Electronics & Communication Engineering Journal
Volume 1, Issue 5, September 1989
Volumes & issues:
Volume 1, Issue 5
September 1989
Whither the UK defence R&D establishments?
- Author(s): K.F. Slater
- Source: Electronics & Communication Engineering Journal, Volume 1, Issue 5, page: 194 –194
- DOI: 10.1049/ecej:19890039
- Type: Article
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194
(1)
Book review: The Story of the IERE 1925-1988
- Author(s): D.L.A. Smith
- Source: Electronics & Communication Engineering Journal, Volume 1, Issue 5, page: 195 –195
- DOI: 10.1049/ecej:19890040
- Type: Article
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195
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Anticollision techniques in multirobot environments
- Author(s): N.D. Duffy ; D. Allan ; J.T. Herd
- Source: Electronics & Communication Engineering Journal, Volume 1, Issue 5, p. 196 –204
- DOI: 10.1049/ecej:19890041
- Type: Article
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The use of multiple assembly robots operating in a shared workspace provides the promise of efficient and flexible assembly operations, but greatly increases the potential for catastrophic damage in the event of robot collisions. The paper describes some of the present techniques used for path planning and collision avoidance and discusses the problems involved in applying them to practical robot workcells. A new path-checking system is described which has been designed to operate in real time and to check for collisions between arbitrarily shaped robots and objects in the workspace, and which will speed path planning by acting as a high-speed validation utility.
Measuring the coherence of wideband dispersive channels
- Author(s): S. Salous and L. Khadra
- Source: Electronics & Communication Engineering Journal, Volume 1, Issue 5, p. 205 –209
- DOI: 10.1049/ecej:19890042
- Type: Article
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Ionospheric propagation at HF suffers from dispersion inboth time and frequency. Time dispersion arises from the presence of multipath propagation and limits the bandwidth of the ionospheric channel to a few kilohertz. Frequency dispersion causes phase nonlinearity, which leads to ‘elongation’ of narrow pulses. If multipath propagation can be resolved the coherent band width of the channel will be determined by frequency dispersion. The purpose of the work reported here was to determine the effect of weighting windows, used to reduce the effects of spectral leakage, on the estimation of the coherent bandwidth of wideband HF radio links. A wideband FMCW sounder was used to collect data over a 234 km link in theUnited Kingdom. Analysis of half-megahertz sections of a 5 MHz sweep via the FFT algorithm permitted multipath propagation to be resolved. To estimate pulse distortiondue to frequency dispersion the 6 dB width of the receivedpulse was estimated.
Vertical radiation patterns of HF curtain arrays
- Author(s): K.L. Beeke and R.G. Manton
- Source: Electronics & Communication Engineering Journal, Volume 1, Issue 5, p. 211 –216
- DOI: 10.1049/ecej:19890043
- Type: Article
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211
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The vertical radiation patterns of high-frequency (HF) curtain arrays are both expensive and time-consuming to measure. In addition, by the time the measurements can be made, it is usually too late to make significant changes to the array or its location. The paper describes a method of predicting the pattern over arbitrary ground and gives comparisons between predictions and measurements.
Parallel architectures for real-time control
- Author(s): D.I. Jones
- Source: Electronics & Communication Engineering Journal, Volume 1, Issue 5, p. 217 –223
- DOI: 10.1049/ecej:19890044
- Type: Article
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Parallel processing is currently a subject of widespread interest to computer scientists, but does it hold any benefit for the control engineer? In fact, the computing and control fields are very firmly interlinked and this paper attempts to explain where some of the potential benefits may lie. Present research on parallel architectures for control is reviewed, concentrating in particular on the Inmos transputer. Finally, some future trends in control systems implementation are identified.
Chaos in electric circuits
- Author(s): L.C. Walters
- Source: Electronics & Communication Engineering Journal, Volume 1, Issue 5, p. 223 –224
- DOI: 10.1049/ecej:19890045
- Type: Article
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223
–224
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Our market stall
- Author(s): M.R. Stephenson
- Source: Electronics & Communication Engineering Journal, Volume 1, Issue 5, page: 224 –224
- DOI: 10.1049/ecej:19890046
- Type: Article
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224
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Artificial neural network and conventional approaches to filtering and pattern recognition
- Author(s): P.M. Grant
- Source: Electronics & Communication Engineering Journal, Volume 1, Issue 5, p. 225 –232
- DOI: 10.1049/ecej:19890047
- Type: Article
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Two approaches to the design of artificial neural networks—the associative memory and multilayer perceptron—are discussed. In particular, the use of nonlinear processing is investigated and the application of these structures to pattern recognition and recall is examined in the context of the conventional matched-filter detection operation, which is widely used in communications systems. One specific application, that of channel equalisation, is examined for the multilayer perceptron, which is shown to offer a performance advantage over conventional linear filter-based equalisers.
Ionospheric probing with an HF radar
- Author(s): M.L. Lees and R.M. Thomas
- Source: Electronics & Communication Engineering Journal, Volume 1, Issue 5, p. 233 –240
- DOI: 10.1049/ecej:19890048
- Type: Article
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The Jindalee over-the-horizon (OTH) radar is designed primarily for extended air defence surveillance of Australia's northern coastline. It achieves its long-range capability by employing ionospheric reflection. This use of the ionosphere allows the radar to have a powerful secondary role in remote sensing because information about the ionosphere can be made available as a byproduct of radar operations. Information about the ionosphere can be estimated for each radar resolution cell in range and azimuth. This information is updated each time the radar scans. The paper describes some of the remote-sensing capabilities of the Jindalee radar and presents some results concerning TIDs (travelling ionospheric disturbances), effects of the dawn terminator passage, geographic variations of ionisation density and meteor backscatter.
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