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Volume 120
Issue 10
Proceedings of the Institution of Electrical Engineers
Volume 120, Issue 10, October 1973
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Volume 120 (1973)

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Volume 120, Issue 10
October 1973
Optimisation of planar aerial arrays for lowest sidelobe level
 Author(s): P.W. James
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1193 –1199
 DOI: 10.1049/piee.1973.0243
 Type: Article
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The paper presents a new method of designing a planar array of discrete elements with respect to the array response in its own plane. Once the beamwidth is specified (using two parameters), the method seeks the set of amplitudes and phases which minimises the sidelobe level. The array elements can have any position, and can have any directional responses of their own, either theoretical or experimental. The procedure is essentially a constrainedgradient search, and uses linear programming at each iteration. As an example, results for a circular array are presented for a range of parameters.
Sun as a broadband source for tropospheric attenuation measurements at millimetre wavelengths
 Author(s): D.L. Croom
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1200 –1206
 DOI: 10.1049/piee.1973.0244
 Type: Article
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The Sun can be used as a broadband extraterrestrial source of centimetre and millimetrewavelength radiation for longterm monitoring of tropospheric attenuation along groundtospace paths. In interpreting these data, it is, however, necessary to take into account the variations in intensity of the source and also its changing position in the sky. Possible effects on the attenuation statistics due to the continuously changing position of the Sun, both diurnally and annually, are considered. Provided that care is taken in the interpretation of the data, the Sun provides a useful, and considerably cheaper, alternative to satelliteborne sources, and it is capable of yielding much of the information that can be obtained from the latter, with the exception of phase data. It has the additional advantage of being usable over a very wide frequency range.
Resonance transmission technique for the measurement of high dielectric permittivities
 Author(s): A.J. Pointon and K.F. Woodman
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1207 –1211
 DOI: 10.1049/piee.1973.0245
 Type: Article
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The difficulties of measurement at microwave frequencies of high dielectric permittivities, such as occur in ferroelectric materials, are discussed, as also are the difficulties of measurement of the dielectric loss tangents which are generally associated with these materials. A method is described which, based on the resonance transmission of a dielectric specimen in a tranmission line, has enabled permittivities of 10 000 ε_{0} and values of tan δ of 0.25 to be measured over the microwave frequency ranges from u.h.f. to X band.
Lowpower semiconductor memory cell
 Author(s): D.J. Kinniment
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1212 –1215
 DOI: 10.1049/piee.1973.0246
 Type: Article
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Because of its low power dissipation and small area, the dynamic semiconductor randomaccess memory cell is currently becoming widely used in computer mainmemory applications. This paper describes an alternative bipolar memory cell which uses the small area and high yield obtainable with the collectordiffusion isolation process, without the disadvantages of the refresh requirement of dynamic memories. A ratio of 15:1 in power dissipation between the selected and the unselected state allows a large number of storage cells on a single silicon chip, while retaining a relatively fast cycle time.
Electronbeam distortion in the region of a klystron gap
 Author(s): A.H. Falkner
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1216 –1218
 DOI: 10.1049/piee.1973.0247
 Type: Article
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Some klystrons incorporate a very dense magnetically focused electron beam. Such a beam is distorted in the region of each tunnel gap by the local changes in the electricfield pattern. The effect has been evaluated in a way allowing its magnitude to be found in any particular case by reference to a set of graphs. The solution includes the effect in the tunnel near the gap and considers both radial motion and axial velocity reduction. The results can be applied to annular and solid beams. The distortion is shown to be small in practical cases, but it does not follow that the overall effects are small.
Attenuation/frequency characteristics of braided coaxial cables at microwave frequencies
 Author(s): R.J. Teperek and F.A. Benson
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1219 –1225
 DOI: 10.1049/piee.1973.0248
 Type: Article
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Investigations to determine losses in braided and solid outerjacketed coaxial cables at microwave frequencies are described. Results of measurements of attenuation in the frequency range 2–40 GHz are given for some specially prepared cables to show the effect of variation the braid parameters, braidwire material, braidwire diameter and lay length. An experimental study is reported which indicates the contribution of leakage of radiation through the braid to the total cable loss. A theoretical explanation for the braiding effects noticed during the study is included, and the experimental results are compared with the theoretical predictions.
New method for frequency stabilisation of transistor multivibrator
 Author(s): D.D. Damljanović
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1226 –1227
 DOI: 10.1049/piee.1973.0249
 Type: Article
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An efficient and practical method is presented for reducing the effects of changes in temperature or supply voltage on the frequency of transistor astable multivibrators. The method is based on the use of diodes and the associated control of the time constants in the feedback paths.
Performance of recursive digital movingtargetindicator radar filters with Butterworth frequency response
 Author(s): S.S. Haykin and J.F. Boulter
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1227 –1229
 DOI: 10.1049/piee.1973.0250
 Type: Article
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Angular and temporal variations in the radar crosssections of insects
 Author(s): J.R. Riley
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1229 –1232
 DOI: 10.1049/piee.1973.0251
 Type: Article
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Stability of a d.c. transmission link between strong a.c. systems
 Author(s): J.P. SucenaPaiva and L.L. Freris
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1233 –1242
 DOI: 10.1049/piee.1973.0252
 Type: Article
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The paper is concerned with the steadystate stability of and h.v.d.c. transmission line linking two strong a.c. networks. The conventional individualphase pulsing system is considered as no voltageloop instability is liable to occur under these conditions. A linearised discrete model of the rectifier is used and a model for the invertor under constantextinctionangle control is developed along the same lines. A rigorous and an approximate lumped representation of the d.c. line are considered in turn. Discretedatasystems theory, namely the ztransformation in conjunction with frequencyresponse techniques, is employed in the stability study of the system. The resulting complex transfer functions are evaluated by a digital computer. The calculated stability boundary is in good agreement with test results from an h.v.d.c. simulator. The pioneering study by Busemann of h.v.d.c. system stability in which the rectifier is represented by a constant gain, and the commutation angle as well as the sampling action of the convertors are neglected is shown to be inadequate. In fact, it is shown that all these neglected items profoundly affect the frequency of oscillations and the stability boundaries. It is also shown that the phase difference between the two a.c. networks has negligible effect on the stability of the system.
Design and analysis of closeratio twospeed shadedpole induction motors
 Author(s): J.F. Eastham and S. Willamson
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1243 –1249
 DOI: 10.1049/piee.1973.0253
 Type: Article
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The paper shows how the technique of stepphase modulation can be used to obtain a twospeed shadedpole induction motor. An analysis is presented that allows prediction of the performance of such a machine, and the validity of the analysis is verified by the experimental work presented. A simple technique of design, based on a numericaloptimisation routine, is introduced, and an improved design is theoretically compared with the original, using the above analysis.
Performance of a 5 kVA synchronous generator with an optimal excitation regulator
 Author(s): J.P. Bartlett ; M.J. Gibbard ; J.L. Woodward
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1250 –1256
 DOI: 10.1049/piee.1973.0254
 Type: Article
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The feasibility of applying optimal control to the excitation of a synchronous generator is examined in the laboratory, using a 5 kVA 3phase alternator connected through line reactors to an infinite busbar. The regulator is a small digital computer, which monitors the states of the system and computes the control signal applied to an electronic amplifier exciting the alternator field. The feedback gains of the optimal regulator satisfy a simple quadratic cost function. These are calculated offline for a grid of operating points in the complex power plane, and stored in the controlling computer. The gains used at any particular operating point are those corresponding to the nearest gridpoint. Comparisons of predicted and actual smalldisturbance responses are made for leadingpowerfactor operation well beyond the openloop stability limit, and, for low real power, beyond the closedloop limit with voltage feedback alone.
Discussion on “Feasibility of turbogenerator with superconducting rotor and conventional stator”
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1256 –1259
 DOI: 10.1049/piee.1973.0255
 Type: Article
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Voltage surges induced on overhead lines by lightning strokes
 Author(s): C. Singarajah and Pritindra Chowdhuri
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1259 –1260
 DOI: 10.1049/piee.1973.0256
 Type: Article
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p.
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Erratum: Calculation of the external thermal resistance of buried cables through conformal transformation
 Author(s): G. Luoni ; A. Morello ; H.W. Holdup
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, page: 1260 –1260
 DOI: 10.1049/piee.1973.0257
 Type: Article
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Spectral estimator for dynamictest data from turbineblade vibrations
 Author(s): J.M. Nightingale and T.S. Durrani
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1261 –1266
 DOI: 10.1049/piee.1973.0258
 Type: Article
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This paper presents an analysis of the distribution of occurrence times for pulse trains which can arise in the measurement of turbineblade vibrations. The problem arises where a proximity probe, mounted in the casing, detects the passing of a rotorblade tip and generates a pulse. Since the pulse timing depends on the magnitude of the blade vibration an irregular distribution of time intervals arises, and here the properties of the pulseoccurrence distribution are related to the bladevibration statistics. In particular, a spectral estimator is considered and its errors are evaluated. The analysis provides a solution to a general problem in the estimation of the powerspectraldensity function of a Gaussian process from observations of crossings at an arbitrary barrier.
Digitalcomputer control of vehicles in an automated transportation system
 Author(s): A.F. Rumsey and E.T. Powner
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1267 –1272
 DOI: 10.1049/piee.1973.0259
 Type: Article
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In recent years considerable interest has been focused on the possibility of introducing some form of automatic vehicle control as a means of easing congestion in densely populated urban areas. Automatic control enables vehicles to operate safely at high speeds and with small headways, and hence results in increased system capacity. In this paper the authors consider how vehicles in an automated network can be controlled electronically using an online digital computer. A ‘cellfollowing’ control philosophy is assumed and the problem of controlling vehicles on a mainline guideway is modelled as a linearstate regulator problem in discretetime form. The resulting optimalcontrol law is found to be stationary, independent of initial conditions and capable of yielding good vehicleresponse characteristics. Finally the authors show how the system model can be extended to cater for the problem of merging vehicles from an offline station onto the mainline guideway. In this case the optimalcontrol law is shown to be no longer time invariant but can again be precomputed for a given set of initial conditions.
Trajectorysensitivity design of loadfrequency control systems
 Author(s): N.G. Malek ; O.T. Tan ; P.M. Julich ; E.C. Tacker
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1273 –1277
 DOI: 10.1049/piee.1973.0260
 Type: Article
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A method is described for limiting the trajectory dispersion of a loadfrequency control system due to parameter variations with a controller subject to structure constant. The parameter variations are assumed to be small, so that linear sensitivity equations are obtained for the trajectorysensitivity function. The desensitisation problem is then formulated as a suboptimalcontrol problem with a specified feedback structure and a quadratic performance index which also includes the trajectorysensitivity function. The controller gain minimising the cost function is determined by iterative application of an algorithm for parameter optimisation based on averaging the performance criterion. Applied to a 2area system, the design procedure is shown to produce a loadfrequency control system with a trajectory sensitivity to the varyingincrementalspeedregulation parameter greatly reduced compared with that of the corresponding suboptimalcontrol system designed without sensitivity considerations, while maintaining a satisfactory performance.
Generation of signals with specified statistics
 Author(s): J.L. Douce and P.W. Davall
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1278 –1282
 DOI: 10.1049/piee.1973.0261
 Type: Article
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The paper describes one technique for generating a random or pseudorandom signal with an amplitudeprobability function and powerspectraldensity function approximating to specified functions. Some limitations of the technique are given and some results are presented.
Numerical method for the design of insensitive control systems
 Author(s): C.S. Berger
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1283 –1292
 DOI: 10.1049/piee.1973.0262
 Type: Article
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A design method has been developed that enables the designer to satisfy random and transient specifications for linear plant, subject to parameter variations. The controller structure is determined by the designer, who can thus incorporate specific features such as integral control. The method uses efficient numerical procedures. Controllers are designed for fairly large superheater problems. It is shown that insensitivity to plant parameter changes can be obtained with very little loss in nominal performance. Computational details of the method are discussed.
Effects of nonlinearities on the measurement of weighting functions by crosscorrelation using pseudorandom signals
 Author(s): H.A. Barker and S.N. Obidegwu
 Source: Proceedings of the Institution of Electrical Engineers, Volume 120, Issue 10, p. 1293 –1300
 DOI: 10.1049/piee.1973.0263
 Type: Article
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p.
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In this paper, expressions are obtained for the errors introduced into the estimate of a system weighting function obtained by crosscorrelation when nonlinearities that may be described by a Volterra functional series are present. Explicit results are given for systems with secondand thirdorder nonlinearities, tested by pseudorandom signals derived from binary and ternary m sequences. It is shown that the principal errors are of two distinct types: a systematic error that is the same for all pseudorandom signals of a common type, and an unsystematic error that depends on relationships between members of the m sequence from which the pseudorandom signal is derived. The unsystematic error may be removed from a range of interest extending over the settling time of the system by an appropriate choice of test signal, and those pseudorandom signals most suitable for this purpose are identified. An example is used both to illustrate and to validate the results obtained.
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