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Electrical Engineers, Proceedings of the Institution of

Issue 3 • Date March 1967

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Displaying Results 1 - 25 of 26
  • Theoretical investigation of cylindrical dielectric-rod antennas

    Page(s): 309 - 319
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1430 KB)  

    Present-day theory of uniform cylindrical dielectric-rod antennas rests on the three theoretical treatments of Horton, Bouix and Fradin (leaky-guide theory), and on Brown's end-fire theory. A digression on the general relationship between Schelkunoff's equivalence principle and the vector Kirchhoff formula reveals that these radiation formulas may only be applied to regions in which the vector potentials are known to satisfy the inhomogeneous wave equation. On applying this axiom to the theories, all but Brown's are shown to be fallacious. A detailed application of the vector Kirchhoff formula to uniform cylindrical dielectric rods supporting the HE11 mode produces an expression for the far-field radiation pattern, which, when computed, gives good agreement with existing experimental data. The analysis allows for dielectric losses and can also be extended to nonuniform dielectric antennas with gradual tapers. Fresnel interaction of the apertures and lens effects are considered. Finally, some design recommendations for dielectric rod antennas are made. View full abstract»

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  • Range and Doppler resolution of a frequency-scanned filter

    Page(s): 321 - 326
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (797 KB)  

    The paper is an analysis of a radar-signal-processing system¿the frequency-scanned filter¿which is designed to extract both range and velocity information from a single echo. The transmitted signal is a pulse train, which can be represented as a sequence. The echo is processed in a tapped delay line, with the taps weighted according to another sequence. The tap output is modulated by phase-coherent oscillators and summed to form the output. It can be shown that the output is the ambiguity function of the two sequences. By using some well known properties of the ambiguity function, both range and velocity can be estimated from the output, and the errors inherent in this estimation are also calculated. It should be noted that the system is time varying owing to the action of the modulators; this property is emphasised when the system is connected to operate as a frequency analyser. It is also shown that, except for some small and, in practice, insignificant differences, the frequency-scanned filter is equivalent to a bank of matched filters. View full abstract»

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  • Use of multivibrators in small telemetry systems

    Page(s): 327 - 332
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (706 KB)  

    In many small telemetry systems it is convenient to use information derived from a transducer to modulate the period of a multivibrator, the multivibrator waveform being used in turn to modulate a radio or line link. In this way, the measurement is easily made in digital form, and errors due to nonlinearity of the carrier modulator are removed. The use of multivibrators in this application is considered, and accurate equations are derived for the period of a conventional collector-coupled multivibrator and for the period of a multivibrator, using constant-current charging of the coupling capacitors. The mechanisms of variation of the period with varying ambient temperature are discussed, and the temperature stability is determined. The use of the two timing periods of a multivibrator as a double-channel system is considered, and a method is given which reduces crosstalk between the two channels to a negligible amount. View full abstract»

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  • Application of binary devices and Boolean algebra to the realisation of 3-valued logic circuits

    Page(s): 335 - 338
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    It has been shown previously that ternary functions can be constructed from binary elements. The paper proposes the application of Boolean algebra to a generalised procedure for the design of 3-valued functions using binary elements. The final logical layout is essentially symmetrical and uses complementary electronic devices. Component tolerance is the same as that for a binary system. The particular ternary functions chosen for discussion are modulo-3 addition and carry, using +1, 0 and ¿1 as the arithmetic states. View full abstract»

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  • Residual attenuation equalisation of broadband systems by generalised transversal networks

    Page(s): 339 - 348
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1572 KB)  

    Residual attenuation equalisation of broadband coaxial-cable systems has been achieved elsewhere by a set of harmonic cosine characteristics based on an almost linear frequency scale. This method is, however, not efficient for systems which exhibit high distortion near the bandedges. A simple analysis of measured characteristics yields the requirements for suitably transforming, or `warping¿, the frequency scale. Generalisations of the transversal-equaliser principle offer the realisation of cosine characteristics with frequency scales which match particular problems. The investigation on which the paper is based was concerned with the coaxial-cable network of the British Post Office, and led to novel designs, of which the `twin cosine equaliser¿ has been accepted for service use. This device enables residual distortion of up to 6dB to be reduced to rather less than 1dB, with a minimum of auxiliary instrumentation. View full abstract»

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  • Improved method of adjustment of medium-wave directional-antenna systems

    Page(s): 349 - 351
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (518 KB)  

    An improved method is described for adjusting medium-wave directional-antenna systems containing high radiators (of the order of ¿¿). It is pointed out that the determination of radiator driving-point impedances corresponding to the desired radiation pattern requires special consideration; namely, the radiation pattern determines the relationship between radiator currents near the current maximum, and not that between those at the base which is necessary for the calculation of driving-point impedances. It is shown that the two sets of current relationships may differ considerably. Since no reliable data for current distribution along high radiators in an array exist, an experimental method is proposed for obtaining the correlation between the two sets of current relations. Radiator driving-point impedances can then be calculated on the basis of circuit theory, the relationship found between currents at the radiator bases (corresponding to the desired radiation pattern), and the measured values of self and mutual impedances. For practical reasons, the method is limited to a few simple, but important, arrays. In order to avoid the usual lengthy trial-and-error method, the adjustment of the feeder system with dummy loads instead of the radiators is recommended, with the impedances of the dummy loads corresponding to the calculated driving-point impedances of the radiators. View full abstract»

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  • Boundary-value problems associated with source-excited planar-equiangular-spiral antennas

    Page(s): 352 - 359
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1072 KB)  

    Several boundary-value problems associated with the planar-spiral geometry are considered. A source-excited-sheath problem is formulated exactly, and a formal solution in terms of Hankel's inverse transform is presented. The approximate form of the current density on the sheath structure is obtained. A push-pull-excited 2-arm thin-wire antenna is discussed next. It is found that the approximate current-density solution is closely related to that of the corresponding sheath version. The approximate form of the current density is found to exhibit a slow-wave character along the radial dimension. Some far-field patterns are computed by the vector-potential method. The results of the current densities and the radiation patterns are found to be in favourable agreement with the experimental results. A short discussion on the solution of a multiarm antenna is also given. The approximate current density and the far-field patterns are also computed for a 4-arm antenna. Some general conclusions are presented. View full abstract»

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  • Time-domain analysis of the invertor-fed induction motor

    Page(s): 361 - 369
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (898 KB)  

    The paper investigates induction motors running at constant speed and fed by invertors. It is based on linear 2-axis theory, and shows that an exact equivalent circuit can be drawn which includes a back e.m.f. opposed to the applied voltage, as in the synchronous motor. A rigorous analysis leads to explicit expressions in forms suitable for computation of the axis currents as time functions; samples of computed curves are given. In addition, a short approximate method is given for deriving the axis currents as time functions, including the current at commutation. Comparisons with experiments are included. View full abstract»

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  • Application of Newton's method to load-flow calculations

    Page(s): 372 - 374
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    Newton's method is adapted to the solution of load-flow problems, and a simple condition for its convergence is derived. It is shown that the fast convergence rate justifies its use, despite the fact that it needs more memory space than methods used at present. View full abstract»

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  • Thermal transients in linear systems with heat generation linearly temperature-dependent. Application to buried cables

    Page(s): 375 - 377
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (410 KB)  

    A simple method is proposed whereby the formulas for the transient conductor-temperature rise above ambient of a buried cable, following the application of a constant load, may be modified in order to take account of the variation of the electrical resistivity of the conductor with temperature during the transient. The result is an upper bound for the conductor transient that is more accurate than existing formulas, although the temperature differences involved are not large. A technique is given for obtaining arbitrarily close upper and lower bounds. The method is of more general applicability than the field of thermal transients in buried cables. View full abstract»

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  • Transition characteristics of the jump phenomenon in nonlinear resonant circuits

    Page(s): 381 - 392
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1343 KB)  

    Currents in resonant circuits containing nonlinear elements, and amplitudes of oscillations in other nonlinear systems with periodic forcing functions, display two modes in certain ranges of frequency and amplitude of the forcing functions. The characteristics of the transition from one mode to another in an RLCcircuit are affected by the changes in parameters, and at the instants of time when these changes or disturbances are introduced into the circuit. Analysis of the critical conditions for second-order equations containing cubic-and, in certain cases, higher-order nonlinearities is carried out to determine these transients. View full abstract»

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  • Design of multivariable feedback systems

    Page(s): 395 - 399
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (594 KB)  

    A canonical form for a multivariable linear control system is described. This canonical form is important because it enables a linear-feedback law to be chosen to produce arbitrary characteristic modes in the closed-loop system. The computational difficulties and methods suggested for minimising then are discussed. View full abstract»

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  • Training for fault diagnosis

    Page(s): 400 - 404
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (699 KB)  

    The diagnosis of randomly occurring faults in complex electronic equipment is a difficult task which is generally not done well. The paper reviews some of the work on the content of the fault-diagnosis training course. In particular, the approach of the Technical Training Command of the Royal Air Force is discussed. Research has shown that the teaching of electronic theory is of much less importance than the teaching of fault-finding principles and strategies and a functional knowledge of the equipment. View full abstract»

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  • Theory of an improved thermomagnetic generator

    Page(s): 405 - 409
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (570 KB)  

    Heat energy may be used directly to produce electrical work in devices having no moving parts, by employing the properties of ferromagnetic substances near their Curie points. While thermomagnetic generators proposed in the past had poor theoretical efficiencies, the study discloses an improved generator having a circuit arrangement which allows the load current to assist in obtaining a better thermodynamic path. By resonating the current in the load circuit, the generator produces sufficient self modulation of the field to allow the improved thermodynamic cycle to be achieved in a very simple manner. Expressions are derived by thermodynamic and electrical analyses for current, voltage, field quantities, cyclical work and heat addition and efficiency. The specific power, which was proportional to the square of the magnetisation change in previous generators, is now proportional to the product of the applied field and the first power of the magnetisation change. This leads to devices whose performance in ordinary applied magnetic fields is conservatively doubled, while in the high-intensity magnetic fields of superconductors there is more than an order of magnitude improvement in performance. View full abstract»

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  • Voltage impact excitation of rectangular solid iron core

    Page(s): 411 - 418
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (917 KB)  

    Voltage impact excitation of a solid iron core creates eddy currents in the core, retarding the rise of flux. An analysis of the problem involves the simultaneous solution of partial and ordinary differential equations. The boundary condition for the partial differential equation contains an unknown quantity, which is variable with respect to time in the ordinary differential equation associated with the physical system. Such situations are commonly termed field-circuit problems. The paper presents the method of eigenvalues for solving linear field-circuit problems. The eigenfunctions are mutually orthogonal, enabling an exact fit of the boundary condition by a linear combination of these eigenfunctions. The final equations, when applied to a practical voltage-impact-excitation problem, show favourable agreement with experimental results for current and flux transients. A special and interesting feature of the paper is the predetermination of contours of constant magnetising force and eddy-current-density distribution within the rectangular section during the transient period. The contours, obtained rigorously for the first time, give insight into the phenomena involved in the magnetisation of a rectangular solid iron core. 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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