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Antennas and Propagation, IEEE Transactions on

Issue 10 • Date Oct. 1990

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Displaying Results 1 - 25 of 29
  • Comments on "A hundred years of radio propagation" [with reply]

    Publication Year: 1990 , Page(s): 1723 - 1726
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (365 KB)  

    The commenter corrects a number of historical errors in the above-titled paper (see ibid. vol.AP-33, no.2, p.126-30, Feb. 1985). The author concedes some points and defends others.<> View full abstract»

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  • Synthesis of multireflector antennas by kinematic and dynamic ray tracing

    Publication Year: 1990 , Page(s): 1587 - 1599
    Cited by:  Papers (39)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1056 KB)  

    A technique for synthesizing reflector surfaces that transform a known input ray-field (e.g., the radiation field of a feed) to a desired output ray-field (e.g. an aperture distribution) is presented. The synthesis problem is reduced to solving linear equations by local biparabolic expansions of the reflector surfaces. Because the solution is easier to control, this is advantageous compared to existing techniques based on solving nonlinear differential equations. The condition to obtain low cross polarization can therefore be readily included, and the requirements for an exact solution to exist can be found clearly. The latter has been the subject of discussion in the literature for several years. The synthesis technique is applied to a shaped-offset dual-reflector antenna and to the proposed dual-reflector feed of the spherical reflector antenna in Arecibo. In both cases circular and elliptical apertures are considered View full abstract»

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  • Gaussian beam analysis of propagation from an extended plane aperture distribution through dielectric layers. II. Circular cylindrical layer

    Publication Year: 1990 , Page(s): 1618 - 1624
    Cited by:  Papers (11)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    For pt.I see ibid., vol.38, no.10, p.1607-17 (1990). The theory developed in pt.I of this paper for transmission of fields from an extended planar aperture through a plane dielectric layer is applied to transmission from such an aperture through an arbitrarily located cylindrical dielectric layer. By the self-consistency considerations enunciated previously, it is argued that the narrow-beam algorithm for near and far zone fields is truly predictive, although no other reference solution is now available for an independent check. As in pt.I, the aperture distributions are smoothly tapered or abruptly truncated, and they may generate beam tilts and focusing in the layer or its vicinity View full abstract»

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  • Analysis of numerically specified multireflector antennas by kinematic and dynamic ray tracing

    Publication Year: 1990 , Page(s): 1600 - 1606
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    A technique for tracing rays and fields with several numerically specified reflectors by using geometrical optics (GO) is described. The ray paths are determined by launching individual rays from the feed point and following them by reflection from all the reflector surfaces to the output aperture of the last reflector. This procedure is referred to as kinematic ray tracing. Thereafter, the amplitude, phase and polarization of the E-field is traced along the ray paths to the aperture; this is referred to as dynamic ray tracing. The aperture field is then integrated to find the aperture efficiency, which is factorized into convenient subefficiencies. The technique has been implemented in a computer code that has been used to analyze the proposed new shaped-offset dual-reflector feed for the spherical reflector antenna at the Arecibo Observatory View full abstract»

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  • Analysis of a two-dimensional radome of arbitrarily curved surface

    Publication Year: 1990 , Page(s): 1565 - 1568
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    The transmission effect of a dielectric shell on electromagnetic radiation is analyzed by a modal cylindrical-wave spectrum technique. This method takes into consideration the curvature effect, which is generally ignored in classical approaches such as the ray method and the plane-wave spectrum analysis. The technique is applied to the analysis of radomes of elliptic shape. Numerical results are presented View full abstract»

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  • A contribution to scattering calculation for small wavelengths-the high frequency panel method

    Publication Year: 1990 , Page(s): 1625 - 1630
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    Numerical treatment of electromagnetic scattering in the case of small wavelengths-too small for reasonable matrix sizes when using discretization methods and too large for traditional asymptotic methods-is considered. An approach which takes advantage of the user-friendly nature of matrix-discretization methods while avoiding the explosive increase in computing effort as the wavelength decreases is suggested. It appears that no sensible increase of matrix size is required as the wavelength decreases. Since this is an untried technique applied in an inaccessible computational domain, the preliminary work described is confined to two-dimensional conducting circular cylinders where the answers are well known and well understood. The overall idea, however, appears to be quite general View full abstract»

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  • Equivalence of radiation properties of square and circular microstrip patch antennas

    Publication Year: 1990 , Page(s): 1710 - 1711
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (112 KB)  

    The radiation properties of a circular microstrip antenna are compared with those of an equivalent square microstrip antenna. On the basis of this comparison, a simple method of computing the far field of a circular microstrip antenna is suggested View full abstract»

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  • Performance of a modified feedback loop adaptive array with TVRO satellite signals

    Publication Year: 1990 , Page(s): 1701 - 1709
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1044 KB)  

    Performance of an experimental adaptive antenna array system is evaluated using television receive-only (TVRO) satellite signals. The experimental system is a sidelobe canceller with two auxiliary channels. Modified feedback loops are used to enhance the suppression of weak interfering signals. The modified feedback loops used two spatially separated antennas, each with an individual amplifier for each auxiliary channel. Thus, the experimental system uses five antenna elements. Instead of using five separate antennas, a reflector antenna with multiple feeds is used to receive signals from various TVRO satellites. The details of the earth station are given. It is shown that the experimental system can null up to two signals originating from interfering TVRO satellites while receiving the signals from a desired TVRO satellite View full abstract»

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  • Characterization of tapered slot antenna feeds and feed arrays

    Publication Year: 1990 , Page(s): 1559 - 1564
    Cited by:  Papers (14)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    A class of feed antennas and feed antenna arrays used in the focal plane of paraboloid reflectors and exhibiting higher than normal levels of cross-polarized radiation in the diagonal planes is addressed. A model which allows prediction of element gain and aperture efficiency of the feed/reflector system is presented. The predictions are in good agreement with experimental results. Tapered slot antenna (TSA) elements are used as an example of an element of this type. It is shown that TSA arrays used in multibeam systems with small beam spacings are competitive in terms of aperture efficiency with other, more standard types of arrays incorporating waveguide type elements View full abstract»

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  • Frequency domain mechanism extraction [EM scattering]

    Publication Year: 1990 , Page(s): 1716 - 1719
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    A time-domain analysis is applied to a frequency-domain technique which recovers the individual frequency characteristics of localized scattering mechanisms from a composite signature with two scattering mechanisms. This technique constructs a matrix which has filter characteristics with similar properties to a physically realizable filter based upon convolution concepts. This similarity is expanded to evaluate the rows of the matrix as filters, as demonstrated in the time domain to provide an alternate interpretation of the extraction process View full abstract»

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  • Ground-based radiometric observations of atmospheric emission and attenuation at 20.6, 31.65, and 90.0 GHz: a comparison of measurements and theory

    Publication Year: 1990 , Page(s): 1569 - 1580
    Cited by:  Papers (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (964 KB)  

    During 1987 and 1988, ground-based zenith-viewing observations of atmospheric thermal emission were made at frequencies of 20.6, 31.65, and 90.0 GHz. At the locations of the experiments (San Nicolas Island, CA, and Denver, CO) radiosonde observations of temperature and humidity were also available. Both National Weather Service and CLASS radiosondes were used in the study. After conversion to attenuation by use of the mean radiating temperature approximation, the data were processed to derive attenuation statistics. Both clear and cloudy attenuation characteristics were examined and compared with results from recent theories. For the clear atmosphere, water-vapor models of Waters (1976) and of Liebe (1989) were compared. At 20.6, and 31.65 GHz, the model of Waters agrees better with measurements; at 90.0 GHz, the model of Liebe is far superior. A recent model of P.W. Rosenkranz (1988) was used for oxygen absorption. For the average mass absorption coefficients for liquid clouds, measurement and theory generally agreed to within 30%. The predictability and interdependence of the three separate channels were also examined. It was found that attenuation for any two channels can predict that of the third to within 25% View full abstract»

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  • A numerical pattern synthesis algorithm for arrays

    Publication Year: 1990 , Page(s): 1666 - 1676
    Cited by:  Papers (71)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (772 KB)  

    A numerical technique for pattern synthesis in arrays is presented. For a given set of elements, the technique allows one to find a set of array coefficients that steer the main beam in a given direction and yield sidelobes meeting a specified criterion, if such a set of array coefficients exists. If the pattern specifications cannot be met with the given elements, the algorithm finds the best attainable pattern. The advantage of this technique is that it can be used with an arbitrary set of array elements. Different elements in the array can have different element patterns, and the array can have arbitrary nonuniform spacing between elements. The synthesis technique is based on adaptive array theory. The given array elements are assumed to be used as the elements of an adaptive array. The main beam is pointed in the proper direction by choosing the steering vector for that direction, and the sidelobes are controlled by introducing a large number of interfering signals at many angles throughout the sidelobe region. The algorithm iterates on the interference powers until a suitable pattern is obtained View full abstract»

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  • A multiradius, reciprocal implementation of the thin-wire moment method

    Publication Year: 1990 , Page(s): 1636 - 1644
    Cited by:  Papers (30)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB)  

    An implementation of the moment method, entitled the multiradius bridge-current (MBC) moment method, for electromagnetic analysis of multiradius thin-wire structures (including multiwire, multiradius junctions) is presented. It is extension of the authors' uniradius bridge-current reformulation (see ibid., vol.37, p.1224-34, Oct. 1989) of Richmond's uniradius thin-wire theory (1974). The method features an exactly symmetric mutual impedance matrix ensuring reciprocity between sources, it is unconstrained with respect to both the length ratio and the radius ratio of adjoining segments (provided that the wires are electrically thin), and it permits the self-consistent inclusion of coaxial cable sections in the configurations under analysis. The method is validated through comparison with transmission-line theory for a two-wire line and a coaxial cable, and through comparison with measurements on a sleeve monopole antenna and a log-periodic dipole antenna. The MBC moment method program is shown to surpass the Numerical Electromagnetics Code (NEC) in terms of reciprocity and convergence for both an AM broadcast tower detuning stub problem and a bent two-wire transmission-line problem View full abstract»

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  • CFIE MM solution for TE and TM incidence on a 2-D conducting body with dielectric filled cavity

    Publication Year: 1990 , Page(s): 1645 - 1649
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    The problem of determining the scattering cross section of an arbitrarily shaped two-dimensional conducting body with an arbitrarily shaped dielectric filled cavity is considered. The problem is solved using a method-of-moments solution for the combined field integral equations. The particular form of the method of moments solution used here uses a minimum number of expansion coefficients. Results are given for transverse electric and transverse magnetic incident waves View full abstract»

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  • Broad-band gap coupled microstrip antenna

    Publication Year: 1990 , Page(s): 1581 - 1586
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    A microstrip antenna with large bandwidth is developed using a parasitic technique. Compared to the available wideband antennas, the proposed antenna structure is very compact and gives a less distorted radiation pattern with frequency. An impedance bandwidth eight times that of a conventional patch antenna of the same size is achieved. The concept of coupled microstrip line model is extended for theoretical interpretation of the impedance loci. The experimental procedure and results are described, and a theoretical analysis is presented View full abstract»

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  • Gaussian beam analysis of propagation from an extended plane aperture distribution through dielectric layers. I. Plane layer

    Publication Year: 1990 , Page(s): 1607 - 1617
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (840 KB)  

    High-frequency propagation of electromagnetic wavefields from an extended planar aperture distribution through a complicated environment is addressed. Geometric optical ray tracing provides a versatile approximate approach to the class of problems, but it fails in transition regions surrounding shadow boundaries and caustics. The uniformity required there can be established by field tracking with Gaussian beams. The basic theory is summarized and applied to the two-dimensional test problem of transmission of radiation from a finite one-dimensional plane aperture through a planar dielectric layer. For a truncated uniform or focused aperture illumination, tracking the edge or caustic transition regions through the layer when it is located within the Fresnel zone of the aperture poses a problem of substantial complexity. It is shown that narrow-waisted beams, which can be propagated in their far zone as complex ray fields, reconstruct the correct transmitted field in these cases, as established independently by numerical evaluation of an exact spectral integral View full abstract»

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  • Extension of on-surface radiation condition theory to scattering by two-dimensional homogeneous dielectric objects

    Publication Year: 1990 , Page(s): 1551 - 1558
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    A recent analytical formulation by G.A. Kriegsmann et al. (see ibid., vol.AP-35, p.153-61, Feb. 1987) of electromagnetic wave scattering by perfectly conducting two-dimensional objects using the on-surface radiation boundary condition approach is extended to the case of two-dimensional homogeneous convex dielectric objects. It is shown that a substantial simplification in the analysis can be obtained by applying the outgoing radiation boundary condition on the surface of the object. The analysis procedure decouples the fields in the two regions to yield explicitly a differential equation relationship between the external incident field excitation and the corresponding field distribution in the interior of the dielectric object. The interior fields can be obtained by solving the differential equation using either an analytical approach or a suitable numerical method. Two-dimensional scattering examples along with validations are reported, showing the near-surface field distributions for a homogeneous circular dielectric cylinder and an elliptic dielectric cylinder, with with transverse magnetic plane-wave excitation View full abstract»

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  • Frequency diversity effects of evaporation duct propagation

    Publication Year: 1990 , Page(s): 1694 - 1700
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    A comparison of 3, 9.6, and 18-GHz low-altitude over-the-horizon propagation (as influenced by the evaporation duct) is presented. Theoretical and experimental results are given for a 35-km over-water path, where the transmitters were located about 5 m above mean sea level and the receivers were located either 4-5 m or 18-19 m above sea level. Results are presented in terms of the one-way propagation factor in decibels at each frequency. Long-term cumulative frequency distributions of calculated and observed propagation factors are presented. Particular attention is given to the relative performance of each radio frequency to investigate frequency-diversity improvements that may be available on such paths. In most cases presented, there is a close agreement between theory and observations. It is concluded that substantial improvements in received signal levels are likely to be achieved in most areas of the world by a suitable choice of two frequencies in the 10-20-GHz range View full abstract»

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  • A study of the quadrifilar helix antenna for Global Positioning System (GPS) applications

    Publication Year: 1990 , Page(s): 1545 - 1550
    Cited by:  Papers (49)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    An analytic model for computing the radiation properties of the quadrifilar helix volute antenna is discussed and various design considerations for GPS applications are presented. The effects of modifying the antenna length and diameter on the antenna amplitude and phase performance are presented, and using the antenna for dual-frequency operation is discussed. The effects of phase imbalances are presented and compared with measured pattern anomalies View full abstract»

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  • Spatial variability of rain rate and slant path attenuation distributions at 28 GHz in the mid-Atlantic coat region of the United States

    Publication Year: 1990 , Page(s): 1711 - 1716
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    Rain rate and corresponding estimated slant-path attenuation distributions derived from two years of measurements are presented for a network of nine rain-gauge sites located in a region whose extent is 70 km north-south and 47 km east-west in the mid-Atlantic coast of the United States in the vicinity of the NASA (US National Aeronautics and Space Administration) Wallops Flight Facility, Wallops Island, VA. The network average rain-rate distribution was compared with a previously measured six year average at one of the site locations. Agreement in rain rates was found to be within approximately 1 mm/h over the percentage range of 1-0.01% of the year, signifying the constancy of the rain-rate climatology for the region, and implying an ergodic rainfall process. Slant-path attenuation statistics were estimated at 28.56 GHz by interfacing the measured rain-rate distributions at each of nine site locations with Crane's Global Model View full abstract»

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  • Improved LMS algorithm for adaptive beamforming

    Publication Year: 1990 , Page(s): 1631 - 1635
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    Two adaptive algorithms which make use of all the available samples to estimate the required gradient are proposed and studied. The first algorithm is referred to as the recursive LMS (least mean squares) and is applicable for a general array. The second algorithm is referred to as the improved LMS algorithm and exploits the Toeplitz structure of the array correlation matrix and can be used only for an equispaced linear array View full abstract»

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  • Sidelobe level performance of adaptive sidelobe canceller arrays with element reuse

    Publication Year: 1990 , Page(s): 1684 - 1693
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (784 KB)  

    The performance of adaptive sidelobe canceller (SLC) arrays that use the same elements for the main channel and auxiliary signals is studied. The SLC with element reuse is different from the conventional SLC because the thermal noise components of the main channel and auxiliary signals may be correlated. The noise correlation may cause serious sidelobe-level (SLL) degradation when the number of degrees of freedom exceeds the number necessary to cancel the jammers present. It is shown how his degradation can be eliminated by forming each auxiliary from subarrays rather than single elements so that an orthogonality condition is satisfied. It is shown that good cancellation and SLL performance can be obtained by using small subarrays with directive auxiliary patterns satisfying the orthogonality condition View full abstract»

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  • Artificially soft and hard surfaces in electromagnetics

    Publication Year: 1990 , Page(s): 1537 - 1544
    Cited by:  Papers (214)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    A transversely corrugated surface as used in corrugated horn antennas represents a soft boundary. A hard boundary is made by using longitudinal corrugations filled with dielectric material. The concept of soft and hard surfaces is treated in detail, considering different geometries. It is shown that both the hard and soft boundaries have the advantage of a polarization-independent reflection coefficient for geometrical optics ray fields, so that a circularly polarized wave is circularly polarized in the same sense after reflection. The hard boundary can be used to obtain strong radiation fields along a surface for any polarization, whereas the soft boundary makes the fields radiated along the surface zero View full abstract»

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  • Spectral domain analysis of conducting patches of arbitrary geometry in multilayer media using the CG-FFT method

    Publication Year: 1990 , Page(s): 1530 - 1536
    Cited by:  Papers (20)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    A conjugate gradient-fast Fourier transform (CG-FFT) scheme for analyzing finite, flat, metallic patches in multilayer structures is presented. Rooftop and razor-blade functions are considered as basis and testing functions, respectively. An equivalent periodic problem in both domains (real and spectral) is obtained and solved. Aliasing problems are avoided by performing a window on the Green's function. The spectral domain periodicity makes it feasible to take into account almost all the harmonics and to reduce the ripple in the computed current distributions. Nearly all the operations are performed in the spectral domain, including Green's function computations. Several results of convergence rates, current distributions and radar cross-section (RCS) values are given and compare favorably with measurements or results obtained by other methods View full abstract»

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  • Electromagnetic fields of a vertical electric dipole over a laterally anisotropic surface

    Publication Year: 1990 , Page(s): 1719 - 1723
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    The exact solution for the electric dipole is obtained for the case where the ground plane, of infinite extent, is characterized by surface impedances which are different in two orthogonal directions. The integral representations for the transverse magnetic (TM) and the converted transverse electric (TE) fields are evaluated by two asymptotic methods which have overlapping regions of validity. A simple expression is obtained for the ratio of the TE and TM fields produced by the vertical dipole when it is on the surface View full abstract»

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Aims & Scope

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

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Editor-in-Chief                                                 Kwok W. Leung