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Electrical Engineers, Proceedings of the Institution of

Issue 4 • Date April 1976

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Displaying Results 1 - 22 of 22
  • Technique for Doppler-invariant detection in fixed-range radar and communication systems using surface-acoustic-wave devices

    Publication Year: 1976 , Page(s): 277 - 280
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (557 KB)  

    A scheme for a coherent fixed-range miniature radar in which surface-acoustic-wave devices are used to provide an output function insensitive to Doppler shift is described. The transmitted signal is a high-duty-cycle pulse train coded with biphase modulation according to a pseudorandom binary sequence. In the interpulse period, the total electrical quiescence of the transmitter is achieved. Receiver processing occurs during these quiescent intervals using autocorrelation followed by postdetection integration with a filter bandwidth matched to the integration time. In both transmitter and receiver the necessity for surface-acoustic-wave devices is demonstrated. Potential applications of the techniques to communications are discussed. View full abstract»

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  • Aircraft antenna system analysis

    Publication Year: 1976 , Page(s): 281 - 284
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (529 KB)  

    Diffraction techniques in conjunction with classical geometrical optics methods have been used to analyse the elevation plane patterns of antennas mounted on different locations of an aircraft. The frame of the aircraft has been modelled using wedged and curved surfaces. Computed results have been compared with scaled-model measurements and are in very good agreement. Antenna locations examined are typical for communication and landing systems on an airframe. View full abstract»

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  • Precise dielectric measurements at 35 GHz using an open microwave resonator

    Publication Year: 1976 , Page(s): 285 - 290
    Cited by:  Papers (37)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (731 KB)  

    An investigation has been carried out into the use of an open microwave resonator for dielectric measurements. The resonator is of the hemispherical type and consists of one plane and one concave copper mirror. The sample is a plane parallel sheet of lateral dimensions ¿ 50 mm and is placed on the plane mirror. The theory has been extended to cover this type of resonator. Measurements on unsintered polytetrafluoroethylene, high-density polyethylene and TPX show that for materials with loss angles in the range 50¿500 ¿rad the loss can be measured with standard deviation of ± 2% + 1¿rad. The standard deviation for permittivity measurements is about ± 0.1%. A full discussion of the possible sources of error is given. View full abstract»

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  • Numerical solution for nonreciprocal inhomogeneous waveguide interface

    Publication Year: 1976 , Page(s): 291 - 297
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (721 KB)  

    Mode matching is used to analyse the interface between a reciprocal homogeneous waveguide and a nonreciprocal inhomogeneous waveguide. The configuration used for the nonreciprocal structure is that of the twin-slab ferrite-loaded waveguide. The investigation is restricted to symmetrical E-plane loading, and to lossless structures in which only one mode may propagate. Based on the analysis, the interface and the nonreciprocal waveguide are described by relatively simple equivalent transmission circuits. In these circuits, unique equivalent transmission-line characteristic admittances are defined for the nonreciprocal waveguide. Results show that although the phase coefficients in the two directions of propagation can be very different, the equivalent characteristic admittances are nearly the same. Measurements on a practical version of the twin-slab configuration yield similar results. It is also noted that the energy stored, which is associated with the inhomogeneous interface, does not depend solely on the type of modes excited, in contrast to the case of (reciprocal) dielectric loading. View full abstract»

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  • Transition section spurious mode program

    Publication Year: 1976
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (146 KB)  

    A transition section spurious mode program is presented to calculate the magnitude and phase of propagating modes in H-plane waveguide transition sections with large flare angles. This program is based on a full wave analysis which employs local radial waveguide modes. This program is particularly suitable when some of the waveguide modes change from propagating to evanescent modes in the transition sections. View full abstract»

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  • Study of high-order vertical-aperture correction

    Publication Year: 1976 , Page(s): 299 - 308
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1009 KB)  

    Vertical aperture correction has been treated as a spatial transversal filter problem. A method of deriving filter coefficients for infinite-order correction is described and examples are given in the appendix. Finite-order correction based on a maximally-flat frequency characteristic is then discussed. The effects of interlace and noise are considered and the conclusion is reached that correction beyond lst-order obeys a law of diminishing returns. Subjective tests are described including the measurement of source aperture and these confirm the theoretical findings. View full abstract»

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  • Decision-directed demodulation of frequency-shift-keyed signals

    Publication Year: 1976 , Page(s): 309 - 313
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (533 KB)  

    Coherent demodulation of continuous-phase frequency-shift keyed (f.s.k.) signals is achieved by generating the receiver waveforms according to previous demodulator decisions. Convolution of phase information in the signaling waveform gives rise to the possibility of an error-detection process. A particularly simple process can be implemented for f.s.k. signals with deviation ratios in the range 0.7¿0.8. If the error-detection capability is combined with a request for retransmission, the undetected error performance of the system can approach the optimum for binary-data transmission. Analysis of the error-detecting performance of the system, and simulation results for demodulators employing high-resolution waveforms and binary (sliced) waveforms, are given. View full abstract»

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  • Improved retransmission logics for bidirectional ARQ systems

    Publication Year: 1976 , Page(s): 314 - 318
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    Two retransmission logics are described which, when used in conjunction with high-reliability bidirectional datatransmission systems, can improve the throughput by up to 17% compared with systems using Metzner's `newword¿ strategy. Only a small amount of additional logic is required at transmitter and receiver. View full abstract»

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  • Design of differential-voltage-controlled current source

    Publication Year: 1976 , Page(s): 319 - 324
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (666 KB)  

    General purpose, precise, d.c.-coupled, large-signal and wide-band differential-voltage-controlled current source (d.v.c.c.s.) suitable for monolithic fabrication has been designed. The transconductance is controlled by an external precision resistor and hence is linear and relatively temperature insensitive. The influence of transistor parameters and bias conditions on the behaviour of d.v.c.c.s. has been discussed. Tests on bread-boarded circuits using monolithic transistor arrays indicate a precision in transconductance of about 0.25% over a temperature range of 75 deg C, excellent linearity, and bandwidth in excess of 20 MHz. View full abstract»

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  • Reliability evaluation of electrical systems with switching actions

    Publication Year: 1976 , Page(s): 325 - 330
    Cited by:  Papers (16)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (726 KB)  

    The paper presents a new approach for comparing the reliability of different designs for electrical systems with switching actions; this switching taking place following a fault in the system. An efficient program to evaluate the failure modes of each load point and its associated reliability indices has been developed. Also a concept of system minimal cutsets is introduced to assess the overall system-reliability indices. This is a powerful concept for systems that have many load points and also those that have a single overall objective. It permits comparison of the reliability between systems that are different in design, although meeting all the operating requirements. The program incorporates this technique and was used to obtain the results presented in the paper. View full abstract»

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  • Optimal cable profile of l.v. radial distributors. Two mathematical programming methods

    Publication Year: 1976 , Page(s): 331 - 334
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (443 KB)  

    Two different methods for finding the optimal cable profile of tapered low-voltage multibranched distributors are presented. One method is for tapering between nodes assuming a change in cable size can occur anywhere within a branch, the other is for tapering at nodes where a change in cable size is allowed only from branch to branch. Both can be embedded in a general procedure for designing distribution networks. Also, both cater for interconnectors, existing branches and the cost of losses. View full abstract»

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  • New improvements in the computation of the polyphase induction-motor magnetic circuit

    Publication Year: 1976 , Page(s): 335 - 341
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (988 KB)  

    The present paper introduces a method of determining the airgap-flux-density waveshape in a polyphase induction motor operating under saturation conditions. It proposes to characterise the magnetic-circuit saturation by means of two independent factors, considering both the tooth and core saturation - and it produces new computative curves required to determine the magnetising current. The paper also proposes a new method of determining the field distribution in magnetic cores, considering the variable permeability, as well as curves for the computation of the core m.m.f. Comparison with other computative curves cited in the literature, as well as experimental results, has shown good correlation. View full abstract»

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  • Discussion on ¿Control of power on a large diesel-electric locomotive of new design¿

    Publication Year: 1976 , Page(s): 341 - 342
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  • Programmable testing equipment for power-system protective equipment

    Publication Year: 1976 , Page(s): 343 - 349
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1047 KB)  

    Present testing equipment does not enable the performance of protective equipment to be assessed over the wide range of conditions encountered on modern power systems. System behaviour may be determined by digital-computer studies or measurements made either on transient analysers or the actual networks. Thereafter it is desirable that the appropriate voltages and currents be regenerated in laboratories for use during the development of new protective equipment, or when assessing the suitability of established schemes for particular applications. The authors have developed equipment into which details of any desired aperiodic testing waveform can be fed, either in digital form on punched paper tapes, or in analogue form on magnetic tapes. Although the signals so derived may be amplified and fed to any voltage circuits associated with protective schemes, the apparent power demands made by current circuits under fault conditions may be so great, if current transformers are included, that the necessary amplifiers would be too large to be practical. An arrangement has been developed in which the correct currents are produced for feeding to the relay current circuits by including small model transformers that simulate the effects of the actual current transformers and enable the necessary allowances to be made. In this way the required power handling capability of each amplifier is much reduced. Details are given of the complete prototype equipment which has been produced, and test results are provided to illustrate its effectiveness. View full abstract»

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  • Discussion on ¿Internally force-cooled power cables; optimum working temperature in the range 70¿358 K¿

    Publication Year: 1976 , Page(s): 350 - 352
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  • Digital simulation of faulted e.h.v. transmission lines with particular reference to very-high-speed protection

    Publication Year: 1976 , Page(s): 353 - 359
    Cited by:  Papers (28)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (862 KB)  

    Increasing demands for ultralow fault clearance times in electrical power systems require that measurements be made from information derived from power lines during a very short interval after fault inception. For research and development purposes, the precise nature of this information is required, and in this paper modern transmission-line theory is used to predict the fault-transient behaviour of multiconductor overhead lines to a greater degree of accuracy than has hitherto been possible. The nonlinear nature of simulating fault-transient phenomena has been overcome, and it is shown that even on lines which have traditionally been regarded as electrically short, very severe transient conditions can exist. The necessity for an accurate representation of the frequency variance of line parameters is established, and the various factors which influence fault transient phenomena are considered. The paper concludes with a presentation of the results of studies relating to a very long transmission line. View full abstract»

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  • Circuit analysis of metal-halide lamp with inductive-capacitive ballast

    Publication Year: 1976 , Page(s): 360 - 362
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    An idealised characteristic for the dynamic behaviour of the metal-halide lamp at 50 Hz is used in the circuit analysis for the series inductive-capacitive ballast. Distortion of the current waveform is shown to increase when the capacitor-impedance/inductor-impedance ratio is increased, or when the supply-voltage/lamp-voltage ratio is decreased. The voltage developed across the inductor at the end of each halfcycle determines the condition for commutation. This voltageis evaluated as a function of supply and lamp voltage and the commutation of the series inductive-capacitive ballast is compared with an inductive ballast. View full abstract»

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  • Improved solid-state direction-sensitive phase-angle monitor

    Publication Year: 1976
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  • Static torque production in saturated doubly-salient machines

    Publication Year: 1976
    Save to Project icon | PDF file iconPDF (120 KB)  
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  • Nonlinear power-system optimisation using dynamic sensitivity analysis

    Publication Year: 1976 , Page(s): 365 - 370
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (761 KB)  

    A number of applications of the concepts of dynamic sensitivity analysis to power-system-stability problems are considered in the paper and sensitivity equations for a nonlinear power-system model have been derived in a form suitable for solution on a digital computer. A comparison of sensitivity curves for variations in typical system parameters has been made, and these curves have been used to predict changes in system performance produced by parameter variations. An important application of dynamic sensitivity concepts is in the optimisation of nonlinear models of power systems, and alternative techniques are considered. Finally, the design of a control system resulting in a power system with optimum performance and optimum sensitivity is illustrated. View full abstract»

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  • Asymptotic approximation method of optimal control applied to a power-system problem

    Publication Year: 1976 , Page(s): 371 - 376
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (658 KB)  

    A single machine power system connected to an infinite bus with both voltage regulator and speed governor controls is considered. This system mathematically can be described by an 8th-order nonlinear time-delay model. However, by perturbing a small scalar parameter, this 8th-order model can be reduced to a 3rd-order ordinary model without any pure time delays. An asymptotic approximate solution is constructed with respect to the scalar parameter for the 8th-order time delay model by using the solution of only the 3rd-order ordinary model. Numerical results indicate that the asymptotic solution is close to the optimal solution. Computationally, the asymptotic method is compared with the 2-variation method and is shown to be superior. View full abstract»

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  • Box, Jenkins-Åström and Kalman linear control laws and their equivalence

    Publication Year: 1976 , Page(s): 377 - 380
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (365 KB)  

    A state-space equivalent of the general Box, Jenkins¿Åström single input/output, discrete stochastic-system model is given. The `noise¿ estimates from them are shown to be the same. It is suggested that equivalence of the controls, for the same cost function, follows directly; but the equivalence is also demonstrated more formally. The relation of these results to those for a model with uncorrelated system and measurement noise, and to `multistage¿ control, is also dealt with. 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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