BOHM, B, SCHOONEES, JA & 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
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 1994, 'Offset Fresnel lens antenna', IEE Proceedings - Microwaves, Antennas and Propagation, vol. 141, no. 6, pp. 517-517.
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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.
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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AbstractThe 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.
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
Veitch, D 1994, 'Renormalization of C0 bimodal maps', Physica D: Nonlinear Phenomena, vol. 71, no. 3, pp. 269-284.
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Cucchiara, R, Di Stefano, L, Monacelli, M, Piccardi, M & Rustichelli, G 1970, 'A parallel vision subsystem for robotic inspection and manipulation', Proceedings of IECON'94 - 20th Annual Conference of IEEE Industrial Electronics, IECON'94 - 20th Annual Conference of IEEE Industrial Electronics, IEEE, 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 1970, 'A multi-oscillator approach to CPFSK signal creation', Proceedings of COMSIG '94 - 1994 South African Symposium on Communications and Signal Processing, COMSIG '94 - 1994 South African Symposium on Communications and Signal Processing, IEEE, 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 1970, 'A novel code phase synchronization network for direct sequence spread spectrum', Proceedings of COMSIG '94 - 1994 South African Symposium on Communications and Signal Processing, COMSIG '94 - 1994 South African Symposium on Communications and Signal Processing, IEEE, 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.
Golda, PJ, Benzakein, A, van de Groenendaal, JG & Braun, RM 1970, 'VLSI appropriate design of a trace-back Viterbi decoder', Proceedings of COMSIG '94 - 1994 South African Symposium on Communications and Signal Processing, COMSIG '94 - 1994 South African Symposium on Communications and Signal Processing, IEEE, 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.
Nkambule, VO & Braun, RM 1970, '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.
van de Groenendaal, JG & Braun, RM 1970, 'Phase-plane analysis of phase-locked loops used for clock recovery', Proceedings of COMSIG '94 - 1994 South African Symposium on Communications and Signal Processing, COMSIG '94 - 1994 South African Symposium on Communications and Signal Processing, IEEE, 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.
