is applied to predict the outage probability of 4 phase shift keying (PSK), 8-PSK, and 16 quadrature amplitude modulation (QAM) high capacity radio links with specified parameters. The results obtained compare favorably with measured data View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimum networks for simultaneous multiple beam antennas

    Publication Year: 1992 , Page(s): 1 - 7
    Cited by:  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    The design of passive microwave circuits for the formation of simultaneous multiple beams with arbitrary but specified shapes is considered. The maximum possible efficiency is derived from energy conservation and is determined from a Hermitian matrix whose elements are the correlation coefficients between all beam pairs. The eigenfunctions of the correlation matrix are the basis of a synthesis procedure for a practical network that will achieve the maximum efficiency. Several practical examples are given where unavoidable losses are typically 1 dB or more 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