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Electrical Engineers, Proceedings of the Institution of

Issue 10 • Date October 1965

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Displaying Results 1 - 25 of 33
  • Subjective quality of colour-television pictures impaired by gain and delay inequalities between the luminance and chrominance channels

    Page(s): 1819 - 1824
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    Using a previously proposed quality-grading method, tests have been made of the effects of gain and delay inequalities between the luminance and chrominance channels of a 625-line NTSC-type broadcast colour-television system. 50% favourable opinions are obtained with pictures impaired by a gain inequality, expressed as the error in chrominance-channel voltage gain, of ±56% 95% favourable opinions are obtained with a gain inequality of ±36%. For delay inequality the corresponding values are ±350 and ±210ns, respectively. View full abstract»

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  • Transistor-feedback-amplifier design

    Page(s): 1825 - 1834
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    Formulas are given to help in the estimation of the positions of poles and zeros of the open-loop gain of an uncorrected transistor amplifier. Design curves are provided to enable the determination of a modified pole-zero configuration which will yield a desired gain and phase margin against oscillation. A synthesis procedure is described which yields a network making the necessary modifications to the pole-zero configuration. Formulas for element values enable the process to be carried out with simple arithmetic calculations for a type of amplifier commonly encountered. This process does not involve the usual practice of measuring the open-loop frequency response of the uncorrected amplifier and then correcting this to approximate to Bode's ideal-loop-gain characteristic. This correction usually involves either fitting a required loss curve with a rational function or an equally tedious `cut-and-try¿ experimental process. View full abstract»

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  • Method of correlating binary signals

    Page(s): 1835 - 1837
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    The paper describes a method of measuring correlation functions of binary time signals. The use and application of correlation functions are discussed in a general manner, and the authors point out the diversity of fields in which these functions are found. A method of correlation employing logic switching devices is detailed, and, as an example of operation, the autocorrelation of binary noise which has zero crossings occurring at random intervals is described. Finally it is shown that the method is satisfactory and has certain advantages. View full abstract»

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  • Polar patterns of phase-corrected circular arrays

    Page(s): 1839 - 1848
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (813 KB)  

    The paper considers the polar response of an array of similar radiators placed uniformly around a circle, in which each radiator is phase-corrected to bring the radiation from all radiating elements into common phase in one direction. Such an array tends to have a pattern with undesirably large side lobes. The effects of varying (a) the polar response of the individual elements, (b) the relative weighting of the elements and (c) the element spacing, are examined. It is found that the side-lobe level can be greatly reduced if (a) each element has a polar pattern confined mainly to the forward hemisphere, with, in particular, a null at 90°, (b) only elements within ±90° of the main beam are used, and (c) the spacing between elements is not more than half the wavelength. View full abstract»

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  • Negative magnetoresistance effect in evaporated indium-antimonide films

    Page(s): 1849 - 1855
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    The paper discusses the results of an experimental investigation of an anomalous galvanomagnetic effect in an evaporated indium-antimonide film. The film used was prepared by the step-by-step method of evaporation in a vacuum, producing successive deposits on a clean glass substrate. The electrical characteristics of the film were measured in a steady magnetic field and showed some unusual features such as high resistivity, a relatively large Hall coefficient dependent on the applied magnetic field and a negative magnetoresistance effect at room temperature. These anomalous effects have been analysed qualitatively in terms of the inhomogeneous nature of the film. View full abstract»

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  • Radiation resistance of elementary electric-current sources in a magnetoionic medium

    Page(s): 1856 - 1868
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    Integral expressions for the radiation resistances of a point source of electric current and a filament of finite length with a triangular current distribution are obtained for the case in which these sources are immersed in a loss-free and unbounded magnetoionic medium so that they are parallel to the direction of the magnetostatic field. The radiation resistance of the point source of electric current is found to become infinite in two frequency ranges, whose values are stated precisely, and this infinite behaviour is related to the medium resonances. It is found that, for the current filament, the radiation resistance remains finite for all frequencies except the upper hybrid resonant frequency. The reasons for the infinite behaviour of the radiation resistance at the upper hybrid resonant frequency are due to the limitations of the magnetoionic theory on which the present work is based. Numerical results for the radiation resistances of the two elementary electric-current sources are given for some typical values of the parameters of interest. View full abstract»

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  • Wideband transistor amplifier for use in submerged repeaters

    Page(s): 1869 - 1877
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    The problems involved in the design and the construction of a wideband transistor amplifier for use in a submerged repeater are discussed in the paper. The maximum transmission frequency is 4284 kc/s. The amplifier consists of two three-stage feedback amplifier units. Only one type of transistor is used throughout to simplify reliability assessment. The factors leading to the choice of this type from among those commercially available are discussed. A brief account of the special components employed, and their effect on the design of the amplifier, is given. Several prototype models and the amplifiers used in the repeaters have been constructed to the design given in the paper. Two repeaters have been installed in the St. Margaret's Bay-La Panne No. 6 cable to extend the circuit capacity from 216 to 420 channels. View full abstract»

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  • Trunking of a t.d.m. electronic exchange with subscribers' lines having permanently allocated multiplex channels

    Page(s): 1878 - 1884
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    A t.d.m.-exchange system is described in which the subscribers' line equipments have permanently allocated channels. If n channel multiplexes are used, the subscribers' lines are effectively divided into n separate space-division exchanges with common registers and junctions. Existing trunking theory still applies, but with the unusual aspects that the division by n results in an aggregation of n small, or even very small, exchanges, and that the relatively high cost of the switching elements justifies greater care in trunking design to minimise the number of switching elements. View full abstract»

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  • Communication for air-traffic services

    Page(s): 1885 - 1893
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    This paper discusses the technical problems of traffic flow encountered in the overall design of a communication system for a specific purpose, namely the provision of air-traffic services to civil aircraft. The major part of the paper deals with (a) the evaluation of queueing delays on aeronautical mobile (aeromobile) speech channels, from which the number of channels required to meet a chosen delay criterion is estimated (b) the minimum signal/noise ratio required for satisfactory communication on aeronautical radio channels, and the transmitter power required to produce it. Statistics of operator loading, channel holding times and message-arrival rates are given, and the role of the human operator as a component of the system is evaluated. View full abstract»

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  • Two-speed induction motors using fractional-slot windings

    Page(s): 1899 - 1913
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    It has already been shown how to obtain 2-speed single-winding squirrel-cage induction motors, using a normal stator with all coils identical, and with only six terminals to the winding. The earlier methods showed how an integral-slot winding may be modulated to give a 2-speed winding for any pole combination, and also how to design a fractional-slot 2-speed winding for pole combinations which do not include a multiple of 6. The fractional-slot windings are the best, and this paper completes the record of close-ratio pole-amplitude modulation in its basic form by showing how to design a fractional-slot winding for any close-ratio pole combination. The performance of machines with such fractional-slot windings very nearly approaches that of a single-speed motor, for both speeds; and it is thought that, for most applications, these fractional-slot windings will supersede the earlier integral-slot ones. Tables of finished winding designs for one pole combination are given in full, together with details of the design methods, which are illustrated by the complete working of one particular design. The basic part of the task of converting the single-winding squirrel-cage induction motor into a close-ratio 2-speed machine has therefore been completed and recorded in full. The application of the same principles to wide-ratio 2-speed machines has been separately described, as will also be certain further developments of the work already recorded. View full abstract»

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  • Linearised analysis of induction-motor transients

    Page(s): 1917 - 1926
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    The effect of supply frequency on the speed transients of an induction motor due to small voltage and torque disturbances is discussed. The transients which depend on four nondimensional parameters are obtained by a graphical (root-locus) method which could well be followed at the design stage. The transfer functions between speed and small changes in input voltage and torque are given. It is shown that in low-frequency motors a lightly damped transient speed oscillation will occur at a frequency just below the supply frequency, which is influenced only slightly by the machine parameters. View full abstract»

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  • Digital calculation of lightning surge voltages in high-voltage transmission systems

    Page(s): 1933 - 1941
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    The paper describes a digital-computer programme for calculating lightning surge voltages in high-voltage power systems. The voltages due to an injected lightning current in a transmission line are calculated simultaneously in the whole system considered. The flashover characteristics of the suspension insulators, the surge impedance and earth resistance of the towers, the surge impedance for mutually coupled conductors, the surge capacitance for station equipment and the characteristic of lightning arresters are all taken into account. The programme may, for instance, be used to evaluate general rules for the location of lightning arresters as a function of a few important parameters for conventional station arrangement. It may also be applied to calculate the voltages and to determine the protection requirement necessary for each special case. View full abstract»

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  • Field plotting by fourier synthesis and digital computation

    Page(s): 1945 - 1950
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    The paper shows how the method of separation of variables, digital computation and Fourier synthesis may be combined to give the approximate solution of a particular field problem. The problem concerns the fringing flux at the tip of a cylindrical permeable magnetic pole face. Selected co-ordinate surfaces subdivide the volume of the field into regions within which the scalar potential may be expressed by Fourier expansions with unknown coefficients. A set of simultaneous equations for solution in these coefficients by digital computer is derived by satisfying continuity at chosen points which lie on the interfaces separating the several regions. The exact solution is approached by increasing the number of interface points. View full abstract»

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  • Electric water-heating development

    Page(s): 1951 - 1961
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    The paper is arranged in three Sections following an Introduction. Section 2 deals with factors affecting the development of electric water heating such as the increasing standards of home comfort and the effects of recent legislation calling for supplies of running hot water in the home, office, shop and factory. Progress in the development of the water-heating load is discussed, together with the scope for off-peak water heating. Section 3 covers developments in the design of electric water-heating appliances, compliance with the appropriate British Standards and approval by both electricity- and water-supply authorities. It deals with the performance of self-contained electric water heaters of both the storage and instantaneous types, and water heaters for use with off-peak supplies of electricity. Section 4 discusses developments in the design of immersion heaters, and compares their performance when installed in different positions in a storage vessel. The effects of water hardness on the life of immersion heaters are reviewed, and remedies are suggested to overcome problems of premature failure. The function of the thermostat and its performance are also considered, and the paper concludes with a consideration of the important subject of heat insulation of the water-storage vessel. View full abstract»

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  • Discussion on "Marine electric propulsion"

    Page(s): 1972 - 1976
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Aims & Scope

The Proceedings of the Institution of Electrical Engineers was published by the IET between 1963 and 1979.

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