Bird, TS 1990, 'Analysis of Mutual Coupling in Finite Arrays of Different-Sized Rectangular Waveguides', IEEE Transactions on Antennas and Propagation, vol. 38, no. 2, pp. 166-172.
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A Green's function approach is used to analyze mutual coupling in a finite array of different-sized rectangular waveguides arranged on a rectangular grid. In calculating the self- and mutual admittances for mode coupling, a quadruple integration over the source and observer apertures is involved. Possible means of reducing the order of integration are discussed, with the change of variables approach (due to Lewin) being selected. This approach is generalized to allow coupling between different-sized apertures, and leads to derivation of mutual admittance expressions for all possible combinations of transverse electric (TE) and transverse magnetic (TM) mode coupling. Calculations using these expressions are shown to be in good agreement with results published earlier by Mailloux and measured data for an antenna comprising a square waveguide and two rectangular waveguides. Coupling between closely spaced different-sized square waveguides is investigated also, and for small apertures minimum coupling is shown to occur when the aperture sidelength is about 1.15 λ. © 1990 IEEE
Bird, TS 1990, 'Behaviour of multiple elliptical waveguides opening into a ground plane', IEE Proceedings H: Microwaves, Antennas and Propagation, vol. 137, no. 2, pp. 121-126.
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Radiation from elliptical waveguides terminating in a ground plane is analysed using a Green's function approach. In the waveguides the field is expressed as a sum of the TEcmn, TMcmn, TEsmn and TMsmn elliptical waveguide modes, and expressions for the mutual admittances of modes excited at the apertures are obtained. From these expressions the mode reflection and conversion coefficients are determined. Of the techniques available for calculating the mutual admittances, the transform representation and direct integration approaches are used, with the latter preferred for detailed calculations. Results obtained for elliptical waveguides are compared with corresponding results for rectangular waveguides in a ground plane. Within limits, the less computationally intense rectangular waveguide solution can be a useful first approximation to the elliptical waveguide solution.
Bird, TS & Hay, SG 1990, 'Mismatch in Dielectric-Loaded Rectangular Waveguide Antenna', Electronics Letters, vol. 26, no. 1, pp. 59-61.
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A method is described for calculating mode reflection and conversion at the aperture of a dielectric-loaded waveguide terminating in a groundplane. Theoretical and measured results are presented for the mismatch in a rectangular waveguide with dielectric placed parallel to the principal electric field. These results demonstrate the importance of high-order modes in estimating mismatch. © 1990, The Institution of Electrical Engineers. All rights reserved.
Bird, TS & Sprey, MA 1990, 'Scan limitations of shaped dual-offset reflector antennas for multiple satellite access', Electronics Letters, vol. 26, no. 4, pp. 228-230.
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The performance of offset Cassegrain antennas, shaped to provide wide scan angles, is outlined for use in earth stations which are capable of accessing several satellites simultaneously. The effect on the beam efficiency of scanning over a rectangular-shaped coverage region located about the geostationary arc is described. Limitations on scan performance are discussed as is the effect of satellite tracking by feed movement. © 1990, The Institution of Electrical Engineers. All rights reserved.
Candy, JV, Ziolkowski, RW & Lewis, DK 1990, 'Transient wave estimation: A multichannel deconvolution application', Journal of the Acoustical Society of America, vol. 88, no. 5, pp. 2235-2247.
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The evolution of new concepts in wave theory have led to proof-in-principle experiments aimed at validating the generation of a specified wave front. Not only have these concepts initiated research in transient wave theory, but they have also caused renewed effort in multichannel signal processing. In this paper, the development of a processor to deconvolve a transient acoustic wave from sensor array measurements is discussed. The design of the multichannel deconvolver coupled with model-based signal processing techniques using acoustic pressure field measurements is discussed. Here, it is shown that an efficient solution to this problem can be obtained using a vector form of the Levinson-Wiggins-Robinson (LWR) algorithm. © 1990, Acoustical Society of America. All rights reserved.
Candy, JV, Ziolkowski, RW & Lewis, DK 1990, 'Transient waves: Reconstruction and processing', Journal of the Acoustical Society of America, vol. 88, no. 5, pp. 2248-2258.
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New solutions to the wave equation have been shown to exhibit enhanced localization and energy fluence characteristics. The transmission and reception of these localized waves create unique problems, since they are essentially transient wave fronts in both time and space. Nonetheless, the ability to transmit wave energy through space with these interesting properties has many potential applications in a variety of applications areas. To realize their potential, new methods must be developed to analyze and process these waves. In this paper, approaches to design receiving arrays to reconstruct these special transient waves from noisy measurement data are discussed. © 1990, Acoustical Society of America. All rights reserved.
Dajani, I, Dipeso, G, Morse, EC & Ziolkowski, R 1990, 'Gaussian beam propagation in a weakly nonlinear medium: A geometrical optics approach', Physical Review A, vol. 41, no. 7, pp. 3740-3745.
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A geometrical optics method for solving wave propagation in weakly nonlinear, weakly inhomogeneous media is presented and applied to the propagation of a two-dimensional Gaussian beam. A complex distorted phase ; is obtained. This complex phase is used to describe both the zeroth-order amplitude and the nonlinear rays along which the energy propagates. This approach recovers standard self-focusing and self-blooming effects in a quadratically nonlinear medium. © 1990 The American Physical Society.
MADSEN, NK & ZIOLKOWSKI, RW 1990, 'A 3-DIMENSIONAL MODIFIED FINITE VOLUME TECHNIQUE FOR MAXWELL EQUATIONS', ELECTROMAGNETICS, vol. 10, no. 1-2, pp. 147-161.
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SHAARAWI, AM, BESIERIS, IM & ZIOLKOWSKI, RW 1990, 'A NOVEL-APPROACH TO THE SYNTHESIS OF NONDISPERSIVE WAVE PACKET SOLUTIONS TO THE KLEIN-GORDON AND DIRAC EQUATIONS', JOURNAL OF MATHEMATICAL PHYSICS, vol. 31, no. 10, pp. 2511-2519.
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Veitch, D & Glendinning, P 1990, 'Explicit renormalisation in piecewise linear bimodal maps', Physica D: Nonlinear Phenomena, vol. 44, pp. 149-167.
Veitch, D, Asten, MW & Van Leeuwen, EH 1990, 'Electrical and magnetometric fields in a layered earth containing buried electrodes', Geophysics, vol. 55, pp. 1605-1612.
Ziolkowski, RW & Lewis, DK 1990, 'Verification of the localized-wave transmission effect', Journal of Applied Physics, vol. 68, no. 12, pp. 6083-6086.
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An acoustic array driven with a designed set of localized-wave (LW) solutions of the scalar-wave equation generates a robust, well-behaved, transient pencil beam of ultrasound in water. The performance of the LW-pulse-driven array theoretically and experimentally exceeds a tenfold improvement over related continuous-wave excitations of the same array.
Huang, XJ & Chen, HB 1990, 'Born migration and its fast implementation in the wavenumber-time domain', 1990 SEG Annual Meeting, pp. 1136-1139.
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© 1990 Society of Exploration Geophysicists. All rights reserved. A new method for wave equation migration is presented in this paper. This migration method, named Born Migration, is formulated by solving the boundary-value problem of the wave equation in an integral closed-form and applying the Born approximation for the Green's function in the inhomogeneous media. The major features of Born migration are: 1. it has no limitation in dip angle; 2. it can accommodate gentle vertical and lateral velocity variations; and 3. it can be implemented by using fast Fourier transformation. It is believed that this technique is especially suitable for migration in 3D seismic survey application.
Poulton, GT, Bird, TS, Hay, SG & Choi, YK 1990, 'Rigorous design of an antenna for AUSSAT-B', IEEE Antennas and Propagation Society, AP-S International Symposium (Digest), pp. 1900-1903.
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The prototype antenna designed, constructed, and tested for the AUSSAT-B western Australia regional beam has operated within specifications in all regards. More importantly, the overall design approach of using highly accurate software tools to obtain a successful first-time design has been vindicated. The antenna, comprising an array of horns illuminating an offset paraboloidal reflector, has a beamforming network (BFN) to provide correct power distribution and phasing to the feed elements. The antenna geometry is defined, showing the specified racetrack projected aperture. The other main constraint imposed on the antenna design was a volumetric limit on the feed and beamforming network. The far-field pattern obtained at 12.5 GHz is shown, with the beam pattern computed from measured BFN excitations superimposed. It is shown that the correspondence between theory and experiment is excellent.