Guo, YJ & Barton, SK 1993, 'Fresnel zone plate reflector incorporating rings', IEEE Microwave and Guided Wave Letters, vol. 3, no. 11, pp. 417-419.
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A novel high-efficiency Fresnel zone plate reflector antenna is presented. The reflector consists of an inhomogeneous array of circular conducting rings printed on a grounded substrate. By adjusting the geometrical parameters of the rings and the distances between them, the reflector provides a space-varying phase correction required for focusing an incoming plane wave. Compared with a phase reversal zone plate, an average of 3-dB gain improvement and significant sidelobe reduction have been obtained. © 1993 IEEE
Guo, YJ & Barton, SK 1993, 'Multilayer phase correcting fresnel zone plate reflector antennas', International Journal of Satellite Communications, vol. 11, no. 2, pp. 75-80.
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AbstractOwing to its flat nature and light weight etc., the Fresnel zone plate antenna is becoming very attractive for such applications as DBS reception and receive‐only VSAT. The disadvantages of low efficiency and high sidelobes of the simple and the phase reversing zone plates can be improved by using phase correcting techniques. In this paper, a systematic investigation on the efficiency and sidelobe performance of subzone phase correcting zone plate antennas is presented. The design of a form of multilayer phase correcting zone plate reflector is described. A quarter‐wave zone plate reflector constructed with three dielectric layers and metallized rings is reported, with measured peak efficiency of 55 per cent.
Guo, YJ & Barton, SK 1993, 'On the subzone phase correction of fresnel zone plate antennas', Microwave and Optical Technology Letters, vol. 6, no. 15, pp. 840-843.
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AbstractSubzone phase correction is a practical technique to produce high‐efficiency Fresnel zone plate antennas. In this article a strict theory underlying the technique is presented. A closed‐form expression of the focal field for the subzone phase correcting Fresnel zone plate (FZP) illuminated by a plane wave is given first. The subzone division and the corresponding phase correction are then optimized to produce the maximum focal field intensity. To overcome the difficulty of placing many subzone phase shifters in the narrow outer full‐wave zones, an aperiodic subzone phase correction technique is proposed.
Veitch, D 1993, 'The approach to constrained equations', Physics Letters A, vol. 183, no. 4, pp. 319-326.
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Chee, YJ & Berton, SK 1970, 'High efficiency zone plate reflector incorporating printed resonators', IEE Conference Publication, 8TH INTERNATIONAL CONF ON ANTENNAS AND PROPAGATION, INST ELECTRICAL ENGINEERS, HERIOT WATT UNIV, EDINBURGH, SCOTLAND, pp. 620-622.
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A novel phase correcting zone plate reflector with a single layer metallic printing is presented. By using reflective phase shifters consisting of printed resonators, the new reflector antenna achieved 65% aperture phase efficiency. Compared with the conventional phase reversing zone plate reflector, an average of 2dB gain increase and a IIdB sidelobe reduction have been obtained in the operating band. The new reflector showed much narrower main beam.
Piccardi, M, De Stefano, L, Cucchiara, R & Cinotti, TS 1970, 'Processing of variable size images on a cellular array: Performance analysis with the Abingdon Cross Benchmark', Proceedings of International Conference on Application Specific Array Processors (ASAP '93), International Conference on Application Specific Array Processors (ASAP '93), IEEE Comput. Soc. Press, pp. 172-175.
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© 1993 IEEE. Handling a continuous flow of variable size images is a requirement for real time computer vision machines. A modular system based on a small size SIMD cellular array of 1-bit processing elements has been developed with this goal in mind and it is now evaluated against the Abingdon Cross Benchmark specifications. The benchmark tests the combination of algorithms and architecture and generates a quality factor expressed as the ratio of the image lateral size and the processing time. The examined machine supports an efficient means to automatically partition, process and reconstruct images larger than the array size. The authors briefly describe the system, discuss the selected algorithms and present performance results and estimates for several system configurations.
van de Groenendaal, JG & Braun, RM 1970, 'Rural communications in multi-path channels: Spread spectrum applications', 1993 IEEE South African Symposium on Communications and Signal Processing, 1993 IEEE South African Symposium on Communications and Signal Processing, IEEE, pp. 167-172.
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© 1993 IEEE. All radio communications occur in channels that have definite multipath characteristics. Two effects that are predominant in such a model, depending on the delay relative to the bit period, are Inter Symbol Interference (ISI) and fading. In this paper ISI is investigated in greater detail and the theoretical error performance for BPSK in a multi-path channel is derived. It is also shown how spread spectrum improves the error performance of BPSK without a "rake" receiver in such an environment and the selection of parameters of spread spectrum to maximize error performance is briefly discussed.
Veitch, D 1970, 'Novel models of broadband traffic', IEEE Global Telecommunications Conference, IEEE, pp. 1057-1061.
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We provide models which are capable of describing the long term correlations and self similar burstiness structure found in recent measurements of packet networks and VBR video. Two families of `fractal' arrival processes are presented which capture these features extremely compactly. We show the equivalence of one of these to processes with unsummable auto-correlation functions used recently to describe long term correlation and burstiness. Our approach however has advantages. The other (1 parameter) family generates burstiness on all time scales. It shows how blocking can occur even for arrival streams with zero arrival rate. This illustrates how parameters describing scaling of burstiness and correlation must replace useless long terms averages.
