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Proceedings of the Institution of Electrical Engineers

Volume 113, Issue 11, November 1966

Volumes & issues:

Volume 113, Issue 11

November 1966

Advances in microwave direction finding
  • Author(s): D.G. Kiely
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1697 –1711
  • DOI:  10.1049/piee.1966.0295
  • Type: Article
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  • p. 1697 –1711 (15)
    The purpose of the paper is to describe three new microwave direction-finding (d.f.) systems employing the principle of amplitude comparison. Though designed, in this case, for use with pulse signals, application of the systems could also be extended to continuous-wave signals. Theoretical predictions of performance and considerations of design requirements are supported by experimental confirmation from complete laboratory models of two of the systems, and from measurements on certain component parts of the third system. The systems are individually suitable for different types of application, and collectively they represent advances in increasing bearing accuracy and system sensitivity, and in reducing equipment bulk and cost, without degrading broadband frequency coverage. The first system employs a switching and storage technique which enables a single, preferably a tunable narrowband, receiver to be used with four (or more) fixed aerials, thereby saving three (or more) receivers, which would otherwise need to be used for amplitude-comparison d.f. The switch rate is relatively slow, so that a few cycles are accomplished within the time that the transmitting aerial illuminates the d.f. site. The second system employs a modulation-marking technique to achieve the same objects as the first system. Its operation is continuous in time, as opposed to that of the first system, which is cyclic, and so it is capable of employment with signals of duration short compared with the cycle period of the first system. The third system employs very fast (intrapulse) switching of a pair of receivers around a fixed circular array of sixteen aerials. Theoretically, it is capable of high-accuracy d.f. on a pulse-by-pulse basis, since the larger number of aerials in the array reduces the aerial contribution to d.f. errors, which is usually dominant. Its d.f. performance is also dependent on the amplitude balance (tracking) of either radio-frequency switches or frequency changers, which, at present, may be the factor limiting d.f. accuracy.
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Use of Mills cross receiving arrays in radar systems
  • Author(s): B.R. Slattery
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1712 –1722
  • DOI:  10.1049/piee.1966.0296
  • Type: Article
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  • p. 1712 –1722 (11)
    The use of Mills cross arrays has been found to be an important contribution to radio astronomy, where accurate angular resolution in azimuth and elevation can be achieved without prohibitive costs. An analysis is made of methods for applying a Mills cross array to radar. Such an array could consist of two linear arrays positioned at right angles to each other. The arrays have fan-shaped directivity patterns, which are swept across a given sector at different rates. The result is to provide the intersection of the two beams with a raster sweep. A receiving array has been constructed to demonstrate the essential difficulties of processing radar-echo signals. Mathematical analysis gives the output of an array correlator in the form of probability density functions, assuming certain characteristis of the target signals. The calculations are extended to the performance of pulse-to-pulse integrators. On a basis of detection probability and false-alarm rate, a correlator cross array is compared with an additive array, and it is shown that, in the case of a single target, the correlation technique may be preferable. It is concluded that there can be a limited application of such techniques, depending on target density and the nature of interfering signals.
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Instrument for rapid measurement of surface deformations of a 210ft radio telescope
  • Author(s): M.J. Puttock  and  H.C. Minnett
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1723 –1730
  • DOI:  10.1049/piee.1966.0297
  • Type: Article
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  • p. 1723 –1730 (8)
    A description is given of an instrument designed for the rapid measurement of the surface deformations of the 210ft (64 m) radio telescope at Parkes, Australia. The method is based on the measurement, from the vertex, of small differences in the angular positions of targets, fixed to the dish surface, at known radial distances. The results are recorded photographically for later analysis. It is shown that the instrument, in conjunction with auxiliary attachments, can measure the dish shape with errors not exceeding 1.2mm at the zenith, and deformation due to tilting of the telescope with errors generally not exceeding 1.5mm at a zenithal angle of 60°. A complete survey of the dish at any zenithal angle can be made in 9–13h. Measurements with the equipment also permit the radio axis of the dish, computed from the measured feed position and geometrical dish axis, to be related to the ‘vertical’ of the telescope (defined as the mean normal to the azimuthal track).
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Experimental studies of sea-surface effects on low-angle radars
  • Author(s): I.M. Hunter  and  T.B.A. Senior
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1731 –1740
  • DOI:  10.1049/piee.1966.0298
  • Type: Article
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  • p. 1731 –1740 (10)
    This paper presents results of measurements made during the years 1953–56 on the effects of sea-surface reflections on low-angle radars at Xband frequencies. The work was done in three parts and comprised a study of the polarisation properties of sea clutter as a function of sea state, wind direction and incidence angle, a study of the position and depth of interference minima close to the sea surface and a study of the reflecting properties of the sea over a wide range of incidence angles, in so far as these affect the properties of a possible image target. The sea-clutter measurements yielded a well marked polarisation pattern, but the effect of incidence angle did not conform to the conventional linear theory. The interference minima were located close to the positions predicted by the 4/3-earth theory when the aircraft flew at heights of 400ft or more. At lower altitudes, however, the range of the horizon and of the farthest minima considerably exceeded the theoretical values. The peak voltage-reflection coefficients over a range of angles between 1° and 40° relative to glancing incidence very seldom exceeded 0.3 for vertical polarisation and 0.6 for horizontal polarisation. Brewster-angle behaviour was clearly visible for all sea states, and the horizontally polarised reflection was always dominant. In all the results, features were observed for which no theoretical explanations are apparent.
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Propagation of radio waves in a model nonuniform terrestrial waveguide
  • Author(s): E. Bahar
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1741 –1750
  • DOI:  10.1049/piee.1966.0299
  • Type: Article
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  • p. 1741 –1750 (10)
    The paper deals with propagation of radio waves in multimode waveguides of arbitrary height. In this work the boundaries are assumed to be perfectly reflecting. For the case when the height of the multimode waveguide increases monotonically in the direction of propagation, the required solution is obtained by a generalised quasioptical approach which assumes that the waveguide consists of an infinity of infinitesimal radial waveguides cascaded together. To extend the solution for both directions of propagation, the reciprocity theorem has been employed, thereby accounting for reflections. The results have been applied to the study of v.l.f. radio propagation when the effective height of reflection at the ionosphere varies along the path of propagation. Laboratory measurements obtained from a two-dimensional microwave model are compared with the theoretical solution to substantiate the analysis.
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Design of bidirectional coherent counters
F.E.T. high-frequency analysis
  • Author(s): B. Reddy  and  F.N. Trofimenkoff
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1755 –1762
  • DOI:  10.1049/piee.1966.0301
  • Type: Article
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  • p. 1755 –1762 (8)
    The equations describing the small-signal sinusoidal operation of the ‘intrinsic’ field-effect transistor are derived from a consideration of the basic physical principles of the operation of the device. Expressions for the small-signal short-circuit parameters in series form are obtained. Truncated forms of these series are used to compute the elements of a convenient equivalent circuit. The dependence of the computed equivalent-circuit elements on bias voltages is presented. An indication of the frequency at which the equivalent circuit derived from the truncated series for the admittance parameters becomes inaccurate is obtained by considering higher-order terms. Finally, consideration is given to ‘extrinsic’ equivalent-circuit elements, and a convenient form of the complete equivalent circuit is presented.
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Generation of high-speed waveforms using nonlinear delay lines
  • Author(s): A.R. Owens  and  G. White
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1763 –1768
  • DOI:  10.1049/piee.1966.0302
  • Type: Article
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  • p. 1763 –1768 (6)
    In nonlinear delay lines employing back biased p-n junctions as variable capacitors, the velocity of propagation is a function of signal amplitude. This effect may be used to produce short-risetime pulses which may be of high repetition rate. Two circuit applications are discussed, these being the processing of sinewaves to produce fast-edge triangular pulses, and also the processing of long-risetime pulses to produce short-risetime pulses. The analysis employed is in the time domain, and stems from linear delay-line theory, relying upon certain qualifications and restrictions being imposed when applied to nonlinear delay lines. This approach produces good agreement with experimental results. The questions of ‘ringing’ and overshoot are discussed in some detail, and design criteria are obtained for eliminating these undesirable features from delay lines.
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Synchronised oscillatory systems with nonuniform gain in the feedback loop
Direct synchronisation of a sinewave oscillator to a pulse
  • Author(s): B. Moorhouse
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1775 –1782
  • DOI:  10.1049/piee.1966.0304
  • Type: Article
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  • p. 1775 –1782 (8)
    An analysis is given of the phenomenon of direct synchronisation of a sinewave oscillator to a rectangular pulse. The effect of an applied step function is investigated first, and the pulse is then considered as the application of a step, followed by its removal. By considering the action of the nth pulse in an applied pulse train, expressions are derived for most of the important effects, in terms of pulse size and frequency difference, both inside and outside the synchronising band. These include the synchronising bandwidth, the phase while synchronised, the form of the transient after application of the first pulse, beats and pulling effects just outside the synchronising band, and the waveform of the beats. The case in which the sinewave frequency is close to a large harmonic of the p.r.f. is also considered.
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General formula for power spectra of digital f.m. signals
Mode nomenclature for helix waveguide
Comparison of Herbst and Horowitz polynomial decompositions in RC active filter synthesis
Calculation of the magnetic field of rotating machines. Part 5: Field in the end region of turbogenerators and the eddy-current loss in the end plates of stator cores
  • Author(s): R.L. Stoll  and  P. Hammond
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1793 –1804
  • DOI:  10.1049/piee.1966.0308
  • Type: Article
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  • p. 1793 –1804 (12)
    A method of calculating the magnetic field in the end region of a turbogenerator is described. Allowance is made for nonmagnetic stator-core clamping plates and for the magnetic shaft and casing of the machine. The effect of a magnetic rotor-retaining ring is studied, the ring being regarded as a tube of finite permeability separating the stator and rotor end windings. Calculations are compared with experimental results. The field calculated at the surface of the stator-core end plates is used to estimate the eddy-current loss in these plates, and the effect upon this loss of the retaining-ring permeability and the stator-winding cone angle is considered.
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Effects of asymmetry of induction-machine windings upon the slot leakage reactance
Discussion on “Recent developments in battery electric vehicles”
Variable-characteristic d.c. machines
  • Author(s): B.M. Bird  and  R.M. Harlen
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1813 –1819
  • DOI:  10.1049/piee.1966.0311
  • Type: Article
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  • p. 1813 –1819 (7)
    The paper deals with the application of pulsed voltage waveforms to the field windings of separately excited d.c. machines, and describes the development of an unusual form of control scheme, which holds the field current and the armature current in a fixed relationship. A wide range of torque/speed characteristics are shown to be possible, using simple and inexpensive control apparatus. One arrangement, which allows the separately excited machine to behave as a series machine in the motoring region, and as a constant-torque machine in the braking region, is described in detail, and its possible application as a battery electric traction drive is discussed.
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Discussion on “Electric process heating for UKAEA works”
Operational statistics in the management of large distribution systems
  • Author(s): R.A.W. Connor  and  R.A. Parkins
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1823 –1834
  • DOI:  10.1049/piee.1966.0313
  • Type: Article
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  • p. 1823 –1834 (12)
    In order to manage a large distribution system in the best manner, it is considered necessary to have comprehensive, accurate and up-to-date records of the number and types of equipment items in service, together with properly analysed records of their performance.With the advent of nationalisation of the supply industry in 1948, and the formation of a small number of large undertakings, it became possible to study the performance of large networks in a manner not previously possible. The paper gives details of the way in which the necessary data are collected, analysed and used in one Area Board. Details are given of some of the conclusions reached to date of some other problems which are being studied, and some observations are made on reliability and security of supplies.Although some problems do not lend themselves to analytical treatment of the type described, many do, and it is contended that a great deal of valuable information on design, construction, operation and maintenance of networks can be obtained from the analysis of properly compiled data.
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New method for the assessment of switching-impulse insulation strength
  • Author(s): M. Ouyang
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1835 –1841
  • DOI:  10.1049/piee.1966.0314
  • Type: Article
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  • p. 1835 –1841 (7)
    By examining the nature of the variate of the breakdown frequency, the conventional method of analysing data is shown to be incorrect, unless some breakdowns occur on the wavetail. A new method is devised for the derivation of the cumulative frequency distribution of breakdown voltage (or ‘time to breakdown’), which is an estimate of the corresponding probability distribution. The new method extracts all the relevant information contained in the test data and gives more significant results, which are likely to be fairly reproducible. Practical experience indicates that the new method is particularly suited to the assessment of voltages of low breakdown probability, and its use should lead to simplifications of testing technique. It is shown that problems of insulation co-ordination can readily be solved on a probability basis by the use of the cumulative frequency distribution of time to breakdown.
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Discussion on “A seasonal tariff for domestic supplies”
Tooth-ripple losses in solid poles
Current-compounded self-excitation circuits
Dielectric properties of polythene for submarine telephone cables
  • Author(s): I.T. Barrie ; K.A. Buckingham ; W. Reddish
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1849 –1854
  • DOI:  10.1049/piee.1966.0318
  • Type: Article
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  • p. 1849 –1854 (6)
    Increases in the signal-carrying capacity of submarine telephone cables by extensions of the frequency bandwidth have led to progressively tighter specifications for the relative permittivity and losses of the polythene dielectric. A study of the factors determining the dielectric losses of low-density, i.e. high-pressure-process, polythene has resulted in a low-loss material, of precise relative permittivity, for which comprehensive data are presented, and has brought about improved techniques of low-loss measurement. An attempt is made to distinguish the losses of pure polythene from those due to additives and process residues, and an ultimate loss/frequency profile is estimated. Lower losses can be achieved with polythenes of higher density, but this is at the expense of higher relative permittivity, and hence of higher overall cable attenuation; a continuous gradation in these properties is possible.
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Theoretical considerations of magnetostriction in silicon iron
  • Author(s): C.M. Brownsey  and  G.C. Maples
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1855 –1858
  • DOI:  10.1049/piee.1966.0319
  • Type: Article
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  • p. 1855 –1858 (4)
    The magnetostriction of well oriented silicon iron is discussed on the basis of a simple domain model containing only 180° domains. The effect of an externally applied magnetic field on the domain configuration is examined on an energy basis, which indicates that the magnetostatic energy is the principal factor involved and that rotation of the domain magnetisation vector can occur at low field strengths. It is further shown that such rotation gives rise to negative magnetostriction. The possible effects on the observed magnetostriction of a few badly oriented crystals in a polycrystalline specimen are also discussed.
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Magnetostriction characteristics of 3.1% grain-oriented silicon-iron transformer steel
  • Author(s): C.M. Brownsey  and  G.C. Maples
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1859 –1862
  • DOI:  10.1049/piee.1966.0320
  • Type: Article
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  • p. 1859 –1862 (4)
    An apparatus has been developed for the measurement of the a.c. magnetostriction of laminations of transformer steel subjected to a 50c/s excitation. The apparatus employs a ceramic displacement transducer and is capable of measuring a.c. displacements in the range 10−4–10−8cm. Data are presented on the observed variation of magnetostriction, core loss and permeability with mechanical stress. It was found that the magnetostriction coefficient of 46-grade oriented transformer steel, in the fully annealed state and at a peak induction of 15000Gs, is usually negative and has a median measured value of −3.0 × 10−7.
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Time lags and the breakdown and corona characteristics in sulphur hexafluoride
  • Author(s): E. Kuffel  and  R.O. Radwan
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1863 –1872
  • DOI:  10.1049/piee.1966.0321
  • Type: Article
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  • p. 1863 –1872 (10)
    Investigations were made into the factors such as irradiation, gap length, gas pressure and electrode conditioning which affect the time lag and the corona and breakdown characteristics in sulphur hexafluoride. The measurements of time lags were made with uniform-field electrodes, using approximately square-pulse voltages superimposed upon direct-approach voltages. Time lags in SF6 under these conditions were long, and the results were widely scattered. At low overvoltages, the time-lag distribution curves were characterised by a region free from time lags, which separated two groups of time lags. In air under the same conditions, the observed time lags were much shorter, with correspondingly smaller scatter. Additional measurements of time lags in SF were made using impulse voltages of 0.5/320μs, without the approach voltage, with uniform-field electrodes and 6.25cm-diameter spheres. The average time lags measured with the impulse voltage were of the same order as those measured with a square voltage pulse superimposed upon direct-approach voltages. Illuminating the cathode by ultraviolet light (emission current of approximately 10−11 A/cm2 caused a large reduction in the direct breakdown voltage (up to 30%) for the short gaps. This large reduction could not be explained by considering the statistical scatter observed in the breakdown voltages. It is suggested that the effect is associated with the spark mechanism in SF6 Investigations were also made of the growth of corona current, and the corona-onset voltage in SF6 and SF6-air mixtures. In SF6, large corona currents were observed over a wide range of voltage, while in air under similar conditions, corona could be detected only at voltages close to breakdown. The addition of SF6 to air caused a large increase in the corona current, the corona-onset voltage, the corona-voltage range and the breakdown voltage.
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Circuit analysis of electromagnetic force in terms of effective inductance
  • Author(s): M.R. Harris
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1873 –1875
  • DOI:  10.1049/piee.1966.0322
  • Type: Article
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  • p. 1873 –1875 (3)
    In certain circumstances, the force on a secondary conducting body carrying induced eddy currents can be calculated from the gradient of effective inductance, measured in the primary circuit at the operating frequency. Uncertainty as to the exact circumstances is resolved by an approach through matrix algebra. Either the self parameters of the secondary impedance matrix must be constant, or the secondary circuits must be effectively resistanceless. In the resistanceless case, the theory extends to cover multiple primary circuits, but not otherwise. The theory is verified by application to the single-phase induction motor, and other physical implications are discussed.
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Electromagnetic momentum in a material medium
Sphere-hemisphere spark gap
Electrical breakdown of air and SF6 mixtures
Factors affecting the use of simulators for training
  • Author(s): M. Hammerton
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1881 –1884
  • DOI:  10.1049/piee.1966.0326
  • Type: Article
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  • p. 1881 –1884 (4)
    The paper reviews and discusses the implications of a series of experiments germane to the use of simulators for training purposes. Problems of measuring transfer of training are briefly discussed, and a series of nine experiments is summarised. Each of these experiments is concerned with visual or environmental factors which can affect the usefulness of a training simulator. The results obtained are discussed, and their limitations and fields of application are stated. A number of conclusions are presented, those chiefly of interest to designers and those chiefly of interest to users being given separately.
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Ripple performance and choice of sampling frequency for a direct digital control system
  • Author(s): J.B. Knowles  and  R. Edwards
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1885 –1892
  • DOI:  10.1049/piee.1966.0327
  • Type: Article
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  • p. 1885 –1892 (8)
    A method of computing the steady-state output ripple power for single-rate and multirate direct digital control systems with a stochastic input is presented in the paper. The formulas derived appear to be more easily evaluated than those proposed in earlier work. Experimental evidence obtained for sinusoidal inputs to two practical systems confirms the theoretical results. Considerable attention is given to the choice of a sampling frequency which produces a ripple power consistent with the specified design accuracy and component wear and tear. The results show that the sampling frequency cannot be chosen directly, and that an iterative design procedure is generally necessary. A simplification of the expression for the steady-state output ripple power of a single-rate system subjected to a particular sinusoidal input is suggested as providing a realistic starting point for the iteration procedure. The sufficiency of this initial estimate as a worst-case design is established for a practical system.
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Aspects of subrate digital control systems
  • Author(s): J.B. Knowles  and  R. Edwards
  • Source: Proceedings of the Institution of Electrical Engineers, Volume 113, Issue 11, p. 1893 –1901
  • DOI:  10.1049/piee.1966.0328
  • Type: Article
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  • p. 1893 –1901 (9)
    The paper suggests an original design procedure for subrate digital compensators, which is based on an approximate transfer function. Theoretical and experimental evidence is presented which justifies the design technique in practice. However, the main body of the paper is an extension of the authors' previous work on quantisation effects to the case of a closed-loop linear subrate direct digital control system. A slide-rule calculation provides an upper bound for the loss of steady-state control-system performance for all computer word lengths and inputs. Furthermore, the actual increase in steady-state mean-square system error may be evaluated by a simple iterative computer program. An application of the analysis is to specify the precision required in the digital compensator and peripheral equipment, for consistency with the overall accuracy demanded of the closed-loop system. It also enables the selection of the programming technique which requires the shortest computer word length for this accuracy. These calculations can result in better utilisation of computer facilities, thereby implying an economic saving. As a means of verifying the analysis, the performance of two different subrate digital compensators for a practical system are each compared with a counterpart having negligible quantisation and roundoff errors.
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Performance criteria for the free and forced motion of discrete control systems
Corporate simulation

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