BESIERIS, IM, SHAARAWI, AM & ZIOLKOWSKI, RW 1994, 'NONDISPERSIVE ACCELERATING WAVE-PACKETS', AMERICAN JOURNAL OF PHYSICS, vol. 62, no. 6, pp. 519-521.
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Bird, TS, Kot, JS, Nikolic, N, James, GL, Barker, SJ, Cooray, F & Bateman, DG 1994, 'Millemetre-wave antenna and propagation studies for indoor wireless LANs', IEEE Antennas and Propagation Society, AP-S International Symposium (Digest), vol. 1, pp. 336-339.
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The work on millimeter wave antennas and propagation relating to wireless local area networks is outlined. The basic arrangement for such systems involves a hub antenna, located in the ceiling and a number of roamable antennas located on desks throughout the room. Signals that are transmitted are subject to considerable multipath interference and this limits the system performance. Optimization of the WLAN performance involves the understanding of propagation effects in rooms and the development of antennas whose characteristics match overall requirements, including cost.
Bohm, B, Schoonees, J & Braun, RM 1994, 'Data To Frequency Mappings In Various Msk Schemes', Electronics & Communication Engineering Journal, vol. 6, no. 1, pp. 13-20.
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Minimum shift keying (MSK) is a digital modulation scheme which is suited to demanding applications requiring good bandwidth efficiency and error performance. It can be regarded as continuous phase frequency shift keying (CPFSK) with two signalling frequ
CANNING, J & SCEATS, MG 1994, 'PI-PHASE-SHIFTED PERIODIC DISTRIBUTED STRUCTURES IN OPTICAL FIBERS BY UV POST-PROCESSING', ELECTRONICS LETTERS, vol. 30, no. 16, pp. 1344-1345.
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CANNING, J & SCEATS, MG 1994, 'SPATIAL-DISTRIBUTION OF 650-NM LUMINESCENCE IN UV-PROCESSED GERMANOSILICATE PREFORMS', OPTICS LETTERS, vol. 19, no. 15, pp. 1119-1121.
DAVIDSON, DB & ZIOLKOWSKI, RW 1994, 'BODY-OF-REVOLUTION FINITE-DIFFERENCE TIME-DOMAIN MODELING OF SPACE-TIME FOCUSING BY A 3-DIMENSIONAL LENS', JOURNAL OF THE OPTICAL SOCIETY OF AMERICA A-OPTICS IMAGE SCIENCE AND VISION, vol. 11, no. 4, pp. 1471-1490.
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DONNELLY, R & ZIOLKOWSKI, RW 1994, 'ELECTROMAGNETIC-FIELD GENERATED BY A MOVING POINT-CHARGE - A FIELDS-ONLY APPROACH', AMERICAN JOURNAL OF PHYSICS, vol. 62, no. 10, pp. 916-922.
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DONNELLY, R & ZIOLKOWSKI, RW 1994, 'SOLUTIONS OF NONLINEAR PARTIAL-DIFFERENTIAL EQUATIONS IN PHASE-SPACE', PHYSICA D, vol. 78, no. 1-2, pp. 115-123.
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Dutkiewicz, E & Anido, G 1994, 'Performance evaluation of hierarchical control systems in switching exchanges', ATR. Australian telecommunication research, vol. 28, no. 1, pp. 15-24.
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Optimal placement of software functionality in distributed control systems of switching exchanges can be used to achieve a cost effective design in the ISDN and IN environments. New telecommunications services have emerged which will place quite disparate processing demands on control systems, and the optimal system configuration will depend on the call mix to be supported by the exchange. Optimal function allocation can also be used to facilitate the evolution of existing control systems to broadband network applications without the need for high-cost system re-design. A simple control system model based on queueing networks, and able to capture the main features of the system, is proposed and used to investigate the effect of various system and call parameters on the optimal function allocation. The resultant algorithms can be used as evaluation tools allowing designers to compare the performance of candidate systems to satisfy particular specifications in a cost effective manner. Applying the model to a hierarchical control system shows the potential benefits of optimal function allocation.
Guo, YJ & Barton, SK 1994, 'Offset Fresnel zone plate antennas', International Journal of Satellite Communications, vol. 12, no. 4, pp. 381-385.
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The theory of offset Fresnel zone plate antennas is presented. Explicit formulae for the design of the zone boundaries for the offset Fresnel zone plate are given. Theorectical equations and numerical results for the far‐field analysis are presented. It is found that when the offset angle increases, the zone boundaries become more elliptic and the plate becomes more asymmetric in the E‐plane. With the number of full wave zones and the plate width in the W‐plane fixed, the plate width in the E‐plane increases with the offset angle, which keeps the projected aperture area constant. Within a limited range of offset angles, the offset configuration can be employed without degrading the radiation performance much. For large offset angles, however, the asymmetry of the configuration may lead to increased sidelobes and decreased antenna directivity. An experiment with one particular phase reversal zone plate antenna with 30° offset angle shows good agreement between the measured antenna pattern and the theoretical prediction. Copyright © 1994 John Wiley & Sons, Ltd.
Guo, YJ, Sassi, IH & Barton, SK 1994, 'Multilayer Offset Fresnel Zone Plate Reflector', IEEE Microwave and Guided Wave Letters, vol. 4, no. 6, pp. 196-198.
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An offset phase-correcting Fresnel zone plate (FZP) reflector antenna based on the multilayer configuration is presented. The reflector consists of a conducting ground and four layers of conducting patterns separated by four dielectric substrates. An experimental prototype designed at 10.39 GHz was fabricated and tested. With a 0.32 m by 0.34 m elliptical reflector aperture and a pyramidal feedhorn, the antenna achieved –20-dB sidelobe level and 61% maximum efficiency. Compared with a phase reversal FZP of the same size, a 3.3-dB gain improvement and significant sidelobe reduction were obtained. © 1994 IEEE
Guo, YJ, Sassi, IH & Barton, SK 1994, 'Offset Fresnel lens antenna', IEE Proceedings: Microwaves, Antennas and Propagation, vol. 141, no. 6, pp. 517-522.
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An analysis of the offset Fresnel lens antenna is presented using the vectorial Kirchhoff diffraction theory. Equations for predicting the copolarized and crosspolarized radiation patterns are given. Two approaches to evaluating the far-field integration are introduced. Antenna performance such as the sidelobe and the crosspolarization levels is investigated. An experimental offset Fresnel lens is reported. Measured results agree well with the theoretical prediction.
Newell, P & Bird, TS 1994, 'Effects of mutual coupling in the design of high‐performance multifeed satellite antennas', Radio Science, vol. 29, no. 1, pp. 145-152.
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Predicted and measured results are presented for the effect of mutual coupling on the performance of shaped beam antennas having feed clusters that are irregular arrays of closely shaped small rectangular horn elements. The effects of mutual coupling on the primary and secondary patterns and on gain at specific points within beams are described for the Orion satellite antennas. Also shown is how excitation coefficients can be modified to overcome the changes in performance caused by mutual coupling. Copyright 1994 by the American Geophysical Union.
Plane, G, Bird, TS & Bateman, DG 1994, 'Mutual Coupling Between Rotated Horns in a', IEEE Transactions on Antennas and Propagation, vol. 42, no. 7, pp. 1000-1006.
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Two formulations are presented for the mutual admittance of rotated rectangular apertures in a ground plane. One extends an earlier solution, and the other is a third-order asymptotic formula that is shown to be accurate when the apertures satisfy the Rayleigh distance criterion. These formulations are combined with a conventional mode-matching approach to study coupling between rotated horns. Results are presented for both coupling formulations, and these demonstrate excellent agreement with experiment for coplanar pyramidal and sectoral horns. © 1994 IEEE
Shaarawi, AM, Besieris, IM & Ziolkowski, RW 1994, 'Diffraction of a nondispersive wave packet in the two slit interference experiment', Physics Letters A, vol. 188, no. 3, pp. 218-224.
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In Young's two slit interference experiment, a single light particle or "photon" imparts its energy onto a dot on one of the light fringes of the diffracted field. In this work, it will be shown that a pulse solution of the scalar wave equation, or Maxwell's equations, going through a two slit screen reproduces the aforementioned single event interference effect. This solution, called the focus wave mode, is one of a class of solutions capable of accomodating both the wave and corpuscular aspects of light. © 1994.
Veitch, D 1994, 'Renormalization of C0 bimodal maps', Physica D: Nonlinear Phenomena, vol. 71, pp. 269-284.
ZIOLKOWSKI, RW 1994, '[title field missing]', JOSA, B, vol. 11, no. 9, pp. 1565-1575.
Ziolkowski, RW & Davidson, DB 1994, 'Designer pulsed beams for enhanced space-time focusing.', Optics letters, vol. 19, no. 4, pp. 284-286.
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We have demonstrated analytically and numerically that at least 10-100-fold enhancements in intensities for similar input energies can be achieved in the focal region of a thin dielectric lens by the use of pulsed beams specifically designed for that purpose.
Ziolkowski, RW & Judkins, JB 1994, 'Nonlinear finite-difference time-domain modeling of linear and nonlinear corrugated waveguides', Journal of the Optical Society of America B: Optical Physics, vol. 11, no. 9, pp. 1565-1575.
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A multidimensional, nonlinear finite-difference time-domain (NL-FDTD) simulator, which is constructed from a self-consistent solution of the full-wave vector Maxwell equations and dispersive (Lorentz), nonlinear (finitetime- response Raman and instantaneous Kerr) materials models, is used to study finite-length, corrugated, optical waveguide output couplers and beam steerers. Multiple-cycle, ultrashort-optical-pulse interactions with these corrugated, nonlinear, dispersive waveguides are characterized. An all-optical nonlinear beam-steering device is designed, and its output-coupling performance is characterized with this NL-FDTD simulator. © 1994 Optical Society of America.
Bird, TS 1994, 'Multibeam feed for the parkes radio-telescope', IEEE Antennas and Propagation Society, AP-S International Symposium (Digest), pp. 966-969.
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Discussed is a preliminary study of the Parkes antenna performance having a cluster of nine feed horns of which each horn is responsible for two orthogonal linear polarizations within a beam. This study aims to optimize Parkes radio-telescope antenna used to study the southern sky. Conventional horns are selected and arranged in the focal region in order to achieve a 2 HPBW beam spacing. The required sampling in u-v space is derived by the proposed rectangular grid of beams through simple two-fold interleaving in each spatial dimension.
Bird, TS, Sprey, MA, Greene, KJ & James, GL 1994, 'Antenna system for an x-band satellite earth terminal', National Conference Publication - Institution of Engineers, Australia, pp. 27-30.
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The reflector-optics and feed system of an 11 m diameter earth-station antenna that operates in circular polarization at X-band is described. The reflector-optics are required to have high G/T, sidelobes that satisfy the CCIR recommendation and low mismatch at the feed due to the subreflector. The feed system is required to have high isolation between the transmit and receive ports (> 40 dB) at the centre of the band. This isolation is achieved by minimizing reflections from all components forward of the polarizer. As well as meeting the high-isolation requirement, the feed system has an insertion loss < 0.15 dB and an axial ratio < 0.5 dB. A feed system was constructed and tested and some results are described.
Cucchiara, R, Di Stefano, L, Monacelli, M, Piccardi, M & Rustichelli, G 1994, 'Parallel vision subsystem for robotic inspection and manipulation', IECON Proceedings (Industrial Electronics Conference), pp. 862-866.
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The paper describes an SIMD massively parallel computer conceived for robot vision, and presents an application where the system is installed on a mobile robot to support inspection and manipulation tasks. The system consists of a scalable array of up to 4K single-bit processors controlled by a general-purpose microcomputer through a dedicated interface. The system's architecture is overviewed, addressing the available prototype as well as the functional units currently under design. We provide examples of image analysis goals that can be efficiently reached using spatially-organized parallel architectures such as SIMD array and give measurements of present performances. Using code profiles we also evaluate the speedup associated with the configuration being designed.
Cuthbert, J, Crawford, B & Braun, RM 1994, 'Multi-oscillator approach to CPFSK signal creation', pp. 20-23.
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The development of a MSK modulator/demodulator by Massey [1] and the Hodgart and Schoones implementation [2] has prompted the development of a multi-oscillator multi-h modulator/demodulator. The approach taken has been an investigation and extension of basic CPFSK multi-oscillator modulator/demodulator design using digital logic. In this paper the multi-oscillator MSK modulator as developed by Massey [1] is first re-examined before introducing the scheme developed by Crawford [3]. Thereafter elements of the related digital logic demodulator design are discussed.
Davidson, AM, van de Groenendaal, J & Braun, RM 1994, 'Novel code phase synchronization network for direct sequence spread spectrum', pp. 95-98.
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Direct sequence spread spectrum systems require that the receiver's replica of the spreading waveform be in code-phase and frequency lock with that of the transmitter's. Present methods of achieving synchronization involve correlation and energy detection. This paper presents the development of an alternative synchronization network. The network is a novel robust feedback loop where the input is the differentiated transmitter pseudo-noise sequence. The effects of these positive and negative going voltage spikes modulate the receiver clock until lock is achieved. The loop is further adapted to a data driven environment.
DAVIDSON, DB, ZIOLKOWSKI, RW & JUDKINS, JB 1994, 'FDTD MODELING OF 3D OPTICAL PULSE-PROPAGATION IN LINEAR AND NONLINEAR MATERIALS', SECOND INTERNATIONAL CONFERENCE ON COMPUTATION IN ELECTROMAGNETICS, 2nd International Conference on Computation in Electromagnetics, INST ELECTRICAL ENGINEERS, UNIV NOTTINGHAM, NOTTINGHAM, ENGLAND, pp. 166-169.
FIDEL, B, HEYMAN, E, KASTNER, R & ZIOLKOWSKI, RW 1994, 'HYBRID RAY-FDTD MOVING FRAME APPROACH TO PULSE-PROPAGATION', IEEE ANTENNAS AND PROPAGATION SOCIETY INTERNATIONAL SYMPOSIUM 1994, VOLS I-III, IEEE Antennas-and-Propagation-Society International Symposium 1994, I E E E, UNIV WASHINGTON, SEATTLE, WA, pp. 1414-1417.
Golda, PJ, Benzakein, A, vd Groenendaal, JG & Braun, RM 1994, 'VLSI appropriate design of a trace-back Viterbi decoder', pp. 76-80.
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This paper concerns the research into the implementation of an efficient Viterbi algorithm for the decoding of convolutional codes. The original algorithm, as presented by Truong in his 1992 paper, is described, with many new points being noted. A detailed discussion of the improvements made to the algorithm follows, along with a full example of the operation of the algorithm.
HAYES, JD, NEIFELD, MA, SRIDHARAN, SK & ZIOLKOWSKI, RW 1994, 'ADJACENT DETECTOR CROSS TALK IN CMOS SMART DETECTOR ARRAYS', INTEGRATED OPTICS AND MICROSTRUCTURES II, 2nd Conference on Integrated Optics and Microstructures, at the SPIE International Symposium on Optics, Imaging, and Instrumentation, SPIE - INT SOC OPTICAL ENGINEERING, SAN DIEGO, CA, pp. 102-107.
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James, GL, Clark, PR, Bird, TS & Graves, GR 1994, 'Meeting the multifarious demands on the feed system for TERSS', National Conference Publication - Institution of Engineers, Australia, pp. 23-26.
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The numerous requirements of a feed system for an earth-resources-satellite earth station is described. These include simultaneous S/X-band circular polarisation operation, a rejection filter for a local interference signal and electronic tracking. Most of the feed system was designed theoretically and the accuracy of the methods used is demonstrated by the excellent agreement with measured data. We argue that, without this design capability, it would be difficult to realise such a complex feed system.
Nkambule, VO & Braun, RM 1994, 'Power spectral density of duobinary-signalled minimum shift keying (MSK) with arbitrary pulse shaping', pp. 16-19.
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We present a general method for computing the power spectral density (PSD) of a partial-response, continuous phase modulated (CPM), constant-envelope signal. The modulation scheme employed is minimum shift keying (MSK). The frequency modulating signals are a random baseband pulse train in which the arbitrary pulse is time limited. Random data symbols transmitted during different time slots are assumed to be identically distributed and statistically independent.
OUELLETTE, F, CANNING, J, EGGLETON, B, HILL, P, KING, PA, SCEATS, MG & IEEE 1994, 'ADDING FUNCTIONALITY TO FIBRE BRAGG GRATINGS', LEOS '94 - CONFERENCE PROCEEDINGS, VOL 2, pp. 129-130.
van de Groenendaal, JG & Braun, RM 1994, 'Phase-plane analysis of phase-locked loops used for clock recovery', pp. 99-104.
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The transient analysis of phase-locked loops is not an easy analytical task. Although linearisation of these devices is common practice, the exact nature of the loop is not obtained. Using phase-plane techniques it is possible to determine both the transient and steady-state responses of phase-locked loops. In this paper we investigate the application of phase-plane techniques to a second-order phase-locked loop and to a more complex clock-recovery loop. A number of interesting results were obtained and are discussed.