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Electrical Engineers, Proceedings of the Institution of

Issue 9 • Date September 1964

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Displaying Results 1 - 22 of 22
  • High-speed ferrite-core storage system

    Page(s): 1501 - 1510
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1302 KB)  

    A high-speed random-access ferrite-core storage system is described, designed for use in faster computing machines of the future, and in other applications such as pulse `sorters¿ and `buffer¿ stores. A storage system of this type, of 1024 words, 25 bits each, using one core per bit and a partial switching technique has been simulated and tested. The system tested, which employs ferrite cores with an outside diameter of 0.030in, has a cycle time of about 500ns and a read access time of about 260ns. These times represent an improvement in speed of about four times that of present-day comparable systems. View full abstract»

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  • Backward diodes as microwave detectors

    Page(s): 1511 - 1516
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (689 KB)  

    This paper examines the potential of pulse-bonded germanium backward diodes as microwave detectors. Use is made of I/V relationships derived from both theoretical considerations and measurements on larger area alloyed diodes, in estimating the l.f. short-circuit current sensitivity in the unbiased state, from which it is deduced that the signal/noise performance (tangential sensitivity) at Xband should be superior to that of conventional silicon detector crystals. The manufacture of point-contact backward diodes in a CV7180type cartridge is investigated with a range of materials and processes. Expected sensitivities at Xband are of the order 57dbm for diodes of 1k¿ video resistance, and this figure has been achieved with some samples. Some incidental properties are also discussed, such as flicker noise and burnout. View full abstract»

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  • Gain and directional properties of three- and four-frequency parametric devices

    Page(s): 1517 - 1522
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (759 KB)  

    An examination is made of the properties of three- and four-frequency parametric devices using nonlinear resistance, capacitance and inductance, pumped at the same frequency but at different phase angles, more conventional parametric amplifiers and convertors being treated as special cases. It is shown with the aid of an equivalent circuit that there are fundamental differences between three-frequency devices with and without nonlinear resistance, only the former, for example, being capable of unidirectional operation. The difference is less marked in four-frequency devices, and it is shown that a wide range of properties are available, depending on the complication that can be tolerated. View full abstract»

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  • Effect of weather on performance of an 8mm radar

    Page(s): 1523 - 1533
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1226 KB)  

    The signal strength of echoes from a target (at a range of 2¿ miles over a sea path) were recorded over a period of two years and subsequently analysed to give the probability of fades greater than certain values. At the same time the rain-intensity régime was examined using several types of rain recorder. The results are given in the form of graphs showing the average frequency per year that a fade of a certain minimum intensity is to be expected, and its minimum duration. Graphs also show the fraction of time that signal strengths and signal/clutter ratios were less than certain limiting values. Various aspects of the results which concern the design of 8 mm radar, and its use at sea, are discussed. View full abstract»

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  • Atmospheric radio noise and signals received on directional aerials at high frequencies

    Page(s): 1534 - 1540
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    Results are presented of amplitude-probability-distribution measurements of atmospheric radio noise received simultaneously on a vertical monopole and on horizontal rhombic aerials at a site in Singapore. Observations were taken at frequencies close to those for which the directional aerials were normally used to receive commercial signals, and by choosing observation periods in relation to thunderstorm activity, two typical communication aerials directed on Hong Kong and Nairobi have been studied under a wide range of receiving conditions. The noise powers received by the omnidirectional and directional aerials are compared, and their relative values are explained in terms of the nonuniform spatial distribution of the noise sources. The effects of the use of directional aerials upon the noise structure are also discussed. In addition, the field strengths of the commercial signals have been examined. The measured improvements in the signal/noise ratio for the rhombic aerials compared with the monopole aerial are discussed in relation to the theoretical improvements to be expected from a knowledge of the gain and directivity of the rhombic aerials. View full abstract»

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  • Results of noise measurements on an operational s.h.f. radio link

    Page(s): 1541 - 1545
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (650 KB)  

    The CCITT and CCIR have recommended to administrations at various times since 1957 the measurement of certain characteristics of the noise in telephone and television channels routed over s.h.f. radio-relay systems, with particular reference to variations in the noise which might arise from fading or other effects of the propagation path. An extended series of measurements on an s.h.f. radio link operating in the band 3800¿4200Mc/s has now been completed, and the results are presented in the paper. Details are given of the noise parameters required to be measured, and salient features of the measuring equipment are mentioned. The variation with time of one type of noise is remarked upon, and a source of the noise is suggested. The performance of the radio system is found to be within recommended limits. View full abstract»

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  • Trigger mechanism and sensitivity in cold-cathode tubes

    Page(s): 1546 - 1550
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (613 KB)  

    Although cold-cathode trigger tubes are widely used in computer and control circuits, their firing mechanism is not completely understood, particularly when a capacitor is connected between the trigger and cathode. The paper describes an investigation of the firing mechanism with d.c. input circuits of high impedance. At breakdown of the trigger-cathode gap, relaxation oscillations occur, and it was found that the trigger current for onset of oscillations, ITosc, was related to the value of the capacitor C, according, to an approximate equation (ITosc¿IC)(C+CT)=A, where IC, CT and A are constants. The effect of the priming current and tube geometry have been examined and the results are in agreement with a simple theory which has been proposed. The effect of the trigger current on the anode breakdown has also been investigated. At onset of oscillations there is a large reduction in the anode breakdown-voltage. Thereafter, increasing the mean trigger current has only a small effect. This is particularly true of large capacitances. As a result, it is possible to describe the sensitivity in terms of the trigger capacitance needed to lower the anode breakdown voltage to a given value. View full abstract»

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  • Characteristic impedance of two special forms of transmission line

    Page(s): 1551 - 1555
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (455 KB)  

    Two specialised forms of transmission line which have been used in the past are, firstly, one in which the two conductors are opposing arcs of a circle and, secondly, one consisting of a thin strip in a rectangular outer tube. Exact theoretical solutions for the characteristic impedances have been found for infinitely thin (perfect) conductors, and corrections are given which show the effect of finite thickness in the conductors. View full abstract»

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  • Q band ferrite isolator for the circular TE01 wave mode

    Page(s): 1556 - 1561
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (641 KB)  

    The paper discusses possible configurations of ferrite elements for application to an 8 mm isolator operating in the circular TE01 mode. It is concluded that, when using this wave mode at such a frequency, there is one configuration that offers particular advantages¿namely that of an eccentrically mounted rod of a highly anisotropic ferrite transversely magnetised to give gyromagnetic resonance at the frequency of operation. The application of perturbation theory to this arrangement shows that there are two alternative positions of the ferrite rod, at different radii, for which the reverse/forward loss ratio is a maximum, and it indicates that the position nearer to the axis of the waveguide should provide the better performance. As the TE01 mode is not dominant in a circular waveguide, the isolator must inevitably operate under conditions capable of providing for the support of a number of other modes at the same time. In the reverse direction of the isolator, the ferrite introduces strong coupling between the TE01 mode and some of these other propagating modes, so that a mode filter forms an essential part of the isolator. Results are given of an experimental investigation showing that a worthwhile degree of isolation can be obtained with a device of this kind. View full abstract»

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  • Survey of basic stray losses in squirrel-cage induction motors

    Page(s): 1565 - 1574
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    A study of the literature reveals that there is still considerable confusion on various aspects of stray losses, particularly with regard to their definition and origin. Accordingly the theoretical information is presented in a rationalised and systematic way to obtain a fully comprehensive approach, based on classifying stray losses into two groups, namely those due to main flux variations (stray no-load losses) and those due to leakage fluxes (stray load losses). In this way three and six main basic types of stray losses can be recognised under the two headings, respectively. Having identified the physical origin of these stray losses, their effect on motor design parameters can be ascertained qualitatively, and available methods of quantitative calculation, which are mostly semiempirical, can then be judged. A critical appraisal of two synthetic test methods for stray load losses, the reverse-rotation and d.c./a.c.-short-circuit tests, is made in the light of basic theory, and the fundamental deficiencies of these tests, particularly the reverse-rotation test, are demonstrated theoretically and by tests carried out on a number of medium-to-large induction motors ranging from 400hp, 4pole, to 1700hp, 8pole. The importance of insulating squirrel cages to avoid circulating-current losses deduced theoretically is confirmed by experiment. Additionally, a direct investigation into squirrel-cage circulating-current losses on a 1500hp 4pole motor shows how such losses can be controlled by a suitable current-displacement rotor design; these additional losses being directly measurable at no load on this machine with open stator slots. Consideration is also given to the fact that modern, high-efficiency (particularly totally enclosed) machine designs cannot cater thermally for substantially increased losses, e.g. excessive stray losses of any kind. There is therefore already an overriding and definite safeguard that the declaration of efficiency to BS 269 is substantially c- orrect, or, more specifically, that there cannot be any major error in the value of the declared losses. However, a modification of the fixed allowance for stray load losses is suggested. From the theoretical and practical investigations carried out, it is concluded that making a nominal allowance for stray load losses is at present the only reasonable and practicable method of declaring efficiency. View full abstract»

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  • Numerical techniques in solution of power-system load-flow problems

    Page(s): 1575 - 1588
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1758 KB)  

    The literature describing methods of analysis suitable for use with electronic digital computers in the power-system load-flow problem has grown until the papers can now be numbered in hundreds. This paper presents a classification that can be applied to all methods, with theory and discussion of the important problems of acceleration of the solution, criteria for convergence and of the inherent difficulties that enable only general comparisons to be made between methods. An extensive bibliography lists the more significant papers on the subject. View full abstract»

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  • Discussion on flashover of polluted insulation

    Page(s): 1589 - 1592
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  • Some comparisons of power-measuring standards at 300 and 400 Mc/s

    Page(s): 1597 - 1601
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    The paper describes the comparison of coaxial power-measuring standards developed in the United Kingdom with transfer standards from the United States and Japan, at 300 and 400 Mc/s. The average difference between the US and UK values was 0.2%; and that between the Japanese and UK values was 2.1%. The differences are less than the combined limits of error claimed for the instruments being compared; the limits being (a) US transfer standard: ±0.5%, (b) Japanese transfer standard: ±1.4%, (c) UK standards: ±1% (up to 400mW), ±2.3% (up to 10W). View full abstract»

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  • Theory of a ferromagnetic heat engine

    Page(s): 1602 - 1606
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (545 KB)  

    A ferromagnetic wheel may be made to do mechanical work if the rim is passed through a magnetic field and a source of heat. The theory of this device is developed, first when the wheel is paramagnetic, and then for the ferromagnetic case. Expressions for the efficiency, work done per revolution and mean torque are derived for the general case. Relatively high torques are possible. For an iron wheel the efficiency would be only about 0.05%, but much higher efficiencies could be attained at low temperatures in the region of 20°K using materials of low Curie points. The maximum possible efficiency is calculated to be 27.6%. View full abstract»

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  • Time-domain matrix analysis of nonlinear hybrid control systems

    Page(s): 1607 - 1614
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    The paper describes a numerical method using time-domain matrixes for evaluating the response of nonlinear discrete-continuous systems to deterministic inputs. The concept of generating matrixes introduced in the paper provides a powerful tool for the analysis of such systems. The method may be applied to systems containing continuous elements of any order, discrete elements of any order, synchronous skip or multirate samplers and multiple nonlinearities of any order associated with zero-order hold elements. Numerical examples of the step response of a prototype system subject to amplitude constraints are given. View full abstract»

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  • Discusion on simulator assessment of tandem cold-rolling-mill automatic gauge-control systems

    Page(s): 1615 - 1618
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    Freely Available from IEEE
  • Sources of ionisation in high-pressure gases above 2000°K

    Page(s): 1619 - 1623
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (729 KB)  

    Previous experiments with inert gases at high pressure between coaxial graphite electrodes, at temperatures above 2000° K, have shown unexpectedly high electrical conductivities for quite small voltages across the electrodes. In the present experiments the influences of electrode geometry and supply frequency are examined, and the gas pressure is steadily reduced until the classical regions of low pressure (several mmHg) and high vacuum (mean free path ¿ electrode spacing) are reached. Spectroscopic observations confirm the presence in the gas of `seed¿ impurities from the electrodes, and results are described for the deliberate addition to the gas of aluminium vapour as a `seed¿ element. 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.

Full Aims & Scope