1989 Sixth International Conference on Antennas and Propagation, ICAP 89 (Conf. Publ. No.301)

4-7 Apr 1989

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Displaying Results 1 - 25 of 211
  • Case studies of transhorizon propagation: reliability of predictions using radiosonde data

    Publication Year: 1989, Page(s):456 - 460 vol.2
    Cited by:  Papers (1)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (428 KB)

    Presents a case study of transhorizon propagation, based on minisonde refractivity measurements and COST 210 signal strength data. This study is a test of the Parabolic Equation Method against real data, and an example of the possibilities now open for modelling anomalous propagation in clear air. The sensitivity of field-strength predictions to radiosonde errors is examined. Although a method lik... View full abstract»

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  • Uniform asymptotic analysis of diffraction by convex conducting surfaces

    Publication Year: 1989, Page(s):454 - 457 vol.1
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (180 KB)

    Develops an asymptotic formulation for the diffraction by perfectly conducting convex surfaces starting from a uniform approximation of the canonical problem radiation integral. The asymptotic solution for the field radiated by a line source in the presence of a circular cylinder is thus uniformly derived and formulated according to a ray-optic scheme View full abstract»

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  • X-band tropospheric transhorizon propagation under differing meteorological conditions

    Publication Year: 1989, Page(s):451 - 455 vol.2
    Cited by:  Papers (1)  |  Patents (101)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (344 KB)

    As part of a European project to assess the level of cochannel interference due to microwave propagation beyond line-of-sight, Portsmouth Polytechnic, supported by the Centre National d'Etudes des Telecommunications (CNET) and the Rutherford-Appleton Laboratories (RAL) have set up a network of X-band transhorizon links across the English Channel. The paper presents a method of modelling the receiv... View full abstract»

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  • Endfire tapered slot antenna characteristics

    Publication Year: 1989, Page(s):432 - 436 vol.1
    Cited by:  Papers (5)  |  Patents (1)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (368 KB)

    Many of the characteristics of endfire tapered slot antennas that make them useful for array applications are discussed. Two different applications have motivated most of the work to date; wideband scanning arrays and focal plane arrays for imaging and multiple beam reflector systems. Typical configurations are presented along with data on impedance and radiation patterns. Recent results disclosin... View full abstract»

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  • An investigation into the experimental determination of diffraction coefficients

    Publication Year: 1989, Page(s):449 - 453 vol.1
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (280 KB)

    Reports the results of a study investigating the possibility of obtaining diffraction coefficients using empirical methods based on measurements. Half-plane scatterers of conducting and of dielectric materials, with diffracting edges parallel to as well as perpendicular to the electric field vector of the incident field, were examined. Despite the limitations of the measurement system the experien... View full abstract»

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  • Electromagnetic field coupling between two parallel flanged waveguides

    Publication Year: 1989, Page(s):412 - 415 vol.1
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (204 KB)

    The authors analyze the mutual coupling between two parallel, flanged waveguides of arbitrary width and separation by using the moment method. The solution is based on the generalized admittance matrix formulation which may handle both TM and TE field coupling. Numerical results are presented graphically for the magnitudes and the phases of the equivalent magnetic current sheets over the apertures... View full abstract»

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  • Atmospheric effects on the propagation of very short pulses at millimetric wavelengths

    Publication Year: 1989, Page(s):432 - 436 vol.2
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (360 KB)

    An alternative approach to the solution of the Fourier integral in closed form was adopted by Terina (1967) for reflections from the ionosphere of pulsed HF (3-6 MHz) transmissions. This technique, appropriate to any line shape, assumes that the atmospheric channel transfer function can be approximated by a truncated Taylor series of frequency; its validity thus relies on the presumption that high... View full abstract»

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  • Experimental studies on millimeterwave and infrared propagation in arid land: the effect of sand storms

    Publication Year: 1989, Page(s):268 - 270 vol.2
    Cited by:  Papers (3)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (172 KB)

    Summarizes the measured sand/dust storm parameters and its effect on the radio links. Nine sand storms were experienced in the city of Riyadh during 1987, and were observed both by the meteorological sensors and by the radio links. The measurements were used to determine the prominent storm parameters which have considerable effects on wave propagation into such storms. Such parameters include par... View full abstract»

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  • The on-surface radiation condition approach to electromagnetic scattering

    Publication Year: 1989, Page(s):446 - 448 vol.1
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (196 KB)

    The OSRC formulation is used to analyse electromagnetic scattering by a conducting strip and by a dielectric-coated conducting cylinder. The quality of the predictions together with the fact that the method is numerically efficient suggests that the technique will prove useful for application to more complicated scatterers View full abstract»

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  • Developments in HF propagation modelling by microcomputer

    Publication Year: 1989, Page(s):109 - 113 vol.2
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (280 KB)

    MICROP3, a versatile microcomputer-based method of HF sky-wave propagation and circuit performance assessment, is an enhanced version of MICROP2. The input data display has been improved and the capability has been provided to store, for repeated use, a database of circuits specific to user requirements and to replace predicted values of ionospheric parameters by measured or normalised values. An ... View full abstract»

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  • Bistatic rainscatter studies: a theoretical model

    Publication Year: 1989, Page(s):411 - 413 vol.2
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (180 KB)

    The effects of rain and other hydrometeors on radio wave propagation has been the subject of intense study for many years. As the demand for satellite and terrestrial radio services increases more effort is being applied to make efficient use of the available bandwidth and power resources. The paper sets out the model developed by Essex University and British Telecom. The mathematical model and th... View full abstract»

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  • Experimental studies on millimeter wave propagation in arid climate: scintillation and multipath fading

    Publication Year: 1989, Page(s):428 - 431 vol.2
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (276 KB)

    A field study on wave propagation covering a wide range of the electromagnetic spectrum has been actively running for the last four years in the city of Riyadh, Saudi Arabia. The study involves the operation and continuous, computerized, monitoring of two microwave radio links operating at 12 GHz, three millimeter wave links with radio frequency of 40 GHz, and an infrared link with 0.88 μm wave... View full abstract»

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  • Dual mode feed system for contour beam antenna

    Publication Year: 1989, Page(s):268 - 272 vol.1
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (272 KB)

    Future European communication satellites may be required to provide two contoured beam coverages with a high degree of overlap. This can be achieved by use of a single antenna incorporating a so called `dual mode' beamforming network. The authors report on the study carried out for the European Space Agency (ESA) the objective of which was to develop a feed array incorporating such a dual mode bea... View full abstract»

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  • An 11 GHz dual-beamwidth slant-path attenuation experiment carried out at Martlesham Heath, UK

    Publication Year: 1989, Page(s):143 - 149 vol.2
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (444 KB)

    The authors investigate the dependence of measured attenuation on the beamwidth of the antenna used to carry out propagation measurements. Two co-located antennas of different sizes were used to carry out the measurements reported. In order to exaggerate any dependence on beamwidth a ratio of 10:1 (3.0° and 0.3°) was chosen. The experiment was of limited duration and was designed to includ... View full abstract»

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  • Dynamic structure of a transhorizon signal at X-band over a sea path

    Publication Year: 1989, Page(s):446 - 450 vol.2
    Cited by:  Patents (101)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (312 KB)

    Preliminary analyses on the time variant structure of a troposcatter signal at 11.5 GHz are carried out in the time and frequency domains. Both the medium term and short term path loss amplitude (dB) distributions are examined. Results on power spectral density and autocorrelation are presented. The joint statistical analysis of durations D of enhancements above a level F is also presented for a p... View full abstract»

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  • Two-port circularly polarized microstrip antennas

    Publication Year: 1989, Page(s):107 - 111 vol.1
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (272 KB)

    A circularly polarized (CP) two-port microstrip antenna simultaneously operated at two CP states is investigated. The CP bandwidth of the antenna is increased from 0.35% to about 5%, almost 14 times wider than that of single port patch. The antenna directivity due to the loss in the load is reduced by about 3 dB. It is believed that such an advantageous trade-off for both will make this type of an... View full abstract»

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  • Polarization stability of 4 arm-planar spiral structures

    Publication Year: 1989, Page(s):407 - 411 vol.1
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (308 KB)

    The dependence of the crosspolarization discrimination on the antenna shape and the feeding network is reviewed. The influence of the antenna shape is described by a new characteristic quantity: the polarization stability factor. This quantity is considered for four arm planar archimedean and logarithmic spiral antennas. With these structures high polarization stability can be obtained yielding a ... View full abstract»

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  • Loop and spiral line antennas at microstrip substrate surface

    Publication Year: 1989, Page(s):196 - 200 vol.1
    Cited by:  Papers (3)  |  Patents (1)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (280 KB)

    Radiation elements printed on a dielectric material have not been fully addressed due to difficulties in determining the current distributions on the radiation elements. The authors describe some new aspects of the radiation characteristics of a loop antenna. Special attention is paid to generation of a circularly polarised wave with a single voltage source. The numerical results show that a loop ... View full abstract»

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  • Calculation of broadcast coverage based on a digital terrain model

    Publication Year: 1989, Page(s):355 - 359 vol.2
    Cited by:  Papers (6)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (384 KB)

    A new wave propagation model for field strength predictions in the frequency range of VHF and UHF is presented. The basis for the propagation calculations is formed by the Uniform Geometrical Theory of Diffraction (UTD) and the theories for dielectric rough surfaces respectively. Calculated results of models with different complexity are compared with measurements View full abstract»

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  • A novel accelerated convergence technique for adaptive antenna applications

    Publication Year: 1989, Page(s):331 - 335
    Cited by:  Papers (4)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (368 KB)

    The authors introduce a novel adaptive antenna scheme. The technique involves the use of a fast digital processing algorithm in an adaptive feedback loop arrangement to compute updates for an analogue beamformer weighting circuit. This ensures a scenario-independent convergence performance, and because of the feedback path, can accommodate beamformer circuit errors and nonlinearities without undue... View full abstract»

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  • Validation of microcomputer antenna codes

    Publication Year: 1989, Page(s):427 - 431 vol.1
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (276 KB)

    Four specific types of antennas are used in a series of validation exercises to test specifically the accuracy of the PC-based antenna code MININEC. In the process, comparison was also made with results produced by other similar routines. It was found that MININEC can be used with confidence to model a variety of antenna configurations, given its constraints in terms of the number of wires and seg... View full abstract»

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  • Statistics of available/unavailable time due to attenuation on satellite paths

    Publication Year: 1989, Page(s):14 - 18 vol.2
    Cited by:  Papers (1)
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (332 KB)

    The effect of the current CCITT SG XVIII Rec G821 definition of availability on propagation related outage times on a satellite link is examined. The definition commensurate with G821 defines periods of unavailability based on a change of status from available to unavailable. A possible change of status is dependent on the samples during the following ten seconds. Each sample during this period mu... View full abstract»

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  • Propagation modelling-past, present and future

    Publication Year: 1989, Page(s):263 - 267 vol.2
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (356 KB)

    Propagation models are used to represent the wealth of information available about a propagation phenomena. Models are developed from physical analyses and statistical analyses of experimental observations. The modeling process is iterative. As one's understanding of a particular phenomenon improves, so do the models used to describe that phenomenon. Several models that describe propagation throug... View full abstract»

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  • What's new in antennas?

    Publication Year: 1989, Page(s):84 - 97 vol.1
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (1152 KB)

    Innovative designs, novelty and creative ideas reported in the international antenna literature, are highlighted under the headings of elements, travelling-wave arrays, apertures, arrays, measurements, and material developments. Manufacturing and operational aspects are noted and the driving forces identified while the extent to which antenna technology is mature, the role of research, and degrees... View full abstract»

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  • Radiation from small hemispherical lenses

    Publication Year: 1989, Page(s):390 - 393 vol.1
    IEEE is not the copyright holder of this material | Click to expandAbstract | PDF file iconPDF (212 KB)

    The authors show that efficient radiation from the substrate side of the dipole can be achieved by using shaped lenses and matching layers. A theoretical model based on the solution to the half-space problem is presented. Approximate expressions for the electromagnetic fields on the hemispherical surface are derived and the far-field obtained by integration over that surface. Comparison is made wi... View full abstract»

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