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Microwaves, Antennas and Propagation, IEE Proceedings

Issue 1 • Date Feb 1997

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Displaying Results 1 - 10 of 10
  • FD-TD design of short backfire antennas

    Publication Year: 1997 , Page(s): 1 - 6
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (664 KB)  

    The finite difference time domain (FD-TD) method has been used to study the short backfire antenna which is a compact feed for reflector antennas. A parametric study of a short backfire antenna has been performed which, for the first time, enables an optimum design to be obtained. The computed results have been validated by constructing and measuring an experimental antenna which gave measured results in good agreement with the predictions View full abstract»

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  • Cutoff frequencies of circular waveguide loaded with eccentric dielectric cylinder

    Publication Year: 1997 , Page(s): 7 - 12
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    The cutoff frequencies of a conducting circular waveguide loaded eccentrically by a cylinder are calculated. Analytical formulations are developed based on the boundary value method. The cutoff wavenumbers are then calculated as roots of the resulting characteristic determinant. Even and odd hybrid modes are considered and the cutoff frequencies calculated for both cases. Several examples for special cases are introduced for comparison followed by other general examples. The case of a dielectric-filled circular waveguide with an eccentric air core is also examined View full abstract»

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  • Integrated-circuit antenna for high-permittivity substrates

    Publication Year: 1997 , Page(s): 47 - 51
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (548 KB)  

    An integrated antenna which operates well on thick, high-permittivity substrates is analysed using a combined integral-equation and mode-matching method. Results from the numerical solution of the integral equation are compared with measurements on a model antenna. Measured and predicted results are found to agree well for the antenna input impedance and far-field radiation pattern. A theoretical design for a GaAs millimetre-wave MMIC antenna operating at 94 GHz is described View full abstract»

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  • Rain-induced crosspolarisation on line-of-sight systems at 38 GHz

    Publication Year: 1997 , Page(s): 20 - 26
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    Factors affecting rain-induced depolarisation at 38 GHz have been investigated. The effect of raindrop canting on the crosspolar signal levels has been examined together with other, more minor, factors such as water temperature and drop shape model. The intervening medium between the two terminals is assumed to have constant rainfall rate and the crosspolar effects are evaluated for various link separations and for various rain intensities. Additionally, data obtained from the Chilbolton radar are used and the depolarisation effects due to typical precipitation events are assessed. Results indicate that, for a standard 38 GHz PCN (personal communication network) system, the use of linear, orthogonal polarisations is not likely to present operational problems. Compared with the copolar fading of the wanted signal and the depolarisation introduced by antennas typically used by the operators, the effects of rain-induced crosspolarisation are shown to be almost negligible View full abstract»

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  • Quadrifilar conical helical antenna with travelling-wave current distribution

    Publication Year: 1997 , Page(s): 53 - 55
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    The radiation characteristics of a quadrifilar conical helix antenna are analysed. Special attention is paid to the generation of a circularly polarised wave over a hemispherical region above the antenna. The present antenna has wideband characteristics with respect to the radiation pattern and the input impedance by virtue of the radiation mechanism characterised by a travelling-wave current. The effects of the cone angle and the pitch angle on the radiation field are also investigated View full abstract»

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  • Interpolation of reflector surfaces by pseudosplines

    Publication Year: 1997 , Page(s): 42 - 46
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    Global interpolation of numerically defined surfaces is an important step in the synthesis and analysis of reflector antennas. Quintic and cubic pseudosplines have been shown to be adequate for the interpolation of highly shaped reflector surfaces, as compared to other series expansions. The implementation of pseudospline interpolating functions, also incorporating 7th-degree ones, is investigated via comparison of ability in accommodating the smoothness characteristics inherent to geometrical optics (GO) synthesis of reflector surfaces. A known (analytical) surface is first considered, allowing an assessment of resulting errors in corresponding GO analysis. A shaped reflector design is subsequently explored View full abstract»

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  • Green function for radiation and propagation in helicoidal bianisotropic mediums

    Publication Year: 1997 , Page(s): 57 - 59
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    Radiation by prescribed sources in a helicoidal bianisotropic medium (HBM) is investigated. The Oseen transformation and spatial Fourier transforms are used to obtain an inhomogeneous, first-order, matrix differential equation with nonconstant coefficients. As these coefficients are analytic functions of z and can be expanded as polynomials in that variable, the solution of an auxiliary homogeneous differential equation is explicitly and simply obtained. On using this auxiliary equation's solution, the radiated fields are determined and an appropriate Green function is formulated as a 4×4 matrix. Novel results apply to thin-film HBMs as well as to chiral liquid crystals View full abstract»

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  • Evaluation of multiple diffraction integrals: computational speed and accuracy considerations

    Publication Year: 1997 , Page(s): 35 - 41
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    The paper examines the computational efficiency of three methods of evaluating multiple diffraction integrals commonly encountered in electromagnetic problems. The solution based on the repeated integrals of the error function originally derived by Vogler (1981) is elegant, relatively easy to program, computationally inefficient, but accurate. For practical applications, the computational technique used must be amenable to rapid evaluation and yield an acceptable degree of accuracy. Following the analysis of Saunders and Bonar (see IEEE Trans., AP-42, p.137-44, 1994) for propagation over multiple knife-edge models of building rows of irregular height and spacing, the Monte-Carlo integration technique is extended to consider knife-edge and plateau diffraction View full abstract»

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  • Corrugated soft sector horn with different beam properties in the two principal planes

    Publication Year: 1997 , Page(s): 13 - 19
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (824 KB)  

    The authors present a corrugated horn antenna with different beam properties in the two principal planes of radiation. It is designed to give a frequency independent wide beamwidth in the horizontal plane, by making it flare-angle controlled in that plane, and a beamwidth that is decreasing with increasing frequency in the vertical plane, by making it aperture controlled in that plane. The throat of the horn is designed to ensure excitation of the desired mode in the flared part of the horn and achieve the desired aperture distribution. The flare in the horizontal plane is gradually increased to the chosen value and the corrugations on the horizontal walls are curved to follow the curved phase front of the desired mode. Improved mode excitation by introducing dielectric lenses in the throat is studied. The radiation patterns are calculated from an approximate aperture field, representing the lowest-order mode in a radial sector waveguide. A horn was built and measured. Results show that it is possible to make corrugated sector horns with different beam properties in the two principal planes over a relative bandwidth of 1.5. However, it is also clear that it would have been desirable to have available numerical design tools for complicated geometries in order to get better results View full abstract»

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  • Measured and modelled scattering properties of simulated particles of granular and spongy hail at microwave and millimetre-wave frequencies

    Publication Year: 1997 , Page(s): 27 - 34
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (792 KB)  

    The detailed scattering properties of single spherical particles which have been created artificially to represent particles of hail have been measured together with the physical properties of the particles, namely size, shape and percentage content of ice, water and air as applying continuously throughout the process of melting. Specifically, the types of particles represent granular hail and spongy hail. The measurements are of extinction (total-loss) cross-section, and were taken at frequencies of 8, 10, 12, 34 and 70 GHz. Models for describing the observed scattering behaviour are tested, and differentiation is made between the results and models which apply to each of the types of particles, the observation and implications of collapsing size of the two types of particles being an important feature. For types and frequencies, the sets of results allow evaluations to be made of the ratio of the maximum cross-section exhibited during melting to the initial cross-section of a particle when dry View full abstract»

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