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Electrical Engineers, Proceedings of the Institution of

Issue 9 • Date September 1974

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Displaying Results 1 - 25 of 35
  • Response of an m.o.s. integrated circuit to tests at elevated ambient temperatures

    Page(s): 913 - 919
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1104 KB)  

    An earlier exercise seeking life-prediction procedures for complex m.o.s. integrated circuits has been extended, using, as before, a simple integrated circuit, though of different type and origin, as the test vehicle. The acceleration of life is based, as in the earlier work, on the application of electrical stresses at temperatures above the manufacturer's normal rating. Of the various parameters monitored, the threshold voltages of the constituent transistors again exhibit the greatest response, but the behavioural pattern is markedly different from that previously observed. The changes are explained by the superposition of two counteracting drift mechanisms, one of which is similar to that found in the earlier study. Because multiple failure mechanisms preclude the use of simple Arrhenius lines for life-prediction purposes, a modelling procedure is developed allowing the trends of threshold voltage at constant temperature (as in service) to be calculated from temperature step-stress results. Having, in addition, examined the responses of transistor gain factor and parasitic threshold voltage, earlier proposals for procurement specification requirements are revised and augmented assuming the availability of a suitable test unit manufactured in association with the real components. View full abstract»

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  • New bound for the spectrum of an f.m. wave

    Page(s): 920 - 922
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (429 KB)  

    Cheby¿shev and 4th-moment generalised Cheby¿shev bounds on the power in the tail of the spectrum of an f.m. wave have been known for several years. Here it is shown that, when the modulation is Gaussian with r.m.s. frequency deviation D and contains no modulating frequency higher than F, the fraction of the total power lying in frequencies exceeding that of the carrier by more than ¿>0 must be less than (¿eD2/F¿)¿/F. This bound is of the Chernoff type, being based on a suitably chosen value of the `moment-generating function¿ of the f.m. spectrum, which is obtained directly from the autocorrelation function of the f.m. wave. The bound falls off with increasing ¿ much faster than the previous bounds. Although it cannot be expected to be a good approximation to the power in the spectral tail, its simple form makes it convenient for such applications as the study of neighbouring-channel interference. View full abstract»

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  • Differential phase-shift keying applied to chirp data signals

    Page(s): 923 - 928
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (777 KB)  

    Chirp communication systems have been constructed that use signals having ascending and descending linear frequency sweeps to define mark and space data states, respectively. Such signal states are approximately orthogonal, and are generally detected noncoherently. The paper describes preliminary investigations into a method of differential phase modulation applied to chirp data signals. This improves the chirp-system performance in white noise and single carrier interference, and essentially retains the inherent protection that chirp signals have in multipath conditions. Also, improved bandwidth utilisation may be achieved with multiphase operation. View full abstract»

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  • Improved digital aperture corrector

    Page(s): 929 - 934
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (869 KB)  

    A high-speed digital system for the aperture correction of television images is described in which the amount of diagonal correction applied can be varied with respect to that in the horizontal and vertical directions. It is shown that this facility is desirable in order to correct for different forms of spread function, and that the resolution of diagonal detail in the image is improved by using the appropriate amount of diagonal correction. Noise increase in the system is examined and the errors introduced by rounding off the digitised video and correction signals are also considered. View full abstract»

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  • Irreducible polynomials over composite Galois fields and their applications in coding techniques

    Page(s): 935 - 939
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    Tables of irreducible polynomials and their exponents are listed for certain small nonprime Galois fields. These include all such polynomials up to and including degree 5 for GF(4), degree 3 for GF(8) and GF(9), and degree 2 for GF(16). In addition, a single primitive polynomial is given for each degree up to and including degree 11 for GF(4), degree 7 for GF(8) and GF(9), and degree 5 for GF(16). A brief summary is given of several areas where these results may prove useful in providing an alternative to the more conventional approach. View full abstract»

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  • Alternative approach to the design of stored-program-controlled telephone exchanges

    Page(s): 940 - 944
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (728 KB)  

    Stored-program-controlled (s.p.c.) telephone exchanges have been under active development for the last ten years, and many are now in public service. The problem of economic provision of a system, for the smaller exchanges, has not yet been solved. This paper suggests an alternative approach to that of monolithic control, where the system is completely dependent on a single processor complex. The alternative approach is based on well established electromechanical-system principles of system design, but may still provide the advantages claimed for an s.p.c. system. View full abstract»

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  • Quantising noise spectra

    Page(s): 945 - 954
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1405 KB)  

    Bennett's approximation for the spectrum of quantising noise is both numerically accurate and computationally economical, but apparently does not correspond to the physical mechanism of intermodulation producing the noise. On the other hand Velichkin's approach reveals this structure, but Robertson's computation of his formula becomes rather expensive for quantisers with more than 16 levels. In this paper we derive Bennett's result by a new route, starting from the noise analysis of Blachman. We show that Velichkin's intermodulation series has a `line-structure¿ which, when exploited for approximation leads to Bennett's B series. Bennett' s approximation may now be reinterpreted as a genuine intermodulation series in which low-order terms are absent, and we show how this explains the experimentally observed flatness of quantising noise spectra for arbitrary input spectra and for high sampling rates. We also present some experimental results which indicate that the noise/signal ratio defined in terms of Blachman's analysis is a better estimate of system performance than the conventional meansquared-error analysis in cases where the quantiser is not globally linear, as for instance when compandor and expander are mismatched. View full abstract»

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  • IEE Conference Publication 113. CPEM 74: Conference on Precision Electromagnetic Measurements

    Page(s): 958 - 960
    Save to Project icon | PDF file iconPDF (502 KB)  
    Freely Available from IEEE
  • Simulation of high-speed linear-induction-motor end effects in low-speed tests

    Page(s): 961 - 964
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    The paper presents two new possibilities of simulating end effects and transverse edge effects of a high-speed linear induction motor in a rather low-speed test if certain equivalence conditions are satisfied. The basis of simulation is to keep the flux-density distribution in the airgap, as well as in the exit and entry zones, the same in the simulated l.i.m. as in the actual l.i.m. It is demonstrated that a realistic simulation may be obtained in practice. Two examples are given which show the parameter values to simulate a fullsize high-speed l.i.m. by (a) a low-speed l.i.m. and (b) an arch motor. View full abstract»

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  • Vernier reluctance motor

    Page(s): 965 - 974
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1288 KB)  

    Reluctance motors depend for their operation on the existence of alternate zones of higher and lower permeance between stator and rotor round the periphery. In the usual form of reluctance motor this is provided by salient poles on the rotor. In the vernier form of reluctance motor it results from both stator and rotor having teeth, separated by open slots, with the number of teeth on the stator slightly different from the number on the rotor. Then there are zones where stator teeth are most nearly opposite to rotor teeth and the permeance is larger, alternating with zones where the stator teeth are opposite to rotor slots and the permeance is smaller. Such motors run `synchronously¿, with the rotor speed a certain fraction of the speed of the axis of the applied m.m.f. The torque obtainable depends in a rather complicated manner on the proportions of the dimensions of teeth, slots and air gap and on the waveform of m.m.f. Various relationships giving peripheral force and output are derived, and the conditions are found by which the output can be maximised. The possible output coefficient so estimated is compared with the output coefficients of various other forms of machine. It appears from this comparison that the best output coefficient possible is intermediate between the coefficients for a d.c. motor and for an induction motor. Any suggestion that the vernier construction might provide an exceptionally large output coefficient is thus disproved. View full abstract»

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  • Balanced multiunit electric-differential control system

    Page(s): 975 - 979
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (611 KB)  

    Earlier papers established the theory of the electric differential and certain simple practical tests for finding the performance parameters. The present paper is a logical development, and describes the manner in which a multiunit system of 3 N machines, providing that they can be arranged in three identical groups, can be connected to a simple double induction-motor frequency-changer arrangement, so that the supply system is presented with a balanced load. View full abstract»

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  • Distribution of axial flux on the stator surfaces at the ends of turbogenerators

    Page(s): 980 - 990
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1073 KB)  

    The flux distribution in the end region of turbogenerators close to the stator surface is analysed with particular reference to the unwanted axial component of flux. It is shown that axial flux levels at the stator surface can be considerably reduced by making the rotor shorter than the stator and by stepping or rounding the stator ends. The influence of conducting screens is studied, and it is shown that these produce flux concentrations at their edges. View full abstract»

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  • Performance analysis of hysteresis-reluctance motors with segmental rotors

    Page(s): 991 - 992
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (266 KB)  

    The field solution of hysteresis-reluctance motors with segmental rotors is developed, using the method of series matching at the boundaries between the various regions of the system model. New parameters are derived that yield an equivalent circuit and machine-performance equations for this type of machine. Computed results are presented to illustrate the application of the theory, and to demonstrate the performance of the machine and the influence of its design features. Performance is compared with that of a circumferential flux hysteresis motor, by both calculation and a tested example. View full abstract»

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  • Discharge detection under noisy conditions

    Page(s): 993 - 996
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (533 KB)  

    The smallest discharge which may be detected during partial discharge tests on electrical equipment is usually determined by the levels of background interference. To improve the signal/noise ratio the real-time computational technique known as signal recovery has been used. This has the additional advantage that the end result is a permanent record which will allow the user to reliably compare discharge characteristics throughout a component's life. While the approach is applicable to any component, the experimental evaluation programme was based on 11 kV polymer-insulated cable. This was tested in various situations, namely, as a short length in the laboratory, as drum lengths in several factories, and lengths (together with associated switchgear) installed in a number of power stations. In these conditions, discharges of 1 pC and less could be detected, even where the noise levels on conventional display-only equipment were tens of picocoulombs. View full abstract»

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  • Wave propagation in nonhomogeneous systems. Properties of the chain matrix

    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (481 KB)  

    Nonhomogeneous multiconductor transmission systems occur in a number of instances in practice. Examples are crossbonded cable systems and regularly transported overhead-line systems. Recursive methods of analysis fail because of the amount of computation involved. In the paper the theoretical equations for the multiconductor chain matrix are developed. It is proved that the eigenvalues of the chain matrix occur in reciprocal pairs and that the eigenvectors of the reciprocals are simply related to those of the eigenvalues. This reduces computation and avoids numerical instability in evaluating widely separated eigenvalues. These properties have not previously been published and may have applications in a number of fields as well as transmission lines. It is then noted that, provided the system response is only needed at a comparatively small number of points, computation is much more efficient than would be the case for recursive methods. In conclusion it is noted that this paper is the last in a series in which the equivalence between the theorems of simple and multiconductor systems is established by means of matrix functions. View full abstract»

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  • Protective-equipment analysis using a digital computer

    Page(s): 1001 - 1006
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (607 KB)  

    The paper describes a way of studying the behaviour of power-system protective schemes using step-by-step methods on a digital computer. Initially, a current transformer model is developed, and it is shown that it gives accurate results. The equations governing the performance of a moving-coil relay are then given. A program to determine the behaviour of a restricted earth-fault protective circuit incorporating a high-impedance relay is outlined, and computed results for typical conditions and parameters are given. The effects of parameters such as core permeability are quite evident. It is clear that the methods described could be applied to many schemes to determine their performance and factors such as operating times and stability limits. View full abstract»

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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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