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Proceedings of the Institution of Electrical Engineers

Volume 117, Issue 11, November 1970

Volumes & issues:

Volume 117, Issue 11

November 1970

Periodic coupling of waveguide modes
  • Author(s): A.L. Cullen  and  O.J. Davies
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 117, Issue 11, p. 2061 –2068
  • DOI:  10.1049/piee.1970.0371
  • Type: Article
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  • p. 2061 –2068 (8)
    When two waveguide modes are coupled uniformly along the direction of propagation, power is partially transferred from one mode to the other. This transfer is only complete if the phase velocities of the modes are equal. If the phase velocities differ, complete transfer of power is still possible if a certain spatially periodic coupling is provided. The exact conditions for complete transfer for a square-wave and raised-square-wave coupling function are derived. To illustrate the theory, experimental results for coupling between the TE10 and TE20 modes in an overmoded X band guide are presented. Experimental results for a sinusoidal function are also presented. These results provide strong support for the theory of periodic-mode coupling.
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Ferrite-core unit as combined memory and line scanner in electronic telephone exchanges
  • Author(s): D. Spektor ; M. Yoeli ; J. Ben Uri
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 117, Issue 11, p. 2070 –2072
  • DOI:  10.1049/piee.1970.0372
  • Type: Article
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  • p. 2070 –2072 (3)
    The paper describes a ferrite-core unit serving both as memory and line scanner in a 64-subscriber electronic telephone exchange used as a p.a.x. (private automatic exchange). This dual function is realised by ferrite cores with a rectangular hysteresis loop, using working points different from those of conventional computer core memories and determined by m.m.f.s produced by currents in the appropriate windings. The cores are arranged in a square matrix and are scanned by a ‘linear-selection’ mode. A special bridge amplifier, with logic-controlled switches in its four arms and the reading winding at its centre, permits the reading currents to be directed as required by actuating a pair of opposite arms.
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Combined delay- and loss-queuing system
Expansion of public mobile-radiotelephone service in Newfoundland, Canada
Clock synchronisation for mobile radiotelephony
  • Author(s): P.A. Wing
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 117, Issue 11, p. 2093 –2094
  • DOI:  10.1049/piee.1970.0375
  • Type: Article
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  • p. 2093 –2094 (2)
    The case for the use of pulse-code modulation for radiotelephony is summarised. The nature of the problem of achieving clock synchronisation for a time-division-multiplexed/pulse-code-modulation system with mobile terminals is discussed. The problem is first shown to be soluble under the ideal (noiseless) conditions of a perfectly synchronised slave-clock system. Noise in the system has two deleterious effects. It may cause two mark indications to be fed into the system where only one exists, this effect can be eliminated by circuitry arrangements. It may also cause a mark indication to vary its position in the time frame from frame to frame, this effect can be overcome by a clock-phase reversal at a mobile terminal. The parameters used in an experimental system are included as an Appendix to the complete paper.
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Theoretical methods for computing characteristics of Wullenweber antennas
  • Author(s): M.T. Ma ; M.T. Ma ; L.C. Walters
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 117, Issue 11, p. 2095 –2101
  • DOI:  10.1049/piee.1970.0376
  • Type: Article
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  • p. 2095 –2101 (7)
    A theoretical method is formulated for calculating input and mutual impedances, total field radiated, and power gain of a Wullenweber antenna above a lossy flat earth. The Wullenweber antenna considered here is essentially an array of two concentric rings of discrete elements. Each ring is placed in front of a concentric screen. The inner ring is designed to operate at 3–10MHz, and the outer ring at 8–32 MHz. The radiator used for the highband ring is a sleeve antenna, and that for the lowband ring is a 3-wire folded monopole. Numerical results are given as a function of frequency, ground constants, elevation and azimuth angles with a specified set of element and array dimensions.
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Radio propagation at 84.125MHz: measurements with mobile receivers and in the presence of aircraft
  • Author(s): R.B. Herman ; R.B. Herman ; F.G. Jenks ; P.N. Clarkson ; N.E. Broadberry
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 117, Issue 11, p. 2102 –2104
  • DOI:  10.1049/piee.1970.0377
  • Type: Article
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  • p. 2102 –2104 (3)
    The paper is concerned with an investigation of the propagation characteristics relevant to the operation of digital v.h.f. radiocommunication systems with mobile terminals. Appreciable information already exists regarding the statistics of signal-strength distribution as a function of range and aerial heights. However, comparatively little information can be found concerning the signal distortions likely to be produced by multipath propagation, by operation with a moving terminal, or by signal reflections from aircraft. Such information is required in order to assess the relative merits of different modulation and multiplexing methods and to permit prediction of performance against range. The digit rates of primary interest were about 20k bit/s, 150 bit/s and 75 bit/s. The complete paper describes relevant details of the equipment, an investigation of propagation characteristics with the receiving terminal in a moving vehicle, an investigation of the effects of aircraft reflections, and the possibilities of application of the propagation results to the design of digital transmission systems.
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Crosscoupled transistor mixer
Active RC synthesis of transfer function with adjustable coefficients
  • Author(s): N. Fujii
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 117, Issue 11, p. 2109 –2114
  • DOI:  10.1049/piee.1970.0379
  • Type: Article
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  • p. 2109 –2114 (6)
    RC active filters have been constructed using various kinds of active elements, such as negative-impedance convertors, gyrators and amplifiers. The paper shows a new synthesis method which can independently control the coefficients of both numerator and denominator of a transfer function of nth degree. The conventional method which has the above ability needs many integrators, but the proposed circuit contains only amplifiers of finite gain and an RC multiport network. First, the synthesis method of an RC multiport network, which is necessary to fulfil the above condition, and the circuit configuration using feedback and feedforward techniques, are given. We then apply the method to biquadratic transfer functions. The results show that, in view of the sensitivities and the number and values of the elements, it is desirable to construct the function in a cascade of biquadratic functions rather than to construct the whole function in one circuit. As an example, the 4th-degree lowpass filter with one attenuation pole is synthetised, and experimental results show quite good agreement with the theory. The filters designed by this method are intended for use as controlled equalisers in communication systems, speech synthetisers etc.
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Selection of intermodulation-free frequencies for multiple-channel mobile radio systems
Autocorrelation threshold-extension f.m. demodulator
Power-system load scheduling with security constraints using dual linear programming
  • Author(s): C.M. Shen  and  M.A. Laughton
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 117, Issue 11, p. 2117 –2127
  • DOI:  10.1049/piee.1970.0382
  • Type: Article
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  • p. 2117 –2127 (11)
    The optimisation of power-system operating conditions is formulated as a dual linear programming problem. This suboptimal model allows fast solutions to be obtained dependably by applying the revised simplex l.p. method to the problem of minimising total generation costs subject to the constraints imposed. These constraints include the network equations, the inequalities restricting generator loading, runningspare capacity and transmission-line loading under normal and outage conditions. The fast speed of solution and low computer-storage requirements result from the reduced mathematical model developed by means of the variable eleimination and the computing strategy used. The computational procedure automatically adjusts the size of the problem to be solved according to indications obtained of the likely critical lineoutage security constraints, a small number in relation to the prohibitively large number of possible outage constraints. A sample application of the method is given for a 2700MW, 275/132kV system of 23 busbars, 30 lines and transformers, supplied by 24 generators. Using ALGOL 60 on the Atlas computer, solutions were obtained in 5s neglecting line-outage security, and 11.5s including security under all possible single-line-outage conditions. For accuracy, comparisons are also made with the network-flow technique and the full nonlinear programming solutions.
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Discussion on “Performance requirements and test methods for high-voltage a.c.-motor insulation”
Discussion on “Gas-turbine plant for peak-load generation and synchronous compensation”
New possibilities in amplitude- and phase-comparison techniques for distance relays
  • Author(s): H.P. Khincha ; K. Parthasarathy ; B.S. Ashok Kumar ; C.G. Arun
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 117, Issue 11, p. 2133 –2141
  • DOI:  10.1049/piee.1970.0385
  • Type: Article
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  • p. 2133 –2141 (9)
    The paper reports further work on the amplitude-comparison technique described by the same authors in a previous paper. This technique is extended to develop improved polar characteristics. Discontinuous polar characteristics, like directional parallelograms, are obtained by a single measuring gate with a simple mode of relay circuitry, whereas two measuring gates are required to provide a directional-quadrilateral characteristic of potentially general application. The paper also describes some new possibilities in phase-comparison methods for distance-protection schemes. Comparator models which effect the amplitude and phase comparison of the relaying signals are described in their schematic form. A comprehensive theoretical basis for comparison is also presented.
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Eddy-current losses in reactor flux shields
  • Author(s): I. Woolley
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 117, Issue 11, p. 2142 –2150
  • DOI:  10.1049/piee.1970.0386
  • Type: Article
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  • p. 2142 –2150 (9)
    The magnetic-field distribution is analysed for the case of an aluminium plate excited by a circular current loop, and an expression for the eddy-current loss in the plate is deduced. This analysis is tested by comparison with measurements on a model which closely resembles the theoretical geometry, and the results are shown to be in close agreement. A method for measuring the eddy-current losses in plates is described. It is found that the losses in thin plates can be abnormally high. It is shown that the image theory may be used with nonmagnetic conducting plates for all plate thicknesses greater than 0.8 times the characteristic depth of flux penetration in the material. The magnetic field of large air-cored reactors is analysed, and expressions are obtained for the inductance and the loss in the flux shields. It is believed that this method is capable of giving more accurate results than have been hitherto obtained.
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Digital simulation of a fullwave single-phase convertor system
  • Author(s): R.S. Ramshaw  and  K.R. Padiyar
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 117, Issue 11, p. 2151 –2158
  • DOI:  10.1049/piee.1970.0387
  • Type: Article
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  • p. 2151 –2158 (8)
    Steady-state analysis of rectifier systems has been described in the previous literature. However, there is little information available on transient analysis. A transient analysis of a convertor system (to supply reversible direct current) is described here, and the solution is given in a recursive form. The analysis is shown to be easily amenable to digital simulation in order to obtain a fast and accurate solution. The analysis is done first considering an ideal a.c. source, and then by taking the source impedance into account. An example has been worked out to illustrate the method, and the results are shown. It is possible to extend this analysis for a more complicated convertor system including the control variables.
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Discussion on “Induction-excited alternator”
Corrigendum: Self-cascaded machine: a low-speed motor or high-frequency brushless alternator
Corrigendum: Magnetic skin effects in medium-frequency machines
Simple formulas for voltage-regulator gains for best alternator stability
Calculation of the angular back-swing following a short circuit of a loaded alternator
Transient equivalent circuit of the divided-winding-rotor synchronous machine
Real-time hybrid simulation of an adaptive-control technique
  • Author(s): D.J. Sandoz  and  B.H. Swanick
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 117, Issue 11, p. 2165 –2173
  • DOI:  10.1049/piee.1970.0394
  • Type: Article
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  • p. 2165 –2173 (9)
    The paper describes the simulation of an adaptive scheme based on least-squares methods, incorporating a hybrid computer. The analogue computer simulates the process dynamics, while the online digital machine effects the adaptive control via a.d.c. and d.a.c. interfaces. The scheme is shown to be realistic, and to have application to relatively fast-responding systems. The process is repeatedly identified as a series of quasilinear systems. Derived process parameters continuously update a suboptimal-feedback-control law. This control law, valid for a discrete-time environment, is shown to have application in continuous time. In addition, a novel approach to the problem of inaccessible states is investigated.
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Corrigendum: Theoretical analysis of harmonic instability in a.c.-d.c. converters
Describing-function series: a new means for nonlinear-control-system analysis
  • Author(s): Dan Teodorescu
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 117, Issue 11, p. 2175 –2180
  • DOI:  10.1049/piee.1970.0396
  • Type: Article
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  • p. 2175 –2180 (6)
    The general expressions of the describing-function series are determined. These are valid for any single-valued nonlinearities, both asymmetrical and symmetrical, continuous or discontinuous, as well as for combined continuous-discontinuous nonlinearities. The main characteristics of this means of calculation for nonlinear automatic systems are examined and compared with the conventional describing functions. Thus it is shown that, unlike the describing functions, which become imaginary on some parts of the nonlinearities, the describing-function series express the equivalent gain of the nonlinear element over the whole domain. Thus the describing-function series allow a decomposition of the complicated nonlinearities into simple nonlinearities, the series expansion coefficients of which can be found in tables. The expressions for these coefficients are established, forming a table with six primary nonlinearities, from which an extremely large number of nonlinearities can be calculated. The characteristics obtained through describing functions for particular nonlinearities are also compared with those obtained by means of describing-function series.
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Electrostatic field and potential of a supported sphere-plane system inside an earthed chamber
  • Author(s): M.A. Shallal  and  J.A. Harrison
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 117, Issue 11, p. 2181 –2184
  • DOI:  10.1049/piee.1970.0397
  • Type: Article
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  • p. 2181 –2184 (4)
    The electrostatic field and potential of a supported sphere-plane electrode system placed inside a chamber are calculated from solutions of Laplace's equation using the extrapolated Liebmann method with the help of a digital computer. Calculations are made for gap/radius ratios of 1, 0.5 and 0.25, inside chambers of different sizes, and sphere-supporting rods of various dimensions up to a spherically capped cylinder. These calculations show that, in many cases, the electric field on the axis can be calculated using the analytical expression for an isolated sphere-plane system.
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Corrigendum: Use of uniform-field values of Townsend's α to predict current multiplication in nonuniform fields
Measurement of the resistance of physically large earth-electrode systems
  • Author(s): G.F. Tagg
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 117, Issue 11, p. 2185 –2190
  • DOI:  10.1049/piee.1970.0399
  • Type: Article
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  • p. 2185 –2190 (6)
    In two earlier papers, methods were described by which the earth resistances of large electrode systems could be measured. A third method is described in this paper which has one advantage in that it is possible to check the reliability of the results obtained. It is based on the connection between the rate of change of the slope of the earth-resistance curve, and the distance of the potential electrode from the starting-point chosen to measure the distances to the potential and current electrodes. Examples are given of its application, both theoretical and practical, and the effect of nonhomogeneity of the soil is considered.
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Magnetic-domain structure and losses in Goss-textured silicon iron
  • Author(s): J.E.L. Bishop
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 117, Issue 11, p. 2191 –2193
  • DOI:  10.1049/piee.1970.0400
  • Type: Article
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  • p. 2191 –2193 (3)
    A strong positive association between power loss in grain-oriented silicon iron and the percentage of the surface exhibiting fine maze-domain structures has been reported by Daniels. This association appears to conflict with domain-wall theories of anomalous loss, which predict higher losses for larger domain sizes. The present paper, which treats the maze- and slab-domain regions as two magnetic phases of different permeability, shows that Daniels's results can be attributed to the overloading of the higher permeability slab-domain regions, caused by flux bypassing the less permeable maze domains. Thus the losses, though caused by the presence of the maze-domain regions, are actually mainly incurred outside them, and so the conflict with domain-wall theory does not arise.
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Influence of inclusions on domain-wall motion and power loss in oriented electrical steel
  • Author(s): P. Beckley  and  J.E. Thompson
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 117, Issue 11, p. 2194 –2200
  • DOI:  10.1049/piee.1970.0401
  • Type: Article
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  • p. 2194 –2200 (7)
    Domain-wall motion in silicon steel has been studied using the Kerr magneto-optic effect, with a photomultiplier as a detector, in conjunction with an electromagnetic method of assessing the quantity of wall in motion. Low-temperature aging was used as a controlled and reversible source of obstruction to both the easy and uniform motion of the walls. It was found that the hysteresis of wall motion increased as the rate of magnetisation was raised and that the increases in power loss associated with precipitation occurred almost wholly in the ‘hysteresis’ component of loss.
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Cauchy boundary problems in electrostatics
Measurement of skin and proximity effects in circular conductors

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